IRON (Fe)-NICKEL (Ni)-BASED ALLOY POWDER AND METHOD FOR PRODUCING THE SAME

Abstract

To provide an iron-nickel-based alloy powder having a large particle size, which is excellent in powder characteristics and magnetic characteristics, and to provide a method for producing the iron-nickel-based alloy powder.SOLUTION: A method for producing an iron (Fe)-nickel (Ni)-based alloy powder comprising at least iron (Fe) and nickel (Ni) as magnetic metals includes: a magnetic metal source part-oxidizing step of obtaining a partially oxidized magnetic metal source containing a divalent magnetic metal and a trivalent magnetic metal by performing partial oxidation treatment on a magnetic metal source containing the magnetic metals; a crystallization step of crystallizing, by a reduction reaction, a crystallized powder containing the magnetic metals in a reaction liquid containing the partially oxidized magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, a pH adjusting agent, and water; and a recovery step of recovering the crystallized powder from the reaction liquid, wherein: 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 nobler than nickel; the reducing agent is hydrazine (N2H4); and the pH adjusting agent is an alkali hydroxide.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to iron (Fe)-nickel (Ni)-based alloy powder and a method for producing the same. [Background technology]

[0002] The iron-nickel alloy known as permalloy is a soft magnetic material with high magnetic permeability, and is used for the magnetic cores of magnetic components such as choke coils and inductors. In particular, iron-nickel alloy powder is used as a material for magnetic dust cores (dust cores) obtained by compression molding.

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

[0004] In recent years, mobile devices such as laptops and smartphones have become increasingly compact and powerful. This trend has led to demands for magnetic components such as inductors to support higher frequencies in addition to improved magnetic properties. To achieve this, materials for powder cores must have high magnetic flux density and reduced loss. Losses primarily consist of hysteresis loss and eddy current loss. Increasing the particle size of the alloy powder particles and reducing their coercive force are effective ways to reduce hysteresis loss. On the other hand, applying a thin insulating coating to the surface of alloy powder particles, thereby reducing eddy currents between particles, and narrowing the particle size distribution are effective ways to reduce eddy current loss. This is because eddy currents generate loss due to Joule heat.

[0005] Dry processes such as atomization, vapor-phase reduction, and dry reduction have been known as methods for producing alloy powders. The atomization method involves spraying water or gas onto a molten metal to rapidly cool and solidify the molten metal. The vapor-phase reduction method involves hydrogen reduction of a metal halide in a vapor phase. The dry reduction method involves reducing a metal oxide using a reducing agent.

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

[0001] and

[0014] of Patent Document 1). Patent Document 1 also discloses the production of Ni-Fe alloy fine powder by heating a mixture of NiCl2 and FeCl3 and bringing the vaporized chloride into contact with hydrogen gas to cause a reduction reaction (paragraph

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

[0007] On the other hand, it has been proposed to produce finer alloy powders using wet methods. For example, Patent Document 3 discloses a method for producing nickel-iron alloy nanoparticles, which involves adding a reducing agent such as hydrazine to an aqueous solution containing a nickel salt and an iron salt, and simultaneously reducing the nickel ions and iron ions contained in the aqueous solution to produce nickel-iron alloy nanoparticles (claims 1 to 6 of Patent Document 3). This production method is said to enable efficient production of nickel-iron alloy nanoparticles with an average primary particle size of 200 nm or less, which are suitable as a filler for imparting magnetic properties, on an industrial scale at low production cost (paragraph

[0015] of Patent Document 3). Patent Document 4 discloses a method for producing iron-nickel alloy powder or iron-nickel-cobalt alloy powder, which involves a crystallization (reduction) reaction in a reaction solution containing a magnetic metal source (water-soluble iron and nickel salts, and optionally a water-soluble cobalt salt), a nucleating agent (a water-soluble salt of a metal nobler than nickel), a complexing agent (at least one selected from hydroxycarboxylic acids, hydroxycarboxylic acid salts, and hydroxycarboxylic acid derivatives), a pH adjuster (alkali hydroxide), a reducing agent (hydrazine), and water to produce a crystallized powder (iron-nickel alloy powder or iron-nickel-cobalt alloy powder) (claims 1-13 of Patent Document 4). According to this method, by using specific nucleating and complexing agents, it is possible to produce alloy powders with an average particle size of 0.2 μm to 0.6 μm, which have excellent powder properties and magnetic properties, using a small amount of reducing agent (paragraphs

[0011] ,

[0062] , and

[0162] of Patent Document 4). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-193160 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-197474 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-024961 [Patent Document 4] WO2022 / 080487 issue Summary of the Invention [Problem to be solved by the invention]

[0009] Although dry and wet methods for producing alloy powders have been proposed, conventional techniques have room for improvement in obtaining alloy powders with excellent powder properties. For example, the gas-phase reduction method proposed in Patent Document 1 results in a wide particle size distribution of the resulting alloy powder. As a result, the alloy powder is insufficient for reducing eddy current loss. Another problem is that the composition and particle size of the alloy powder are unstable. The dry reduction method proposed in Patent Document 2 requires high-temperature heating, which results in the problem that the resulting alloy powder is prone to sintering and forming agglomerated particles.

[0010] The wet processes proposed in Patent Documents 3 and 4 differ from dry processes in that nucleation and particle growth occur relatively uniformly, resulting in particles with a narrow particle size distribution. Furthermore, the reduction reaction proceeds at low temperatures, making it difficult to generate coarse agglomerated particles. Even if agglomerated particles are formed, they are easily broken down because the bonds between the particles are not strong. However, the methods proposed in Patent Documents 3 and 4 have limitations on particle size control (increasing particle size) by adjusting (reducing) the number of nuclei generated, making it difficult to obtain alloy powders with particle sizes exceeding 0.6 μm. Therefore, even if there was a need for large-particle-size alloy powders (e.g., particle sizes of 1 μm to several μm), they were unable to meet this need.

[0011] The present inventors have conducted extensive research in light of these conventional problems, and have found that when producing iron-nickel alloy powder by a wet method, if a portion of the magnetic metal source containing divalent iron (Fe(II)) or divalent nickel (Ni(II)) as the raw material is oxidized in advance and then subjected to a reduction reaction, it is possible to obtain an alloy powder having a large particle size (for example, a particle size of more than 1 μm) that has excellent powder properties and magnetic properties.

[0012] The present invention was completed based on these findings, and an object of the present invention is to provide large particle size iron-nickel alloy powder that has excellent powder properties and magnetic properties, and a method for producing the same. [Means for solving the problem]

[0013] The present invention includes the following aspects (1) to (33). In this specification, the expression "to" includes the numerical values ​​at both ends. In other words, "X to Y" is synonymous with "at least X and at most Y."

[0014] (1) An iron (Fe)-nickel (Ni) alloy powder containing at least iron (Fe) and nickel (Ni) as magnetic metals, having an average particle size of more than 0.6 μm and a coefficient of variation (CV value) of 25% or less, calculated from the average particle size and standard deviation in the number particle size distribution according to the following formula (1):

number

[0015] (2) The alloy powder of (1) above, further containing cobalt (Co) as a magnetic metal.

[0016] (3) The alloy powder of (1) or (2) above, in which the iron (Fe) content is 10 mol% or more and 95 mol% or less, the nickel (Ni) content is 5 mol% or more and 90 mol% or less, and the cobalt (Co) content is 0 mol% or more and 40 mol% or less.

[0017] (4) The alloy powder of any one of (1) to (3) above, having a saturation magnetic flux density of 1 T (tesla) or more and a coercive force of 2000 A / m or less.

[0018] (5) The alloy powder according to any one of (1) to (4) above, which has an insulating coating layer made of a metal oxide provided on the surface of particles constituting the alloy powder.

[0019] (6) A green compact or sheet containing the alloy powder of any one of (1) to (5) above.

[0020] (7) An inductor, reactor, choke coil, noise filter, transformer, rotating machine, generator, or radio wave absorber comprising the powder compact and / or sheet of (6) above.

[0021] (8) A method for producing an iron (Fe)-nickel (Ni)-based alloy powder containing at least iron (Fe) and nickel (Ni) as magnetic metals, the method comprising the following steps: a magnetic metal source partial oxidation step of obtaining a partially oxidized magnetic metal source containing a divalent magnetic metal and a trivalent magnetic metal by partial oxidation treatment of the magnetic metal source containing the magnetic metal; a crystallization step in which a crystallized powder containing the magnetic metal is crystallized by a reduction reaction in a reaction solution containing the partially oxidized magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, a pH adjuster, and water; and A recovery step of recovering the crystallized powder from the reaction solution, the magnetic metal source comprises a water-soluble iron salt and a water-soluble nickel salt; the nucleating agent is a water-soluble salt of a metal more noble 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), The method wherein the pH adjuster is an alkali hydroxide.

[0022] (9) The method according to (8) above, wherein the partial oxidation treatment is an addition treatment of adding an oxidized magnetic metal source containing a trivalent magnetic metal to a metal salt raw material solution in which a magnetic metal source containing a divalent magnetic metal is dissolved, or an aeration treatment of blowing an oxygen-containing gas into a metal salt raw material solution in which a magnetic metal source containing a divalent magnetic metal is dissolved.

[0023] (10) The method according to (8) or (9), 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).

[0024] (11) Any of the methods (8) to (10) above, wherein the water-soluble nickel salt is at least one selected from the group consisting of nickel chloride (NiCl2), nickel sulfate (NiSO4), and nickel nitrate (Ni(NO3)2).

[0025] (12) The magnetic metal further contains cobalt (Co), The method according to any one of (8) to (11) above, wherein the magnetic metal source further contains a water-soluble cobalt salt.

[0026] (13) The method according to (12) 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).

[0027] (14) The method according to any one of (8) to (13) above, wherein the nucleating agent is at least one selected from the group consisting of copper salts, palladium salts, and platinum salts.

[0028] (15) Any of the above methods (8) to (14), 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).

[0029] (16) The method according to any one of (8) to (15) above, wherein the pH adjuster is at least one selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0030] (17) Any of the methods (8) to (16) above, wherein the reaction solution further contains an amine compound containing two or more primary amino groups (-NH), one primary amino group (-NH) and one or more secondary amino groups (-NH-), or two or more secondary amino groups (-NH-) in the molecule.

[0031] (18) The method according to (17), wherein the amine compound is at least one of an alkyleneamine and an alkyleneamine derivative.

[0032] (19) The method according to (18), wherein the alkyleneamine and / or alkyleneamine derivative has at least a structure represented by the following (A), in which a nitrogen atom of an amino group in the molecule is bonded via a carbon chain having two carbon atoms: [ka]

[0033] (20) 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 tris(2-aminoethyl)amine (N(

[0023] In any of the methods (17) to (19), the alkyleneamine derivative is at least one selected from the group consisting of 2,3-diaminopropionic acid (H2NCH2CH(NH)COOH), ethylenediamine-N,N'-diacetic acid (HOOCCH2NHC2H4NHCH2COOH), 1,2-cyclohexanediamine (H2NC6H10NH2), 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).

[0034] (21) The method according to any one of (17) to (20), wherein the amount of the amine compound to be blended relative to the total amount of the magnetic metal is 0.01 mol % or more and 5.00 mol % or less.

