Method for producing iron (Fe) -nickel (Ni) -based alloy powder

Abstract

The present application provides a manufacturing method of iron-nickel alloy powder with excellent powder characteristics and magnetic characteristics. The method is a manufacturing method of iron-nickel alloy powder containing at least iron (Fe) and nickel (Ni) as magnetic metals. The method comprises the following steps: a preparation step of preparing, as starting materials, a magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, and a pH adjusting agent; a crystallization step of preparing a reaction solution containing the starting materials and water, and crystallizing a crystallization powder containing the magnetic metal by a reduction reaction in the reaction solution; and a recovery step of recovering the crystallization powder from the reaction solution. The magnetic metal source contains a water-soluble iron salt and a water-soluble nickel salt, the nucleating agent is a water-soluble salt of a metal less noble than nickel, and the complexing agent is at least one selected from the group consisting of a hydroxyl carboxylic acid, a salt of a hydroxyl carboxylic acid, and a derivative of a hydroxyl carboxylic acid. The reducing agent is hydrazine (N2H4), and the pH adjusting agent is a hydroxide base.

Description

Technical Field

[0001] This invention relates to a method for manufacturing iron (Fe)-nickel (Ni) alloy powder. Background Technology

[0002] Permalloy, a well-known iron-nickel alloy, is a soft magnetic material with high permeability, used in the cores of magnetic components such as chokes or inductors. In particular, iron-nickel alloy powder is used as a material for pressed powder cores (powder cores) obtained by compressing and molding it.

[0003] Various permalloys, such as 78% permalloy (Permalloy A) and 45% permalloy, are known and classified according to their magnetic properties or applications. 78% permalloy is an iron-nickel alloy with a nickel content of approximately 78.5% by mass, characterized by high magnetic permeability. 45% permalloy is an iron-nickel alloy with a nickel content of 45% by mass, characterized by slightly lower magnetic permeability but higher saturation magnetic flux density.

[0004] In recent years, mobile devices such as laptops and smartphones have seen rapid miniaturization and performance improvements. Consequently, magnetic components such as inductors require not only enhanced magnetic properties but also higher frequency performance. This necessitates materials with high flux density and reduced losses in powder-pressed magnetic cores. The main losses are hysteresis loss and eddy current loss. To suppress hysteresis loss, reducing the coercivity of the alloy powder is effective. On the other hand, to suppress eddy current loss, coating the surface of the alloy powder particles with a thin insulating coating, thereby reducing eddy currents between particles, or making the alloy powder finer and reducing its particle size distribution, is effective. This is because when coarse particles are present, eddy currents become more easily flowable, generating Joule heating and resulting in losses.

[0005] As methods for producing fine alloy powders, dry methods such as atomization, gas-phase reduction, and dry reduction have long been known. Atomization involves blowing water or gas into molten metal, causing it to cool and solidify rapidly. Gas-phase reduction involves reducing gaseous metal halides with hydrogen. Dry reduction uses a reducing agent to reduce metal oxides.

[0006] For example, Patent Document 1 describes the manufacture of Ni-Fe alloy powder, used as a material for noise filters, chokes, inductors, etc., by a gas-phase reduction method (Patent Document 1

[0001] and

[0014] ). Furthermore, Patent Document 1 discloses the production of Ni-Fe alloy micropowder by heating a mixture of NiCl2 and FeCl3, contacting vaporized chloride with hydrogen gas to induce a reduction reaction (Patent Document 1

[0016] ). Additionally, Patent Document 2 describes the production of Fe-Ni alloy powder, used as a material for electronic components such as chokes or inductors, by reducing Fe and Ni oxides in a reducing gas (Patent Document 2, claim 1).

[0007] On the other hand, a wet process has been proposed to produce finer alloy powders. For example, Patent Document 3 discloses a method for manufacturing nickel-iron alloy nanoparticles, characterized in that nickel ions and iron ions contained in an aqueous solution containing nickel and iron salts are simultaneously reduced by adding a reducing agent such as hydrazine to the aqueous solution, thereby generating nickel-iron alloy nanoparticles (claims 1-6 of Patent Document 3). Furthermore, according to this manufacturing method, nickel-iron alloy nanoparticles suitable as fillers for imparting magnetic properties can be manufactured efficiently on an industrial scale with low manufacturing costs, and the average primary particle size of the nickel-iron alloy nanoparticles is less than 200 nm (

[0015] of Patent Document 3).

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2003-193160;

[0011] Patent Document 2: Japanese Patent Application Publication No. 2012-197474;

[0012] Patent document 3: Japanese Patent Application Publication No. 2008-024961. Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] Thus, although dry or wet methods have been proposed for producing fine alloy powders, there is still room for improvement in obtaining alloy powders with excellent powder properties in the existing technology. For example, the average particle size of alloy powders produced by atomization is as large as several μm or more, which cannot fully meet the requirements for fineness. In addition, the alloy powder obtained by the gas-phase reduction method proposed in Patent Document 1 has a wide particle size distribution. Therefore, the alloy powder contains coarse particles, which is insufficient in reducing eddy current losses. Furthermore, there is also the problem of unstable composition or particle size of the alloy powder. Since the dry reduction method proposed in Patent Document 2 requires high-temperature heating, there is a problem that the obtained alloy powder is prone to sintering, forming coarse agglomerated particles.

[0015] Because the wet method proposed in Patent Document 3 differs from the dry method in that it carries out the reduction reaction at low temperatures, it has the advantage of not easily forming coarse agglomerated particles. Furthermore, even if agglomerated particles do form, they are easily broken due to the weak bonding between the particles. However, the method proposed in Patent Document 3 requires a large amount of hydrazine as the reducing agent. Therefore, the cost of the reducing agent increases significantly, making it impractical. Additionally, the particle size distribution of the obtained alloy powder is not fine enough.

[0016] The inventors conducted in-depth research based on these existing problems. The results showed that when manufacturing iron-nickel alloy powder using a wet process, alloy powders with excellent powder properties and magnetic properties can be obtained by using specific nucleating and complexing agents. Furthermore, it was found that when the iron content is high, adding a specified proportion of cobalt, through the promoting effects of cobalt reduction and spheroidization, can produce spherical alloy powders with less agglomeration, smooth surfaces, and high saturation magnetic flux density with very little reducing agent.

[0017] This invention is based on the insight that aims to provide a method for manufacturing iron-nickel alloy powder with excellent powder properties and magnetic properties.

[0018] Technical solutions to the problem

[0019] This invention includes the solutions described in (1) to (32) below. It should be noted that the expression “~” in this specification includes the values ​​at both ends. That is, “X~Y” is synonymous with “X and above and Y and below”.

[0020] (1) A method for manufacturing an iron (Fe)-nickel (Ni) alloy powder containing at least iron (Fe) and nickel (Ni) as a magnetic metal, wherein,

[0021] The method comprises the following steps:

[0022] The preparation process involves preparing magnetic metal sources, nucleating agents, complexing agents, reducing agents, and pH adjusters as starting materials.

[0023] The crystallization process involves preparing a reaction solution containing the starting material and water, and then, in the reaction solution, crystallizing the powder containing the magnetic metal through a reduction reaction; and...

[0024] The recovery process involves recovering the crystalline powder from the reaction solution.

[0025] The magnetic metal source contains water-soluble iron salts and water-soluble nickel salts.

[0026] The nucleating agent is a water-soluble salt of a metal less reactive than nickel.

[0027] The complexing agent is at least one selected from the group consisting of hydroxycarboxylic acids, salts of hydroxycarboxylic acids, and derivatives of hydroxycarboxylic acids.

[0028] The reducing agent is hydrazine (N2H4).

[0029] The pH adjuster is an alkali hydroxide.

[0030] (2) The method as described in (1) above, wherein the water-soluble iron salt is at least one selected from the group consisting of ferrous chloride (FeCl2), ferrous sulfate (FeSO4) and ferrous nitrate (Fe(NO3)2).

[0031] (3) The method as described in (1) or (2) above, wherein the water-soluble nickel salt is selected from at least one of the group consisting of nickel chloride (NiCl2), nickel sulfate (NiSO4) and nickel nitrate (Ni(NO3)2).

[0032] (4) Any of the methods in (1) to (3) above, wherein the nucleating agent is selected from at least one of the group consisting of copper salts, palladium salts and platinum salts.

[0033] (5) Any of the methods in (1) to (4) above, wherein the complexing agent is at least one hydroxycarboxylic acid selected from tartaric acid ((CH(OH)COOH)2) and citric acid (C(OH)(CH2COOH)2COOH).

[0034] (6) Any of the methods in (1) to (5) above, wherein the pH adjuster is at least one selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0035] (7) As in any of the methods (1) to (6) above, wherein,

[0036] The magnetic metal also contains cobalt (Co).

[0037] The magnetic metal source also contains water-soluble cobalt salt.

[0038] (8) As in (7) above, wherein,

[0039] In the magnetic metal, the content of iron (Fe) is 60 mol% or more and 85 mol% or less, and the content of cobalt (Co) is 10 mol% or more and 30 mol% or less.

[0040] In the magnetic metal source, the content of water-soluble iron salt is 60 mol% or more and 85 mol% or less, and the content of water-soluble cobalt salt is 10 mol% or more and 30 mol% or less.

[0041] (9) The method as described in (7) or (8) above, wherein the water-soluble cobalt salt is at least one selected from the group consisting of cobalt chloride (CoCl2), cobalt sulfate (CoSO4) and cobalt nitrate (Co(NO3)2).

[0042] (10) Any of the methods in (1) to (9) above, wherein the starting material further comprises an amine compound containing two or more primary amino groups (-NH2), one primary amino group (-NH2) and one or more secondary amino groups (-NH-), or two or more secondary amino groups (-NH-) within the molecule.

[0043] (11) The method as described in (10) above, wherein the amine compound is at least one of an alkylene amine and an alkylene amine derivative.

[0044] (12) The method of (11) above, wherein the alkylene amine and / or alkylene amine derivative has at least the following structure: the nitrogen atom of the amino group in the molecule is linked via a carbon chain having two carbon atoms, represented by (A) below.

[0045]

[0046] (13) As in any of (10) to (12) above, wherein the amine compound is at least one alkyleneamine selected from the group consisting of ethylenediamine (H2NC2H4NH2), diethylenetriamine (H2NC2H4NHC2H4NH2), triethylenetetramine (H2N(C2H4NH)2C2H4NH2), tetraethylenepentamine (H2N(C2H4NH)3C2H4NH2), pentaethylenehexamine (H2N(C2H4NH)4C2H4NH2) and propylenediamine (CH3CH(NH2)CH2NH2). And / or at least one alkyleneamine derivative selected from the group consisting of tris(2-aminoethyl)amine (N(C2H4NH2)3), N-(2-aminoethyl)ethanolamine (H2NC2H4NHC2H4OH), N-(2-aminoethyl)propanolamine (H2NC2H4NHC3H6OH), 2,3-diaminopropionic acid (H2NCH2CH(NH)COOH), ethylenediamine-N,N'-diacetic acid (HOOCCH2NHC2H4NHCH2COOH), and 1,2-cyclohexanediamine (H2NC6H10NH2).

[0047] (14) Any of the methods in (10) to (13) above, wherein the amount of the amine compound is more than 0.01 mol% and less than 5.00 mol% relative to the total amount of the magnetic metal.

[0048] (15) As in any of the methods (1) to (14) above, wherein when preparing the reaction solution in the crystallization process, a metal salt raw material solution, a reducing agent solution and a pH adjustment solution are prepared respectively, the metal salt raw material solution and the pH adjustment solution are mixed to form a mixed solution, the mixed solution and the reducing agent solution are mixed, the metal salt raw material solution is formed by dissolving the magnetic metal source, the nucleating agent and the complexing agent in water, the reducing agent solution is formed by dissolving the reducing agent in water, and the pH adjustment solution is formed by dissolving the pH adjustment agent in water.

[0049] (16) The method described in (15) above, wherein, in preparing the reaction solution, the pH adjustment solution and the reducing agent solution are added sequentially to the metal salt raw material solution and mixed.

[0050] (17) The method as described in (15) or (16) above, wherein the time required for mixing the mixed solution and the reducing agent solution is more than 1 second and less than 180 seconds.

[0051] (18) Any of the methods in (1) to (14) above, wherein when preparing the reaction solution in the crystallization process, a metal salt raw material solution and a reducing agent solution are prepared respectively, and the metal salt raw material solution and the reducing agent solution are mixed. The metal salt raw material solution is prepared by dissolving the magnetic metal source, the nucleating agent and the complexing agent in water, and the reducing agent solution is prepared by dissolving the reducing agent and the pH adjusting agent in water.

[0052] (19) The method as described in (18) above, wherein, in preparing the reaction solution, the reducing agent solution is added to the metal salt raw material solution, or conversely, the metal salt raw material solution is added to the reducing agent solution and mixed.

[0053] (20) The method as described in (18) or (19) above, wherein the time required for mixing the metal salt raw material solution and the reducing agent solution is more than 1 second and less than 180 seconds.

[0054] (21) Any of the methods in (1) to (20) above, wherein, in the crystallization process, before the reduction reaction is completed, an additional raw material liquid is added to the reaction solution and mixed, wherein the additional raw material liquid is formed by dissolving at least one of the water-soluble nickel salt and the water-soluble cobalt salt in water.

[0055] (22) Any of the methods described in (15) to (21) above, wherein an amine compound is incorporated into at least one of the metal salt raw material solution, the reducing agent solution, the pH adjustment solution and the reaction solution.

[0056] (23) As in any of the methods (1) to (22) above, wherein the temperature of the reaction solution (reaction start temperature) at the start of crystallization of the crystallization powder is above 40°C and below 90°C, and the temperature of the reaction solution (reaction holding temperature) maintained during crystallization after the start of crystallization is above 60°C and below 99°C.

[0057] (24) Any of the methods (1) to (23) above, wherein a crushing process is further provided, wherein the crystallized powder after the recycling process or the crystallized powder during the recycling process is subjected to crushing treatment using impact energy to crush the aggregated particles contained in the crystallized powder.

[0058] (25) The method described in (24) above, wherein the crystal powder is crushed after the recovery process by dry crushing or wet crushing, or the crystal powder is crushed during the recovery process by wet crushing.

[0059] (26) The method described in (25) above, wherein the dry crushing is a spiral jet crushing.

[0060] (27) The method described in (25) above, wherein the wet crushing is high-pressure fluid impact crushing.

[0061] (28) Any of the methods in (1) to (27) above, wherein a high-temperature heat treatment step is further provided, wherein the crystallized powder after the recycling process or the crystallized powder during the recycling process is subjected to a heat treatment of greater than 150°C and less than 400°C in an inactive environment, a reducing environment or a vacuum environment, thereby improving the uniformity of the composition within the particles of the iron (Fe)-nickel (Ni) alloy powder.

[0062] (29) Any of the methods (1) to (28) above, wherein an insulating coating process is further provided, wherein the crystallized powder obtained through the recycling process is subjected to an insulating coating treatment, and an insulating coating composed of metal oxides is formed on the particle surface of the crystallized powder, thereby improving the insulation between particles.

[0063] (30) The method as described in (29) above, wherein, in the insulating coating step, the crystallized powder is dispersed in a mixed solvent containing water and an organic solvent, and a metal alkoxide is further added to the mixed solvent and mixed to prepare a slurry, in which the metal alkoxide is hydrolyzed and dehydrated and polycondensed to form an insulating coating of metal oxide on the particle surface of the crystallized powder, thereafter the crystallized powder with the insulating coating is recovered from the slurry.

[0064] (31) The method described in (30) above, wherein the metal alkoxide is mainly composed of silanol (alkyl silicate) and the metal oxide is mainly composed of silicon dioxide (SiO2).

[0065] (32) The method as described in (30) or (31) above, wherein the hydrolysis of the metal alkoxide is carried out in the presence of a salt-based catalyst (base catalyst).

[0066] Invention Effects

[0067] According to the present invention, a method for manufacturing iron-nickel alloy powder with excellent powder properties and magnetic properties is provided. Attached Figure Description

[0068] Figure 1 This is a process diagram illustrating the manufacturing method of the alloy powder in this embodiment.

[0069] Figure 2 It is a process diagram used to illustrate the preparation of the reaction solution and the manufacturing of the alloy powder in the first scheme.

[0070] Figure 3 It is a process diagram used to illustrate the preparation of the reaction solution and the manufacturing of the alloy powder in the first scheme.

[0071] Figure 4This is a process diagram used to illustrate the preparation of the reaction solution and the manufacturing of the alloy powder in the second scheme.

[0072] Figure 5 This is a process diagram used to illustrate the preparation of the reaction solution and the manufacturing of the alloy powder in the second scheme.

[0073] Figure 6 It is a process diagram used to illustrate the preparation of the reaction solution and the manufacturing of the alloy powder in the third scheme.

[0074] Figure 7 This is a diagram showing the temperature shift in the reaction tank during the crystallization process of Example 1.

[0075] Figure 8 This is an SEM image of the alloy powder obtained in Example 1.

[0076] Figure 9 This is an SEM image of the alloy powder obtained in Example 2.

[0077] Figure 10 This is an SEM image of the alloy powder obtained in Example 6 (before and after spiral jet crushing treatment).

[0078] Figure 11 These are the STEM images and EDS line analysis results of the alloy powder (before and after high-temperature heat treatment) obtained in Example 8.

[0079] Figure 12 These are STEM images and EDS line analysis results of the particle cross-section of the alloy powder obtained in Example 9.

[0080] Figure 13 This is an SEM image of the alloy powder obtained in Example 10.

[0081] Figure 14 This is an SEM image of the alloy powder (before and after insulating coating treatment) obtained in Example 12.

[0082] Figure 15 This is an SEM image of the alloy powder obtained in Example 13.

[0083] Figure 16 This is an SEM image of the alloy powder obtained in Example 14.

[0084] Figure 17 This is a SEM image of the alloy powder obtained in Comparative Example 1.

[0085] Figure 18 This is a SEM image of the alloy powder obtained in Comparative Example 2.

[0086] Figure 19 This is a SEM image of the alloy powder obtained in Comparative Example 3. Detailed Implementation

[0087] The following describes specific embodiments of the present invention (hereinafter referred to as "this embodiment"). It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without changing the essence of the present invention.

[0088] <<1. Manufacturing Method of Iron-Nickel Alloy Powder>>

[0089] The method for manufacturing iron (Fe)-nickel (Ni) alloy powder according to this embodiment includes the following steps: a preparation step, in which starting materials containing a magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, and a pH adjuster are prepared; a crystallization step, in which a reaction solution containing the starting materials and water is prepared, and the crystallized powder containing the magnetic metal is crystallized in the reaction solution by a reduction reaction; and a recovery step, in which the crystallized powder is recovered from the obtained reaction solution. Here, the iron (Fe)-nickel (Ni) alloy powder contains at least iron (Fe) and nickel (Ni) as magnetic metals. In addition, the magnetic metal source contains water-soluble iron salt and water-soluble nickel salt. The nucleating agent is a water-soluble salt of a metal less reactive than nickel. The complexing agent is at least one selected from the group consisting of hydroxycarboxylic acids, salts of hydroxycarboxylic acids, and derivatives of hydroxycarboxylic acids. The reducing agent is hydrazine (N2H4).

[0090] The iron (Fe)-nickel (Ni) alloy powder of this embodiment (hereinafter, sometimes simply referred to as "alloy powder") contains at least iron (Fe) and nickel (Ni). Additionally, the alloy powder may contain cobalt (Co) as needed. That is, the alloy powder can be an iron-nickel alloy powder containing only iron and nickel, or it can be an iron-nickel-cobalt alloy powder containing iron, nickel, and cobalt. Iron, nickel, and cobalt are all magnetic metals exhibiting strong magnetism. Therefore, the iron-nickel alloy powder and the iron-nickel-cobalt alloy powder have high saturation magnetic flux density and excellent magnetic properties. It should be noted that the term "magnetic metal" in this specification is a general term for iron, nickel, and cobalt. That is, when the alloy does not contain cobalt, the term "magnetic metal" is a general term for iron and nickel; when the alloy contains cobalt, the term "magnetic metal" is a general term for iron, nickel, and cobalt.

[0091] The proportions of iron (Fe), nickel (Ni), and cobalt (Co) in the alloy powder of this embodiment are not particularly limited. The iron content can be 10 mol% or more and 95 mol% or less, 25 mol% or more and 90 mol% or less, or 40 mol% or more and 80 mol% or less. The nickel content can be 5 mol% or more and 90 mol% or less, 10 mol% or more and 75 mol% or less, or 20 mol% or more and 60 mol% or less. The cobalt content can be 0 mol% or more and 40 mol% or less, or 5 mol% or more and 20 mol% or less. The total amount of iron, nickel, and cobalt is 100 mol% or less.

[0092] The alloy powder of this embodiment does not exclude the presence of additives other than magnetic metals (Fe, Ni, and Co). Examples of such additives include copper (Cu) and / or boron (B). However, it is preferable to have as little content as possible of additives other than magnetic metals in order to maximize the effect based on magnetic metals. The content of other components can be 10% by mass or less, 5% by mass or less, 1% by mass or less, or even 0% by mass. In addition, there is a possibility that the alloy powder contains impurities that are unavoidably introduced during the manufacturing process (unavoidable impurities). Examples of such unavoidable impurities include oxygen (O), carbon (C), chlorine (Cl), and alkali components (Na, K, etc.). Since unavoidable impurities pose a risk of deteriorating the properties of the alloy powder, it is preferable to suppress their amount as much as possible. Regarding the amount of unavoidable impurities, the oxygen (O) contained in the oxide film that inevitably forms on the surface of the alloy powder is preferably 5% by mass or less, more preferably 3% by mass or less. On the other hand, the carbon (C), chlorine (Cl), and alkali components (Na, K, etc.) are preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less. The alloy powder contains magnetic metals and may have a composition in which the remainder consists of unavoidable impurities.