[0035] (22) Any of the methods (8) to (21) above, wherein in the crystallization step, a partially oxidized metal salt raw material solution containing a partially oxidized magnetic metal source, a nucleating agent, and a complexing agent dissolved in water, a reducing agent solution containing a reducing agent dissolved in water, and a pH adjusting solution containing a pH adjusting agent dissolved in water are prepared, the partially oxidized metal salt raw material solution and the pH adjusting solution are mixed to form a mixed solution, and the mixed solution and the reducing agent solution are mixed to prepare a reaction solution.

[0036] (23) The method of (22) above, wherein the partially oxidized magnetic metal source is obtained by at least one partial oxidation treatment selected from the group consisting of an addition treatment in which an oxidized magnetic metal source containing a trivalent magnetic metal is added to a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent, and an aeration treatment in which an oxygen-containing gas is blown into a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent.

[0037] (24) The method according to (22) or (23) above, wherein, when preparing the reaction solution, the pH adjusting solution and the reducing agent solution are added to the partially oxidized metal salt raw material solution in that order and mixed.

[0038] (25) The method according to any one of (22) to (24), wherein the time required for mixing the mixed solution and the reducing agent solution is 1 second or more and 180 seconds or less.

[0039] (26) The method according to any one of (22) to (25) above, wherein an amine compound is blended into at least one of the partially oxidized metal salt raw material solution, the reducing agent solution, the pH adjusting solution, and the reaction solution.

[0040] (27) Any of the methods (8) to (21) above, wherein in the crystallization step, a partially oxidized metal salt raw material solution containing a partially oxidized magnetic metal source, a nucleating agent, and a complexing agent dissolved in water, and a reducing agent solution containing a reducing agent and a pH adjuster dissolved in water are prepared, and the partially oxidized metal salt raw material solution and the reducing agent solution are mixed to prepare a reaction solution.

[0041] (28) The method of (27) above, wherein the partially oxidized magnetic metal source is obtained by at least one partial oxidation treatment selected from the group consisting of an addition treatment in which an oxidized magnetic metal source containing a trivalent magnetic metal is added to a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent, and an aeration treatment in which an oxygen-containing gas is blown into a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent.

[0042] (29) The method according to (27) or (28), wherein, when preparing the reaction solution, the reducing agent solution is added to the partially oxidized metal salt raw material solution and mixed, or conversely, the partially oxidized metal salt raw material solution is added to the reducing agent solution and mixed.

[0043] (30) The method according to any one of (27) to (29) above, wherein the time required for mixing the partially oxidized metal salt raw material solution and the reducing agent solution is 1 second or more and 180 seconds or less.

[0044] (31) The method according to any one of (27) to (30) above, wherein an amine compound is added to at least one of the partially oxidized metal salt raw material solution, the reducing agent solution, and the reaction solution.

[0045] (32) The method according to any one of (8) to (31), wherein in the crystallization step, an additional raw material solution prepared by dissolving at least one of the water-soluble nickel salt and the water-soluble cobalt salt in water is further added to the reaction solution and mixed before the reduction reaction is completed.

[0046] (33) Any of the methods (8) to (31) above, wherein the temperature of the reaction solution at the start of crystallization of the crystallized powder (reaction initiation temperature) is 40°C or higher and 90°C or lower, and the temperature of the reaction solution maintained during crystallization after the start of crystallization (reaction maintenance temperature) is 60°C or higher and 99°C or higher. [Effects of the Invention]

[0047] According to the present invention, there is provided a method for producing large particle size iron-nickel alloy powder that has excellent powder properties and magnetic properties. [Brief explanation of the drawings]

[0048] [Figure 1] FIG. 2 is a process diagram illustrating the method for producing the alloy powder of the present embodiment. [Figure 2] FIG. 1 is a schematic diagram showing an aeration process in which air bubbles are injected into a solution to oxidize a portion of the magnetic metal source. [Figure 3] FIG. 1 is a process diagram illustrating the preparation of a reaction solution and the production of an alloy powder in a first embodiment. [Figure 4] FIG. 1 is a process diagram illustrating the preparation of a reaction solution and the production of an alloy powder in a first embodiment. [Figure 5] FIG. 2 is a process diagram illustrating the preparation of a reaction solution and the production of an alloy powder in a second embodiment. [Figure 6] FIG. 2 is a process diagram illustrating the preparation of a reaction solution and the production of an alloy powder in a second embodiment. [Figure 7] FIG. 10 is a process diagram illustrating the preparation of a reaction solution and the production of an alloy powder in a third embodiment. [Figure 8] An example of application of a green compact containing alloy powder to an inductor (toroidal coil) is shown below. [Figure 9] An example in which a green compact containing alloy powder is applied to a chip inductor is shown below. [Figure 10] An example of a compact containing alloy powder applied to a reactor is shown below. [Figure 11] An example of application of a green compact containing alloy powder to the stator of a rotating machine (motor) or generator is shown below. [Figure 12] An example of application of a green compact containing alloy powder to the rotor of a rotating machine (motor) or generator is shown below. [Figure 13] FIG. 2 is a graph showing the transition of the liquid temperature in the reaction tank during the crystallization step in Example 1. [Figure 14] 1 is an SEM image of the alloy powder obtained in Example 1. [Figure 15] 1 is an SEM image of the alloy powder obtained in Example 2. [Figure 16] 1 is an SEM image of the alloy powder obtained in Example 3. [Figure 17] 1 shows SEM images of the alloy powder obtained in Example 4 (before and after insulating coating treatment). [Figure 18] 1 is an SEM image of the alloy powder obtained in Comparative Example 1. [Figure 19] 1 is an SEM image of the alloy powder obtained in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0049] A specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described. Note that the present invention is not limited to the following embodiment, and various modifications are possible within the scope of the present invention. Furthermore, in this specification, any combination of suitable aspects can be adopted as long as technical consistency can be achieved. For example, one of the suitable numerical ranges can be combined with the other.

[0050] <<1. Method for producing iron-nickel alloy powder>> The method for producing iron (Fe)-nickel (Ni)-based alloy powder of this embodiment includes the following steps: a magnetic metal source partial oxidation step in which a magnetic metal source containing a magnetic metal is partially oxidized to obtain a partially oxidized magnetic metal source containing a divalent magnetic metal and a trivalent magnetic metal; a crystallization step in which a crystallized powder containing a magnetic metal is crystallized by a reduction reaction in a reaction solution containing the partially oxidized magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, a pH adjuster, and water; and a recovery step in which the crystallized powder is recovered from the resulting reaction solution. Here, the iron (Fe)-nickel (Ni)-based alloy powder contains at least iron (Fe) and nickel (Ni) as magnetic metals. The magnetic metal source also contains a water-soluble iron salt and a water-soluble nickel salt. The nucleating agent is a water-soluble salt of a metal more noble 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 (NH). The pH adjuster is an alkali hydroxide.

[0051] The iron (Fe)-nickel (Ni)-based alloy powder (hereinafter sometimes simply referred to as "alloy powder") of this embodiment contains at least iron (Fe) and nickel (Ni). The alloy powder may also contain cobalt (Co) as needed. That is, the alloy powder may be an iron-nickel alloy powder containing only iron and nickel, or an iron-nickel-cobalt alloy powder containing iron, nickel, and cobalt. Iron, nickel, and cobalt are all magnetic metals that exhibit ferromagnetism. Therefore, iron-nickel alloy powder and iron-nickel-cobalt alloy powder have high magnetic flux density and excellent magnetic properties. In this specification, magnetic metal is a general term for iron, nickel, and cobalt. That is, when the alloy does not contain cobalt, magnetic metal is a general term for iron and nickel, and when the alloy contains cobalt, magnetic metal is a general term for iron, nickel, and cobalt.

[0052] The proportions of iron (Fe), nickel (Ni), and cobalt (Co) contained in the alloy powder of this embodiment are not particularly limited. The iron content may 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 may 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 may be 0 mol% or more and 40 mol% or less, or 5 mol% or more and 20 mol% or less. However, the total content of iron, nickel, and cobalt is 100 mol% or less.

[0053] The alloy powder of this embodiment does not exclude the inclusion of additional components other than the magnetic metals (Fe, Ni, and Co). Examples of such additional components include copper (Cu) and / or boron (B). However, to maximize the effects of the magnetic metals, the lower the content of additional components other than the magnetic metals, the better. The content of components other than the magnetic metals may be 10% by mass or less, 5% by mass or less, 1% by mass or less, or even 0% by mass. The alloy powder may also contain impurities (unavoidable impurities) that are inevitably mixed in during the manufacturing process. Examples of such inevitable impurities include oxygen (O), carbon (C), and alkaline components (Na, K, etc.). Furthermore, when a water-soluble chloride is used as the magnetic metal source, chlorine (Cl) may become an inevitable impurity, and when a water-soluble sulfate is used, sulfur (S) may become an inevitable impurity. Since inevitable impurities may cause deterioration of the properties of the alloy powder, it is preferable to minimize their amount. The amount of inevitable impurities is preferably 5% by mass or less, more preferably 3% by mass or less, for oxygen (O) contained in the oxide film that inevitably forms on the surface of the alloy powder. On the other hand, the contents of carbon (C), chlorine (Cl), sulfur (S), and alkali components (such as Na and K) 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 may have a composition containing a magnetic metal, with the remainder being unavoidable impurities.

[0054] The method for producing alloy powder of this embodiment includes at least a magnetic metal source partial oxidation step, a crystallization step, and a recovery step. A preparation step may also be included as needed. Furthermore, a crushing step or a high-temperature heat treatment step may be included after or during the recovery step, or an insulating coating step may be included after the recovery step.

[0055] Figure 1 shows a schematic diagram of an example of the process in the manufacturing method of this embodiment. While Figure 1 shows a crushing treatment, a high-temperature heat treatment, and an insulating coating treatment, these treatments may be performed as needed and are not essential. Furthermore, when crushing treatment, high-temperature heat treatment, and / or insulating coating treatment are performed, there are no particular restrictions on the order in which these treatments are performed. If anything, it is preferable to perform the crushing treatment after the high-temperature heat treatment. This is because the connections (bonds) between the alloy particles strengthened by the high-temperature heat treatment can be reduced or eliminated.

[0056] Furthermore, it is preferable to perform the crushing treatment before or after the insulation coating, if possible. This is because it allows for a uniform insulation coating over the entire surface of each alloy particle, with connections reduced or eliminated, and also reduces the number of agglomerated particles newly formed by the insulation coating. However, performing the crushing treatment twice, once before and after the insulation coating, complicates the process and leads to a significant increase in costs, so it is preferable to perform it once. If the crushing treatment is performed only before the insulation coating, it is possible to uniformly coat the entire surface of the alloy particles with an insulation coating, but it is not possible to reduce the number of agglomerated particles newly formed by the insulation coating. On the other hand, if the crushing treatment is performed only after the insulation coating, an insulation coating layer is not formed at the connections between the alloy particles, but it is possible to reduce the number of agglomerated particles newly formed by the insulation coating.

[0057] Thus, depending on the timing of the disintegration treatment, either a uniform insulating coating or a reduction in agglomerated particles after the insulating coating can be obtained as the main effect. Therefore, the optimal timing for the disintegration treatment differs depending on which effect is emphasized, and the timing can be set from this perspective. However, in either case, it is preferable to reduce or eliminate the linkages as much as possible before the insulating coating treatment. Details of each process are explained below.

[0058] <Preparation process> The manufacturing method of this embodiment may include a preparation step of preparing starting materials including a magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, and a pH adjuster. The magnetic metal source is a source of divalent iron (Fe(II)) and divalent nickel (Ni(II)), and may also contain a source of divalent cobalt (Co(II)) if necessary. The starting materials may also contain an amine compound. Each of the sources is described below.

[0059] (a) Magnetic metal source The magnetic metal source is a raw material for the magnetic metal, and includes a water-soluble iron salt containing at least divalent iron (Fe(II)) (hereinafter referred to as "divalent iron salt") and a water-soluble nickel salt containing divalent nickel (Ni(II)) (hereinafter referred to as "divalent nickel salt"). The iron salt is a raw material (iron source) for the iron component contained in the alloy powder, and is not particularly limited as long as it is a water-soluble iron salt. The water-soluble iron salt containing divalent iron (Fe(II)) 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 a raw material (nickel source) for the nickel component contained in the alloy powder, and is not particularly limited as long as it is a water-soluble nickel salt. The water-soluble nickel salt containing divalent nickel (Ni(II)) 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).

[0060] Optionally, the magnetic metal may further contain cobalt (Co), and the magnetic metal source may further contain a water-soluble cobalt salt containing divalent cobalt (Co(II)) (hereinafter referred to as "divalent cobalt salt"). This enables the production of iron-nickel-cobalt alloy powder. Iron-nickel-cobalt alloy powder in which part of the iron or nickel is replaced with cobalt is characterized by a particularly high magnetic flux density. The water-soluble cobalt salt is not particularly limited as long as it is a cobalt salt that is easily soluble in water. The water-soluble cobalt salt containing divalent cobalt (Co(II)) is preferably at least one selected from the group consisting of cobalt chloride (CoCl2), cobalt sulfate (CoSO4), and cobalt nitrate (Co(NO3)2), and particularly preferably at least one selected from the group consisting of cobalt chloride (CoCl2) and cobalt sulfate (CoSO4). In the following, divalent iron salts, divalent nickel salts, and divalent cobalt salts may be collectively referred to as divalent magnetic metal salts.

[0061] (b) Nucleating agent The nucleating agent is a water-soluble salt of a metal more noble than nickel. This nucleating agent (water-soluble salt of a metal more noble than nickel) is preferentially reduced in the reaction solution during the subsequent crystallization process to generate initial nuclei, which then promote the precipitation of crystallized powder. Here, a metal more noble than nickel is a metal that has a higher potential in an aqueous solution than nickel in the standard potential series. Metals more noble than nickel can also be said to have a lower tendency to ionize 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).

[0062] Using a water-soluble salt of a metal more noble than nickel as a nucleating agent allows for the control of the formation of crystallized powder in the reaction solution during the subsequent crystallization process. For example, increasing the amount of nucleating agent can produce finer crystallized powder. Specifically, during the crystallization process, magnetic metal ions and complex ions contained in the reaction solution are reduced and precipitated to form crystallized powder. Among magnetic metals, nickel is more noble than iron and cobalt and has a low tendency to ionize. Therefore, if a water-soluble salt (nucleating agent) of a metal more noble than nickel is added to the reaction solution, the metal more noble than nickel will be reduced and precipitated before all the magnetic metals. The precipitated metal more noble than nickel acts as an initial nucleus, and these initial nuclei grow to form crystallized powder composed of the magnetic metal. Therefore, the particle size of the crystallized powder can be controlled by the amount of nucleating agent added, which determines the number of initial nuclei.

[0063] The nucleating agent is not particularly limited as long as it is a water-soluble salt of a metal more noble 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) are particularly noble and have a low tendency to ionize. Therefore, they are particularly effective as nucleating agents. Examples of water-soluble copper salts include, but are not limited to, copper sulfate. Examples of water-soluble palladium salts include, but are not limited to, sodium palladium(II) chloride, ammonium palladium(II) chloride, palladium(II) nitrate, and palladium(II) sulfate. Palladium salts are particularly preferred as nucleating agents. The use of palladium salts makes it possible to further refine the particle size of the crystallized powder (alloy powder).

[0064] The amount of nucleating agent may be adjusted so that the particle size of the final alloy powder is the desired value. However, since it is not reasonable to increase the amount of nucleating agent when attempting to obtain a large-particle-size alloy powder, the amount of nucleating agent relative to the total amount of magnetic metal may be, for example, 0.001 mol ppm or more and 0.1 mol ppm or less, or 0.01 mol ppm or more and 0.05 mol ppm or less. By setting the amount of nucleating agent within this range and performing crystallization using a partially oxidized magnetic metal source in which a portion of the magnetic metal source is oxidized, it is possible to obtain a large-particle-size alloy powder with an average particle size of, for example, 1 μm or more.

[0065] (c) Complexing agent 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.) has the effect of making the reaction uniform in the subsequent crystallization step. That is, the magnetic metal component is dissolved in the reaction solution as magnetic metal ions (Fe 2+ , Ni 2+However, because the reaction solution becomes strongly alkaline due to the addition of a pH adjuster (e.g., NaOH), only a very small amount of magnetic metal ions dissolves in the reaction solution. However, when a complexing agent is present, the magnetic metal components dissolve in large amounts as complex ions (e.g., Fe complex ions, Ni complex ions). The presence of such complex ions increases the reduction reaction rate and suppresses localized uneven distribution of the magnetic metal components, enabling a homogenous reaction system. Complexing agents also have the effect of changing the complex stability balance of multiple magnetic metal ions in the reaction solution. Therefore, the presence of a complexing agent changes the reduction reaction of the magnetic metal, changing the balance between the nucleation rate and the particle growth rate. By using a complexing agent (e.g., hydroxycarboxylic acid) specified in this embodiment, the above-mentioned effects work in combination and the reaction proceeds in a favorable direction, resulting in improved powder properties (particle size, particle size distribution, sphericity, and particle surface properties) of the resulting alloy powder. Furthermore, alloy powders with improved powder properties have excellent packing properties and are suitable as raw materials for powder cores. In this regard, the complexing agent (e.g., hydroxycarboxylic acid) of this embodiment can be said to function as a reduction reaction accelerator, a spheroidization accelerator, and a surface smoothing agent. A suitable complexing agent includes at least one hydroxycarboxylic acid selected from tartaric acid ((CH(OH)COOH)2) and citric acid (C(OH)(CH2COOH)2COOH).

[0066] The amount of complexing agent relative to the total amount of magnetic metal is preferably 5 mol% to 100 mol%, more preferably 10 mol% to 75 mol%, and even more preferably 15 mol% to 50 mol%. When the amount is 5 mol% or more, the complexing agent fully functions as a reduction reaction accelerator, spheroidization accelerator, and surface smoothing agent, resulting in even better powder properties (particle size, particle size distribution, sphericity, particle surface properties) of the alloy powder. Furthermore, when the amount is 100 mol% or less, the amount of complexing agent used can be reduced without significantly affecting the degree of function expression as a complexing agent, leading to reduced production costs.

[0067] (d) reducing agent The reducing agent is hydrazine (N2H4, molecular weight: 32.05). This reducing agent (hydrazine) acts to reduce the magnetic metal ions and complex ions in the reaction solution in the subsequent crystallization process. Hydrazine has the advantage of being a strong reducing agent and not producing by-products in the reaction solution due to the reduction reaction. It is also easy to obtain high-purity hydrazine with few impurities.

[0068] In addition to anhydrous hydrazine, hydrazine hydrate (N2H4·H2O, molecular weight: 50.06), which is a hydrazine hydrate, is known as hydrazine. Either can be used. For example, commercially available industrial grade 60% by mass hydrazine hydrate can be used as hydrazine hydrate.

[0069] The amount of reducing agent required depends largely on the composition of the iron (Fe)-nickel (Ni) alloy powder; the greater the proportion of iron that is difficult to reduce, the greater the amount required. In addition to the composition of the alloy powder, the amount of reducing agent required is also affected by the temperature of the reaction solution, the amount of complexing agent and pH adjuster, and other factors. For example, when the iron content of the alloy powder is 60 mol% or less, the amount of reducing agent relative to the total amount of magnetic metal is preferably 1.8 to 7.0 in molar ratio, more preferably 2.0 to 6.0 in molar ratio, and even more preferably 2.5 to 5.0 in molar ratio. When the iron content of the alloy powder is greater than 60 mol% but less than 75 mol%, the amount of reducing agent relative to the total amount of magnetic metal is preferably 2.5 to 9.0 in molar ratio, more preferably 3.5 to 8.0 in molar ratio. When the iron content of the alloy powder is greater than 75 mol% but less than 95 mol%, the amount of reducing agent relative to the total amount of magnetic metal is preferably 3.5 to 10.0 in molar ratio, more preferably 4.5 to 9.0 in molar ratio. In either case, when the blending amount is equal to or greater than the above-mentioned lower limit, the reduction of the magnetic metal ions and complex ions proceeds sufficiently, and a crystallized powder (alloy powder) can be obtained that is free of unreduced substances such as iron hydroxide. Furthermore, when the blending amount is equal to or less than the above-mentioned upper limit, the amount of the reducing agent (hydrazine) used can be reduced, leading to reduced production costs.

[0070] (e) pH adjuster The pH adjuster is an alkali hydroxide. This pH adjuster (alkali hydroxide) has the effect of strengthening the reduction reaction of hydrazine, which is a reducing agent. In other words, the higher the pH of the reaction solution, the stronger the reducing power of hydrazine. Therefore, using an alkali hydroxide as a pH adjuster promotes the reduction reaction of magnetic metal ions and complex ions in the reaction solution and the resulting precipitation of crystallized powder. The type of alkali hydroxide is not particularly limited. However, in terms of availability and price, it is preferable that the pH adjuster contains at least one selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0071] The amount of pH adjuster (alkali hydroxide) added may be adjusted so that the reducing power of the reducing agent (hydrazine) is sufficiently high. Specifically, the pH of the reaction solution at the reaction temperature is preferably 9.5 or higher, more preferably 10 or higher, and even more preferably 10.5 or higher. Therefore, the amount of alkali hydroxide added may be adjusted so that the pH falls within this range.

[0072] (f) Amine compounds If necessary, the starting material may further contain an amine compound containing two or more primary amino groups (-NH), one primary amino group (-NH) and one or more secondary amino groups (-NH-), or two or more secondary amino groups (-NH-) in the molecule.

[0073] The amine compound has the effect of promoting the reduction reaction in the subsequent crystallization process. In other words, the amine compound functions as a complexing agent, and it acts to bind magnetic metal ions (Fe 2+ , Ni 2+ It has the function of complexing the cations (e.g., Fe complex ions, Ni complex ions, etc.) to form complex ions (e.g., Fe complex ions, Ni complex ions, etc.). It is believed that the presence of complex ions in the reaction solution further accelerates the reduction reaction.