[0093] The method for manufacturing alloy powder according to this embodiment includes at least a preparation step, a crystallization step, and a recycling step. Additionally, depending on the needs, a crushing step, a high-temperature heat treatment step, or an insulating coating step may be included after or during the recycling step. Figure 1 This section provides a simplified example of the process in the manufacturing method of this embodiment. Figure 1 The diagram shows crushing, high-temperature heat treatment, and insulating coating treatment, but these treatments can be included as needed and are not mandatory. Furthermore, there are no particular restrictions on the order in which these treatments are performed. If it must be specified, crushing is preferably performed after high-temperature heat treatment. This is because it reduces or eliminates the bonds (bonds) between alloy particles strengthened during high-temperature heat treatment. Additionally, crushing is preferably performed before insulating coating. This is because it allows for a uniform insulating coating on the surface of each alloy particle after the bonds have been reduced or eliminated. In contrast, when alloy particles are bonded, no insulating coating forms at the bonded areas. Therefore, it is preferable to reduce or eliminate bonds as much as possible before the insulating coating treatment. The details of each process are described below.

[0094] <Preparation Process>

[0095] In the preparation process, a magnetic metal source, nucleating agent, complexing agent, reducing agent, and pH adjuster are prepared as starting materials. The magnetic metal source is made from iron and nickel, but cobalt may also be included if needed. Additionally, amine compounds may be included in the starting materials. The following describes each material.

[0096] (a) Magnetic metal source

[0097] The magnetic metal source is the raw material for the magnetic metal, and contains at least water-soluble iron salts and water-soluble nickel salts. The iron salt is the raw material (iron source) for the iron component contained in the alloy powder; there are no particular limitations as long as it is a readily water-soluble iron salt. Examples of iron salts include ferric chloride, ferric sulfate, ferric nitrate, or mixtures thereof containing divalent and / or trivalent iron ions. The water-soluble iron salt is preferably at least one selected from the group consisting of ferrous chloride (FeCl2), ferrous sulfate (FeSO4), and ferrous nitrate (Fe(NO3)2). The nickel salt is the raw material (nickel source) for the nickel component contained in the alloy powder; there are no particular limitations as long as it is a readily water-soluble nickel salt. The water-soluble nickel salt is preferably at least one selected from the group consisting of nickel chloride (NiCl2), nickel sulfate (NiSO4), and nickel nitrate (Ni(NO3)2), and particularly preferably at least one selected from the group consisting of nickel chloride (NiCl2) and nickel sulfate (NiSO4).

[0098] Depending on the requirements, the magnetic metal may also contain cobalt (Co), and the magnetic metal source may also contain water-soluble cobalt salts. This allows the production of iron-nickel-cobalt alloy powder. Iron-nickel-cobalt alloy powder in which some of the iron or nickel is replaced by cobalt exhibits a particularly high saturation magnetic flux density.

[0099] Water-soluble cobalt salts promote the reduction reaction during the crystallization of alloy powders (reduction promoting effect), especially when the iron (Fe) content in the magnetic metal is 60 mol% or more, this reduction promoting effect becomes more significant. Furthermore, water-soluble cobalt salts also promote the formation of smooth, spherical particles in the alloy powder (spheroidization promoting effect). Therefore, in a magnetic metal source, when the content of water-soluble iron salt is 60 mol% or more and 85 mol% or less, and the content of water-soluble cobalt salt is 10 mol% or more and 30 mol% or less, even with a very small amount of hydrazine used as a reducing agent, it is possible to obtain iron-nickel-cobalt alloy powder with a very high saturation magnetic flux density (e.g., 2 T (Tesla) or more), a smooth surface, and spherical shape. In this alloy powder, for example, the iron content is 60 mol% or more and 85 mol% or less, and the cobalt content is 10 mol% or more and 30 mol% or less.

[0100] There are no particular limitations on water-soluble cobalt salts, as long as they are readily soluble in water. Preferably, the water-soluble cobalt salt is selected from at least one of the groups consisting of cobalt chloride (CoCl2), cobalt sulfate (CoSO4), and cobalt nitrate (Co(NO3)2), and particularly preferably from at least one of the groups consisting of cobalt chloride (CoCl2) and cobalt sulfate (CoSO4).

[0101] (b) Nucleating agent

[0102] The nucleating agent is a water-soluble salt of a metal less reactive than nickel. In the subsequent crystallization process, this nucleating agent (the water-soluble salt of a metal less reactive than nickel) is preferentially reduced in the reaction solution to generate initial nuclei, which promote the precipitation of crystal powder. Here, a metal less reactive than nickel refers to a metal with a higher potential than nickel in the standard potential series in aqueous solution. Alternatively, a metal less reactive than nickel can also be a metal with a lower ionization tendency than nickel. Examples of such metals include tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), copper (Cu), silver (Ag), palladium (Pd), iridium (Ir), platinum (Pt), and gold (Au).

[0103] By using a water-soluble salt of a metal less reactive than nickel as a nucleating agent, the formation of crystallized powder in the reaction solution can be controlled in subsequent crystallization steps. For example, increasing the amount of nucleating agent can yield finer crystallized powder. Specifically, in the crystallization step, ions or complex ions of magnetic metals contained in the reaction solution are reduced and precipitated, forming crystallized powder. Among magnetic metals, nickel is less reactive than iron or cobalt, exhibiting a lower tendency to ionize. Therefore, when the reaction solution contains a water-soluble salt (nucleating agent) of a metal less reactive than nickel, the less reactive metal is reduced and precipitated before all the magnetic metals. The precipitated less reactive metal acts as an initial nucleus, and since this initial nucleus undergoes particle growth and forms crystallized powder composed of magnetic metal, the particle size of the crystallized powder can be controlled based on the amount of nucleating agent added, which determines the number of initial nuclei.

[0104] There are no particular limitations on the nucleating agent, as long as it is a water-soluble salt of a metal less reactive than nickel. However, the nucleating agent is preferably at least one selected from the group consisting of copper salts, palladium salts, and platinum salts. Copper (Cu), palladium (Pd), and platinum (Pt) have particularly strong inert properties and particularly low ionization tendency. Therefore, they are particularly effective as nucleating agents. There are no limitations on the water-soluble copper salt, and copper sulfate can be cited as an example. In addition, there are no limitations on the water-soluble palladium salt, and sodium palladium(II) chloride, ammonium palladium(II) chloride, palladium(II) nitrate, palladium(II) sulfate, etc. can be cited as examples. Palladium salts are particularly preferred as nucleating agents. When using palladium salts, the particle size of the crystallization powder (alloy powder) can be controlled more finely.

[0105] The amount of nucleating agent can be adjusted to achieve the desired particle size of the final alloy powder. For example, the amount of nucleating agent relative to the total amount of magnetic metal can be 0.001 mol ppm or more and 5.0 mol ppm or less, or 0.005 mol ppm or more and 2.0 mol ppm or less. By setting the amount of nucleating agent within this range, alloy powder with an average particle size of 0.2 μm or more and 0.6 μm or less can be obtained. However, the amount of nucleating agent is not limited to the above range. For example, when producing fine alloy powder with an average particle size of less than 0.2 μm, the amount of nucleating agent can be set to more than 5.0 mol ppm.

[0106] (c) Complexing agents

[0107] The complexing agent is at least one selected from the group consisting of hydroxycarboxylic acids, salts of hydroxycarboxylic acids, and derivatives of hydroxycarboxylic acids. This complexing agent (hydroxycarboxylic acid, etc.) plays a role in homogenizing the reaction in the subsequent crystallization process. That is, the magnetic metal component acts as magnetic metal ions (Fe) in the reaction solution. 2+ Ni 2+ While the magnetic metal ions can dissolve in the reaction solution, the amount dissolved is extremely small due to the strong alkalinity of the pH adjuster (NaOH, etc.). However, when a complexing agent is present, the magnetic metal components can dissolve in large quantities as complex ions (Fe complex ions, Ni complex ions, etc.). The presence of these complex ions increases the reduction reaction rate and suppresses uneven local distribution of the magnetic metal components, making homogenization of the reaction system possible. Furthermore, the complexing agent has the effect of altering the balance of complexation stability among multiple magnetic metal ions in the reaction solution. Therefore, the reduction reaction of the magnetic metal changes when a complexing agent is present, and the balance between the nucleus generation rate and the particle growth rate changes. By using a specific complexing agent (hydroxycarboxylic acid, etc.) in this embodiment, the above effects work in combination, and the reaction proceeds in a preferred direction, resulting in improved powder properties (particle size, particle size distribution, sphericity, particle surface properties) of the obtained alloy powder. In addition, the improved powder properties of the alloy powder result in excellent filling properties, making it suitable as a raw material for pressed magnetic cores. In this respect, it can be said that the complexing agent (hydroxycarboxylic acid, etc.) of this embodiment functions as a reduction reaction promoter, a spheroidization promoter, and a surface smoother. A preferred complexing agent contains at least one hydroxycarboxylic acid selected from tartaric acid ((CH(OH)COOH)2) and citric acid (C(OH)(CH2COOH)2COOH).

[0108] The amount of the complexing agent relative to the total amount of the magnetic metal is preferably 5 mol% or more and 100 mol% or less, more preferably 10 mol% or more and 75 mol% or less, and even more preferably 15 mol% or more and 50 mol% or less. When the amount is 5 mol% or more, the powder properties (particle size, particle size distribution, sphericity, and surface properties of the particles) of the alloy powder are more superior because its functions as a reduction reaction promoter, sphericity promoter, and surface smoother are fully utilized. In addition, when the amount is 100 mol% or less, the manufacturing cost is reduced because the amount of complexing agent used can be controlled and the degree of its functional performance as a complexing agent does not change significantly.

[0109] (d) Reducing agent

[0110] The reducing agent is hydrazine (N₂H₄, molecular weight: 32.05). This reducing agent (hydrazine) reduces the magnetic metal ions and complex ions in the reaction solution during the subsequent crystallization process. Hydrazine has the advantages of strong reducing power and does not generate byproducts accompanying the reduction reaction in the reaction solution. Furthermore, hydrazine with few impurities and high purity is readily available.

[0111] Besides anhydrous hydrazine, hydrazine hydrate (N₂H₄·H₂O, molecular weight: 50.06) is also known as a hydrazine hydrate. Both can be used. For example, commercially available industrial-grade 60% by mass hydrazine hydrate can be used as a hydrazine hydrate.

[0112] The amount of reducing agent required largely depends on the composition of the iron (Fe)-nickel (Ni) alloy powder; the higher the proportion of iron that is difficult to reduce, the more reducing agent is needed. In addition to the composition of the alloy powder, the amount is also affected by the temperature of the reaction solution and the amounts of complexing agents and pH adjusters. For example, when the iron content in the iron-nickel alloy powder is 60 mol% or less, the molar ratio of the reducing agent to the total amount of magnetic metal is preferably 1.8 or more and 7.0 or less, more preferably 2.0 or more and 6.0 or less, and even more preferably 2.5 or more and 5.0 or less. When the iron content in the iron-nickel alloy powder is greater than 60 mol% and less than 75 mol%, the molar ratio of the reducing agent to the total amount of magnetic metal is preferably 2.5 or more and 9.0 or less, more preferably 3.5 or more and 8.0 or less. When the iron content of the iron-nickel alloy powder is greater than 75 mol% and less than 95 mol%, the amount of reducing agent added relative to the total amount of magnetic metal is preferably 3.5 or more and less than 10.0, more preferably 4.5 or more and less than 9.0. On the other hand, when manufacturing iron-nickel-cobalt alloy powder, the amount of reducing agent added can be significantly reduced compared to iron-nickel alloy powder due to the effect of the water-soluble cobalt salt described above. The effect of water-soluble cobalt salt is particularly significant in the manufacture of alloy powder with a high iron content. For example, when the iron content is 60 mol% or more and less than 85 mol%, when manufacturing an alloy powder with a cobalt (Co) content of 10 mol% or more and less than 30 mol%, the amount of reducing agent added relative to the total amount of magnetic metal is preferably 1.0 or more and less than 4.0, more preferably 1.2 or more and less than 2.0.

[0113] In any case, when the amount of compounded is above the lower limit mentioned above, the reduction of magnetic metal ions and complex ions is sufficient, and crystallized powder (alloy powder) without the presence of unreduced substances such as ferric hydroxide can be obtained. In addition, when the amount of compounded is below the upper limit mentioned above, the amount of reducing agent (hydrazine) used can be suppressed, thereby reducing manufacturing costs.

[0114] (e) pH adjuster

[0115] The pH adjuster is an alkali hydroxide. This pH adjuster (alkali hydroxide) enhances the reduction reaction of hydrazine as a reducing agent. That is, the higher the pH of the reaction solution, the stronger the reducing power of hydrazine. Therefore, by using an alkali hydroxide as a pH adjuster, the reduction reaction of magnetic metal ions and complex ions in the reaction solution, as well as the precipitation of the accompanying crystal powder, are promoted. There is no particular limitation on the type of alkali hydroxide. However, in terms of availability and price, the pH adjuster preferably contains at least one selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0116] The amount of pH adjuster (base hydroxide) is adjusted to make the reducing power of the reducing agent (hydrazine) sufficiently high. Specifically, the pH of the reaction solution under the reaction temperature conditions is preferably 9.5 or higher, more preferably 10 or higher, and even more preferably 10.5 or higher. Therefore, the amount of base hydroxide is adjusted to bring the pH into this range.

[0117] (f) Amine compounds

[0118] Depending on the requirements, the starting material may further contain an amine compound. This amine compound contains two or more primary amino groups (-NH2), one primary amino group (-NH2) and one or more secondary amino groups (-NH-), or two or more secondary amino groups (-NH-) within its molecule.

[0119] Amine compounds promote the reduction reaction in subsequent crystallization processes. That is, amine compounds function as complexing agents, enabling them to bind magnetic metal ions (Fe2+, Fe2+, Fe2+) in the reaction solution. 2+ Ni 2+ The reaction involves the formation of complex ions (such as Fe complex ions, Ni complex ions, etc.) through complexation. Furthermore, the presence of complex ions in the reaction solution is believed to facilitate further reduction reactions.

[0120] Furthermore, amine compounds have the effect of inhibiting the self-decomposition of hydrazine as a reducing agent. That is, when crystallized powder composed of magnetic metal precipitates in the reaction solution, the nickel (Ni) in the magnetic metal acts as a catalyst, which sometimes leads to the decomposition of hydrazine. This is called the self-decomposition of hydrazine. The decomposition reaction, as shown in equation (1) below, is the reaction in which hydrazine (N2H4) decomposes into nitrogen (N2) and ammonia (NH3). When this self-decomposition occurs, it is not preferred because it impairs the function of hydrazine as a reducing agent.

[0121] 3N2H4→N2↑+4NH3···(1)

[0122] The self-decomposition of hydrazine can be suppressed by adding amine compounds to the complexing solution. The detailed mechanism is unclear, but it is speculated that excessive contact between hydrazine and the crystallized powder in the reaction solution is hindered. Specifically, the amino groups contained in the amine compound molecules, especially primary (-NH2) or secondary (-NH-) amino groups, are strongly adsorbed onto the surface of the crystallized powder in the reaction solution. It is thought that the amine compound molecules cover and protect the crystallized powder, thus hindering excessive contact between hydrazine molecules and the crystallized powder, thereby suppressing the self-decomposition of hydrazine. Since the self-decomposition of hydrazine becomes significant when the proportion of nickel in the magnetic metal is high, the amine compound works particularly effectively in this case.

[0123] The amine compound is preferably at least one of alkylene amines and alkylene amine derivatives. In addition, the alkylene amine and / or alkylene amine derivative preferably have at least the following structure: the nitrogen atom of the intramolecular amino group is linked via a carbon chain having two carbon atoms, as represented by (A) below.

[0124]

[0125] By using such alkylene amines or their derivatives as amine compounds, the self-decomposition inhibition effect of hydrazine (the reducing agent) can be more effectively utilized. The rationale is believed to be that the short carbon chains in these alkylene amines or their derivatives effectively inhibit the contact between hydrazine molecules and the crystallizing powder. In contrast, when the nitrogen atoms of an amino group are bonded via excessively long carbon chains, even if the amino group adsorbs onto the crystallizing powder, the carbon chain has a greater degree of freedom of movement. Therefore, it is speculated that this may be due to the lack of effective obstruction of the contact between the crystallizing powder and hydrazine molecules.

[0126] Specific examples of alkyleneamines having the structure represented by (A) above are selected from one or more of the group consisting of ethylenediamine (abbreviated as EDA)(H2NC2H4NH2), diethylenetriamine (abbreviated as DETA)(H2NC2H4NHC2H4NH2), triethylenetetramine (abbreviated as TETA)(H2N(C2H4NH)2C2H4NH2), tetraethylenepentamine (abbreviated as TEPA)(H2N(C2H4NH)3C2H4NH2), pentaethylenehexamine (abbreviated as PEHA)(H2N(C2H4NH)4C2H4NH2), and propylenediamine (also known as 1,2-diaminopropane, 1,2-propanediamine) (abbreviated as PDA)(CH3CH(NH2)CH2NH2). In addition, specific examples of alkyleneamine derivatives having the structure represented by (A) above are tri(2-aminoethyl)amine (abbreviated as TAEA)(N(C2H4NH2)3), N-(2-aminoethyl)ethanolamine (also known as 2-(2-aminoethylamino)ethanol (abbreviated as AEEA))(H2NC2H4NHC2H4OH), and N-(2-aminoethyl)propanolamine (also known as 2-(2-aminoethylamino)propanol (abbreviated as AEPA))(H2NC2H4NHC3H 6OH), L (or D, DL)-2,3-diaminopropionic acid (also known as: 3-amino-L (or D, DL)-alanine) (abbreviation: DAPA) (H2NCH2CH(NH)COOH), ethylenediamine-N,N'-diacetic acid (also known as: ethylene-N,N'-diglycine) (abbreviation: EDDA) (HOOCCH2NHC2H4NHCH2COOH), 1,2-cyclohexanediamine (also known as: 1,2-diaminocyclohexane) (abbreviation: CHDA) (H2NC6H) 10One or more of the following are selected from NH2. These alkylene amines or alkylene amine derivatives are water-soluble, and ethylenediamine and diethylenetriamine are preferred because they have relatively strong inhibitory effects on the self-decomposition of hydrazine, are readily available and inexpensive.

[0127] The structural formulas of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), propylenediamine (PDA), tri(2-aminoethyl)amine (TAEA), N-(2-aminoethyl)ethanolamine (AEEA), N-(2-aminoethyl)propanolamine (AEPA), and L (or D, DL)-2,3-diaminopropionic acid (DAPA) are shown in (B) to (M) below.

[0128]

[0129]

[0130] The amount of the amine compound relative to the total amount of the magnetic metal is preferably 0.00 mol% or more and 5.00 mol% or less, more preferably 0.01 mol% or more and 5.00 mol% or less, and even more preferably 0.03 mol% or more and 5.00 mol% or less. The amount of the amine compound can be 0.00 mol%, i.e., no amine compound is incorporated. However, by making the amount 0.01 mol% or more, the self-decomposition inhibition effect and reduction reaction promotion effect of hydrazine based on the amine compound can be fully utilized. Furthermore, by making the amount 5.00 mol% or less, the function as a complexing agent can be appropriately exhibited. Therefore, the powder properties (particle size, particle size distribution, sphericity, particle surface properties) of the alloy powder can be improved. When the amount of the amine compound exceeds 5.00 mol% and increases, the effect as a complexing agent becomes too strong. Abnormal particle growth occurs, and there is a risk of deterioration of the powder properties of the alloy powder.

[0131] <Crystallization process>

[0132] In the crystallization process, a reaction solution containing the prepared starting material and water is prepared, and in this reaction solution, the crystallization powder containing the magnetic metal is crystallized by a reduction reaction. The preparation of the reaction solution and the crystallization of the crystallization powder are described below. It should be noted that in actual manufacturing, in most cases, although the crystallization reaction starts at the same time as the preparation of the reaction solution, there is also the possibility that a small amount of crystallization reaction may start during the preparation of the reaction solution. It should be noted that the crystallization reaction mentioned here refers to the reaction that occurs during the crystallization process. That is, although it is mainly based on hydrazine reduction reaction (equation (6) mentioned later), it also includes hydrazine self-decomposition reaction (equation (1) mentioned above). Therefore, the term crystallization reaction is used in a broader sense than reduction reaction.

[0133] In the crystallization process, at least one of several solutions, such as a metal salt raw material solution or a reducing agent solution, is heated and then mixed to prepare a reaction solution. The reaction solution is heated and stirred in a reaction vessel while being maintained at a specified temperature, and the crystallization reaction is carried out under these conditions. Heating can be achieved using common methods; for example, a reaction vessel (reaction container) can be placed in a water bath, or a reaction vessel with a steam jacket or a reaction vessel with a heater can be used. From the viewpoint of not hindering the action of the nucleating agent, the surfaces of the reaction vessel (reaction container) or the stirring blades used for stirring the reaction solution that come into contact with the reaction solution should be made of a non-reactive material that is difficult to nucleate, and excellent strength or thermal conductivity is also required. To meet these requirements, for example, metal containers (such as Teflon-coated stainless steel containers) or stirring blades (such as Teflon-coated stainless steel stirring blades) coated with fluoropolymers (PTFE, PFA, etc.) are preferred.