[0074] Amine compounds also have the effect of suppressing the self-decomposition of hydrazine, which serves as a reducing agent. Specifically, if a crystallized powder of a magnetic metal precipitates in the reaction solution, the magnetic metal (Fe, Ni, etc.) may act as a catalyst, causing the hydrazine to decompose. This is called the self-decomposition of hydrazine. This decomposition reaction, as shown in equation (2) below, involves the decomposition of hydrazine (NH) into nitrogen (N) and ammonia (NH). Such self-decomposition is undesirable because it impairs the function of hydrazine as a reducing agent.

[0075] [ka]

[0076] Adding an amine compound to the mixture solution makes it possible to suppress the self-decomposition of hydrazine. The detailed mechanism is unknown. However, it is speculated that this is because excessive contact between the hydrazine in the reaction solution and the crystallized powder is prevented. In other words, among the amino groups contained in the amine compound molecules, the primary amino group (-NH2) and secondary amino group (-NH-) in particular are strongly adsorbed to the surface of the crystallized powder in the reaction solution. It is thought that the amine compound molecules cover and protect the crystallized powder, preventing excessive contact between the hydrazine molecules and the crystallized powder, thereby suppressing the self-decomposition of hydrazine.

[0077] The amine compound is preferably at least one of an alkyleneamine and an alkyleneamine derivative, and the alkyleneamine and / or alkyleneamine derivative preferably has at least the structure represented by the following formula (A), in which the nitrogen atom of the amino group in the molecule is bonded via a carbon chain having two carbon atoms:

[0078] [ka]

[0079] The use of such alkyleneamines or alkyleneamine derivatives as amine compounds can more effectively inhibit the self-decomposition of hydrazine (reducing agent). The reason for this is believed to be that the short carbon chains contained in such alkyleneamines or alkyleneamine derivatives effectively inhibit the contact of hydrazine molecules with the crystallized powder. In contrast, if the nitrogen atom of the amino group is bonded via an excessively long carbon chain, the carbon chain has a large degree of freedom of movement, even if the amino group is adsorbed to the crystallized powder. Therefore, we speculate that the contact between the crystallized powder and hydrazine molecules is not effectively inhibited.

[0080] Specific examples of alkyleneamines having the structure represented by (A) above include one or more selected from the group consisting of ethylenediamine (abbreviation: EDA) (H2NC2H4NH2), diethylenetriamine (abbreviation: DETA) (H2NC2H4NHC2H4NH2), triethylenetetramine (abbreviation: TETA) (H2N(C2H4NH)2C2H4NH2), tetraethylenepentamine (abbreviation: TEPA) (H2N(C2H4NH)3C2H4NH2), pentaethylenehexamine (abbreviation: PEHA) (H2N(C2H4NH)4C2H4NH2), and propylenediamine (also known as 1,2-diaminopropane, 1,2-propanediamine) (abbreviation: PDA) (CH3CH(NH2)CH2NH2). Specific examples of alkyleneamine derivatives having the structure represented by (A) above include tris(2-aminoethyl)amine (abbreviation: TAEA) (N(C2H4NH2)3), N-(2-aminoethyl)ethanolamine (also known as 2-(2-aminoethylamino)ethanol (abbreviation: AEEA) (H2NC2H4NHC2H4OH), N-(2-aminoethyl)propanolamine (also known as 2-(2-aminoethylamino)propanol (abbreviation: AEPA) (H2NC2H4NHC 3H6OH), L(or D, DL)-2,3-diaminopropionic acid (also known as 3-amino-L(or D, DL)-alanine) (abbreviated as DAPA) (H2NCH2CH(NH)COOH), ethylenediamine-N,N'-diacetic acid (also known as ethylene-N,N'-diglycine) (abbreviated as EDDA) (HOOCCH2NHC2H4NHCH2COOH), 1,2-cyclohexanediamine (also known as 1,2-diaminocyclohexane) (abbreviated as CHDA) (H2NC6H 10 NH2). These alkyleneamines and alkyleneamine derivatives are water-soluble, and among them, ethylenediamine and diethylenetriamine are preferred because they have a relatively strong effect of inhibiting the self-decomposition of hydrazine, and are easily available and inexpensive.

[0081] The structural formulas of ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), propylenediamine (PDA), tris(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.

[0082] [ka]

[0083] [ka]

[0084] [ka]

[0085] [ka]

[0086] [ka]

[0087] [ka]

[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] [ka]

[0092] [ka]

[0093] [ka]

[0094] The amount of the amine compound relative to the total amount of magnetic metal is preferably 0.00 mol% to 5.00 mol%, more preferably 0.01 mol% to 5.00 mol%, and even more preferably 0.03 mol% to 5.00 mol%. The amount of the amine compound may be 0.00 mol%, i.e., no amine compound is required. However, by using an amount of 0.01 mol% or more, the amine compound's effects of inhibiting the self-decomposition of hydrazine and promoting the reduction reaction can be fully exerted. Furthermore, by using an amount of 5.00 mol% or less, the amine compound's function as a complexing agent can be adequately exerted. This allows for improved powder properties (particle size, particle size distribution, sphericity, and particle surface properties) of the alloy powder. If the amount of the amine compound exceeds 5.00 mol%, its function as a complexing agent becomes too strong. This may result in abnormal particle growth and deteriorate the powder properties of the alloy powder.

[0095] <Magnetic metal source partial oxidation process> In the magnetic metal source partial oxidation step, the magnetic metal source is subjected to partial oxidation treatment to obtain a partially oxidized magnetic metal source containing a divalent magnetic metal and a trivalent magnetic metal. By performing the magnetic metal source partial oxidation step in combination with other steps, it is possible to obtain an alloy powder having an average particle size exceeding 0.6 μm and a coefficient of variation of 25% or less. In this specification, the term "metal" may refer to an ionized metal (metal ion).

[0096] Partial oxidation of the magnetic metal source allows for the final alloy powder to have a larger particle size. Specifically, partial oxidation produces a partially oxidized magnetic metal source containing trivalent magnetic metals (Fe(III), Ni(III), Co(III)) along with divalent magnetic metals (Fe(II), Ni(II), Co(II)). In the subsequent crystallization process, the partial magnetic metal source increases the potential of the reaction solution containing it. This uniformly suppresses the formation of initial nuclei by the nucleating agent and heterogeneous nucleation on the surfaces of the reaction vessel and the stirring blades throughout the reaction solution, thereby promoting the formation of larger particles. This is because the reduction reaction of the partially oxidized magnetic metal source (reduction of trivalent iron (Fe(III)) to divalent iron (Fe(II))) has a higher potential and proceeds preferentially than the reduction reaction of the magnetic metal source (reduction of divalent magnetic metal sources (Fe(II), Ni(II), Co(II)) to zero-valent magnetic metals (Fe, Ni, Co)).For this reason, it is possible to achieve larger particle sizes, which was not possible with conventional methods that simply reduce the amount of nucleating agent added.

[0097] The partial oxidation treatment in the magnetic metal source partial oxidation step includes a method of directly partially oxidizing a magnetic metal source containing a divalent magnetic metal to obtain a partially oxidized magnetic metal source containing a trivalent magnetic metal. For example, an aeration treatment may be performed in which an oxygen-containing gas is blown into an aqueous solution (metal salt raw solution) in which a magnetic metal source containing a divalent magnetic metal (divalent iron salt, divalent nickel salt, etc.) is dissolved. Alternatively, a trivalent magnetic metal source containing the same magnetic metal may be simply added to the magnetic metal source containing a divalent magnetic metal without directly partially oxidizing the magnetic metal source containing a divalent magnetic metal. For example, an addition treatment may be performed in which an oxidized magnetic metal source containing a trivalent magnetic metal is added to an aqueous solution (metal salt raw solution) in which a magnetic metal source containing a divalent magnetic metal is dissolved. Furthermore, a method of directly partially oxidizing a magnetic source containing a divalent magnetic metal (e.g., aeration treatment) may be combined with a method of adding a trivalent magnetic metal source to a magnetic metal source containing a divalent magnetic metal (e.g., addition treatment). The method of partial oxidation treatment is not limited as long as the final partially oxidized magnetic metal source contains a divalent magnetic metal and a trivalent magnetic metal. In the magnetic metal source partial oxidation step, a partially oxidized magnetic metal source in a partially oxidized state is obtained.

[0098] The magnetic metal source includes a water-soluble iron salt (divalent iron salt) and a water-soluble nickel salt (divalent nickel salt). When the alloy powder is composed of iron and nickel, the magnetic metal source is a divalent iron salt such as ferrous sulfate (FeSO4) and a divalent nickel salt such as nickel sulfate (NiSO4). When the alloy powder is composed of iron, nickel, and cobalt, the magnetic metal source is a divalent iron salt, a divalent nickel salt, and a divalent cobalt salt such as cobalt sulfate (CoSO4).

[0099] When an oxidized magnetic metal source containing a trivalent magnetic metal is added, a water-soluble iron salt (trivalent iron salt) containing trivalent iron (Fe(III)) may be used as the oxidized magnetic metal source. Specifically, when preparing an aqueous solution containing a partially oxidized magnetic metal source (partially oxidized metal salt raw material solution) described below, a trivalent iron salt may be added to a divalent iron salt, a divalent nickel salt, and, if necessary, a divalent cobalt salt. The trivalent iron salt is preferably at least one selected from the group consisting of iron chloride (FeCl), iron sulfate (Fe(SO)), and iron nitrate (Fe(NO)), and particularly preferably at least one selected from the group consisting of iron chloride (FeCl) and iron sulfate (Fe(SO)). By adding such a trivalent iron salt, a partially oxidized magnetic metal source containing trivalent iron (Fe(III)) can be obtained.

[0100] Instead of or in addition to trivalent iron salts, water-soluble nickel salts (trivalent nickel salts) containing trivalent nickel (Ni(III)) or water-soluble cobalt salts (trivalent cobalt salts) containing trivalent cobalt (Co(III)) may be used as the oxidized magnetic metal source. In this case, as shown in the following formulas (3) and (4), in the partial oxidation step and crystallization step, trivalent nickel ions and cobalt ions in the aqueous solution (reaction solution) are converted to divalent nickel ions and cobalt ions, and trivalent iron ions are generated instead. Therefore, the same effect as when using trivalent iron salts can be obtained.

[0101] [ka] [ka]

[0102] The degree of partial oxidation of the partially oxidized magnetic metal source, i.e., the degree to which the magnetic metal source is oxidized, is determined by the amount of water-soluble salts (trivalent magnetic metal salts) of trivalent magnetic metals (Fe(III), Ni(III), Co(III)) added. The optimal amount of trivalent magnetic metal salt added depends greatly on the particle size, composition, and crystallization conditions of the alloy powder to be obtained. It is usually preferable to set the amount of trivalent magnetic metal salt added so that the amount of trivalent magnetic metal ions relative to the total amount of iron ions in the reaction solution is 0.1 mol% or more and 10 mol% or less. Of course, the amount of divalent magnetic metal salt added should be reduced by the amount of trivalent magnetic metal salt added. In other words, the total amount of divalent magnetic metal salt and trivalent magnetic metal salt added can be determined depending on the composition of the final alloy powder to be obtained.

[0103] Furthermore, the method for adding the oxidized magnetic metal source containing a trivalent magnetic metal is not limited. A divalent magnetic metal salt (divalent iron salt, divalent nickel salt, etc.) may be dissolved in water to prepare a metal salt raw solution, and a trivalent magnetic metal salt (trivalent iron salt, trivalent nickel salt, etc.) may be added to this metal salt raw solution and dissolved. Conversely, a trivalent magnetic metal salt may be dissolved in water to prepare a metal salt raw solution, and the divalent magnetic metal salt may be added to this metal salt raw solution and dissolved. Alternatively, a divalent magnetic metal salt and a trivalent magnetic metal salt may be added to water simultaneously and dissolved. The method of addition and mixing is not limited as long as a partially oxidized magnetic metal source containing a divalent magnetic metal and a trivalent magnetic metal is obtained.

[0104] When aeration is used as a partial oxidation process, an oxygen-containing gas is blown into an aqueous solution containing a divalent magnetic metal. By blowing in the oxygen-containing gas, some of the divalent magnetic metal (e.g., Fe(II)) in the aqueous solution is oxidized and converted to a trivalent magnetic metal (e.g., Fe(III)). For example, as shown in Figure 2, aeration is performed by using a gas injection tube with a porous glass tip to blow air bubbles into a metal salt raw solution, causing oxidation. This results in the divalent iron (e.g., Fe(II)) in the metal salt raw solution being preferentially oxidized and converted to trivalent iron (e.g., Fe(III)). As a result, a partially oxidized metal salt raw solution containing a partially oxidized magnetic metal source is obtained.

[0105] The degree of partial oxidation in the partially oxidized magnetic metal source depends greatly on the particle size, composition, and crystallization conditions of the alloy powder to be obtained. As mentioned above, when performing an additive process in which a trivalent magnetic metal salt is added, the degree of partial oxidation can be controlled by adjusting the amount of trivalent metal salt added. On the other hand, when performing an aeration process, the degree of partial oxidation can be controlled by adjusting the degree of aeration (oxygen-containing gas flow rate and treatment time). In either case, the degree of partial oxidation can be estimated from the oxidation-reduction potential (ORP) value of the partially oxidized metal salt raw material solution obtained through the partial oxidation process.

[0106] The redox potential of the partially oxidized metal salt raw solution is higher than that of the metal salt raw solution before the partial oxidation step. However, the redox potential values ​​of the metal salt raw solution and the partially oxidized metal salt raw solution vary greatly depending on the ability of the complexing agent used to form complexes with divalent iron (Fe(II)) ions or trivalent iron (Fe(III)) ions, making it difficult to specify a preferred range. For example, if the redox potential of the metal salt raw solution before the partial oxidation step is a negative value of about -40 mV, the redox potential of the partially oxidized metal salt raw solution after the partial oxidation step can be a positive value of 70 mV or more.

[0107] In the magnetic metal source partial oxidation step, the partial oxidation treatment may be performed on an aqueous solution containing only water and a divalent magnetic metal salt (a magnetic metal source containing a divalent magnetic metal), or on an aqueous solution containing water, a divalent magnetic metal salt, and other components. For example, in the first to third embodiments described below, an aqueous solution containing a divalent magnetic metal source, a nucleating agent, and an oxidizing agent may be subjected to a partial oxidation treatment such as an addition treatment or an aeration treatment. Specifically, the partially oxidized magnetic metal source may be obtained by a partial oxidation treatment selected from an addition treatment in which an oxidized magnetic metal source containing a trivalent magnetic metal is added to a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent, and an aeration treatment in which an oxygen-containing gas is blown into a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal and a nucleating agent.

[0108] <Crystallization process> In the crystallization process, a reduction reaction of the partially oxidized magnetic metal source and a reduction reaction of the magnetic metal source occur in a reaction solution containing a partially oxidized magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, a pH adjuster, and water, and finally, a crystallized powder containing the magnetic metal is crystallized by the reduction reaction. Here, the reduction reaction of the partially oxidized magnetic metal source refers to a reaction in which trivalent iron (Fe(III)) is reduced to divalent iron (Fe(II)). Also, the reduction reaction of the magnetic metal source refers to a reaction in which divalent magnetic metals (Fe(II), Ni(II), Co(II)) are reduced to zero-valent magnetic metals (Fe, Ni, Co).

[0109] The preparation of the reaction solution and the crystallization of the crystallized powder are explained below. In actual production, in most cases, the crystallization reaction begins simultaneously with the preparation of the reaction solution, but there is a possibility that the crystallization reaction may begin, even if only slightly, during the preparation of the reaction solution. The crystallization reaction referred to here refers to the reaction that occurs during the crystallization process. That is, although it mainly refers to the reduction reaction of the magnetic metal source by hydrazine (such as the formula (10) described below), it also includes the reduction reaction of the partially oxidized magnetic metal source by hydrazine (formula (4) described below) and the self-decomposition reaction of hydrazine (formula (2) described above). Therefore, the term crystallization reaction is used in a broader sense than reduction reaction.

[0110] The crystallization process involves preparing a partially oxidized metal salt raw material solution containing at least a partially oxidized magnetic metal source, a nucleating agent, and a complexing agent dissolved in water, a reducing agent solution containing at least a reducing agent dissolved in water, and a pH-adjusted solution containing at least a pH adjuster dissolved in water. At least one of these solutions, including the partially oxidized metal salt raw material solution and the 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 maintaining a predetermined temperature, allowing the crystallization reaction to proceed under these conditions. Conventional heating methods can be used, such as placing the reaction vessel in a water bath or using a steam-jacketed or heater-equipped reaction vessel. The reaction vessel and the stirring blades used to stir the reaction solution must be made of inert materials that minimize nucleation on their surfaces when in contact with the reaction solution, in order to avoid interfering with the function of the nucleating agent. Furthermore, they must have excellent strength and thermal conductivity. To satisfy these requirements, for example, a metal container (such as a Teflon (registered trademark) coated stainless steel container) or stirring blade (such as a Teflon (registered trademark) coated stainless steel stirring blade) coated with a fluororesin (such as PTFE or PFA) is suitable.

[0111] (a) Preparation of reaction solution First, the starting materials, magnetic metal source, nucleating agent, complexing agent, reducing agent, pH adjuster, and optionally an amine compound, are prepared and dissolved in water as needed. The magnetic metal source is partially oxidized in a magnetic metal source partial oxidation step to form a partially oxidized magnetic metal source, and then mixed to prepare a reaction solution. The water used to prepare this reaction solution is preferably highly pure in order to reduce the amount of impurities in the final alloy powder. Examples of highly pure water include pure water with a conductivity of 1 μS / cm or less and ultrapure water with a conductivity of 0.06 μS / cm or less. Among these, inexpensive and readily available pure water is preferred.

[0112] When the starting materials are solids, such as iron salts, nickel salts, cobalt salts, and alkali hydroxides, it is preferable to preliminarily mix and dissolve them in water to form an aqueous solution. The starting materials and water can be mixed by a known method, such as stirring and mixing. The procedure for mixing the starting materials and aqueous solutions is not particularly limited as long as the homogeneity of the reaction solution is not impaired. However, from the viewpoint of ensuring the homogeneity of the reaction solution, it is preferable to prepare aqueous solutions containing each starting material separately in advance, and in the case of a magnetic metal source, to partially oxidize the magnetic metal source in a magnetic metal source partial oxidation step, and then mix the prepared aqueous solutions. It is particularly preferable to prepare the reaction solution according to the first or second embodiment described below.

[0113] In the first embodiment, when preparing a reaction solution in the crystallization step, a partially oxidized metal salt raw material solution containing a partially oxidized magnetic metal source, a nucleating agent, and a complexing agent dissolved in water, a reducing agent solution containing a reducing agent dissolved in water, and a pH adjusting solution containing a pH adjusting agent dissolved in water are prepared, and the partially oxidized metal salt raw material solution and the pH adjusting solution are mixed to form a mixed solution, and the resulting mixed solution is mixed with the reducing agent solution. Figures 3 and 4 show process diagrams illustrating an example of reaction solution preparation and alloy powder production in the first embodiment.

[0114] In the first aspect, three solutions, a partially oxidized metal salt raw material solution, a reducing agent solution, and a pH adjusting solution, are prepared separately. The partially oxidized metal salt raw material solution is prepared by dissolving a partially oxidized magnetic metal source (e.g., water-soluble iron salt, water-soluble nickel salt), a nucleating agent (a water-soluble salt of a metal more noble than nickel), and a complexing agent (e.g., hydroxycarboxylic acid) 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. The partially oxidized metal salt raw material solution and the pH adjusting solution are then mixed to produce a mixed solution. During this process, the magnetic metal salt (e.g., water-soluble iron salt, water-soluble nickel salt) contained in the partially oxidized metal salt raw material solution reacts with the alkali hydroxide contained in the pH adjusting agent to form a hydroxide of the magnetic metal. These hydroxides include iron hydroxide (Fe(OH)2 and a small amount of Fe(OH)3), nickel hydroxide (Ni(OH)2), cobalt hydroxide (Co(OH)2), iron nickel hydroxide ((Fe, Ni)(OH)2 and a small amount of (Fe, Ni)(OH)3), iron nickel cobalt hydroxide ((Fe, Ni, Co)(OH)2 and a small amount of (Fe, Ni, Co)(OH)3), etc. Then, a reducing agent solution is mixed with the resulting mixed solution to form a reaction solution.

[0115] A specific procedure for preparing the reaction solution in the first embodiment is preferably to sequentially add the pH adjusting solution and the reducing agent solution to the partially oxidized metal salt raw material solution and mix them. In the first embodiment, which uses three types of solutions, the partially oxidized metal salt raw material solution, the reducing agent solution, and the pH adjusting solution, the partially oxidized metal salt raw material solution has the largest liquid volume. Therefore, sequentially adding other solutions to the partially oxidized metal salt raw material solution with a larger liquid volume and mixing them can achieve a more uniform mixed state than adding the partially oxidized metal salt raw material solution to the other solutions, and can allow the reduction reaction to proceed uniformly in the reaction solution.

[0116] When an amine compound is added, it can be added to at least one of the partially oxidized metal salt raw material solution, the reducing agent solution, and the pH adjuster solution. Alternatively, the amine compound can be added to a reaction liquid obtained by mixing all of these solutions. Figure 3 shows an embodiment in which an amine compound is added to at least one of the partially oxidized metal salt raw material solution, the reducing agent solution, and the pH adjuster solution. Figure 4 shows an embodiment in which an amine compound is added to a reaction liquid obtained by mixing all of the partially oxidized metal salt raw material solution, the reducing agent solution, and the pH adjuster solution.

[0117] In the first embodiment, a reaction solution is prepared by mixing a reducing agent solution with a mixed solution of a partially oxidized metal salt raw material solution and a pH adjuster. The reduction reaction begins when the reducing agent solution is added. When the reducing agent solution is mixed, the reducing agent (hydrazine) concentration rises sharply locally in the microregion where the reducing agent is added. Furthermore, the mixed solution contains a pH adjuster (alkali hydroxide), and the pH of the mixed solution (reaction solution) remains high in the initial stage of mixing the reducing agent solution with this mixed solution. 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 become locally high, and nucleation due to the nucleating agent and a reduction reaction that produces crystallized powder 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 final stage of mixing the reducing agent solution, the reducing power of the reducing agent is not as strong as in the initial stage, and the nucleation and reduction reaction proceed slowly. Therefore, there will be a difference in the reducing power of the reducing agent between the initial stage and the final stage of mixing the reducing solution.