[0134] (a) Preparation of reaction solution

[0135] First, a reaction solution is prepared by dissolving the magnetic metal source, nucleating agent, complexing agent, reducing agent, pH adjuster, and, if necessary, amine compound as starting materials, in water and then mixing them. To reduce impurities in the final alloy powder, high-purity water is preferably used when preparing this reaction solution. High-purity water can be pure water with a conductivity of 1 μS / cm or less, or ultrapure water with a conductivity of 0.06 μS / cm or less; inexpensive and readily available pure water is preferred.

[0136] When the starting materials are solids such as iron salts, nickel salts, cobalt salts, and alkali hydroxides, it is preferable to premix and dissolve these with water to form an aqueous solution. The mixing of the starting materials and water can be carried out by known methods such as stirring. There are no particular limitations on the mixing steps of the starting materials or the aqueous solution, as long as the homogeneity of the reaction solution is not compromised. However, from the viewpoint of ensuring the homogeneity of the reaction solution, it is preferable to prepare aqueous solutions containing each starting material separately beforehand, and then mix the prepared aqueous solutions; particularly, it is preferable to prepare the reaction solution according to the first or second scheme described below.

[0137] In the first scheme, during the preparation of the reaction solution in the crystallization process, a metal salt raw material solution, a reducing agent solution, and a pH adjustment solution are prepared separately. The metal salt raw material solution and the pH adjustment solution are mixed to form a mixed solution, and the obtained mixed solution is then mixed with the reducing agent solution. The metal salt raw material solution is prepared by dissolving a magnetic metal source, a nucleating agent, and a complexing agent in water. The reducing agent solution is prepared by dissolving a reducing agent in water, and the pH adjustment solution is prepared by dissolving a pH adjuster in water. A process diagram illustrating an example of the reaction solution preparation and alloy powder manufacturing in the first scheme is shown below. Figure 2 and Figure 3 .

[0138] In the first scheme, three solutions are prepared separately: a metal salt raw material solution, a reducing agent solution, and a pH adjusting solution. The metal salt raw material solution is prepared by dissolving a magnetic metal source (water-soluble iron salt, water-soluble nickel salt, etc.), a nucleating agent (water-soluble salt of a metal less reactive than nickel), and a complexing agent (hydroxycarboxylic acid, etc.) in water. The reducing agent solution is prepared by dissolving a reducing agent (hydrazine) in water. The pH adjusting solution is prepared by dissolving a pH adjusting agent (alkali hydroxide) in water. Next, the metal salt raw material solution and the pH adjusting solution are mixed to prepare a mixed solution. At this point, the magnetic metal salt (water-soluble iron salt, water-soluble nickel salt, etc.) contained in the metal salt raw material solution reacts with the alkali hydroxide contained in the pH adjusting agent to form a magnetic metal hydroxide. This hydroxide can be ferrous hydroxide (Fe(OH)₂), nickel hydroxide (Ni(OH)₂), cobalt hydroxide (Co(OH)₂), iron-nickel hydroxide ((Fe,Ni)(OH)₂), iron-nickel-cobalt hydroxide ((Fe,Ni,Co)(OH)₂), etc. Subsequently, a reducing agent solution is mixed into the obtained mixed solution to obtain a reaction solution.

[0139] As a specific step in preparing the reaction solution in the first scheme, it is preferable to sequentially add a pH adjustment solution and a reducing agent solution to the metal salt raw material solution and mix them. In the first scheme, which uses three solutions—metal salt raw material solution, reducing agent solution, and pH adjustment solution—the metal salt raw material solution has the largest volume. Therefore, adding other solutions sequentially to the metal salt raw material solution with a large volume and mixing them, compared to adding the metal salt raw material solution to other solutions, achieves a more uniform mixing state, because the reduction reaction can be carried out uniformly in the reaction solution.

[0140] When using an amine compound, the amine compound can be added to at least one of the metal salt raw material solution, the reducing agent solution, and the pH adjusting agent solution. Alternatively, the amine compound can be added after all these solutions have been mixed. Figure 2 A scheme is shown for adding an amine compound to at least one of a metal salt raw material solution, a reducing agent solution, and a pH adjusting solution. Figure 3 A scheme is shown for adding an amine compound to a reaction solution obtained by mixing a metal salt raw material solution, a reducing agent solution, and a pH adjustment solution.

[0141] In the first scheme, a reducing agent solution is mixed with a mixed solution of a metal salt raw material and a pH adjuster to prepare a reaction solution, and the reduction reaction begins from the moment the reducing agent solution is added. During the mixing of the reducing agent solution, the concentration of the reducing agent (hydrazine) locally and rapidly increases in a small region where the reducing agent is added. Furthermore, the mixed solution contains a pH adjuster (alkali hydroxide), and in the initial stage of mixing the reducing agent solution into this mixed solution, the pH of the mixed solution (reaction solution) remains high. As mentioned above, the higher the pH, the stronger the reducing power of the reducing agent (hydrazine). Therefore, in the initial stage of mixing the reducing agent solution, the reducing agent concentration and pH locally increase, and the nucleation and crystallization reduction reactions caused by the nucleating agent occur rapidly. On the other hand, as the reducing agent solution is added, the pH of the mixed solution (reaction solution) gradually decreases. Therefore, in the later stage of mixing the reducing agent solution, the reducing power of the reducing agent is not as strong as in the initial stage, and nucleation and reduction reactions proceed slowly. Thus, a difference in the reducing power of the reducing agent occurs between the initial and final stages of mixing the reducing agent solution.

[0142] When the difference in reducing power between the initial and final stages is large, there is a risk of reduced uniformity in the nucleation and reduction reactions, leading to increased deviations in the powder properties (particle size, surface smoothness, etc.) of the obtained crystallized powder. Therefore, it is preferable to minimize the difference in reducing power as much as possible. To this end, it is preferable to mix the reducing agent solution as quickly as possible. The time required to mix the mixed solution of the metal salt raw material and the pH adjuster with the reducing agent solution (mixing time) is preferably 180 seconds or less, more preferably 120 seconds or less, and even more preferably 60 seconds or less. On the other hand, due to limitations of the manufacturing apparatus, it may be difficult to excessively shorten the mixing time. The mixing time can be 1 second or more, 3 seconds or more, or 5 seconds or more.

[0143] It should be noted that when mixing the pH adjuster solution into the metal salt raw material solution, a longer mixing time may lead to deviations in the properties of the formed magnetic metal hydroxide, resulting in deviations in the powder properties of the crystallized powder. While the impact is not as significant as when mixing the reducing agent solution, a shorter mixing time is preferred. The mixing time required to mix the pH adjuster is preferably 180 seconds or less, more preferably 120 seconds or less, and even more preferably 80 seconds or less. Alternatively, the mixing time can be 1 second or more, 3 seconds or more, or 5 seconds or more.

[0144] To suppress deviations in the powder properties of crystallized powder, stirring while mixing the reducing agent solution or pH adjusting agent solution is also effective. Since stirring prevents a rapid increase in the concentration of components in the solution, it suppresses deviations in the properties of the crystallized powder. Stirring can be performed using stirring devices such as stirring blades.

[0145] In the second scheme, during the preparation of the reaction solution in the crystallization process, a metal salt raw material solution and a reducing agent solution are prepared separately and mixed. The metal salt raw material solution is prepared by dissolving a magnetic metal source, nucleating agent, and complexing agent in water, and the reducing agent solution is prepared by dissolving a reducing agent and a pH adjuster in water. A process diagram illustrating an example of the reaction solution preparation and alloy powder manufacturing in the second scheme is shown below. Figure 4 and Figure 5 .

[0146] In the second scheme, two solutions are prepared separately: a metal salt raw material solution and a reducing agent solution. The metal salt raw material solution is prepared by dissolving a magnetic metal source (water-soluble iron salt, water-soluble nickel salt, etc.), a nucleating agent (a water-soluble salt of a metal less reactive than nickel), and a complexing agent (hydroxycarboxylic acid, etc.) in water. The reducing agent solution is prepared by dissolving a reducing agent (hydrazine) and a pH adjuster (alkali hydroxide) in water. Next, the metal source raw material solution and the reducing agent solution are mixed to form a reaction solution. The second scheme differs from the first scheme in that the reducing agent solution contains a pH adjuster.

[0147] The specific preparation steps of the reaction solution in the second scheme can be either adding a reducing agent solution to the metal salt raw material solution and mixing, or vice versa. Unlike the first scheme, the volume of the reducing agent solution containing both the reducing agent and the pH adjuster (alkali hydroxide) is equal to the volume of the metal salt raw material solution. Therefore, by adding one to the other and mixing, a essentially uniform mixture can be achieved, enabling a homogeneous reduction reaction to occur in the reaction solution.

[0148] In crystallization conditions where the proportion of reducing agent or pH adjuster (alkali hydroxide) to metal salt raw material is high, it is preferable to add the metal salt raw material solution to the reducing agent solution and mix. This is because, from the viewpoint of ensuring the productivity of the crystallization process, the concentration of the metal salt raw material in the reaction solution is preferably maintained above a specified level (30-40 g / L based on metal content). That is, under the above crystallization conditions, the volume of the reducing agent solution is much larger than the volume of the metal salt raw material solution. Therefore, when a smaller volume of metal salt raw material solution is added to the larger volume of the reducing agent solution and mixed, a more uniform mixing state can be achieved, and the reduction reaction can proceed uniformly in the reaction solution.

[0149] In the second embodiment, for the same reasons as the first embodiment, the time required to mix the metal salt solution and the reducing agent solution (mixing time) is preferably 180 seconds or less, more preferably 120 seconds or less, and even more preferably 60 seconds or less. Furthermore, the mixing time can be 1 second or more, 3 seconds or more, or 5 seconds or more. Additionally, stirring during the mixing of the reducing agent solution is also effective.

[0150] In the third embodiment, during the crystallization process of the first or second embodiment, before the reduction reaction is completed, an additional raw material liquid is further added to the reaction liquid and mixed. This enriches the surface of the crystallized powder with nickel or cobalt components. Here, the additional raw material liquid is a liquid in which at least one of the aforementioned water-soluble nickel salt and water-soluble cobalt salt is dissolved in water. A process diagram illustrating an example of alloy powder manufacturing in the third embodiment is shown below. Figure 6 .

[0151] In the third approach, in addition to the solutions used in the preparation of the reaction solution in the first or second approach, an additional feedstock solution is prepared. This additional feedstock solution is prepared by dissolving at least one of a water-soluble nickel salt and a water-soluble cobalt salt in water. The addition of the additional feedstock solution to the reaction solution can be carried out by methods such as one-time addition, partial addition, and / or dropwise addition. Although addition is not mandatory, it is preferred to add it just before the reduction reaction ends. When the reduction reaction is completely finished, aggregates begin to form between the crystallized particles. Adding the additional feedstock solution at this moment and promoting the precipitation of metal components based on the reduction reaction can strengthen the bonding between the particles contained in the aggregates.

[0152] Furthermore, according to the third scheme, compared to the first or second scheme, it has the advantage of reducing the amount of reducing agent used. Iron ions (or ferric hydroxide) are less easily reduced than nickel ions (or nickel hydroxide) or cobalt ions (or cobalt hydroxide). This is because adding an additional feed solution containing nickel or cobalt to the reaction solution can promote the reduction reaction of the less easily reduced iron ions (or ferric hydroxide) in the final stage of crystallization.

[0153] The amount of magnetic metals (Ni, Co) added to the feed solution can be set according to the degree to which the surface of the crystallized powder is rich in nickel or cobalt. However, considering the overall uniformity of the particle composition, it is preferable to be 5 mol% to 50 mol% relative to the total amount of magnetic metals (Ni, Co) other than iron in the alloy powder. When the particle surface is rich in nickel or cobalt, the iron content, which easily forms a porous oxide film, is reduced. Therefore, since the oxidation of the particle surface is suppressed due to the formation of a dense oxide film, it is not only more stable in the atmosphere, but also the magnetic properties such as saturation magnetic flux density are improved.

[0154] (b) Crystallization of crystallized powder

[0155] When the reaction solution is prepared, a reduction reaction occurs in it. That is, in the presence of a pH adjuster (alkali hydroxide) and a nucleating agent (a salt of a metal less reactive than nickel), the ions or complex ions of the magnetic metal source are reduced by the reducing agent (hydrazine), thereby forming a crystalline powder containing the magnetic metal.

[0156] The reduction reactions in the crystallization process are explained using reaction equations. The reduction reactions of iron (Fe), nickel (Ni), and cobalt (Co) are shown in equations (2) to (4) below, and are two-electron reactions. On the other hand, the reaction of hydrazine (N2H4) as a reducing agent is shown in equation (5) below, and is a four-electron reaction.

[0157] Fe 2+ +2e - →Fe↓(two-electron reaction)···(2)

[0158] Ni 2+ +2e - →Ni↓(two-electron reaction)···(3)

[0159] Co 2+ +2e - →Co↓(two-electron reaction)···(4)

[0160] N2H4→N2↑+4H + +4e - (Four-electron reaction)···(5)

[0161] When using the chlorides of magnetic metals (FeCl2, NiCl2, CoCl2) as the magnetic metal source and sodium hydroxide (NaOH) as the pH adjuster, as shown in equation (6) below, the magnetic metal chloride first undergoes a neutralization reaction with sodium hydroxide to generate hydroxides ((Fe, Ni, Co)(OH)2, etc.). Then, these hydroxides ((Fe, Ni, Co)(OH)2, etc.) are reduced to crystal powder by the reducing agent (hydrazine). To reduce 1 mole of magnetic metal (Fe, Ni, Co), 0.5 moles of reducing agent (hydrazine) are required. In addition, as shown in equation (5) above, the higher the alkalinity (pH), the higher the reducing power of hydrazine. Therefore, sodium hydroxide, used as a pH adjuster, also has the effect of promoting hydrazine-based reduction reactions.

[0162] (Fe, Ni, Co)Cl2+1 / 2N2H4+2NaOH

[0163] →(Fe, Ni, Co)(OH)2↓+1 / 2N2H4+2NaCl

[0164] →(Fe, Ni, Co)↓+1 / 2N2↑+2NaCl+2H2O···(6)

[0165] In the reduction reaction described in equation (6) above, the reduction of the ions (or hydroxides) of the respective elements of the magnetic metals (Fe, Ni, Co) occurs simultaneously to some extent through co-reduction. Here, co-reduction refers to the phenomenon where other reduction reactions occur incidentally during the reduction reaction of one element. However, as mentioned above, iron ions (or iron hydroxide) are less easily reduced than nickel ions (or nickel hydroxide) or cobalt ions (or cobalt hydroxide). Therefore, in the final stage of the crystallization reaction, there is a tendency for nickel ions (or nickel hydroxide) or cobalt ions (or cobalt hydroxide) in the reaction solution to be consumed and disappear by the reduction reaction, while iron ions (or iron hydroxide) remain. This tendency is particularly pronounced when the iron content is high (e.g., the iron content of the alloy powder is greater than 60 mol%). When this phenomenon occurs, not only does it take a long time until the crystallization reaction (reduction reaction) is completed, but it is also easy to form a tilted structure with uneven composition within the particles. When a tilted structure is formed, the central part of the obtained alloy powder particles is rich in nickel or cobalt, and the composition is richer in iron closer to the particle surface.

[0166] In contrast, in the third approach described above, an additional raw material solution is added to the reaction solution during the crystallization reaction, promoting the reduction of iron ions (or ferric hydroxide) that are difficult to reduce in the final stage of crystallization. Therefore, when the iron content is particularly high, it can improve the situation where the crystallization reaction (reduction reaction) time is longer and the compositional inhomogeneity within the obtained alloy powder particles is reduced.

[0167] The temperature of the reaction solution at the start of crystallization (reaction start temperature) is preferably 40°C or higher and 90°C or lower, more preferably 50°C or higher and 80°C or lower, and even more preferably 60°C or higher and 70°C or lower. Here, the reaction solution at the start of crystallization refers to a reaction solution containing freshly prepared starting material and water. Furthermore, the temperature of the reaction solution maintained during crystallization after the start of crystallization (reaction holding temperature) is preferably 60°C or higher and 99°C or lower, more preferably 70°C or higher and 95°C or lower, and even more preferably 80°C or higher and 90°C or lower. To adjust the reaction start temperature to the preferred range, it is preferable to preheat at least one of the multiple solutions used in the preparation of the reaction solution, such as the metal salt raw material solution and the reducing agent solution. To adjust the reaction holding temperature to the preferred range, it is preferable to continuously heat the reaction solution after its preparation.

[0168] From the viewpoint of achieving more uniform nucleation to obtain crystallized powder with a narrow particle size distribution, it is preferable, if possible, to preheat (e.g., to 70°C) one of several solutions, such as a metal salt raw material solution or a reducing agent solution, while the other solutions are not preheated (e.g., maintained at 25°C), and then add and mix them to prepare a reaction solution at a specified temperature (e.g., 55°C). In contrast, when both solutions (e.g., the metal salt raw material solution and the reducing agent solution) are preheated (e.g., to 70°C), uneven nucleation is easily caused. That is, when the two solutions are added and mixed, the mixing of the solutions causes heat generation. Therefore, the added mixed solution (reaction solution) locally becomes very hot (e.g., around 78°C) at the start of mixing, instantly inducing nucleation. This state of simultaneous nucleation and the addition of the two mixed solutions easily leads to uneven nucleation.

[0169] While methods such as drastically shortening the addition time of the two solutions or vigorous stirring can be considered to improve the homogenization of nucleation, these methods cannot be considered the preferred approach. In the method described above, where only one solution is preheated (e.g., to 70°C) before being added and mixed to prepare the reaction solution, the mixed solution (reaction solution) is kept at a low temperature (e.g., 55°C), preventing localized hyperthermia. Due to the delayed nucleation time, nucleation occurs after thorough mixing of the two solutions. Therefore, uniform nucleation is more likely to occur. The above describes a preferred example and does not exclude the possibility of preheating all solutions, such as the metal salt raw material solution and the reducing agent solution. The solution can be heated and its temperature set so that the reaction start temperature and the reaction holding temperature fall within the aforementioned range.

[0170] When the reaction initiation temperature is too low, nucleus formation becomes more uniform, but the reduction reaction progresses slowly, and the heating time required to raise the temperature to the reaction holding temperature that promotes the reduction reaction becomes longer. Similarly, when the reaction holding temperature is too low, the reduction reaction progresses slowly, and the heating time required for crystallization becomes longer. In either case, the cycle time required for the crystallization process becomes longer, reducing productivity. Furthermore, due to the self-decomposition of hydrazine, a large amount of hydrazine is required, resulting in increased manufacturing costs. When the reaction initiation temperature or reaction holding temperature is high, the reduction reaction is promoted, and the cycle time required for the crystallization process is shortened, and there is a tendency for the obtained crystallized powder to be highly crystallized. However, at the same time, the self-decomposition rate of hydrazine increases. Therefore, when the reaction initiation temperature or reaction holding temperature is too high, there is a risk of not only causing non-uniform nucleus formation but also deteriorating the smoothness of the particle surface and increasing surface roughness due to excessive high crystallization. In addition, if crystallization is not terminated at the appropriate time, there is a risk that hydrazine will self-decompose due to the reduction reaction and be preferentially consumed. Therefore, a large amount of hydrazine is required, which poses a risk of increased manufacturing costs. By setting the reaction start temperature or reaction holding temperature within the above-mentioned preferred range, high-performance alloy powder can be manufactured at low cost while maintaining high productivity.

[0171] <Recycling Process>

[0172] In the recovery process, crystallized powder is recovered from the reaction solution obtained in the crystallization process. The recovery of crystallized powder can be carried out using known methods. For example, methods such as using a Denver filter, filter press, centrifuge, or decanter to separate the crystallized powder from the reaction solution into solid and liquid phases can be employed. Alternatively, the crystallized powder can be washed during or after solid-liquid separation. Washing can be performed using a washing solution. High-purity pure water with a conductivity of less than 1 μS / cm can be used as the washing solution. The washed crystallized powder can then be dried. Drying can be performed using common drying equipment such as an atmospheric dryer, hot air dryer, inactive gas environment dryer, reducing gas environment dryer, or vacuum dryer, at a temperature of 40°C to 150°C, preferably 50°C to 120°C. From the viewpoint of preventing the deterioration of magnetic properties due to excessive oxidation of the crystallized powder during the drying process, it is more preferable to use an inactive gas environment dryer, a reducing gas environment dryer, or a vacuum dryer than an atmospheric dryer or a hot air dryer that uses the atmosphere.

[0173] It should be noted that crystallized powder dried in a closed container within an inert gas environment dryer, a reducing gas environment dryer, or a vacuum dryer has minimal surface oxidation. Therefore, if it is immediately removed from the dryer and exposed to the atmosphere after drying, there is a risk of rapid surface oxidation of the particles, leading to combustion of the crystallized powder due to the heat generated by the oxidation reaction. This phenomenon is particularly prone to occur with fine crystallized powders (e.g., particle sizes below 0.1 μm). Therefore, it is preferable to perform a slow oxidation treatment on the surface of the dried crystallized powder, where the surface has minimal oxidation, to pre-form a thin oxide film and stabilize it. As a specific slow oxidation treatment step, one could consider lowering the temperature of the crystallized powder, which has been heated and dried in a closed container within an inert gas environment dryer, a reducing gas environment dryer, or a vacuum dryer, to approximately room temperature to 40°C, and then supplying a gas with a low oxygen concentration (e.g., nitrogen or argon containing 0.1 to 2% oxygen by volume) into the closed container, allowing the surface of the crystallized powder particles to gradually and slowly oxidize to form a thin oxide film. Because the crystallized powder, which has undergone slow oxidation treatment, is not easily oxidized and is stable, there is no risk of heating or combustion even when placed in the atmosphere.