[0118] If the difference in reducing power between the initial and final stages is large, the uniformity of the nucleation reaction and the reduction reaction may decrease, and the powder properties (particle size, surface smoothness, etc.) of the resulting crystallized powder may vary greatly. Therefore, it is desirable to minimize the difference in reducing power. To achieve this, it is preferable to mix the reducing agent solution as quickly as possible. The time required to mix the reducing agent solution with the mixed solution of the partially oxidized metal salt raw material solution and the pH adjuster (mixing time) is preferably 180 seconds or less, more preferably 120 seconds or less, and even more preferably 60 seconds or less. However, due to limitations of the manufacturing equipment, it may be difficult to shorten the mixing time excessively. The mixing time may be 1 second or more, 3 seconds or more, or 5 seconds or more.

[0119] Furthermore, when preparing a mixed solution by mixing a partially oxidized metal salt raw material solution with a pH adjuster solution, a long mixing time can cause variations in the properties of the magnetic metal hydroxide formed, which can lead to variations in the powder properties of the crystallized powder. Although this effect is not as great as when mixing a reducing agent solution, a shorter mixing time is preferable. The time required to mix the pH adjuster (mixing time) is preferably 180 seconds or less, more preferably 120 seconds or less, and even more preferably 80 seconds or less. The mixing time may be 1 second or more, 3 seconds or more, or 5 seconds or more.

[0120] In order to suppress variations in the powder properties of the crystallized powder, it is also effective to perform agitation and mixing, in which the reducing agent solution and pH adjuster solution are mixed while stirring the solution. Stirring prevents a sudden increase in the concentration of components in the solution, making it possible to suppress variations in the properties of the crystallized powder. Agitation and mixing can be performed using a stirring device such as a stirring blade.

[0121] In the second embodiment, when preparing a reaction solution in the crystallization step, a partially oxidized metal salt raw material solution containing a partially oxidized magnetic metal source, a nucleating agent, and a complexing agent dissolved in water, and a reducing agent solution containing a reducing agent and a pH adjuster dissolved in water are prepared, and then the partially oxidized metal salt raw material solution and the reducing agent solution are mixed. Figures 5 and 6 show process diagrams illustrating an example of the preparation of a reaction solution and the production of an alloy powder in the second embodiment.

[0122] In the second embodiment, two solutions, a partially oxidized metal salt raw material solution and a reducing agent solution, are prepared separately. The partially oxidized metal salt raw material solution is prepared by dissolving a partially oxidized magnetic metal source (such as a water-soluble iron salt or a water-soluble nickel salt), a nucleating agent (a water-soluble salt of a metal more noble than nickel), and a complexing agent (such as a hydroxycarboxylic acid) in water. The reducing agent solution is prepared by dissolving a reducing agent (hydrazine) and a pH adjuster (alkali hydroxide) in water. The metal source raw material solution and the reducing agent solution are then mixed to form a reaction solution. The second embodiment differs from the first embodiment in that the reducing agent solution contains a pH adjuster.

[0123] In the second embodiment, the reaction solution can be prepared in two ways: by adding a reducing agent solution to a partially oxidized metal salt raw material solution and mixing them together, or by adding a partially oxidized metal salt raw material solution to a reducing agent solution and mixing them together. Unlike the first embodiment, the volume of the reducing agent solution, which contains both a reducing agent and a pH adjuster (alkali hydroxide), is the same as the volume of the partially oxidized metal salt raw material solution. Therefore, by adding one to the other and mixing them, a uniform mixture can be achieved, allowing a uniform reduction reaction to occur in the reaction solution.

[0124] However, under crystallization conditions where the blending ratio of the reducing agent or pH adjuster (alkali hydroxide) to the metal salt raw material is high, it is preferable to add the partially oxidized metal salt raw material solution to the reducing agent solution and mix them. This is because, from the viewpoint of ensuring productivity in the crystallization process, it is desirable to maintain the metal salt raw material concentration in the reaction solution at a predetermined level or higher (30 to 40 g / L of metal components). That is, under the above-mentioned crystallization conditions, the liquid volume of the reducing agent solution is significantly greater than the liquid volume of the partially oxidized metal salt raw material solution. Therefore, adding and mixing a partially oxidized metal salt raw material solution with a large liquid volume of the reducing agent solution allows for a more uniform mixture and allows the reduction reaction to proceed uniformly in the reaction solution.

[0125] When an amine compound is added, the amine compound may be added to at least one of the partially oxidized metal salt raw material solution and the reducing agent solution, or the amine compound may be added to a reaction liquid obtained by mixing all of these solutions.

[0126] In the second embodiment, for the same reasons as in the first embodiment, the time required to mix the partially oxidized metal salt solution 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. The mixing time may be 1 second or more, 3 seconds or more, or 5 seconds or more. It is also effective to stir the reducing agent solution when mixing it.

[0127] In the third embodiment, in the crystallization step of the first or second embodiment, an additional raw material liquid is added to and mixed with the reaction solution before the reduction reaction is completed. This enriches the surface of the crystallized powder with nickel and cobalt components. The additional raw material liquid is prepared by dissolving at least one of the water-soluble nickel salt and water-soluble cobalt salt described above in water. A process diagram showing an example of alloy powder production in the third embodiment is shown in Figure 7.

[0128] In the third embodiment, an additional raw material solution is prepared in addition to the solution used to prepare the reaction solution in the first or second embodiment. This additional raw material solution is prepared by dissolving at least one of a water-soluble nickel salt and a water-soluble cobalt salt in water. The additional raw material solution may be added to the reaction solution by a single addition, divided addition, and / or dropwise addition. Although not essential, the addition is preferably performed before the reduction reaction is completed. When the reduction reaction is completely completed, the crystallized particles begin to form aggregates. Adding the additional raw material solution at this time to promote the precipitation of metal components by the reduction reaction may strengthen the bonds between the particles contained in the aggregates.

[0129] Furthermore, the third embodiment has the advantage of being able to reduce the amount of reducing agent used compared to the first and second embodiments. Divalent iron ions (or iron hydroxide (Fe(OH)2)) are less easily reduced than divalent nickel ions (or nickel hydroxide (Ni(OH)2)) and divalent cobalt ions (or cobalt hydroxide (Co(OH)2)). This is because adding an additional raw material liquid containing a nickel component or a cobalt component to the reaction solution can promote the reduction reaction of the iron ions (or iron hydroxide (Fe(OH)2)), which are less easily reduced, towards the end of the crystallization process.

[0130] The amount of magnetic metals (Ni, Co) in the additional raw material solution can be set depending on the degree to which the crystallized powder surface is enriched in nickel and cobalt components. However, considering the uniformity of the overall particle composition, it is preferable that the amount be 5 mol % to 50 mol % of the total amount of magnetic metals (Ni, Co) excluding iron in the alloy powder. When the particle surface becomes rich in nickel and cobalt components, the iron component, which is prone to forming a porous oxide film, decreases. As a result, a dense oxide film is formed, suppressing the amount of oxidation on the particle surface, which not only makes the powder more stable in air but also improves magnetic properties such as saturation magnetic flux density.

[0131] (b) Crystallization of crystallized powder Once the reaction solution is prepared, a reduction reaction occurs in the reaction solution. Specifically, in the presence of a pH adjuster (alkali hydroxide) and a nucleating agent (a salt of a metal more noble than nickel), the partially oxidized magnetic metal source, ions of the magnetic metal source, and complex ions are reduced by a reducing agent (hydrazine), ultimately forming a crystallized powder containing the magnetic metal.

[0132] The reduction reaction in the crystallization process will be explained using reaction equations. Trivalent iron (Fe(III)) is present in the reaction solution due to the magnetic metal source partial oxidation process, and trivalent iron (Fe(III)) is first reduced to divalent iron (Fe(II)) according to the following equation (5). The reduction reactions of divalent iron (Fe(II)), divalent nickel (Ni(II)), and divalent cobalt (Co(II)) are two-electron reactions as shown in the following equations (6) to (8). On the other hand, the reaction of hydrazine (N2H4) as a reducing agent is a four-electron reaction as shown in the following equation (9).

[0133] [ka] [ka] [ka] [ka] [ka]

[0134] Using magnetic metal sulfates (FeSO4, NiSO4, CoSO4) as the magnetic metal source and sodium hydroxide (NaOH) as the pH adjuster, as shown in equation (10) below, the magnetic metal chlorides and sodium hydroxide first undergo a neutralization reaction to produce hydroxides (e.g., (Fe, Ni, Co)(OH)2). For simplicity, this reaction ignores the small amount of partially oxidized magnetic metal source produced during the partial oxidation step. These hydroxides (e.g., (Fe, Ni, Co)(OH)2) are then reduced by a reducing agent (hydrazine) to form a crystallized powder. To reduce 1 mole of magnetic metal (Fe, Ni, Co), 0.5 moles of reducing agent (hydrazine) are required. Furthermore, as shown in equation (9) above, the higher the alkalinity (pH), the stronger the reducing power of hydrazine. Therefore, the sodium hydroxide used as a pH adjuster also has the effect of accelerating the reduction reaction by hydrazine.

[0135] [ka]

[0136] In the reduction reaction of Equation (10) above, the reduction of the ions (or hydroxides) of each magnetic metal (Fe, Ni, Co) element proceeds simultaneously to some extent due to co-reduction. Here, co-reduction refers to the phenomenon in which the reduction reaction of one element occurs concomitantly with the reduction reaction of another element. However, as mentioned above, divalent iron ions (or iron hydroxide (Fe(OH)2)) are less easily reduced than divalent nickel ions (or nickel hydroxide (Ni(OH)2)) and divalent cobalt ions (or cobalt hydroxide (Co(OH)2)). Therefore, at the end of the crystallization reaction, divalent nickel ions (or nickel hydroxide (Ni(OH)2)) and divalent cobalt ions (or cobalt hydroxide (Co(OH)2)) are consumed and disappear in the reduction reaction in the reaction solution, while divalent iron ions (or iron hydroxide (Fe(OH)2)) tend to remain. This tendency is particularly pronounced when the iron content is high (for example, when the iron content of the alloy powder exceeds 60 mol %). When this phenomenon occurs, not only does it take a long time for the crystallization reaction (reduction reaction) to complete, but it also tends to form a gradient structure with a non-uniform composition within the particle. When a gradient structure is formed, the center of the resulting alloy powder particle has a nickel- and cobalt-rich composition, and the composition becomes more iron-rich closer to the particle surface.

[0137] In contrast, in the third embodiment described above, an additional raw material liquid is added to the reaction solution during the crystallization reaction, promoting the reduction reaction of the divalent iron ions (or iron hydroxide (Fe(OH)2)), which are difficult to reduce, towards the end of the crystallization. This makes it possible to improve the time required for the crystallization reaction (reduction reaction), particularly when the iron content is high, and to prevent compositional non-uniformity within the resulting alloy powder particles.

[0138] The temperature of the reaction solution at the start of crystallization of the crystallized powder (reaction initiation temperature) is preferably 40°C to 90°C, more preferably 50°C to 80°C, and even more preferably 60°C to 70°C. Here, the reaction solution at the start of crystallization refers to a reaction solution containing the starting materials and water immediately after preparation. Furthermore, the temperature of the reaction solution maintained during crystallization after the start of crystallization (reaction holding temperature) is preferably 60°C to 99°C, more preferably 70°C to 95°C, and even more preferably 80°C to 90°C. To adjust the reaction initiation temperature within a suitable range, it is desirable to preheat at least one of the multiple solutions used to prepare the reaction solution, such as the partially oxidized metal salt raw material solution and the reducing agent solution. To adjust the reaction holding temperature within a suitable range, it is desirable to continue heating the reaction solution after preparation.

[0139] To achieve more uniform nucleation and obtain a crystallized powder with a sharp particle size distribution, it is preferable to preheat one of the multiple solutions, such as the partially oxidized metal salt raw material solution and the reducing agent solution, (e.g., to 70°C) while preheating the other solution (e.g., keeping it at 25°C), and then adding and mixing them to prepare a reaction solution at a predetermined temperature (e.g., 55°C). In contrast, if both solutions (e.g., the partially oxidized metal salt raw material solution and the reducing agent solution) are preheated (e.g., to 70°C), non-uniform nucleation is likely to occur. In other words, when the two solutions are added and mixed, heat is generated during mixing. Therefore, the mixed solution (reaction solution) becomes locally hot (e.g., about 78°C) at the start of mixing, and nucleation occurs instantaneously. The two solutions are added and mixed while nucleation is occurring, which tends to result in non-uniform nucleation.

[0140] Although it is conceivable to improve uniformity of nucleation by shortening the addition time of the two solutions drastically or by vigorously stirring the two solutions, such methods are not necessarily preferable. In the aforementioned method of preheating only one of the solutions (e.g., to 70°C) and then adding and mixing to prepare a reaction solution, the added and mixed solution (reaction solution) is maintained at a low temperature (e.g., 55°C) and no localized high temperature occurs. Because the timing of nucleation is delayed, nucleation proceeds only after the two solutions are thoroughly mixed. Therefore, uniform nucleation is likely to occur. The above is a more preferable example and does not exclude the case where all of the multiple solutions, such as the partially oxidized metal salt raw material solution and the reducing agent solution, are preheated. The heating of the solutions and their temperatures may be set so that the reaction initiation temperature and reaction holding temperature fall within the aforementioned ranges.

[0141] If the reaction initiation temperature is too low, nucleation becomes more uniform, but the reduction reaction proceeds slowly and the heating time required to reach the reaction holding temperature at which the reduction reaction can be accelerated becomes longer. Similarly, if the reaction holding temperature is too low, the reduction reaction proceeds slowly and the heating time required for crystallization becomes longer. In either case, the cycle time required for the crystallization process becomes longer, resulting in reduced productivity. Furthermore, the self-decomposition of hydrazine progresses, requiring a large amount of hydrazine, resulting in increased production costs. If the reaction initiation temperature or reaction holding temperature is high, the reduction reaction is accelerated, shortening the cycle time required for the crystallization process and tending to result in highly crystalline crystals. However, at the same time, the self-decomposition rate of hydrazine increases. Therefore, if the reaction initiation temperature or reaction holding temperature is too high, not only will nucleation become nonuniform, but excessively high crystallization may also deteriorate the smoothness of the particle surface, resulting in increased surface irregularities. Furthermore, if the crystallization is not terminated at the appropriate time, hydrazine may self-decompose during the reduction reaction and be preferentially consumed. Therefore, a large amount of hydrazine is required, which raises concerns about increased production costs. By setting the reaction initiation temperature and reaction holding temperature within the aforementioned preferred ranges, it becomes possible to produce high-performance alloy powders inexpensively while maintaining high productivity.

[0142] <Recovery process> In the recovery step, the crystallized powder is recovered from the reaction solution obtained in the crystallization step. The recovery of the crystallized powder may be carried out by a known method. For example, a method of solid-liquid separation of the crystallized powder from the reaction solution using a separation device such as a Denver filter, a filter press, a centrifuge, or a decanter may be used. The crystallized powder may also be washed during or after solid-liquid separation. The washing may be carried out using a washing liquid. High-purity pure water with a conductivity of 1 μS / cm or less may be used as the washing liquid. The washed crystallized powder may be dried. The drying may be carried out using a general-purpose drying device such as an atmospheric dryer, a hot air dryer, an inert gas atmosphere dryer, a reducing gas atmosphere dryer, or a vacuum dryer at a temperature of 40°C to 150°C, preferably 50°C to 120°C. However, from the viewpoint of preventing deterioration of magnetic properties due to excessive oxidation of the crystallized powder during the drying process, it is preferable to use an inert gas atmosphere dryer, a reducing gas atmosphere dryer, or a vacuum dryer rather than an atmospheric air dryer or a hot air dryer using the atmosphere.

[0143] Crystallized powders dried in a sealed container of an inert gas atmosphere dryer, a reducing gas atmosphere dryer, or a vacuum dryer have a relatively low oxidation level on the particle surface. Therefore, if the powder is immediately removed from the dryer into the atmosphere after drying, the particle surface will rapidly oxidize, and the heat generated by the oxidation reaction may cause the powder to burn. This phenomenon is particularly likely to occur with fine crystallized powders (e.g., particle size 0.1 μm or less). Therefore, it is desirable to perform a gradual oxidation treatment on the surface of crystallized powders that are not significantly oxidized after drying, by forming a thin oxide film on the surface of the particles to stabilize them. Specifically, the gradual oxidation treatment procedure involves lowering the temperature of the crystallized powder that has been heated and dried in a sealed container of an inert gas atmosphere dryer, a reducing gas atmosphere dryer, or a vacuum dryer to room temperature to approximately 40°C, and then supplying a gas with a low oxygen concentration (e.g., nitrogen gas or argon gas containing 0.1 to 2% oxygen by volume) into the sealed container to slowly oxidize the particle surface of the crystallized powder gradually and form a thin oxide film. The crystallized powder that has been subjected to the gradual oxidation treatment is less susceptible to oxidation and is stable, so there is no risk of it generating heat or burning even if it is left in the air.

[0144] The crystallized powder (iron-nickel alloy powder) obtained in the crystallization step can be subjected to additional steps such as a high-temperature heat treatment step, an insulating coating step, and a crushing step, which will be described below.

[0145] <High-temperature heat treatment process> If necessary, a high-temperature heat treatment step may be performed after or during the recovery step, in which the crystallized powder is subjected to high-temperature heat treatment. If high-temperature heat treatment is performed after the recovery step, it may be performed after a drying process. If high-temperature heat treatment is performed during the recovery step, it may be performed instead of a drying process. The high-temperature heat treatment may be performed in an inert atmosphere, a reducing atmosphere, or a vacuum atmosphere at a temperature above 150°C and below 400°C, preferably between 200°C and 350°C. The high-temperature heat treatment promotes the diffusion of heterogeneous elements such as Fe and Ni within the iron (Fe)-nickel (Ni)-based alloy particles, thereby improving the compositional uniformity within the particles or adjusting magnetic properties such as magnetic force. If necessary, the aforementioned gradual oxidation treatment may be performed after the high-temperature heat treatment.

[0146] <Insulation coating process> If necessary, an insulating coating process may be performed after the recovery process. In this process, the crystallized powder obtained through the recovery process is subjected to an insulating coating treatment to form an insulating coating layer made of a highly resistive metal oxide on the particle surfaces of the crystallized powder, thereby improving the insulation between particles. Similar to the increase in loss due to eddy currents in coarse agglomerated particles, in a powder core obtained by compression molding an iron-nickel alloy powder, contact between alloy particles may increase eddy currents flowing between particles. By forming an insulating coating layer, it is possible to suppress the generation of eddy currents due to contact between alloy particles.

[0147] In the insulation coating process, the crystallized powder is dispersed in a mixed solvent containing water and an organic solvent, and a metal alkoxide is added to and mixed with the mixed solvent to prepare a slurry. The metal alkoxide is hydrolyzed and subjected to dehydration polycondensation in the resulting slurry to form an insulation coating layer on the particle surfaces of the crystallized powder. The cake-like crystallized powder with the insulation coating layer is then solid-liquid separated from the slurry, and the separated crystallized powder is dried to recover the crystallized powder with the insulation coating layer made of a high-resistance metal oxide. If necessary, the separated and dried crystallized powder may be subjected to a heat treatment. Because the hydrolysis reaction of metal alkoxide in a mixed solvent containing water and an organic solvent proceeds very slowly on its own, a small amount of a hydrolysis catalyst, such as an acid or base (alkali), is generally added to promote the reaction. In this embodiment, the addition of a base catalyst (alkali catalyst) is also preferred.

[0148] As the high-resistance metal oxide, those containing at least one selected from the group consisting of silicon dioxide (SiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), and titanium dioxide (TiO2) as a main component are preferred. In particular, those containing silicon dioxide (SiO2) as a main component are particularly preferred because they are inexpensive and have excellent insulating properties.

[0149] To obtain such metal oxides, metal alkoxides that can ultimately form metal oxides through hydrolysis and dehydration polycondensation are selected as the metal alkoxides used in the slurry for the insulating coating process. Specifically, those primarily composed of at least one selected from the group consisting of silicon alkoxides (alkyl silicates), aluminum alkoxides (alkyl aluminates), zirconium alkoxides (alkyl zirconates), and titanium alkoxides (alkyl titanates) are preferred, with silicon alkoxides (alkyl silicates) being particularly preferred. If necessary, a small amount of a component (e.g., boron alkoxide) that will be incorporated into the insulating coating layer through hydrolysis or other processes when the metal alkoxide is hydrolyzed and dehydration polycondensed to form the insulating coating layer may be added to the metal alkoxide.

[0150] Specific examples of silicon alkoxides (alkyl silicates) include tetramethoxysilane (also known as tetramethyl orthosilicate, silicon tetramethoxide) (abbreviation: TMOS) (Si(OCH3)4), tetraethoxysilane (also known as tetraethyl orthosilicate, silicon tetraethoxide) (abbreviation: TEOS) (Si(OC2H5)4), tetrapropoxysilane (also known as tetrapropyl orthosilicate, silicon tetrapropoxide) (Si(OC3H7)4), tetrabutoxysilane (also known as tetrabutyl orthosilicate, and silicon tetrapropoxide) (abbreviation: TEOS) (Si(OC2H7)4), Examples of the alkyl silicate include one or more selected from the group consisting of tetraethoxysilane (Si(OC4H9)4), tetraethoxysilane (Si(OC4H9)4), and the like. Alternatively, the alkoxide may be one in which the alkoxyl group of the above alkoxide is substituted with another alkoxyl group, or a commercially available alkyl silicate as a silicate oligomer that has already been polymerized to a tetramer or pentamer (for example, Erusilicate 40 (trade name), Erusilicate 48 (trade name), Methylsilicate 51 (trade name), etc., manufactured by Colcoat Co., Ltd.). Among these, tetraethoxysilane (TEOS) is preferred because it is less harmful, easily available, and inexpensive.