[0174] <High-Temperature Heat Treatment Process>

[0175] A high-temperature heat treatment process for the crystallized powder can be performed after or during the recycling process. When high-temperature heat treatment is performed after the recycling process, it can be done after drying. Alternatively, when high-temperature heat treatment is performed during the recycling process, it can replace drying. The high-temperature heat treatment can be performed in an inactive environment, a reducing environment, or a vacuum environment at temperatures greater than 150°C and below 400°C, preferably above 200°C and below 350°C. High-temperature heat treatment can promote the diffusion of different elements such as Fe and Ni within the iron (Fe)-nickel (Ni) alloy particles and improve the compositional uniformity within the particles, or adjust magnetic properties such as magnetic force. It should be noted that, if necessary, the aforementioned slow oxidation treatment can be performed after the high-temperature heat treatment.

[0176] <Crushing Process>

[0177] As needed, a crushing process can be set up to crush the crystallized powder recovered in the recycling process or the crystallized powder before drying during the recycling process. During the crystallization process, when the alloy particles constituting the crystallized powder precipitate, the alloy particles come into contact and melt, forming agglomerated particles. Therefore, the crystallized powder obtained after the crystallization process may contain large agglomerated particles. As mentioned above, large agglomerated particles may increase Joule heat loss due to the eddies flowing within them, or hinder the filling properties of the powder. By setting up a crushing process after or during the recycling process, the agglomerated particles can be crushed. Crushing can be carried out using dry crushing methods such as spiral jet crushing or reverse jet mill crushing, or wet crushing methods such as high-pressure fluid impact crushing, or other common crushing methods. Dry crushing can be directly applied to the dry powder, i.e., the crystallized powder, recovered in the recycling process. Furthermore, if the crystallized powder, which is dry powder after the recycling process, is transformed into a slurry, wet crushing can be applied to it. In addition, wet crushing can also be directly applied to the slurry-like crystallized powder obtained during the recycling process before drying. In these crushing methods, the impact energy of particles is utilized to break agglomerated particles into smaller pieces. Since the surface is smoothed by impact during the crushing process, this also helps to improve the filling properties of the powder.

[0178] <Insulation Coating Process>

[0179] If necessary, an insulating coating process can be added after the recycling process. In this process, the crystallized powder obtained from the recycling process is coated with an insulating layer of high-resistivity metal oxide to form an insulating coating on the particle surface, thereby improving the insulation between particles. Similar to the increased losses due to eddy currents in coarsely aggregated particles, there is a risk of increased inter-particle eddy currents in pressed powder cores obtained by compressing iron-nickel alloy powder, due to contact between alloy particles. Forming an insulating coating can suppress eddy currents generated by contact between alloy particles.

[0180] In the insulating coating process, crystalline powder is dispersed in a mixed solvent containing water and an organic solvent. A metal alkoxide is then added to the mixed solvent and mixed to prepare a slurry. The metal alkoxide is hydrolyzed and dehydrated in the resulting slurry to form an insulating coating on the surface of the crystalline powder particles. Subsequently, the cake-shaped crystalline powder with the insulating coating is separated from the slurry through solid-liquid separation. The separated crystalline powder is dried to recover the crystalline powder with the insulating coating composed of a high-resistivity metal oxide. Heating treatment can be performed on the separated and dried crystalline powder as needed. Since the hydrolysis reaction of the metal alkoxide in the mixed solvent containing water and an organic solvent proceeds very slowly when carried out directly, a trace amount of a hydrolysis catalyst such as an acid or base is usually added to promote the reaction. In this embodiment, a base catalyst (base catalyst) is also preferably added.

[0181] As a high-resistivity metal oxide, it is preferable to have at least one main component selected from the group consisting of silicon dioxide (SiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), and titanium dioxide (TiO2). In particular, metal oxides with silicon dioxide (SiO2) as the main component are especially preferred because they are inexpensive and have excellent insulating properties.

[0182] To obtain such a metal oxide, the metal alkoxide used in the slurry during the insulating coating process is selected as an alkoxide capable of ultimately forming a metal oxide through hydrolysis and dehydration condensation. Specifically, it is preferable to have at least one main component selected from the group consisting of silanolates (alkylsilicates), aluminum alkoxides (alkylaluminates), zirconium alkoxides (alkylzirconates), and titanium alkoxides (alkyltitanates), with silanolates (alkylsilicates) being particularly preferred as the main component. It should be noted that, as needed, when the metal alkoxide is hydrolyzed and dehydrated to form an insulating coating, a small amount of a component that is added to the insulating coating through hydrolysis or the like (e.g., borosilicates, etc.) may be added to the aforementioned metal alkoxide.

[0183] The surface of the alloy powder after insulating coating is coated with a high-resistivity metal oxide, which is an inorganic material. Organic functional groups can be introduced onto the surface of this inorganic material as needed. Specifically, for example, a method can be used where a small amount of silicon-based, titanium-based, zirconium-based, or aluminum-based coupling agent is added to the metal alkoxide used in the insulating coating process, and the organic functional groups are added to the metal oxide during the hydrolysis / dehydration polycondensation of the metal alkoxide. Alternatively, another method can be used to surface-treat the alloy powder after insulating coating with the aforementioned coupling agent, and then modify the surface of the metal oxide with organic functional groups. Regardless of the method, since the introduction of organic functional groups increases the affinity with the resin, an increase in the strength of the molded article can be expected when the alloy powder after insulating coating is combined with a resin binder and molded.

[0184] Specific examples of silanols (alkyl silicates) include, for instance, tetramethoxysilane (also known as tetramethyl orthosilicate, tetramethyl orthosilicate) (abbreviated as TMOS) (Si(OCH3)4), tetraethoxysilane (also known as tetraethyl orthosilicate, tetraethyl orthosilicate) (abbreviated as TEOS) (Si(OC2H5)4), tetrapropoxysilane (also known as tetrapropyl orthosilicate, tetrapropyl orthosilicate) (Si(OC3H7)4), and tetrabutoxysilane (also known as tetrabutyl orthosilicate and tetrabutyl orthosilicate) (Si(OC3H7)4). One or more of the following can be selected: butyl oxide (Si(OC4H9)4, etc. Alternatively, it can be an alkoxide in which the alkoxy group is replaced by another alkoxy group, or it can be a commercially available alkyl silicate (e.g., ethyl silicate 40 (trade name), ethyl silicate 48 (trade name), methyl silicate 51 (trade name), etc. manufactured by Corcotec). Tetraethoxysilane (TEOS) is preferred because it has low toxicity, is readily available, and is inexpensive.

[0185] Specific examples of aluminum alkoxides (alkyl aluminum esters) include, for example, one or more selected from aluminum trimethoxy (Al(OCH3)3), aluminum triethoxy (Al(OC2H5)3), aluminum triisopropoxy (Al(O-iso-C3H7)3), aluminum tri-n-butoxy (Al(On-C4H9)3), aluminum tri-sec-butoxy (Al(Os-C4H9)3), aluminum tri-tert-butoxy (Al(Ot-C4H9)3), aluminum tri-tert-butoxy (Al(Ot-C4H9)3), etc.

[0186] Specific examples of zirconium alkoxides (alkyl zirconates) include, for example, one or more selected from zirconium tetraethoxy (Zr(OC2H5)4), zirconium tetran-n-propoxy (Zr(On-C3H7)4), zirconium tetraisopropoxy (Zr(O-iso-C3H7)4), zirconium tetran-n-butoxy (Zr(On-C4H9)4), zirconium tetratert-butoxy (Zr(Ot-C4H9)4), zirconium tetraisobutoxy (Zr(O-iso-C4H9)4), and so on.

[0187] Specific examples of titanium alkoxides (alkyl titanates) include, for example, one or more selected from tetramethoxytitanium (Ti(OCH3)4), tetraethoxytitanium (Ti(OC2H5)4), tetraisopropoxytitanium (Ti(O-iso-C3H7)4), tetraisobutoxytitanium (Ti(O-iso-C4H9)4), tetran-butoxytitanium (Ti(On-C4H9)4), tetratert-butoxytitanium (Ti(Ot-C4H9)4), tetrasec-butoxytitanium (Ti(Os-C4H9)4), etc.

[0188] Boron alkoxides (alkyl borates) that are other metal alkoxides include, for example, one or more selected from trimethoxyboron (B(OCH3)3), triethoxyboron (B(OC2H5)3), tritert-butoxyboron (B(Ot-C4H9)3), etc.

[0189] For the organic solvents used in the slurry during the insulating coating process, organic solvents that form water-soluble mixtures and are moderately easy to dry are preferred. That is, organic solvents with high water compatibility and relatively low boiling points (around 60°C to 90°C) are preferred. Furthermore, organic solvents that are safe, easy to handle, readily available, and inexpensive are preferred. Considering these factors, modified alcohols with ethanol as the main component are preferred.

[0190] When silanol salts (Si(OR)4, R: alkyl) are used as metal alkoxides, the hydrolysis and dehydration condensation reactions of the metal alkoxides in the insulating coating process are illustrated using reaction formulas.

[0191] In the hydrolysis reaction, in the presence of a base catalyst such as ammonia (NH3), as shown in equation (7) below, silicon atoms (Si) are attracted by nucleophilic hydroxyl ions (OH-). - The alkoxy group (-OR) is the first to hydrolyze due to direct attack from the silicon atom. Thus, the reduced charge on the silicon atom makes it increasingly susceptible to nucleophilic hydroxyl ions (OH-). - The attack of ) results in the complete hydrolysis of all four alkoxy groups (-OR) into silanol groups (Si-OH), as shown in equation (8) below. Thus, when a salt-based catalyst (base catalyst) is used, since all the alkoxy groups (-OR) in the hydrolyzed silanolate molecules are hydrolyzed, a state in which completely hydrolyzed molecules (Si(OH)4) and completely unhydrolyzed molecules (Si(OR)4) coexist in the slurry.

[0192] Si(OR)₄ + H₂O [+OH] - ]

[0193] →Si(OH)(OR)3+ROH[+OH - ]···(7)

[0194] Si(OR)₄ + 4H₂O [+OH] - ]

[0195] →Si(OH)₄ + 4ROH[+OH - ]···(8)

[0196] On the other hand, in the presence of acid catalysts such as nitric acid (HNO3), as shown in equation (9) below, due to the presence of protons (H +The protonation of the alkoxy group (-OR) caused by the hydrogen atom makes the silicon atom (Si) more susceptible to attack by water (H₂O). Therefore, one of the alkoxy groups (-OR) first hydrolyzes to a silanol group (Si-OH). (Details omitted, but if this happens, the silicon atom becomes less susceptible to proton attack due to the reduced charge on both the silicon and oxygen atoms (O).) + The attack of ) . Therefore, the next hydrolysis will not occur immediately, and the alkoxy groups (-OR) of other unhydrolyzed silanolate molecules become more susceptible to hydrolysis. Thus, when an acid catalyst is used, as shown in equation (10) below, the alkoxy groups (-OR) are hydrolyzed equally in all silanolate molecules. Therefore, the slurry contains molecules that are not completely hydrolyzed and molecules that are not completely hydrolyzed, but rather molecules that are equally hydrolyzed (Si(OH)). X (OR) 4-X The state of ; 0 < x < 4.

[0197] Si(OR)₄ + H₂O [+H + ]

[0198] →Si(OH)(OR)3+ROH[+H - ]···(9)

[0199] Si(OR)₄+xH₂O[+H + ]

[0200] →Si(OH) x (OR) 4-x +xROH[+H + ]···(10)

[0201] (0 < x < 4)

[0202] As shown in equation (11) below, the dehydration condensation reaction is a reaction that forms siloxane bonds (Si-O-Si) through the dehydration condensation reaction of silanol groups (Si-OH) between hydrolyzed silanol molecules. As shown in equation (12) below, when the dehydration condensation reaction is completed, silicon dioxide (SiO2) is generated.

[0203] Si(OH)4+Si(OH)4

[0204] →(OH)3Si-O-Si(OH)3+H2O···(11)

[0205] Si(OH)4→SiO2+2H2O···(12)

[0206] In summary, when the hydrolysis and dehydration condensation of the silanol salt are completed, silicon dioxide (SiO2) and an alcohol are generated as shown in equation (13) below. For example, when using tetraethoxysilane (TEOS: Si(OR)4, R: C2H5), silicon dioxide (SiO2) and ethanol (C2H5OH) are generated.

[0207] Si(OR)4+2H2O→SiO2+4ROH···(13)

[0208] For the above formula (13), it holds true as long as the silanol salt is hydrolyzed, regardless of whether it is a salt-based catalyst (alkaline catalyst) or an acid catalyst. However, the form of silicon dioxide (SiO2) generated during the dehydration polycondensation is greatly affected by the hydrolysis state of the above-mentioned catalyst used for hydrolysis.

[0209] Silanolate molecules (Si(OH)) are uniformly hydrolyzed by an acid catalyst. X (OR) 4-X In the range (0 < x < 4), unhydrolyzed alkoxy groups (-OR) exist within the molecule. Therefore, during the dehydration condensation of intermolecular silanol groups (Si-OH), hydrolyzed polymers that polymerize into linear or branched structures are generated. When this occurs in the slurry during insulating coating, hydrolyzed polymers of silanols are formed on the surface of the crystallized powder particles composed of iron oxide (FeO) or nickel oxide (NiO). However, because they polymerize into linear or branched structures, they are not easily densified in the slurry solvent, thus making it difficult to form a dense insulating coating.

[0210] On the other hand, when using a salt-based catalyst (alkaline catalyst), completely hydrolyzed molecules (Si(OH)4) exist. Therefore, during the dehydration and polycondensation of intermolecular silanol groups (Si-OH), a dense, blocky hydrolyzed polymer is generated. Thus, even in the solvent of the slurry during the insulating coating process, a dense hydrolyzed polymer of silanol is generated on the surface of the crystallized powder particles composed of iron oxide (FeO) or nickel oxide (NiO), resulting in the formation of a dense insulating coating. It should be noted that when using a salt-based catalyst (alkaline catalyst), completely unhydrolyzed molecules (Si(OR)4) may exist. However, as described later, the completely unhydrolyzed molecules or very small-molecule granular hydrolyzed polymers of silanol (silica sol) remaining in the slurry are not consumed by the insulating coating of the crystallized powder during the insulating coating process and are removed from the system along with the filtrate during the filtration and washing process of the insulating coating step. Therefore, they do not affect the insulating coating process.

[0211] For the reasons mentioned above, the hydrolysis of metal alkoxides in the insulating coating process is preferably carried out using a salt-based catalyst (base catalyst) rather than an acid catalyst. In this regard, the preferred catalyst differs when the solvent is applied to the substrate for coating. That is, when the binder of the coating liquid used to coat the substrate and dry the solvent is used instead of coating the particle surface in the solvent, it is preferable to polymerize the aforementioned acid catalyst into a linear or branched linear form.

[0212] Regarding the timing of hydrolysis of metal alkoxides in insulating coating processes, the above describes a method of hydrolysis using a hydrolysis catalyst while the crystallized powder and metal alkoxide are uniformly mixed in a slurry. However, this embodiment is not limited to the hydrolysis method at this specific time. For example, a metal oxide sol (or silica sol in the case of silanols) obtained by pre-hydrolyzing the metal alkoxide using a hydrolysis catalyst can be prepared, and this metal oxide sol can be mixed with the crystallized powder to form a slurry. When the average molecular weight of the metal oxide sol is as small as approximately 500 to 5000, it has almost no impact on the timing of metal alkoxide hydrolysis. This is because the surface of the crystallized powder particles is covered by small metal oxide sol particles through the combination of iron oxide (FeO) or nickel oxide (NiO) on the surface of the crystallized powder with the hydrolysis groups of the metal oxide sol (or silanol groups (Si-OH) in the case of silanols), and then polymerization between the sol particles occurs.

[0213] In insulating coating processes, from the viewpoint of uniformly forming an insulating coating, it is preferable to perform stirring using a stirring blade on a mixer or stirring using a rotating container with a dedicated drum in a slurry containing crystallizing powder, water, organic solvent, metal alkoxide, and a hydrolysis catalyst. The processing time and temperature of the insulating coating process vary depending on the type of metal alkoxide used or the desired thickness of the insulating coating. For example, the hydrolysis rate of metal methyl oxides is generally greater than that of metal ethoxides. Therefore, the processing time or temperature can be set appropriately, without particular limitations. For example, the processing time can be from a few hours to about one week, and the processing temperature can be from room temperature to 60°C. When the processing temperature is at a high temperature of about 40°C to 60°C, the processing speed can be increased to several times that at room temperature.

[0214] Since the thickness of the insulating coating also depends on the required level of insulation, it cannot be limited indiscriminately. If a specific thickness is required, 1 nm to 30 nm is preferred, more preferably 2 nm to 25 nm, and even more preferably 3 nm to 20 nm. Even if it is too thick, it only results in insulation saturation but a decrease in the proportion of soft magnetic components, leading to a deterioration in magnetic properties such as saturation magnetic flux density. When the thickness is within the above range, the insulating function of the insulating coating can be maintained without causing such significant deterioration in magnetic properties and other characteristics.

[0215] For crystalline powder with an insulating coating formed by the hydrolysis and dehydration condensation of metal alkoxides, solid-liquid separation is performed from the slurry as cake-like crystalline powder using known separation devices such as denver filters, filter presses, centrifuges, or decanters. If necessary, the crystalline powder can be washed during solid-liquid separation. During washing, the washing solution can be water, organic solvents such as alcohols with relatively low boiling points, or mixtures thereof. As mentioned above, if metal alkoxides or their hydrolyzed polymers (unhydrolyzed molecules or small molecular weight metal oxide sols) remain in the slurry without being consumed during the insulating coating, they are removed from the system along with the filtrate or washing waste liquid during solid-liquid separation or washing.

[0216] The cake-shaped crystalline powder obtained after solid-liquid separation is dried and, if necessary, heated to recover the crystalline powder with an insulating coating composed of a high-resistivity metal oxide. There are no particular limitations on the drying process as long as excessive oxidation during drying is prevented. However, drying equipment such as a dryer in an inert gas environment, a dryer in a reducing gas environment, or a vacuum dryer is preferred, and the drying can be carried out at temperatures above 40°C and below 150°C. The higher the drying temperature, the more progressive the dehydration and polycondensation of the metal alkoxide hydrolysate polymer constituting the insulating coating, resulting in a harder, denser, and more insulating metal oxide. When further improvements are desired, heating treatment at temperatures above 150°C and below 450°C can be performed in an inert gas environment, a reducing gas environment, or a vacuum. It should be noted that since an insulating coating has already been formed, slow oxidation treatment is generally not required after drying.

[0217] The insulation properties of crystallized powder (alloy powder) are significantly improved through insulating coating treatment. For example, the resistivity of uncoated iron-nickel alloy powder (applied pressure: 64 MPa) is typically below 0.1 Ω·cm. In contrast, when an insulating coating treatment is performed to form an insulating coating of silicon dioxide (SiO2) with a thickness of approximately 0.015 μm (15 nm) on the iron-nickel alloy powder, the resistivity of the powder is improved to 10 Ω·cm. 6 Ω·cm or higher.

[0218] In this way, the iron (Fe)-nickel (Ni) alloy powder of this embodiment can be manufactured. The manufacturing method of this embodiment is characterized by using a specific nucleating agent (a water-soluble salt of a metal less reactive than nickel) that has a micronization effect on the alloy powder, and a specific complexing agent (hydroxycarboxylic acid, etc.) that has the effects of promoting reduction reaction, promoting spheroidization, and smoothing the surface. Therefore, the powder properties can be improved while maintaining the magnetic properties of the manufactured alloy powder. Specifically, the average particle size of the manufactured alloy powder can be freely controlled, and fine alloy powder can be obtained. Furthermore, the obtained alloy powder has a narrow particle size distribution and uniform particle size. In addition, the alloy powder is spherical with a smooth surface, resulting in excellent filling properties. Furthermore, although not limited, by using an amine compound that functions as a self-decomposition inhibitor of hydrazine and a reduction reaction promoter, the amount of hydrazine used can be suppressed. Therefore, manufacturing costs can be reduced, and the powder properties of the alloy powder can be improved.

[0219] <<2. Iron-nickel alloy powder>>

[0220] The iron (Fe)-nickel (Ni) alloy powder of this embodiment has a small particle size distribution. Furthermore, the average particle size of this alloy powder can be freely controlled. Therefore, it can be easily miniaturized and the particle size distribution reduced. In addition, it is spherical, with high surface smoothness and excellent filling properties. With these advantages, the alloy powder of this embodiment can be used in various electronic components such as noise filters, chokes, inductors, and electromagnetic wave absorbers, and is particularly suitable as a material for pressed powder cores for chokes or inductors.

[0221] The average particle size of the alloy powder is preferably 0.10 μm or more and 0.60 μm or less, more preferably 0.10 μm or more and 0.50 μm or less. By appropriately increasing the average particle size, the deterioration of magnetic properties or the reduction of filling capacity caused by surface oxidation can be suppressed. In addition, by appropriately decreasing the average particle size, eddy current losses can be suppressed.

[0222] The coefficient of variation (CV value) in the particle size distribution of the alloy powder is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less. Here, the coefficient of variation is an indicator of particle size deviation; the smaller the coefficient of variation, the narrower the particle size distribution. By suppressing the coefficient of variation to a small value, the increase in eddy current loss can be prevented while maintaining excellent magnetic properties, as the number of coarse particles or excessively fine particles with large surface oxidation is reduced. It should be noted that the coefficient of variation (CV value) is calculated by taking the average particle size and standard deviation in the particle size distribution of the alloy powder and using them according to the following equation (14).

[0223] CV value (%) = Standard deviation of particle size / Average particle size × 100 ···(14)

[0224] The compacted powder density of alloy powder depends on its composition or particle size. When the iron content is high, the compacted powder density decreases due to the reduced specific gravity of the alloy. Conversely, when the particle size is small, the particles become less easily packed, also tending towards a decrease in compacted powder density. Therefore, for an iron-nickel alloy powder with an average particle size of 0.3 μm to 0.5 μm, a specific gravity of 8.2 to 8.3, and an iron content of 45 mol% to 60 mol% (Fe), the compacted powder density (applied pressure: 100 MPa) is preferably 3.60 g / cm³. 3 The above, more preferably 3.70 g / cm³ 3 That's all. Furthermore, in the case of an iron-nickel alloy powder with an average particle size of 0.3 μm to 0.5 μm, a specific gravity of 7.9 to 8.0, and an iron content of 10 mol% to 20 mol% (Fe), its compressed powder density (applied pressure: 100 MPa) is preferably 3.45 g / cm³. 3 The above, more preferably 3.55 g / cm³ 3 That's all. Regarding the particle size of the alloy powder, when it is refined to an average particle size of approximately 0.3μm~0.5μm to 0.2μm~0.25μm, the powder density (applied pressure: 100MPa) decreases by 0.1g / cm³. 3 The magnetic properties (magnetic flux density) of the pressed powder core are improved by increasing the density of the pressed powder. The grain diameter of the alloy powder is preferably 30 nm or less, more preferably 10 nm or less. By suppressing the grain diameter to a moderately small size, it is easy to obtain a coercivity similar to that of amorphous soft magnetic materials. The saturation magnetic flux density of the alloy powder is preferably 1 T (Tesla) or more, more preferably 1.2 T or more, and even more preferably 1.5 T (Tesla) or more. More preferably, the saturation magnetic flux density of pure iron powder is 1.95 T to 2.0 T or more. By increasing the saturation magnetic flux density of the alloy powder, the magnetic properties (magnetic flux density) of the pressed powder core can be improved. The coercivity of the alloy powder is preferably 2000 A / m or less, more preferably 1600 A / m or less, and even more preferably 1200 A / m or less. By suppressing the coercivity of the alloy powder, an increase in hysteresis loss can be prevented.

[0225] As described above, because iron ions (or iron hydroxide) are less easily reduced than nickel ions (or nickel hydroxide) or cobalt ions (or cobalt hydroxide), iron (Fe)-nickel (Ni) alloy powders with a high iron content (e.g., iron content greater than 60 mol%) tend to form a tilted structure (or core-shell structure) within the particles, where the particle center is rich in nickel or cobalt and the composition becomes increasingly rich in iron closer to the particle surface. This leads to a tendency for the composition within the particles to become inhomogeneous.

[0226] Regardless of how such intraparticle inhomogeneity affects the properties of the alloy powder, it does not significantly impact magnetic properties (saturation flux density, coercivity, etc.). This is because, for example, saturation flux density is positively correlated with the iron content (the higher the iron content, the higher the saturation flux density). Therefore, even if the intraparticle composition becomes inhomogeneous, resulting in regions with iron content higher than or lower than the average, regions with saturation flux densities higher and lower than the average will also form. When the alloy powder is averaged as a whole, the result is almost unchanged compared to cases with inhomogeneous composition. Furthermore, regarding coercivity, since the composition dependence in the iron-nickel (-cobalt) system is not particularly high to begin with, the degree of intraparticle inhomogeneity does not change significantly.

[0227] On the other hand, the inhomogeneous composition within the aforementioned particles may affect chemical and physical properties such as oxidation resistance or thermal expansion coefficient. For example, regarding oxidation resistance, in cases where the particle surface becomes more iron-rich due to the tilted structure, there is a risk of increased oxidizability and deterioration of oxidation resistance. However, by modifying the particle surface to a nickel-rich composition according to the aforementioned third scheme, there is a possibility of improving oxidation resistance. Regarding thermal expansion coefficient, unlike the case of saturation magnetic flux density, the thermal expansion coefficient of iron-nickel alloys is not positively or negatively correlated with the iron content. It is characterized by becoming very small only when the iron content is around 65 mol% (64 wt%). This low thermal expansion coefficient alloy is called an Invar alloy (with 65 mol% iron and 35 mol% nickel as the main components). In this case, when the composition within the particles is not uniform, the coefficient of thermal expansion does not decrease, whether in regions with an iron content greater than 65 mol% or less than 65 mol%. Therefore, when using iron (Fe)-nickel (Ni) alloy powder as Invar alloy powder, it is necessary to homogenize the composition through the aforementioned high-temperature heat treatment.

[0228] To the best of the inventors' knowledge, a simple and inexpensive method for manufacturing iron-nickel alloy powder with excellent properties is not yet known. For example, while Patent Document 3 discloses a method for manufacturing nickel-iron alloy nanoparticles using a wet process, this method does not use a nucleating agent composed of a water-soluble salt of a metal less reactive than nickel, nor a complexing agent composed of hydroxycarboxylic acids, etc. Therefore, it is presumed that the alloy powder produced by this method has poor powder properties (particle size, particle size distribution, sphericity, particle surface properties). In fact, Patent Document 3 shows a transmission electron microscope image of the microparticles used as an example sample (Patent Document 3). Figure 1 Based on the photograph, it is estimated that the coefficient of variation (CV) of the particle size distribution of the micro powder is large, approximately 35%.

[0229] Furthermore, in the method of Patent Document 3, which does not use nucleating agents or complexing agents, a large amount of reducing agent (hydrazine) is required to obtain fine alloy powder. In fact, in the embodiments of Patent Document 3, 16.6 g of nickel chloride hexahydrate, 4.0 g of ferrous chloride tetrahydrate, and 135 g of hydrazine monohydrate are used as raw materials to manufacture alloy nanoparticles. Based on this amount, approximately 30 times the molar ratio of hydrazine is required relative to the total amount of iron and nickel. In such a method requiring a large amount of hydrazine, the cost of the reducing agent increases significantly, making it impractical.

[0230] Example

[0231] The invention is described in more detail using the following examples and comparative examples. However, the invention is not limited to the following examples.

[0232] (1) Preparation of iron-nickel alloy powder

[0233] [Example 1]

[0234] In Example 1, according to Figure 5 The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel alloy powder) containing 50 mol% iron (Fe) and 50 mol% nickel (Ni). In Example 1, when preparing the reaction solution, a room-temperature reducing solution was added to the metal salt raw material solution heated in a water bath and mixed.

[0235] <Preparation Process>

[0236] Ferrous chloride tetrahydrate (FeCl2·4H2O, molecular weight: 198.81, reagent manufactured by Wako Pure Chemical Industries Co., Ltd.) was prepared as a water-soluble iron salt, and nickel chloride hexahydrate (NiCl2·6H2O, molecular weight: 237.69, reagent manufactured by Wako Pure Chemical Industries Co., Ltd.) was prepared as a water-soluble nickel salt. In addition, the following reagents were prepared: ammonium palladium(II) chloride (also known as ammonium tetrachloropalladium(II)ate) ((NH4)2PdCl4, molecular weight: 284.31, manufactured by Wako Pure Chemical Industries, Ltd.) as a nucleating agent; trisodium citrate dihydrate (Na3(C3H5O(COO)3)·2H2O, molecular weight: 294.1, manufactured by Wako Pure Chemical Industries, Ltd.) as a complexing agent; commercially available industrial-grade 60% hydrazine hydrate (manufactured by MGC Otsuka Chemical Co., Ltd.) as a reducing agent; and sodium hydroxide (NaOH, molecular weight: 40.0, manufactured by Wako Pure Chemical Industries, Ltd.) as a pH adjuster. The 60% hydrazine hydrate was prepared by diluting hydrazine hydrate (N2H4·H2O, molecular weight: 50.06) with pure water to a ratio of 1.67. In addition, ethylenediamine (EDA; H2NC2H4NH2, molecular weight: 60.1, reagent manufactured by Wako Pure Chemical Industries, Ltd.) was prepared as an amine compound.

[0237] <Crystallization process>

[0238] (a) Preparation of metal salt raw material solution

[0239] A metal salt raw material solution containing ferrous chloride tetrahydrate (water-soluble iron salt), nickel chloride hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.037 ppm by mass (0.02 ppm by mole). The amount of trisodium citrate was also weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.362 (36.2 mol%). Specifically, 173.60 g of ferrous chloride tetrahydrate, 207.55 g of nickel chloride hexahydrate, 9.93 μg of palladium(II) ammonium chloride, and 185.9 g of trisodium citrate dihydrate were dissolved in 1200 mL of pure water to prepare the metal salt raw material solution.

[0240] (b) Preparation of reducing agent solution

[0241] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) is 4.85. Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) is 4.96. Specifically, 346 g of sodium hydroxide is dissolved in 850 mL of pure water to prepare a sodium hydroxide solution, and 707 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0242] (c) Preparation of amine compound solutions

[0243] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the amount of ethylenediamine in the reaction solution prepared in the subsequent crystallization step is weighed such that the amount is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe and Ni). Specifically, 1.05 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0244] (d) Preparation of reaction solution and precipitation of crystal powder

[0245] The prepared metal salt raw material solution was placed into a Teflon-coated stainless steel container (reaction tank) equipped with stirring blades and placed in a water bath. The mixture was heated to 70°C while stirring. Then, a reducing agent solution at 25°C was added to the heated metal salt raw material solution and mixed for 10 seconds to obtain a reaction solution at 55°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 32.3 g / L. This initiated the reduction reaction (crystallization reaction) (reaction start temperature 55°C). Figure 7 As shown, from the start of the reaction, the temperature of the reaction solution continuously rises due to water bath heating, and the solution temperature is maintained at 70°C for 10 minutes after the start of the reaction (the reaction temperature is maintained at 70°C). As for the color of the reaction solution, it is dark green at the beginning of the reaction (when the reaction solution is prepared), but turns dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction is due to the formation of a coprecipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution according to the above formula (6). In addition, it is believed that the dark gray color a few minutes after the start of the reaction is due to the nucleating agent (palladium salt) causing nucleation.

[0246] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray to 13 minutes after the reaction begins, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. As a result, iron-nickel crystals precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 20 minutes of the reaction beginning. It is considered that the reduction reaction described in equation (6) above is complete, and all the iron and nickel components in the reaction solution are reduced to metallic iron and metallic nickel. The reaction solution after the reaction is complete is a slurry containing iron-nickel crystals.

[0247] <Recycling Process>

[0248] The slurry-like reaction liquid obtained in the crystallization process was filtered, washed, and subjected to solid-liquid separation to recover cake-shaped iron-nickel crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Furthermore, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded an iron-nickel alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.41 μm.

[0249] [Example 2]

[0250] In Example 2, according to Figure 3The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 50 mol% iron (Fe), 40 mol% nickel (Ni), and 10 mol% cobalt (Co). In Example 2, when preparing the reaction solution, a room-temperature pH-adjusting solution (alkali hydroxide solution) was first added to the metal salt raw material solution heated in a water bath, followed by a room-temperature reducing agent solution, and the mixture was stirred.

[0251] <Preparation Process>

[0252] The same raw materials as in Example 1 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, complexing agents, reducing agents, pH adjusters, and amine compounds. Additionally, as a water-soluble cobalt salt, cobalt chloride hexahydrate (CoCl2·6H2O, molecular weight: 237.93, manufactured by Wako Pure Chemical Industries, Ltd.) was prepared.

[0253] <Crystallization process>

[0254] (a) Preparation of metal salt raw material solution

[0255] A metal salt raw material solution containing ferrous chloride tetrahydrate (water-soluble iron salt), nickel chloride hexahydrate (water-soluble nickel salt), cobalt chloride hexahydrate (water-soluble cobalt salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. In this process, the amount of palladium (Pd) in the obtained metal salt raw material solution was weighed such that the amount of palladium relative to the total amount of magnetic metals (Fe, Ni, and Co) was 0.037 ppm by mass (0.02 ppm by mole). Furthermore, the amount of trisodium citrate was weighed such that the molar ratio of trisodium citrate relative to the total amount of magnetic metals (Fe, Ni, and Co) was 0.362 (36.2 mol%). Specifically, 173.60 g of ferrous chloride tetrahydrate, 166.04 g of nickel chloride hexahydrate, 41.55 g of cobalt chloride hexahydrate, 9.93 μg of palladium(II) ammonium chloride, and 185.9 g of trisodium citrate dihydrate were dissolved in 1200 mL of pure water to prepare a metal salt raw material solution.

[0256] (b) Preparation of reducing agent solution

[0257] A reducing agent solution containing hydrazine (reducing agent) and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is set such that its molar ratio relative to the total amount of magnetic metals (Fe, Ni, and Co) is 4.85. Specifically, 707 g of 60% by mass hydrazine hydrate is weighed to prepare the reducing agent solution.

[0258] (c) Preparation of pH-adjusting solution (alkali hydroxide solution)

[0259] A pH-adjusting solution (alkali hydroxide solution) containing sodium hydroxide (pH adjuster) and water is prepared. In this step, the reaction solution prepared in the subsequent crystallization process is weighed such that the amount of sodium hydroxide is in a molar ratio of 4.96 relative to the total amount of magnetic metals (Fe, Ni, and Co). Specifically, 346 g of sodium hydroxide is dissolved in 850 mL of pure water to prepare the pH-adjusting solution.

[0260] (d) Preparation of amine compound solutions

[0261] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed into the reaction solution prepared in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe, Ni, and Co). Specifically, 1.05 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0262] (e) Preparation of reaction solution and precipitation of crystal powder

[0263] The prepared metal salt raw material solution was placed into a Teflon-coated stainless steel container (reaction tank) equipped with stirring blades and placed in a water bath. The solution was heated to 70°C while stirring. Then, a pH-adjusting solution (alkali hydroxide solution) at 25°C was added to the heated metal salt raw material solution and mixed for 10 seconds. Next, a reducing agent solution at 25°C was added and mixed for 10 seconds to obtain a reaction solution at 55°C. The concentration of magnetic metals (Fe, Ni, and Co) in the reaction solution was 32.3 g / L. This initiated the reduction reaction (crystallization reaction) (reaction start temperature 55°C). From the start of the reaction, the temperature of the reaction solution continuously increased due to the water bath heating, and was maintained at 70°C for 10 minutes after the start of the reaction (reaction holding temperature 70°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. The initial dark green hue is believed to be due to the formation of coprecipitates of ferric hydroxide (Fe(OH)2), nickel hydroxide (Ni(OH)2), and cobalt hydroxide (Co(OH)2) in the reaction solution, following the reaction according to equation (6) above. Furthermore, the dark gray hue a few minutes after the start of the reaction is believed to be due to nucleation caused by the nucleating agent (palladium salt).

[0264] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray to 13 minutes after the reaction begins, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. As a result, iron-nickel-cobalt crystals precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 20 minutes of the reaction beginning. It is assumed that the reduction reaction described in equation (6) is complete, and all the iron, nickel, and cobalt components in the reaction solution are reduced to metallic iron, metallic nickel, and metallic cobalt. The reaction solution after the reaction is complete is a slurry containing iron-nickel-cobalt crystals.

[0265] <Recycling Process>

[0266] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel-cobalt crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel-cobalt alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.33 μm.

[0267] [Example 3]

[0268] In Example 3, according to Figure 5 The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel alloy powder) containing 50 mol% iron (Fe) and 50 mol% nickel (Ni). In Example 3, when preparing the reaction solution, a room-temperature reducing solution was added to the metal salt raw material solution heated in a water bath and mixed.

[0269] <Preparation Process>

[0270] The same raw materials as in Example 1 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, reducing agents, pH adjusters, and amine compounds. Additionally, tartaric acid ((CH(OH)COOH)2, molecular weight: 150.09, manufactured by Wako Pure Chemical Industries, Ltd.) was prepared as a complexing agent to replace trisodium citrate dihydrate.

[0271] <Crystallization process>

[0272] (a) Preparation of metal salt raw material solution

[0273] A metal salt raw material solution containing ferrous chloride tetrahydrate (water-soluble iron salt), nickel chloride hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), tartaric acid (complexing agent), and water was prepared. The obtained metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.037 ppm by mass (0.02 ppm by mole). The amount of tartaric acid was also weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.200 (20.0 mol%). Specifically, 173.60 g of ferrous chloride tetrahydrate, 207.55 g of nickel chloride hexahydrate, 9.93 μg of palladium(II) ammonium chloride, and 52.4 g of tartaric acid were dissolved in 1200 mL of pure water to prepare the metal salt raw material solution.

[0274] (b) Preparation of reducing agent solution

[0275] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) is 4.85. Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) is 4.96. Specifically, 346 g of sodium hydroxide is dissolved in 850 mL of pure water to prepare a sodium hydroxide solution, and 707 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0276] (c) Preparation of amine compound solutions

[0277] The amine compound solution was prepared in the same manner as in Example 1.

[0278] (d) Preparation of reaction solution and precipitation of crystal powder

[0279] The reaction solution and crystallization powder were prepared in the same manner as in Example 1, using the aforementioned metal salt raw material solution, reducing agent solution, and amine compound solution. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 33.0 g / L.

[0280] <Recycling Process>

[0281] Iron-nickel alloy powder (iron-nickel alloy powder) was prepared from the slurry-like reaction solution obtained in the crystallization process, similar to Example 1. The obtained alloy powder consists of smooth-surfaced spherical particles. It has a narrow particle size distribution with an average particle size of 0.40 μm.

[0282] [Example 4]

[0283] In Example 4, according to Figure 5The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel alloy powder) containing 56 mol% iron (Fe) and 44 mol% nickel (Ni). In Example 4, when preparing the reaction solution, a room-temperature metal salt raw material solution was added to the reduction solution heated in a water bath and mixed.

[0284] <Preparation Process>

[0285] The same raw materials as in Example 1 were prepared as nucleating agents, reducing agents, pH adjusters, complexing agents, and amine compounds. Additionally, ferrous sulfate heptahydrate (FeSO4·7H2O, molecular weight: 278.05, manufactured by Wako Pure Chemical Industries, Ltd.) was prepared instead of ferrous chloride tetrahydrate as the water-soluble iron salt, and nickel sulfate hexahydrate (NiSO4·6H2O, molecular weight: 262.85, manufactured by Wako Pure Chemical Industries, Ltd.) was prepared instead of nickel chloride hexahydrate as the water-soluble nickel salt.

[0286] <Crystallization process>

[0287] (a) Preparation of metal salt raw material solution

[0288] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.37 ppm by mass (0.2 ppm by mole). The amount of trisodium citrate dihydrate was also weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.318 (31.8 mol%). Specifically, 272.0 g of ferrous sulfate heptahydrate, 202.0 g of nickel sulfate hexahydrate, 99.3 μg of palladium(II) ammonium chloride, and 163.5 g of trisodium citrate dihydrate were dissolved in 950 mL of pure water to prepare the metal salt raw material solution.

[0289] (b) Preparation of reducing agent solution

[0290] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) is 6.41. Additionally, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) is 4.67. Specifically, 326 g of sodium hydroxide is dissolved in 800 mL of pure water to prepare a sodium hydroxide solution, and 934 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0291] (c) Preparation of amine compound solutions

[0292] The amine compound solution was prepared in the same manner as in Example 1.

[0293] (d) Preparation of reaction solution and precipitation of crystal powder

[0294] The prepared reducing agent solution was placed in a Teflon-coated stainless steel container (reaction tank) with stirring blades in a water bath and heated to 70°C while stirring. Then, a metal salt raw material solution at 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at 59°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 32.6 g / L. Thus, the reduction reaction (crystallization reaction) began (reaction start temperature 59°C). From the start of the reaction, the temperature of the reaction solution continued to rise due to water bath heating, and the temperature was maintained at 70°C for 10 minutes after the start of the reaction (reaction maintenance temperature 70°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction was due to the formation of a co-precipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution during the reaction according to equation (6) above. In addition, it is believed that the hue turns dark gray a few minutes after the start of the reaction due to nucleation caused by the nucleating agent (palladium salt).

[0295] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray to 13 minutes after the reaction begins, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. As a result, iron-nickel crystals precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 30 minutes of the reaction beginning. It is considered that the reduction reaction described in equation (6) above is complete, and all the iron and nickel components in the reaction solution are reduced to metallic iron and metallic nickel. The reaction solution after the reaction is complete is a slurry containing iron-nickel crystals.

[0296] <Recycling Process>

[0297] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.38 μm.

[0298] [Example 5]

[0299] In Example 5, according to Figure 6 The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel alloy powder) with a nickel-rich surface composition and containing 51 mol% iron (Fe) and 49 mol% nickel (Ni). At this point, an additional feed solution is added and mixed in the final stage of the crystallization process. Specifically, firstly, the iron-nickel alloy powder (iron-nickel alloy powder) containing 56 mol% iron (Fe) and 44 mol% nickel (Ni) is crystallized in the same manner as in Example 4, except for a different amount of hydrazine used as a reducing agent. Then, during this crystallization process, an aqueous solution of a water-soluble nickel salt is added to the reaction solution as an additional feed solution and mixed.

[0300] <Preparation Process>

[0301] The same raw materials as in Example 4 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, reducing agents, pH adjusters, complexing agents, and amine compounds.

[0302] <Crystallization process>

[0303] (a) Preparation of metal salt raw material solution

[0304] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.37 ppm by mass (0.2 ppm by mole). Additionally, the trisodium citrate dihydrate was weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.318 (31.8 mol%). Specifically, 272.0 g of ferrous sulfate heptahydrate, 202.0 g of nickel sulfate hexahydrate, 99.3 μg of palladium(II) ammonium chloride, and 163.5 g of trisodium citrate dihydrate were dissolved in 950 mL of pure water to prepare the metal salt raw material solution.

[0305] (b) Preparation of reducing agent solution

[0306] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 4.85 (4.41 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added). Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 4.67 (4.24 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added is 4.24). Specifically, 326 g of sodium hydroxide is dissolved in 800 mL of pure water to prepare a sodium hydroxide solution, and 707 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0307] (c) Preparation of amine compound solutions

[0308] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed in the reaction solution in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe and Ni) after the addition of the feed solution. Specifically, 1.16 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0309] (d) Preparation of additional feed liquid

[0310] An additional feed solution containing nickel sulfate hexahydrate (a water-soluble nickel salt) and water was prepared. The feed solution was weighed such that the amount of magnetic metal (Ni) in the obtained additional feed solution was 0.175 mol, which was 0.10 times the total amount of magnetic metal (Fe and Ni) in the metal salt feed solution (1.747 mol). Specifically, 46.0 g of nickel sulfate hexahydrate was dissolved in 200 mL of pure water to prepare the additional feed solution.

[0311] (e) Preparation of reaction solution and precipitation of crystal powder

[0312] The prepared reducing agent solution was placed in a Teflon-coated stainless steel container (reaction tank) with stirring blades in a water bath and heated to 70°C while stirring. Then, a metal salt raw material solution at 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at 57°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 35.2 g / L. Thus, the reduction reaction (crystallization reaction) began (reaction start temperature 57°C). From the start of the reaction, the temperature of the reaction solution continued to rise due to water bath heating, and the temperature was maintained at 70°C for 10 minutes after the start of the reaction (reaction maintenance temperature 70°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction was due to the formation of a co-precipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution during the reaction according to equation (6) above. In addition, it is believed that the hue turns dark gray a few minutes after the start of the reaction due to nucleation caused by the nucleating agent (palladium salt).

[0313] For 10 minutes, from 3 to 13 minutes after the start of the reaction (when the color of the reaction solution turns dark gray), an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. This precipitates iron-nickel crystals in the reaction solution. From 11 to 16 minutes after the start of the reaction, additional feed solution is added dropwise and mixed to promote the reduction of iron ions (or ferric hydroxide) that are not easily reduced, while simultaneously allowing the reduction reaction to proceed so that the surface of the precipitated iron-nickel crystals becomes more nickel-rich. The concentration of magnetic metals (Fe and Ni) in the reaction solution after the addition of feed solution is 32.8 g / L. At this point, the reaction solution is black, but the supernatant becomes transparent within 30 minutes of the start of the reaction. The reduction reaction is considered complete, and all iron and nickel components in the reaction solution are reduced to metallic iron and metallic nickel. The completed reaction solution is a slurry containing iron-nickel crystals.

[0314] <Recycling Process>

[0315] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.40 μm.

[0316] [Example 6]

[0317] In Example 6, a miniature jet mill (Pneumatic Co., Ltd., Japan, JKE-30) was used to perform a dry crushing process, using a spiral jet mill, on the crystallized powder obtained in Example 1 to produce an iron-nickel alloy powder containing 50 mol% iron (Fe) and 50 mol% nickel (Ni). The obtained alloy powder, like that of Example 1, had a narrow particle size distribution with an average particle size of 0.41 μm. Furthermore, the spiral jet milling process reduced agglomerated particles to improve filling properties (increased powder density) and reduced surface unevenness, resulting in a powder composed of very smooth spherical particles.

[0318] [Example 7]

[0319] In Example 7, as described below, after the crystallization process, during the recycling process, the slurry-like crystallized powder before drying is subjected to high-pressure fluid impact crushing as a wet crushing process to produce an iron-nickel alloy powder (iron-nickel alloy powder) containing 50 mol% iron (Fe) and 50 mol% nickel (Ni).

[0320] <Recycling process (including crushing process)>

[0321] After filtering and washing the slurry containing iron-nickel crystallized powder obtained through the same crystallization process as in Example 1, a cleaned crystallized powder slurry with a concentration of 20% by mass was prepared using pure water with a conductivity of 1 μS / cm. The filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The cleaned crystallized powder slurry was subjected to two high-pressure fluid impact crushing devices (high-speed mechanical manufacturing; pressure: 200 MPa) for crushing, followed by solid-liquid separation to recover cake-shaped iron-nickel crystallized powder. The recovered cake-shaped crystallized powder was dried in a vacuum dryer set at 50°C. Furthermore, after cooling the dried crystallized powder to 35°C in a vacuum, nitrogen gas containing 1.0% by volume oxygen was supplied to slowly oxidize the crystallized powder to obtain iron-nickel alloy powder. The obtained alloy powder, like that of Example 1, has a narrow particle size distribution with an average particle size of 0.41 μm. In addition, the high-pressure fluid impact crushing process reduces agglomerated particles and improves filling properties (increases powder density), and reduces surface unevenness, resulting in a powder composed of very smooth spherical particles.

[0322] [Example 8]

[0323] In Example 8, according to Figure 6The steps shown involve subjecting the obtained crystallized powder to high-temperature heat treatment to produce an iron-nickel alloy powder (iron-nickel alloy powder) containing 65 mol% iron (Fe) and 35 mol% nickel (Ni). In Example 8, during the preparation of the reaction solution, a room-temperature metal salt raw material solution was added to and mixed with a reduction solution heated in a water bath.

[0324] <Preparation Process>

[0325] The same raw materials as in Example 4 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, reducing agents, pH adjusters, complexing agents, and amine compounds.

[0326] <Crystallization process>

[0327] (a) Preparation of metal salt raw material solution

[0328] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 2.81 ppm by mass (1.50 ppm by mole). Additionally, the trisodium citrate dihydrate was weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.724 (72.4 mol%). Specifically, 318.1 g of ferrous sulfate heptahydrate, 161.9 g of nickel sulfate hexahydrate, 750.5 μg of palladium(II) ammonium chloride, and 374.7 g of trisodium citrate dihydrate were dissolved in 950 mL of pure water to prepare the metal salt raw material solution.

[0329] (b) Preparation of reducing agent solution

[0330] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 8.98. Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 7.07. Specifically, 497.5 g of sodium hydroxide is dissolved in 1218 mL of pure water to prepare a sodium hydroxide solution, and 1318 g of 60% (w / w) hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0331] (c) Preparation of amine compound solutions

[0332] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed into the reaction solution in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe and Ni) after the addition of the feed solution. Specifically, 1.06 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0333] (d) Preparation of reaction solution and precipitation of crystal powder

[0334] The prepared reducing agent solution was placed in a Teflon-coated stainless steel container (reaction tank) with stirring blades set in a water bath, and heated to a liquid temperature of 80°C while stirring. Then, a metal salt raw material solution at a liquid temperature of 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at a liquid temperature of 71°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 25.0 g / L. Thus, the reduction reaction (crystallization reaction) was started (reaction start temperature 71°C). From the start of the reaction, the temperature of the reaction solution continued to rise due to the heating in the water bath, and the liquid temperature was maintained at 80°C for 10 minutes after the start of the reaction (reaction maintenance temperature 80°C). As for the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction was due to the formation of a coprecipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution during the reaction according to the above formula (6). In addition, it is believed that the hue turns dark gray a few minutes after the start of the reaction due to nucleation caused by the nucleating agent (palladium salt).

[0335] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray until 13 minutes later, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. This causes iron-nickel crystals to precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 40 minutes of the reaction starting. This indicates that the reduction reaction is complete, and all iron and nickel components in the reaction solution have been reduced to metallic iron and metallic nickel. The completed reaction solution is a slurry containing iron-nickel crystals.

[0336] <Recycling Process>

[0337] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder.

[0338] <High-Temperature Heat Treatment Process>

[0339] The resulting crystallized powder was subjected to a high-temperature heat treatment at 350°C for 60 minutes in a nitrogen environment to produce an iron-nickel alloy powder containing 65 mol% iron (Fe) and 35 mol% nickel (Ni). The resulting alloy powder, like that of Example 1, exhibited a narrow particle size distribution with an average particle size of 0.27 μm. Furthermore, the aforementioned high-temperature heat treatment promoted the diffusion of Fe and Ni within the iron (Fe)-nickel (Ni) alloy particles, improved the compositional uniformity within the particles, and reduced characteristic deviations within the particles.

[0340] [Example 9]

[0341] In Example 9, according to Figure 6 The steps shown involve preparing an iron-nickel alloy powder (iron-nickel alloy powder) with a nickel-rich surface composition and containing 65 mol% iron (Fe) and 35 mol% nickel (Ni). During the crystallization process, an additional feed solution is added and mixed. Specifically, a room-temperature metal salt feed solution is added to a reduction solution heated in a water bath and mixed to prepare a reaction solution. First, the crystallization of the iron-nickel alloy powder (iron-nickel alloy powder) containing 67.4 mol% iron (Fe) and 32.6 mol% nickel (Ni) is carried out. Additionally, during this crystallization process, an aqueous solution of a water-soluble nickel salt, as an additional feed solution, is added to the reaction solution and mixed.

[0342] <Preparation Process>

[0343] The same raw materials as in Example 4 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, reducing agents, pH adjusters, complexing agents, and amine compounds.

[0344] <Crystallization process>

[0345] (a) Preparation of metal salt raw material solution

[0346] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.97 ppm by mass (0.52 ppm by mole). Additionally, the trisodium citrate dihydrate was weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.750 (75.0 mol%). Specifically, 318.1 g of ferrous sulfate heptahydrate, 145.7 g of nickel sulfate hexahydrate, 250.0 μg of palladium(II) ammonium chloride, and 374.7 g of trisodium citrate dihydrate were dissolved in 500 mL of pure water to prepare the metal salt raw material solution.

[0347] (b) Preparation of reducing agent solution

[0348] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 7.62 (7.36 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added). Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 7.33 (7.07 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added is 7.07). Specifically, 497.5 g of sodium hydroxide is dissolved in 1218 mL of pure water to prepare a sodium hydroxide solution, and 1080 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0349] (c) Preparation of amine compound solutions

[0350] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed into the reaction solution in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe and Ni) after the addition of the feed solution. Specifically, 1.06 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0351] (d) Preparation of additional feed liquid

[0352] An additional feed solution containing nickel sulfate hexahydrate (a water-soluble nickel salt) and water was prepared. The feed solution was weighed such that the amount of magnetic metal (Ni) in the obtained additional feed solution was 0.0616 mol, which was 0.035 times the total amount of magnetic metal (Fe and Ni) in the metal salt feed solution (1.760 mol). Specifically, 16.2 g of nickel sulfate hexahydrate was dissolved in 200 mL of pure water to prepare the additional feed solution.

[0353] (e) Preparation of reaction solution and precipitation of crystal powder

[0354] The prepared reducing agent solution was placed in a Teflon-coated stainless steel container (reaction tank) with stirring blades in a water bath, and heated to 80°C while stirring. Then, a metal salt raw material solution at 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at 75°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 29.1 g / L. Thus, the reduction reaction (crystallization reaction) began (reaction start temperature 75°C). From the start of the reaction, the temperature of the reaction solution continued to rise due to water bath heating, and the temperature was maintained at 80°C for 10 minutes after the start of the reaction (reaction maintenance temperature 80°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction was due to the formation of a co-precipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution during the reaction according to equation (6) above. In addition, it is believed that the hue turns dark gray a few minutes after the start of the reaction due to nucleation caused by the nucleating agent (palladium salt).

[0355] For 10 minutes, from 3 to 13 minutes after the start of the reaction when the reaction solution turns dark gray, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. This precipitates iron-nickel crystals in the reaction solution. From 25 to 35 minutes after the start of the reaction, additional feed solution is added dropwise and mixed to promote the reduction of iron ions (or ferric hydroxide) that are not easily reduced, while simultaneously allowing the reduction reaction to proceed so that the surface of the precipitated iron-nickel crystals becomes more nickel-rich. The concentration of magnetic metals (Fe and Ni) in the reaction solution after the addition of feed solution is 28.4 g / L. At this point, the reaction solution is black, but the supernatant becomes transparent within 40 minutes of the start of the reaction. The reduction reaction is considered complete, and all iron and nickel components in the reaction solution are reduced to metallic iron and metallic nickel. The completed reaction solution is a slurry containing iron-nickel crystals.

[0356] <Recycling Process>

[0357] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.39 μm.

[0358] [Example 10]

[0359] In Example 10, according to Figure 6 The steps shown involve preparing an iron-nickel alloy powder (iron-nickel alloy powder) with a high iron content, containing 80 mol% iron (Fe) and 20 mol% nickel (Ni). During the crystallization process, an additional raw material solution is added and mixed. Specifically, a room-temperature metal salt raw material solution is added to a reduction solution heated in a water bath and mixed to prepare a reaction solution. First, the iron-nickel alloy powder (iron-nickel alloy powder) containing 83.3 mol% iron (Fe) and 16.7 mol% nickel (Ni) is crystallized. Then, during this crystallization process, a water-soluble nickel salt aqueous solution is added to the reaction solution as an additional raw material solution and mixed.

[0360] <Preparation Process>

[0361] The same raw materials as in Example 4 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, reducing agents, pH adjusters, complexing agents, and amine compounds.

[0362] <Crystallization process>

[0363] (a) Preparation of metal salt raw material solution

[0364] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.79 ppm by mass (0.42 ppm by mole). Additionally, the trisodium citrate dihydrate was weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.754 (75.4 mol%). Specifically, 394.3 g of ferrous sulfate heptahydrate, 74.6 g of nickel sulfate hexahydrate, 201.6 μg of palladium(II) ammonium chloride, and 377.5 g of trisodium citrate dihydrate were dissolved in 836 mL of pure water to prepare the metal salt raw material solution.

[0365] (b) Preparation of reducing agent solution

[0366] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 9.40 (9.02 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added). Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 7.37 (7.07 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added is 7.07). Specifically, 501.3 g of sodium hydroxide is dissolved in 1228 mL of pure water to prepare a sodium hydroxide solution, and 1334 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0367] (c) Preparation of amine compound solutions

[0368] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the amount of ethylenediamine in the reaction solution during the subsequent crystallization step is weighed such that the amount is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe and Ni) after the addition of the feed solution. Specifically, 1.07 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0369] (d) Preparation of additional feed liquid

[0370] An additional feed solution containing nickel sulfate hexahydrate (a water-soluble nickel salt) and water was prepared. The feed solution was weighed such that the amount of magnetic metal (Ni) in the obtained additional feed solution was 0.0709 mol, which was 0.04 times the total amount of magnetic metal (Fe and Ni) in the metal salt feed solution (1.773 mol). Specifically, 18.64 g of nickel sulfate hexahydrate was dissolved in 200 mL of pure water to prepare the additional feed solution.

[0371] (e) Preparation of reaction solution and precipitation of crystal powder

[0372] The prepared reducing agent solution was placed in a Teflon-coated stainless steel container (reaction tank) with stirring blades set in a water bath, and heated to a liquid temperature of 80°C while stirring. Then, a metal salt raw material solution at a liquid temperature of 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at a liquid temperature of 71°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 24.5 g / L. Thus, the reduction reaction (crystallization reaction) was started (reaction start temperature 71°C). From the start of the reaction, the temperature of the reaction solution continued to rise due to the heating in the water bath, and the liquid temperature was maintained at 80°C for 10 minutes after the start of the reaction (reaction maintenance temperature 80°C). As for the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction was due to the formation of a coprecipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution during the reaction according to the above formula (6). In addition, it is believed that the hue turns dark gray a few minutes after the start of the reaction due to nucleation caused by the nucleating agent (palladium salt).

[0373] For 10 minutes, from 3 to 13 minutes after the start of the reaction (when the color of the reaction solution turns dark gray), an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. This precipitates iron-nickel crystals in the reaction solution. From 8 to 18 minutes after the start of the reaction, additional feed solution is added dropwise and mixed to promote the reduction of iron ions (or ferric hydroxide) that are difficult to reduce, while simultaneously allowing the reduction reaction to proceed so that the surface of the precipitated iron-nickel crystals becomes more nickel-rich. The concentration of magnetic metals (Fe and Ni) in the reaction solution after the addition of feed solution is 24.2 g / L. At this point, the reaction solution is black, but the supernatant becomes transparent within 60 minutes of the start of the reaction. The reduction reaction is considered complete, and all iron and nickel components in the reaction solution are reduced to metallic iron and metallic nickel. The completed reaction solution is a slurry containing iron-nickel crystals.

[0374] <Recycling Process>

[0375] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.48 μm.

[0376] [Example 11]

[0377] In Example 11, according to Figure 6 The steps shown involve preparing an iron-nickel alloy powder (iron-nickel alloy powder) with a high iron content, containing 90 mol% iron (Fe) and 10 mol% nickel (Ni). During the crystallization process, an additional raw material solution is added and mixed. Specifically, a room-temperature metal salt raw material solution is added to a reducing solution heated in a water bath and mixed to prepare a reaction solution. First, the crystallization of the iron-nickel alloy powder (iron-nickel alloy powder) containing 91.8 mol% iron (Fe) and 8.2 mol% nickel (Ni) is carried out. Additionally, during this crystallization process, a water-soluble nickel salt aqueous solution is added to the reaction solution as an additional raw material solution and mixed.

[0378] <Preparation Process>

[0379] The same raw materials as in Example 4 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, reducing agents, pH adjusters, complexing agents, and amine compounds.

[0380] <Crystallization process>

[0381] (a) Preparation of metal salt raw material solution

[0382] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.77 ppm by mass (0.41 ppm by mole). Additionally, the trisodium citrate dihydrate was weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.369 (36.9 mol%). Specifically, 446.0 g of ferrous sulfate heptahydrate, 37.5 g of nickel sulfate hexahydrate, 202.6 μg of palladium(II) ammonium chloride, and 189.7 g of trisodium citrate dihydrate were dissolved in 720 mL of pure water to prepare the metal salt raw material solution.

[0383] (b) Preparation of reducing agent solution

[0384] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 9.15 (8.97 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added). Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) at the start of the reaction is 8.29 (8.13 molar ratio of the total amount of magnetic metals (Fe and Ni) when the additional feed solution is added is 8.13). Specifically, 579 g of sodium hydroxide is dissolved in 1418 mL of pure water to prepare a sodium hydroxide solution, and 1334 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0385] (c) Preparation of amine compound solutions

[0386] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the amount of ethylenediamine in the reaction solution during the subsequent crystallization step is weighed such that the amount is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe and Ni) after the addition of the feed solution. Specifically, 1.07 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0387] (d) Preparation of additional feed liquid

[0388] An additional feed solution containing nickel sulfate hexahydrate (a water-soluble nickel salt) and water was prepared. The feed solution was weighed such that the amount of magnetic metal (Ni) in the obtained additional feed solution was 0.0356 mol, which was 0.02 times the total amount of magnetic metal (Fe and Ni) in the metal salt feed solution (1.747 mol). Specifically, 9.37 g of nickel sulfate hexahydrate was dissolved in 100 mL of pure water to prepare the additional feed solution.

[0389] (e) Preparation of reaction solution and precipitation of crystal powder

[0390] The prepared reducing agent solution was placed in a Teflon-coated stainless steel container (reaction tank) with stirring blades in a water bath and heated to a liquid temperature of 85°C while stirring. Then, a metal salt raw material solution at a liquid temperature of 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at a liquid temperature of 78°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 25.0 g / L. Thus, the reduction reaction (crystallization reaction) was started (reaction start temperature 78°C). From the start of the reaction, the temperature of the reaction solution continued to rise due to the heating in the water bath, and the liquid temperature was maintained at 85°C for 10 minutes after the start of the reaction (reaction maintenance temperature 85°C). As for the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction was due to the formation of a coprecipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution during the reaction according to the above formula (6). In addition, it is believed that the hue turns dark gray a few minutes after the start of the reaction due to nucleation caused by the nucleating agent (palladium salt).

[0391] For 10 minutes, from 3 to 13 minutes after the start of the reaction (when the color of the reaction solution turns dark gray), an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. This precipitates iron-nickel crystals in the reaction solution. From 8 to 18 minutes after the start of the reaction, additional feed solution is added dropwise and mixed to promote the reduction of iron ions (or ferric hydroxide) that are difficult to reduce, while simultaneously allowing the reduction reaction to proceed so that the surface of the precipitated iron-nickel crystals becomes more nickel-rich. The concentration of magnetic metals (Fe and Ni) in the reaction solution after the addition of feed solution is 24.8 g / L. At this point, the reaction solution is black, but the supernatant becomes transparent within 50 minutes of the start of the reaction. The reduction reaction is considered complete, and all iron and nickel components in the reaction solution are reduced to metallic iron and metallic nickel. The completed reaction solution is a slurry containing iron-nickel crystals.

[0392] <Recycling Process>

[0393] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.38 μm.

[0394] [Example 12]

[0395] In Example 12, according to Figure 5 The steps shown involve applying an insulating coating to the obtained crystallized powder to produce an iron-nickel alloy powder (iron-nickel alloy powder) containing 55 mol% iron (Fe) and 45 mol% nickel (Ni) coated with silicon dioxide (SiO2), which is an insulating metal oxide. In Example 12, during the preparation of the reaction solution, a room-temperature metal salt raw material solution was added to the reduction solution heated in a water bath and mixed.

[0396] <Preparation Process>

[0397] The same raw materials as in Example 4 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, reducing agents, pH adjusters, complexing agents, and amine compounds.

[0398] <Crystallization process>

[0399] (a) Preparation of metal salt raw material solution

[0400] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe and Ni) was 0.56 ppm by mass (0.3 ppm by mole). The amount of trisodium citrate dihydrate was also weighed such that the molar ratio relative to the total amount of magnetic metals (Fe and Ni) was 0.543 (54.3 mol%). Specifically, 267.7 g of ferrous sulfate heptahydrate, 207.1 g of nickel sulfate hexahydrate, 149.3 μg of palladium(II) ammonium chloride, and 279.6 g of trisodium citrate dihydrate were dissolved in 950 mL of pure water to prepare the metal salt raw material solution.

[0401] (b) Preparation of reducing agent solution

[0402] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) is 4.85. Similarly, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe and Ni) is 4.95. Specifically, 346 g of sodium hydroxide is dissolved in 848 mL of pure water to prepare a sodium hydroxide solution, and 709 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0403] (c) Preparation of amine compound solutions

[0404] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed into the reaction solution in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe and Ni) after the addition of the feed solution. Specifically, 1.05 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0405] (d) Preparation of reaction solution and precipitation of crystal powder

[0406] The prepared reducing agent solution was placed in a Teflon-coated stainless steel container (reaction tank) with stirring blades in a water bath and heated to 70°C while stirring. Then, a metal salt raw material solution at 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at 59°C. The concentration of magnetic metals (Fe and Ni) in the reaction solution was 33.9 g / L. Thus, the reduction reaction (crystallization reaction) began (reaction start temperature 59°C). From the start of the reaction, the temperature of the reaction solution continued to rise due to water bath heating, and the temperature was maintained at 70°C for 10 minutes after the start of the reaction (reaction maintenance temperature 70°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. It is believed that the dark green color at the beginning of the reaction was due to the formation of a co-precipitate of iron hydroxide (Fe(OH)2) and nickel hydroxide (Ni(OH)2) in the reaction solution during the reaction according to equation (6) above. In addition, it is believed that the hue turns dark gray a few minutes after the start of the reaction due to nucleation caused by the nucleating agent (palladium salt).

[0407] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray to 13 minutes after the reaction begins, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. As a result, iron-nickel crystals precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 30 minutes of the reaction beginning. It is considered that the reduction reaction described in equation (6) above is complete, and all the iron and nickel components in the reaction solution are reduced to metallic iron and metallic nickel. The reaction solution after the reaction is complete is a slurry containing iron-nickel crystals.

[0408] <Recycling Process>

[0409] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel crystallized powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate filtered from the slurry was below 10 μS / cm. The recovered cake-shaped crystallized powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystallized powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystallized powder. This yielded crystallized powder (iron-nickel alloy powder) as a dry powder. The obtained crystallized powder (alloy powder) consists of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.39 μm.

[0410] <Insulation Coating Process>

[0411] 50.0g of the crystallized powder (alloy powder) obtained in the above recycling process was placed into a sealed polypropylene container. 7.0g of pure water and 50.0g of ethanol (C2H5OH, molecular weight: 46.07, reagent manufactured by Wako Pure Chemical Industries, Ltd.) were further added. After dispersing the crystallized powder (alloy powder) in the mixed solvent of water and ethanol, 9.8g of tetraethoxysilane (also known as tetraethyl orthosilicate, tetraethyl silicate) (abbreviated as TEOS) (Si(OC2H5)4, molecular weight: 208.33, reagent manufactured by Wako Pure Chemical Industries, Ltd.) as a silanolate was added and mixed thoroughly. Further, while stirring, 2.4g of 1% ammonia water as a salt-based catalyst (base catalyst) for the hydrolysis of silanolate was added to prepare a uniform slurry. It should be noted that the above-mentioned 1% ammonia solution is prepared by diluting 28-30% ammonia solution (NH3, molecular weight: 17.03, reagent manufactured by Wako Pure Chemical Industries Co., Ltd.) with pure water. The crystallization powder (alloy powder), water, ethanol, tetraethoxysilane and 1% ammonia solution are all used at room temperature, and the addition and mixing are also carried out at room temperature.

[0412] The slurry containing crystalline powder (alloy powder), water, ethanol, tetraethoxysilane, and ammonia was kept at 40°C for 2 days in a rotating, sealed polypropylene container. While stirring the slurry, the tetraethoxysilane underwent hydrolysis and dehydration condensation, forming an insulating coating on the surface of the crystalline powder (alloy powder) particles. This coating was primarily composed of a hydrolyzed polymer of tetraethoxysilane (containing a small amount of silanol groups (Si-OH) but almost entirely silicon dioxide (SiO2)). Subsequently, the slurry was filtered, washed, and subjected to solid-liquid separation to recover the cake-shaped crystalline powder (alloy powder). The filtration and washing were first performed using ethanol containing 50% by mass pure water, followed by ethanol. It should be noted that the hydrolyzed polymer of tetraethoxysilane remaining in the slurry, which is not consumed by the insulating coating on the surface of the crystalline powder (alloy powder) particles, consists of very small molecular weight particles (silica sol). This is removed as filtrate during filtration and washing, and therefore does not remain in the recovered cake-shaped crystalline powder (alloy powder).

[0413] The recovered cake-shaped crystalline powder (alloy powder) was dried at 50°C in a vacuum dryer, and then further heated at 150°C in a vacuum for 2 hours. This heat treatment further dehydrated and condensed the hydrolyzed polymer of tetraethoxysilane constituting the insulating coating, resulting in harder and denser silica (SiO2), further improving the insulation properties of the coating. Through this insulating coating process, an iron-nickel alloy powder with an insulating coating composed of high-resistivity silica (SiO2) formed on the particle surface was obtained. The obtained alloy powder consisted of smooth-surfaced spherical particles. The particle size distribution was narrow, with an average particle size of 0.42 μm, and the estimated thickness of the insulating coating was approximately 0.015 μm (approximately 15 nm). Furthermore, through the insulating coating process, the resistivity of the pressed powder (applied pressure: 64 MPa) increased significantly from 0.04 Ω·cm before the coating process to exceed the measurement range (>10). 7 Ω·cm).

[0414] [Example 13]

[0415] In Example 13, according to Figure 5 The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 80 mol% iron (Fe), 10 mol% nickel (Ni), and 10 mol% cobalt (Co). In Example 13, when preparing the reaction solution, a room-temperature metal salt raw material solution was added to the reduction solution heated in a water bath and mixed.

[0416] <Preparation Process>

[0417] The same raw materials as in Example 4 were prepared as water-soluble iron salts, water-soluble nickel salts, nucleating agents, complexing agents, reducing agents, pH adjusters, and amine compounds. In addition, as a water-soluble cobalt salt, cobalt sulfate heptahydrate (CoSO4·7H2O, molecular weight: 281.103, manufactured by Wako Pure Chemical Industries, Ltd.) was prepared.

[0418] <Crystallization process>

[0419] (a) Preparation of metal salt raw material solution

[0420] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), cobalt sulfate heptahydrate (water-soluble cobalt salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe, Ni, and Co) was 0.38 ppm by mass (0.2 ppm by mole). Additionally, the amount of trisodium citrate was weighed such that the molar ratio relative to the total amount of magnetic metals (Fe, Ni, and Co) was 0.362 (36.2 mol%). Specifically, 394.1 g of ferrous sulfate heptahydrate, 46.6 g of nickel sulfate hexahydrate, 49.8 g of cobalt sulfate heptahydrate, 100.8 μg of palladium(II) ammonium chloride, and 188.7 g of trisodium citrate dihydrate were dissolved in 1000 mL of pure water to prepare the metal salt raw material solution.

[0421] (b) Preparation of reducing agent solution

[0422] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe, Ni, and Co) is 3.65. Additionally, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe, Ni, and Co) is 7.07. Specifically, 501 g of sodium hydroxide is dissolved in 1227 mL of pure water to prepare a sodium hydroxide solution, and 540 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0423] (d) Preparation of amine compound solutions

[0424] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed into the reaction solution prepared in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe, Ni, and Co). Specifically, 1.07 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0425] (e) Preparation of reaction solution and precipitation of crystal powder

[0426] The prepared metal salt raw material solution was placed into a Teflon-coated stainless steel container (reaction tank) equipped with stirring blades and placed in a water bath. The mixture was heated to 85°C while stirring. Then, the metal salt raw material solution at 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at 70°C. The concentration of magnetic metals (Fe, Ni, and Co) in the reaction solution was 31.2 g / L. This initiated the reduction reaction (crystallization reaction) (reaction start temperature 70°C). From the start of the reaction, the temperature of the reaction solution continuously increased due to the water bath heating, and was maintained at 85°C for 10 minutes after the start of the reaction (reaction holding temperature 85°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. The initial dark green hue is believed to be due to the formation of coprecipitates of ferric hydroxide (Fe(OH)2), nickel hydroxide (Ni(OH)2), and cobalt hydroxide (Co(OH)2) in the reaction solution, following the reaction according to equation (6) above. Furthermore, the dark gray hue a few minutes after the start of the reaction is believed to be due to nucleation caused by the nucleating agent (palladium salt).

[0427] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray to 13 minutes after the reaction begins, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. As a result, iron-nickel-cobalt crystals precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 40 minutes of the start of the reaction. It is assumed that the reduction reaction described in equation (6) is complete, and all the iron, nickel, and cobalt components in the reaction solution are reduced to metallic iron, metallic nickel, and metallic cobalt. The reaction solution after the reaction is complete is a slurry containing iron-nickel-cobalt crystals.

[0428] <Recycling Process>

[0429] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel-cobalt crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel-cobalt alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.42 μm.

[0430] [Example 14]

[0431] In Example 14, according to Figure 5 The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 70 mol% iron (Fe), 10 mol% nickel (Ni), and 20 mol% cobalt (Co). In Example 14, when preparing the reaction solution, a room-temperature metal salt raw material solution was added to the reduction solution heated in a water bath and mixed.

[0432] <Preparation Process>

[0433] The same raw materials as in Example 13 were prepared as water-soluble iron salts, water-soluble nickel salts, water-soluble cobalt salts, nucleating agents, complexing agents, reducing agents, pH adjusters, and amine compounds.

[0434] <Crystallization process>

[0435] (a) Preparation of metal salt raw material solution

[0436] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), cobalt sulfate heptahydrate (water-soluble cobalt salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The obtained metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe, Ni, and Co) was 0.38 ppm by mass (0.2 ppm by mole). Additionally, the amount of trisodium citrate was weighed such that the molar ratio relative to the total amount of magnetic metals (Fe, Ni, and Co) was 0.362 (36.2 mol%). Specifically, 343.0 g of ferrous sulfate heptahydrate, 46.3 g of nickel sulfate hexahydrate, 99.1 g of cobalt sulfate heptahydrate, 100.2 μg of palladium(II) ammonium chloride, and 187.6 g of trisodium citrate dihydrate were dissolved in 1100 mL of pure water to prepare the metal salt raw material solution.

[0437] (b) Preparation of reducing agent solution

[0438] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe, Ni, and Co) is 1.46. Additionally, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe, Ni, and Co) is 7.07. Specifically, 499 g of sodium hydroxide is dissolved in 1221 mL of pure water to prepare a sodium hydroxide solution, and 215 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0439] (d) Preparation of amine compound solutions

[0440] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed into the reaction solution prepared in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe, Ni, and Co). Specifically, 1.06 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0441] (e) Preparation of reaction solution and precipitation of crystal powder

[0442] The prepared metal salt raw material solution was placed into a Teflon-coated stainless steel container (reaction tank) equipped with stirring blades and placed in a water bath. The mixture was heated to 85°C while stirring. Then, the metal salt raw material solution at 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at 67°C. The concentration of magnetic metals (Fe, Ni, and Co) in the reaction solution was 33.7 g / L. This initiated the reduction reaction (crystallization reaction) (reaction start temperature 67°C). From the start of the reaction, the temperature of the reaction solution continuously increased due to the water bath heating, and was maintained at 85°C for 10 minutes after the start of the reaction (reaction holding temperature 85°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. The initial dark green hue is believed to be due to the formation of coprecipitates of ferric hydroxide (Fe(OH)2), nickel hydroxide (Ni(OH)2), and cobalt hydroxide (Co(OH)2) in the reaction solution, following the reaction according to equation (6) above. Furthermore, the dark gray hue a few minutes after the start of the reaction is believed to be due to nucleation caused by the nucleating agent (palladium salt).

[0443] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray to 13 minutes after the reaction begins, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. As a result, iron-nickel-cobalt crystals precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 40 minutes of the start of the reaction. It is assumed that the reduction reaction described in equation (6) is complete, and all the iron, nickel, and cobalt components in the reaction solution are reduced to metallic iron, metallic nickel, and metallic cobalt. The reaction solution after the reaction is complete is a slurry containing iron-nickel-cobalt crystals.

[0444] <Recycling Process>

[0445] The slurry-like reaction liquid obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover cake-shaped iron-nickel-cobalt crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel-cobalt alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.40 μm.

[0446] [Example 15]

[0447] In Example 15, according to Figure 5 The steps shown are used to prepare an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 65 mol% iron (Fe), 10 mol% nickel (Ni), and 25 mol% cobalt (Co). In Example 15, when preparing the reaction solution, a room-temperature metal salt raw material solution was added to the reduction solution heated in a water bath and mixed.

[0448] <Preparation Process>

[0449] The same raw materials as in Example 13 were prepared as water-soluble iron salts, water-soluble nickel salts, water-soluble cobalt salts, nucleating agents, complexing agents, reducing agents, pH adjusters, and amine compounds.

[0450] <Crystallization process>

[0451] (a) Preparation of metal salt raw material solution

[0452] A metal salt raw material solution containing ferrous sulfate heptahydrate (water-soluble iron salt), nickel sulfate hexahydrate (water-soluble nickel salt), cobalt sulfate heptahydrate (water-soluble cobalt salt), palladium(II) ammonium chloride (nucleating agent), trisodium citrate dihydrate (complexing agent), and water was prepared. The metal salt raw material solution was weighed such that the amount of palladium (Pd) relative to the total amount of magnetic metals (Fe, Ni, and Co) was 0.37 ppm by mass (0.2 ppm by mole). Additionally, the amount of trisodium citrate relative to the total amount of magnetic metals (Fe, Ni, and Co) was weighed such that the molar ratio was 0.362 (36.2 mol%). Specifically, 317.6 g of ferrous sulfate heptahydrate, 46.2 g of nickel sulfate hexahydrate, 123.5 g of cobalt sulfate heptahydrate, 100.0 μg of palladium(II) ammonium chloride, and 187.1 g of trisodium citrate dihydrate were dissolved in 1100 mL of pure water to prepare the metal salt raw material solution.

[0453] (b) Preparation of reducing agent solution

[0454] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe, Ni, and Co) is 1.47. Additionally, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the total amount of magnetic metals (Fe, Ni, and Co) is 7.07. Specifically, 497 g of sodium hydroxide is dissolved in 1216 mL of pure water to prepare a sodium hydroxide solution, and 215 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution.

[0455] (d) Preparation of amine compound solutions

[0456] An amine compound solution containing ethylenediamine (an amine compound) and water is prepared. In this process, the ethylenediamine is weighed into the reaction solution prepared in the subsequent crystallization step, such that the amount of ethylenediamine is a trace molar ratio of 0.01 (1.0 mol%) relative to the total amount of magnetic metals (Fe, Ni, and Co). Specifically, 1.06 g of ethylenediamine is dissolved in 18 mL of pure water to prepare the amine compound solution.

[0457] (e) Preparation of reaction solution and precipitation of crystal powder

[0458] The prepared metal salt raw material solution was placed into a Teflon-coated stainless steel container (reaction tank) equipped with stirring blades and placed in a water bath. The mixture was heated to 85°C while stirring. Then, the metal salt raw material solution at 25°C was added to the reducing agent solution heated in the water bath and mixed for 10 seconds to obtain a reaction solution at 67°C. The concentration of magnetic metals (Fe, Ni, and Co) in the reaction solution was 33.7 g / L. This initiated the reduction reaction (crystallization reaction) (reaction start temperature 67°C). From the start of the reaction, the temperature of the reaction solution continuously increased due to the water bath heating, and was maintained at 85°C for 10 minutes after the start of the reaction (reaction holding temperature 85°C). Regarding the color of the reaction solution, it was dark green at the beginning of the reaction (reaction solution preparation), but turned dark gray after a few minutes. The initial dark green hue is believed to be due to the formation of coprecipitates of ferric hydroxide (Fe(OH)2), nickel hydroxide (Ni(OH)2), and cobalt hydroxide (Co(OH)2) in the reaction solution, following the reaction according to equation (6) above. Furthermore, the dark gray hue a few minutes after the start of the reaction is believed to be due to nucleation caused by the nucleating agent (palladium salt).

[0459] For 10 minutes, from 3 minutes after the reaction begins and the color of the reaction solution turns dark gray to 13 minutes after the reaction begins, an amine compound solution is added dropwise to the reaction solution and mixed to allow the reduction reaction to proceed. As a result, iron-nickel-cobalt crystals precipitate in the reaction solution. At this point, the reaction solution is black, but the supernatant becomes transparent within 30 minutes of the reaction beginning. It is assumed that the reduction reaction described in equation (6) above is complete, and all iron, nickel, and cobalt components in the reaction solution are reduced to metallic iron, metallic nickel, and metallic cobalt. The reaction solution after the reaction is complete is a slurry containing iron-nickel-cobalt crystals.

[0460] <Recycling Process>

[0461] The slurry-like reaction liquid obtained in the crystallization process was filtered, washed, and subjected to solid-liquid separation to recover cake-shaped iron-nickel-cobalt crystal powder. Filtration and washing were performed using pure water with a conductivity of 1 μS / cm until the conductivity of the filtrate from the slurry was below 10 μS / cm. The recovered cake-shaped crystal powder was dried in a vacuum dryer set at 50°C. Then, after cooling the dried crystal powder to 35°C under vacuum, nitrogen gas containing 1.0 vol% oxygen was supplied to slowly oxidize the crystal powder. This yielded iron-nickel-cobalt alloy powder. The obtained alloy powder consisted of smooth-surfaced spherical particles with a narrow particle size distribution and an average particle size of 0.42 μm.

[0462] [Comparative Example 1]

[0463] In Comparative Example 1, palladium(II)ammonium chloride (nucleating agent) was not used when preparing the metal salt raw material solution. Otherwise, the preparation of the reaction solution and the precipitation of the crystallized powder were performed identically to Example 1, producing an iron-nickel alloy powder (iron-nickel alloy powder) containing 50 mol% iron (Fe) and 50 mol% nickel (Ni). The concentration of the magnetic metals (Fe and Ni) in the reaction solution was 32.3 g / L. The obtained alloy powder consisted of spherical particles with an uneven surface. The particle size distribution was narrow, with an average particle size of 0.65 μm.

[0464] [Comparative Example 2]

[0465] In Comparative Example 2, trisodium citrate dihydrate (a complexing agent) was not used when preparing the metal salt raw material solution. Otherwise, the preparation of the reaction solution and the precipitation of the crystallized powder were performed identically to Example 1, producing an iron-nickel alloy powder (iron-nickel alloy powder) containing 50 mol% iron (Fe) and 50 mol% nickel (Ni). The concentration of the magnetic metals (Fe and Ni) in the reaction solution was 33.3 g / L. The obtained alloy powder consisted of deformed particles with an uneven surface. It had a wide particle size distribution with an average particle size of 0.26 μm.

[0466] [Comparative Example 3]

[0467] In Comparative Example 3, palladium(II) ammonium chloride (nucleating agent) and trisodium citrate dihydrate (complexing agent) were not added when preparing the metal salt raw material solution. However, hydrazine (reducing agent) was added in large quantities when preparing the reducing agent solution. Otherwise, the iron-nickel alloy powder (iron-nickel alloy powder) was prepared in the same manner as in Example 1. The metal salt raw material solution and reducing agent solution were prepared as follows.

[0468] (a) Preparation of metal salt raw material solution

[0469] A metal salt raw material solution containing ferrous chloride tetrahydrate (a water-soluble iron salt), nickel chloride hexahydrate (a water-soluble nickel salt), and water was prepared. Specifically, 173.60 g of ferrous chloride tetrahydrate and 207.55 g of nickel chloride hexahydrate were dissolved in 1200 mL of pure water to prepare the metal salt raw material solution.

[0470] (b) Preparation of reducing agent solution

[0471] A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water is prepared. In the reaction solution prepared in the subsequent crystallization step, the amount of hydrazine is weighed such that the molar ratio of hydrazine to the total amount of magnetic metals (Fe and Ni) is 19.4. Additionally, the amount of sodium hydroxide is weighed such that the molar ratio of sodium hydroxide to the amount of magnetic metals (Fe and Ni) is 4.96. Specifically, 346 g of sodium hydroxide is dissolved in 850 mL of pure water to prepare a sodium hydroxide solution, and 2828 g of 60% by mass hydrazine hydrate is added to this sodium hydroxide solution and mixed to prepare the reducing agent solution. It should be noted that when adding the reducing agent solution to the metal salt raw material solution and mixing, the reducing agent solution is heated to a liquid temperature of 37°C before use, so that the reaction starts at 55°C.

[0472] The obtained alloy powder consists of relatively smooth spherical particles. It has a wide particle size distribution with an average particle size of 0.22 μm.

[0473] The manufacturing conditions of the alloy powders of Examples 1 to 15 and Comparative Examples 1 to 3 are shown in Table 1.

[0474]

[0475]

[0476]

[0477] (2) Evaluation of iron-nickel alloy powder

[0478] The iron-nickel alloy powders obtained in Examples 1-15 and Comparative Examples 1-3 were evaluated for various properties as follows.

[0479] <Composition Analysis>

[0480] X-ray diffraction (XRD) was performed using an X-ray diffraction apparatus, and the obtained XRD data were used to confirm whether alloy powder was generated.

[0481] <Analysis of Metallic Impurities>

[0482] The content of impurities was analyzed. Oxygen content was determined using an oxygen analyzer (Lico, TC436) according to the inert gas fusion method; carbon and sulfur content were determined using a carbon-sulfur analyzer (Lico, CS600) according to the combustion method. Additionally, chlorine content was determined using a fluorescence X-ray analyzer (Magix, SC), and silicon and sodium content were determined using an ICP-based spectrophotometer (Agilent Technologies, 5100).

[0483] <Particle size (average particle size, variation coefficient)>

[0484] The alloy powder was observed using a scanning electron microscope (SEM; JEOL Ltd., JSM-7100F) (magnification: 5000-80000x). The observed images (SEM images) were analyzed, and the average particle size and standard deviation of the particle size were calculated based on the results. Then, the coefficient of variation (CV value) was calculated according to the following formula (14), and the particle size (average particle size, coefficient of variation) of the alloy powder was determined.

[0485] CV value (%) = Standard deviation of particle size / Average particle size × 100 ···(14)

[0486] <Intraparticle Composition Analysis>

[0487] The alloy powder embedded in resin was thinned to a thickness of approximately 100 nm using a focused ion beam (FIB) apparatus. The cross-section of the alloy particles in the processed sample was observed using a scanning transmission electron microscope (STEM; Hitachi High Technology Co., Ltd., HD-2300A). Observations were performed at magnifications ranging from 100,000 to 200,000. Then, the compositional distribution within the alloy particles was determined using energy dispersive x-ray spectroscopy (EDS). The composition was calculated based on the detection counts of characteristic X-rays (K-rays) of the analytes.

[0488] <Grain Diameter>

[0489] The alloy powder was analyzed by X-ray diffraction (XRD). The grain diameter was evaluated based on the half-width of the X-ray diffraction peaks on the (111) plane and the Scherrer equation. The XRD measurement conditions were the same as those for compositional analysis. The grain diameter indicates the degree of crystallization; the larger the grain diameter, the higher the crystallinity.

[0490] <Powder Density>

[0491] The compacted powder density was evaluated. Specifically, approximately 0.3 g of alloy powder was filled into the cylindrical orifice (inner diameter 5 mm) of a mold. Then, a press was used to shape the powder into particles with a diameter of 5 mm and a height of 3–4 mm under a pressure of 100 MPa. The mass and height of the obtained particles were measured at room temperature, and the compacted powder density was calculated.

[0492] <Powder resistivity>

[0493] The conductivity (insulation) was evaluated by measuring the pressed powder resistivity of the alloy powder using a powder resistivity measurement system (Mitsubishi Chemical Analysis, MCP-PD51). Specifically, approximately 4 g of alloy powder was filled into the cylindrical sample chamber of the apparatus, and a pressure of 64 MPa was applied using the press attached to the apparatus. The pressed powder resistivity (unit: Ω·cm) was then calculated.

[0494] <Magnetic properties (saturation flux density, coercivity)>

[0495] The magnetic properties (saturation magnetic flux density (T: Tesla) and coercivity (A / m)) of the alloy powder were evaluated using a vibrating sample magnetometer (VSM). The values ​​of saturation magnetic flux density and coercivity were calculated from the obtained BH curves (hysteresis curves). It should be noted that because the alloy powder obtained in Comparative Example 2 was deformed and could not be used in components such as inductors, its magnetic properties were not measured.

[0496] (3) Evaluation Results

[0497] The evaluation results obtained in Examples 1-15 and Comparative Examples 1-3 are shown together in Table 2. Additionally, SEM images of the alloy powders obtained in Examples 1, 2, 10, 13, and 14 are shown in Table 2. Figure 8 , Figure 9 , Figure 13 , Figure 15 and Figure 16 The SEM image of the alloy powder obtained in Example 6 is shown in... Figure 10 (a) and (b). Here, Figure 10 (a) is a SEM image of the alloy powder before spiral jet crushing treatment. Figure 10 (b) is a SEM image of the alloy powder after spiral jet fragmentation treatment. Additionally, STEM images and EDS line analysis results of the particle cross-sections of the alloy powders obtained in Examples 8 and 9 are shown below. Figure 11 (a), (b) and Figure 12 Here, Figure 11 (a) shows the STEM image and EDS line analysis results of the particle cross-section of the alloy powder before high-temperature heat treatment. Figure 11 (b) shows the STEM image and EDS line analysis results of the particle cross-section of the alloy powder after high-temperature heat treatment. The SEM image of the alloy powder obtained in Example 12 is shown below. Figure 14 (a) and (b). Here, Figure 14 (a) is a SEM image of the alloy powder before the insulating coating treatment. Figure 14 (b) is a SEM image of the alloy powder after the insulating coating treatment. Furthermore, SEM images of the alloy powders obtained in Comparative Examples 1-3 are shown below. Figures 17-19 .

[0498] Examples 1, 3, and Comparative Examples 1-3 all illustrate the production of iron-nickel alloy powder by setting the reaction start temperature in the crystallization process to 55°C and the reaction holding temperature to 70°C. In Examples 1 and 3, which used trace amounts of specific nucleating and complexing agents, although the amount of hydrazine used as a reducing agent was small, the average particle size of the obtained alloy powder was as fine as 0.40-0.41 μm, with a small CV value and narrow particle size distribution. In addition, the alloy powder was spherical and had a smooth surface.

[0499] On the other hand, in Comparative Example 1, which did not use a nucleating agent, the average particle size of the obtained alloy powder was as large as 0.65 μm compared to Example 1 or Example 3, making it difficult to refine. Furthermore, although it was spherical, the surface was highly uneven. In Comparative Example 2, which did not use a complexing agent, although the average particle size of the obtained alloy powder was as fine as 0.26 μm, the CV value was large and the particle size distribution was wide. Furthermore, the surface of the alloy powder was highly uneven, exhibiting a deformed shape. In Comparative Example 3, which did not use a nucleating agent and a complexing agent and incorporated a large amount of a reducing agent (hydrazine), the obtained alloy powder was a relatively smooth spherical powder. This is believed to be due to the large amount of hydrazine incorporated, which strongly promoted the reduction reaction. Furthermore, the average particle size of the obtained alloy powder was as fine as 0.22 μm. However, the CV value was large and the particle size distribution was wide.

[0500] Example 2 illustrates the production of iron-nickel-cobalt alloy powder using specific nucleating and complexing agents, with the reaction start temperature in the crystallization process set to 55°C and the reaction holding temperature set to 70°C. Despite using a small amount of hydrazine as a reducing agent, the obtained alloy powder exhibits an average particle size of approximately 0.3 μm and a narrow particle size distribution. Furthermore, the alloy powder has a smooth surface and is spherical. Additionally, the alloy powder exhibits high saturation magnetization.

[0501] Example 5 illustrates the production of an iron-nickel alloy powder containing 51 mol% iron (Fe) and 49 mol% nickel (Ni) with an additional feed solution containing water-soluble nickel salt during crystallization. The nickel-rich surface composition results in the formation of a dense oxide film, suppressing oxidation on the particle surface. Consequently, this alloy powder exhibits superior magnetic properties, including better atmospheric stability and excellent saturation magnetic flux density.

[0502] Example 6 is an example of using a spiral jet crushing process to produce spherical iron-nickel alloy powder with a very smooth surface by subjecting the dry powder obtained after the crystallization and recycling processes to crystallization. Example 7 is an example of using high-pressure fluid impact crushing to produce spherical iron-nickel alloy powder with a very smooth surface by subjecting the slurry-like crystallization powder obtained during the recycling process after the crystallization process to crystallization. In addition to the smooth surface, these alloy powders also exhibit reduced agglomerated particles. Therefore, filling properties are improved (powder density increases). Furthermore, it is expected that reducing agglomerated particles will improve eddy current losses between particles.

[0503] Example 8 is an example of an iron-nickel alloy powder containing 65 mol% iron (Fe) and 35 mol% nickel (Ni) obtained by subjecting the crystallized powder, obtained in the crystallization process with a reaction start temperature of 71°C and a reaction holding temperature of 80°C, to high-temperature heat treatment to improve the compositional uniformity within the particles. Figure 11 (b) It is known that the alloy powder achieves a uniform composition within the particles (65 mol% iron and 35 mol% nickel), and in addition to being a soft magnetic material, it can also be expected to be used as a low thermal expansion material (Invar alloy).

[0504] Example 9 is an example of producing an iron-nickel alloy powder with a nickel-rich surface composition and containing 65 mol% iron (Fe) and 35 mol% nickel (Ni) by adding an additional feed solution containing water-soluble nickel salt to the reaction solution during crystallization and mixing. Figure 12 It is known that a nickel-rich layer with a thickness of about 10-15 nm is formed on the particle surface. Due to the nickel-rich surface composition, a dense oxide film is formed, and the oxidation of the particle surface is suppressed. Therefore, this alloy powder is not only more stable in the atmosphere, but also has excellent magnetic properties such as saturation magnetic flux density.

[0505] Examples 10 and 11 illustrate the production of iron-nickel alloy powders with high iron content. These powders involve adding an additional feed solution containing water-soluble nickel salt to the reaction solution during crystallization and mixing. This promotes the reduction of iron ions (or ferric hydroxide) that are difficult to reduce, while simultaneously enriching the particle surface with a nickel-rich composition. The resulting powders contain 80 mol% iron (Fe) and 20 mol% nickel (Ni), and 90 mol% iron (Fe) and 10 mol% nickel (Ni), respectively. Although the iron content is as high as 80 mol% to 90 mol%, approaching the composition of pure iron, poor reduction does not occur even with relatively low amounts of hydrazine used as a reducing agent. The resulting alloy powders have an average particle size of approximately 0.4 to 0.5 μm, a narrow particle size distribution, a smooth surface, and are spherical. Furthermore, the saturation magnetization of the alloy powder is as high as that of pure iron powder (1.95 T to 2.0 T).

[0506] Compared with Examples 1 to 7, the iron-nickel alloy powders obtained in Examples 8 to 11 have lower compaction density. Among them, the true specific gravity of the iron-nickel alloy powders in Examples 1-7 (iron-nickel alloy powder containing 56-50 mol% Fe and 44-50 mol% Ni, and iron-nickel-cobalt alloy powder containing 50 mol% Fe, 40 mol% Ni and 10 mol% Co) is 8.2-8.25, the true specific gravity of the iron-nickel alloy powders in Examples 8 and 9 (iron-nickel alloy powder containing 65 mol% Fe and 35 mol% Ni) is 8.1, the true specific gravity of the iron-nickel alloy powder in Example 10 (iron-nickel alloy powder containing 80 mol% Fe and 20 mol% Ni) is 8.0, and the true specific gravity of the iron-nickel alloy powder in Example 11 (iron-nickel alloy powder containing 90 mol% Fe and 10 mol% Ni) is 7.9. Considering that the higher the proportion of iron, the lower the true specific gravity of the iron-nickel alloy powder, it can be seen that the pressed powder density of each example is good.

[0507] Example 12 is an example of manufacturing an iron-nickel alloy powder with a particle surface coated with high-resistivity silicon dioxide (SiO2) by performing an insulating coating process on the crystallized powder obtained as dry powder after crystallization and recycling processes. Since the interparticle insulation of this alloy powder is greatly improved (the resistivity of the pressed powder increases significantly), it is expected to improve the eddy current loss between particles.

[0508] Examples 13-15 illustrate the production of iron-nickel alloy powders containing 10 mol% to 25 mol% cobalt and 65 mol% to 80 mol% iron, in addition to water-soluble iron and nickel salts, in a magnetic metal source to promote the reduction of iron ions (or ferric hydroxide), which are difficult to reduce. Specifically, examples include the production of iron-nickel-cobalt alloy powders containing 80 mol% Fe, 10 mol% Ni, and 10 mol% Co; 70 mol% Fe, 10 mol% Ni, and 20 mol% Co; and 65 mol% Fe, 10 mol% Ni, and 25 mol% Co. Although the composition has an iron content of 65 mol% to 80 mol%, the addition of cobalt promotes the reduction reaction, resulting in no poor reduction and obtaining spherical alloy powders even with very small amounts of hydrazine used as a reducing agent. The alloy powder has an average particle size of about 0.4 μm with a narrow particle size distribution and a smooth surface. In addition, the saturation magnetization of the alloy powder is as high as or exceeds that of pure iron powder (1.95T~2.0T).

[0509] Furthermore, the true specific gravity of the iron-nickel alloy powder (iron-nickel-cobalt alloy powder) obtained in Examples 13-15 is estimated to be around 8.0-8.1, but the compacted powder density is high and good. This is believed to be due to the reduction reaction-promoting effect of cobalt addition, which completes the reduction reaction before particle aggregation occurs, thus suppressing particle aggregation in crystallization. Additionally, another effect of cobalt addition, promoting spheroidization, is also believed to be related to improved particle filling properties.

[0510]

[0511]

Claims

1. A method for manufacturing an iron-Fe-nickel-Ni alloy powder containing at least iron (Fe) and nickel (Ni) as a magnetic metal, wherein, The method comprises the following steps: The preparation process involves preparing magnetic metal sources, nucleating agents, complexing agents, reducing agents, and pH adjusters as starting materials. The crystallization process involves preparing a reaction solution containing the starting material and water, and in the reaction solution, crystallizing the powder containing the magnetic metal through a reduction reaction. as well as The recovery process involves recovering the crystalline powder from the reaction solution. The magnetic metal source contains water-soluble iron salts and water-soluble nickel salts. The nucleating agent is at least one selected from the group consisting of copper salts, palladium salts, and platinum salts. The amount of the nucleating agent relative to the total amount of the magnetic metal is more than 0.001 mol ppm and less than 5.0 mol ppm. The complexing agent is at least one selected from the group consisting of hydroxycarboxylic acids, salts of hydroxycarboxylic acids, and derivatives of hydroxycarboxylic acids. The reducing agent is hydrazine (N₂H₄). The pH adjuster is an alkali hydroxide. The magnetic metal also contains cobalt (Co). The magnetic metal source also contains water-soluble cobalt salt. In the magnetic metal, the content of iron (Fe) is 60 mol% or more and 85 mol% or less, and the content of cobalt (Co) is 10 mol% or more and 30 mol% or less. In the magnetic metal source, the content of water-soluble iron salt is 60 mol% or more and 85 mol% or less, and the content of water-soluble cobalt salt is 10 mol% or more and 30 mol% or less.

2. The method as described in claim 1, wherein, The water-soluble iron salt is selected from at least one of the group consisting of ferrous chloride FeCl2, ferrous sulfate FeSO4 and ferrous nitrate Fe(NO3)2.

3. The method as described in claim 1 or 2, wherein, The water-soluble nickel salt is selected from at least one of the group consisting of nickel chloride (NiCl2), nickel sulfate (NiSO4), and nickel nitrate (Ni(NO3)2).

4. The method as described in claim 1 or 2, wherein, The complexing agent is at least one hydroxycarboxylic acid selected from tartaric acid (CH(OH)COOH)2 and citric acid C(OH)(CH2COOH)2COOH.

5. The method as described in claim 1 or 2, wherein, The pH adjuster is at least one selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH).

6. The method of claim 1, wherein, The water-soluble cobalt salt is selected from at least one of the group consisting of cobalt chloride CoCl2, cobalt sulfate CoSO4 and cobalt nitrate Co(NO3)2.

7. The method of claim 1, wherein, The starting materials also include amine compounds containing two or more primary amino groups (-NH2), one primary amino group (-NH2) and one or more secondary amino groups (-NH-), or two or more secondary amino groups (-NH-).

8. The method of claim 7, wherein, The amine compound is at least one of alkylene amines and alkylene amine derivatives.

9. The method of claim 8, wherein, The alkylene amine and / or alkylene amine derivatives have at least the following structure: the nitrogen atom of the amino group within the molecule is linked via a carbon chain having two carbon atoms, as represented by (A) below. 。 10. The method according to any one of claims 7 to 9, wherein, The amine compound is at least one alkyleneamine selected from the group consisting of ethylenediamine H2NC2H4NH2, diethylenetriamine H2NC2H4NHC2H4NH2, triethylenetetramine H2N(C2H4NH)2C2H4NH2, tetraethylenepentamine H2N(C2H4NH)3C2H4NH2, pentaethylenehexamine H2N(C2H4NH)4C2H4NH2, and propylenediamine CH3CH(NH2)CH2NH2 and / or from the group consisting of tris(2-aminoethyl) It is at least one alkylene amine derivative selected from the group consisting of N(C2H4NH2)3, N-(2-aminoethyl)ethanolamine H2NC2H4NHC2H4OH, N-(2-aminoethyl)propanolamine H2NC2H4NHC3H6OH, 2,3-diaminopropionic acid H2NCH2CH(NH)COOH, ethylenediamine-N,N'-diacetic acid HOOCCH2NHC2H4NHCH2COOH, and 1,2-cyclohexanediamine H2NC6H10NH2.

11. The method according to any one of claims 7 to 9, wherein, The amount of the amine compound in combination is more than 0.01 mol% and less than 5.00 mol% relative to the total amount of the magnetic metal.

12. The method of claim 1, wherein, In the crystallization process, when preparing the reaction solution, a metal salt raw material solution, a reducing agent solution, and a pH adjustment solution are prepared respectively. The metal salt raw material solution and the pH adjustment solution are mixed to form a mixed solution. The mixed solution is then mixed with the reducing agent solution. The metal salt raw material solution is prepared by dissolving the magnetic metal source, the nucleating agent, and the complexing agent in water. The reducing agent solution is prepared by dissolving the reducing agent in water. The pH adjustment solution is prepared by dissolving the pH adjusting agent in water.

13. The method of claim 12, wherein, In preparing the reaction solution, the pH adjustment solution and the reducing agent solution are added sequentially to the metal salt raw material solution and mixed.

14. The method of claim 12, wherein, The time required to mix the mixed solution and the reducing agent solution is more than 1 second and less than 180 seconds.

15. The method of claim 13, wherein, The time required to mix the mixed solution and the reducing agent solution is more than 1 second and less than 180 seconds.

16. The method of claim 1, wherein, In the crystallization process, when preparing the reaction solution, a metal salt raw material solution and a reducing agent solution are prepared separately. The metal salt raw material solution and the reducing agent solution are mixed. The metal salt raw material solution is prepared by dissolving the magnetic metal source, the nucleating agent and the complexing agent in water. The reducing agent solution is prepared by dissolving the reducing agent and the pH adjusting agent in water.

17. The method of claim 16, wherein, In preparing the reaction solution, the reducing agent solution is added to the metal salt raw material solution, or conversely, the metal salt raw material solution is added to the reducing agent solution and mixed.

18. The method of claim 16, wherein, The time required to mix the metal salt raw material solution and the reducing agent solution is more than 1 second and less than 180 seconds.

19. The method of claim 17, wherein, The time required to mix the metal salt raw material solution and the reducing agent solution is more than 1 second and less than 180 seconds.

20. The method of claim 1, wherein, In the crystallization process, before the reduction reaction ends, an additional raw material solution is added to the reaction solution and mixed. The additional raw material solution is formed by dissolving at least one of the water-soluble nickel salt and the water-soluble cobalt salt in water.

21. The method according to any one of claims 12 to 20, wherein, An amine compound is incorporated into at least one of the metal salt raw material solution, the reducing agent solution, the pH adjustment solution, and the reaction solution.

22. The method of claim 1, wherein, The temperature of the reaction solution at the start of crystallization of the crystallization powder, i.e., the reaction start temperature, is above 40℃ and below 90℃, and the temperature of the reaction solution maintained during crystallization after the start of crystallization, i.e., the reaction holding temperature, is above 60℃ and below 99℃.

23. The method of claim 1, wherein, It also has a crushing process, which uses impact energy to crush the crystallized powder after the recycling process or during the recycling process, breaking down the aggregated particles contained in the crystallized powder.

24. The method of claim 23, wherein, The crushing treatment of crystalline powder after the recovery process by dry crushing or wet crushing, or the crushing of crystalline powder during the recovery process by wet crushing.

25. The method of claim 24, wherein, The dry crushing is a spiral jet crushing.

26. The method of claim 24, wherein, The wet crushing is a high-pressure fluid impact crushing process.

27. The method of claim 1, wherein, It also has a high-temperature heat treatment process, which heats the crystallized powder after the recycling process or during the recycling process in an inactive environment, a reducing environment or a vacuum environment, at a temperature greater than 150°C and less than 400°C, thereby improving the uniformity of the composition within the Fe-Ni alloy powder particles.

28. The method of claim 1, wherein, It also has an insulating coating process, which applies an insulating coating to the crystallized powder obtained after the recycling process, forming an insulating coating made of metal oxide on the surface of the crystallized powder particles, thereby improving the insulation between particles.

29. The method of claim 28, wherein, In the insulating coating process, the crystallized powder is dispersed in a mixed solvent containing water and an organic solvent. A metal alkoxide is then added to the mixed solvent and mixed to prepare a slurry. The metal alkoxide is hydrolyzed and dehydrated in the slurry to form an insulating coating composed of metal oxides on the surface of the crystallized powder particles. Subsequently, the crystallized powder with the insulating coating is recovered from the slurry.

30. The method of claim 29, wherein, The metal alkoxide is mainly composed of silanol, which is an alkyl silicate, and the metal oxide is mainly composed of silicon dioxide (SiO2).

31. The method of claim 29 or 30, wherein, The hydrolysis of the metal alkoxide is carried out in the presence of a base catalyst, wherein the base catalyst is an alkaline catalyst.

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