[0151] Specific examples of aluminum alkoxides (alkylaluminates) include one or more selected from aluminum trimethoxide (Al(OCH3)3), aluminum triethoxide (Al(OC2H5)3), aluminum triisopropoxide (Al(O-iso-C3H7)3), aluminum tri-n-butoxide (Al(On-C4H9)3), aluminum tri-sec-butoxide (Al(Os-C4H9)3), aluminum tri-tert-butoxide (Al(Ot-C4H9)3), and the like.

[0152] Specific examples of zirconium alkoxides (alkyl zirconates) include one or more selected from zirconium tetraethoxide (Zr(OC2H5)4), zirconium tetra-n-propoxide (Zr(On-C3H7)4), zirconium tetraisopropoxide (Zr(O-iso-C3H7)4), zirconium tetra-n-butoxide (Zr(On-C4H9)4), zirconium tetra-tert-butoxide (Zr(Ot-C4H9)4), zirconium tetraisobutoxide (Zr(O-iso-C4H9)4), and the like.

[0153] Specific examples of titanium alkoxides (alkyl titanates) include one or more selected from titanium tetramethoxide (Ti(OCH3)4), titanium tetraethoxide (Ti(OC2H5)4), titanium tetraisopropoxide (Ti(O-iso-C3H7)4), titanium tetraisobutoxide (Ti(O-iso-C4H9)4), titanium tetra-n-butoxide (Ti(On-C4H9)4), titanium tetra-tert-butoxide (Ti(Ot-C4H9)4), titanium tetra-sec-butoxide (Ti(Os-C4H9)4), and the like.

[0154] Other metal alkoxides include one or more selected from boron alkoxides (alkyl boronates), such as boron trimethoxide (B(OCH3)3), boron triethoxide (B(OC2H5)3), and boron tri-tert-butoxide (B(Ot-C4H9)3).

[0155] The organic solvent used in the slurry for the insulating coating process is preferably one that can be mixed with water and dries easily. That is, it is preferable that it has high compatibility with water and a relatively low boiling point (approximately 60°C to 90°C). In addition, it is preferable that it is highly safe, easy to handle, readily available, and inexpensive. Considering these factors, denatured alcohol, whose main component is ethyl alcohol, is preferable.

[0156] The hydrolysis reaction and dehydration condensation polymerization reaction of metal alkoxide in the insulating coating process will be explained using reaction formulas when silicon alkoxide (Si(OR)4, R: alkyl group) is used as the metal alkoxide.

[0157] In the hydrolysis reaction, in the presence of a base catalyst (alkali catalyst) such as ammonia (NH3), silicon atoms (Si) react with nucleophilic hydroxy ions (OH) as shown in the following formula (11). - Upon direct attack of the silicon atom, one of the alkoxy groups (-OR) is first hydrolyzed. This reduces the charge on the silicon atom, and a nucleophilic hydroxyl ion (OH - ) becomes increasingly susceptible to attack. As a result, all four alkoxy groups (-OR) are hydrolyzed and converted into silanol groups (Si-OH), as shown in formula (12) below. In this way, when a base catalyst (alkali catalyst) is used, all alkoxy groups (-OR) in the hydrolyzed silicon alkoxide molecules are hydrolyzed, resulting in a state in the slurry where completely hydrolyzed molecules (Si(OH)4) and completely unhydrolyzed molecules (Si(OR)4) coexist.

[0158] [ka] [ka]

[0159] On the other hand, in the presence of an acid catalyst such as nitric acid (HNO3), protons (H + The protonation of the alkoxy group (-OR) by silanol makes the silicon atom (Si) more susceptible to attack by water (H2O). Therefore, first one of the alkoxy groups (-OR) is hydrolyzed and turns into a silanol group (Si-OH). I will not go into details here, but when this happens, the charge on the silicon atom and the charge on the oxygen atom (O) decrease, so the proton (H +becomes less susceptible to attack by ( ). Therefore, the hydrolysis does not occur immediately, and the alkoxy group (-OR) of other unhydrolyzed silicon alkoxide molecules becomes more susceptible to hydrolysis. Thus, when an acid catalyst is used, the hydrolysis of the alkoxy group (-OR) proceeds evenly in all silicon alkoxide molecules as shown in the following formula (14). Therefore, there are no completely hydrolyzed molecules or unhydrolyzed molecules at all, and a state where evenly hydrolyzed molecules (Si(OH) X (OR) 4-X ; 0 < x < 4) exist occurs in the slurry.

[0160] [Chemical formula] [Chemical formula]

[0161] The dehydration condensation polymerization reaction is a reaction in which the formation of a siloxane bond (Si-O-Si) proceeds by the dehydration condensation polymerization reaction of silanol groups (Si-OH) between hydrolyzed silicon alkoxide molecules as shown in the following formula (15). When this dehydration condensation polymerization reaction proceeds to completion, silicon dioxide (SiO2) is generated as shown in the following formula (16).

[0162] [Chemical formula] [Chemical formula]<​​​​​​​​​​​

[0165] If the silicon alkoxide hydrolyzes, the above formula (17) holds regardless of whether it is a base catalyst (alkali catalyst) or an acid catalyst. However, the form of silicon dioxide (SiO2) generated by the progress of dehydration polycondensation is greatly affected by the hydrolysis state by the above-mentioned hydrolysis catalyst.

[0166] For silicon alkoxide molecules (Si(OH) X (OR) 4-X ; 0 < x < 4) hydrolyzed evenly by an acid catalyst, unhydrolyzed alkoxy groups (-OR) exist within the molecule. Therefore, when the dehydration polycondensation of silanol groups (Si-OH) between molecules proceeds, a hydrolyzed polymer polymerized into a linear or branched linear form is generated. When this occurs in the slurry during the insulation coating process, a hydrolyzed polymer of silicon alkoxide is generated on the particle surface composed of iron oxide (FeO) or nickel oxide (NiO) of the crystallized powder. However, since these are polymerized into a linear or branched linear form, it is difficult to densify them in the solvent of the slurry, and therefore it is not easy to form a dense insulation coating layer.

[0167] On the other hand, when a base catalyst (alkali catalyst) is used, completely hydrolyzed molecules (Si(OH)4) are present. Therefore, as the dehydration condensation polymerization of intermolecular silanol groups (Si-OH) progresses, dense hydrolysis polymers are formed in agglomerates. Therefore, even in the slurry solvent used in the insulation coating process, dense hydrolysis polymers of silicon alkoxide are formed on the particle surfaces of iron oxide (FeO) and nickel oxide (NiO) crystallized powder, resulting in the formation of a dense insulation coating layer. Note that when a base catalyst (alkali catalyst) is used, completely unhydrolyzed molecules (Si(OR)4) may be present. However, as described below, completely unhydrolyzed molecules and particulate silicon alkoxide hydrolysis polymers (silica sol) with very small molecular weights that remain in the slurry and are not consumed in the insulation coating of the crystallized powder during the insulation coating process are removed from the system along with the filtrate during the filtration and washing process. Therefore, they do not affect the insulation coating process.

[0168] For the above reasons, it is preferable to use a base catalyst (alkaline catalyst) rather than an acid catalyst for the hydrolysis of metal alkoxides in insulating coating treatments. In this respect, the preferred catalyst differs from that used when coating is performed by applying a solvent to a substrate. In other words, when used as a binder in a coating liquid that is applied to a substrate and the solvent is dried, rather than coating the particle surface in a solvent, linear or branched linear polymers produced by the acid catalyst described above are preferred.

[0169] Regarding the timing of hydrolysis of metal alkoxide in the insulating coating process, we have previously described a mode in which the crystallized powder and metal alkoxide are homogeneously mixed in a slurry and then hydrolyzed using a hydrolysis catalyst. However, this embodiment is not limited to this timing of hydrolysis. For example, it is possible to prepare a metal oxide sol (silica sol in the case of silicon alkoxide) by pre-hydrolyzing the metal alkoxide using a hydrolysis catalyst, and then mix this metal oxide sol with the crystallized powder to form a slurry. If the average molecular weight of the metal oxide sol is small, approximately 500 to 5,000, the timing of hydrolysis of the metal alkoxide has almost no effect. This is because the surfaces of the crystallized powder particles are covered with small metal oxide sol particles due to bonding between iron oxide (FeO) or nickel oxide (NiO) on the crystallized powder surface and the hydrolysis groups of the metal oxide sol (silanol groups (Si-OH) in the case of silicon alkoxide), and then polymerization of the sol particles occurs.

[0170] In order to uniformly form an insulating coating layer during the insulating coating process, it is preferable to subject the slurry containing the crystallized powder, water, organic solvent, metal alkoxide, and hydrolysis catalyst to agitation using a stirrer's impeller or a dedicated roller for stirring by rotating the container. The treatment time and temperature of the insulating coating process vary depending on the type of metal alkoxide used and the required thickness of the insulating coating layer. For example, metal methoxides generally have a higher hydrolysis rate than metal ethoxides. Therefore, the treatment time and temperature can be appropriately set and are not particularly limited. For example, the treatment time can be several hours to a week, and the treatment temperature can be room temperature to 60°C. At a high treatment temperature of around 40°C to 60°C, the treatment speed can be increased to several times that at room temperature.

[0171] The thickness of the insulating coating layer is not limited to a specific value, as it depends on the required level of insulation. A thickness of 1 nm to 30 nm is preferred, 2 nm to 25 nm is more preferred, and 3 nm to 20 nm is even more preferred. If the thickness is excessively thick, the insulating properties will saturate, while the content of soft magnetic components will decrease, resulting in deterioration of magnetic properties such as saturation magnetic flux density. If the thickness is within the above range, the insulating function of the insulating coating layer can be exhibited without significantly deteriorating magnetic properties and other characteristics.

[0172] The crystallized powder, which forms an insulating coating layer by hydrolysis and dehydration polycondensation of the metal alkoxide, is separated from the slurry as a cake-like crystallized powder using a known separation device such as a Denver filter, filter press, centrifuge, or decanter. If necessary, the crystallized powder may be washed during solid-liquid separation. For washing, water, an organic solvent such as a relatively low-boiling alcohol, or a mixture thereof may be used as a washing liquid. As mentioned above, if there is metal alkoxide or its hydrolyzed polymer (unhydrolyzed molecules or metal oxide sol with a small molecular weight) remaining in the slurry without being consumed by the insulating coating, these are removed from the system together with the filtrate and washing waste liquid during solid-liquid separation and washing.

[0173] The cake-like crystallized powder obtained after solid-liquid separation is dried and, if necessary, heated to recover the crystallized powder on which an insulating coating layer made of a highly resistive metal oxide is formed. There are no particular restrictions on the drying method, as long as excessive oxidation during drying can be suppressed. However, drying equipment such as an inert gas atmosphere dryer, a reducing gas atmosphere dryer, or a vacuum dryer is preferred, and the drying can be carried out at a temperature of 40°C to 150°C. The higher the drying temperature, the more the dehydration condensation polymerization of the metal alkoxide hydrolysis polymer that constitutes the insulating coating layer progresses, resulting in a harder, denser, and more insulating metal oxide. For further improvement, a heat treatment above 150°C to 450°C in an inert gas atmosphere, a reducing gas atmosphere, or a vacuum may be performed. Since the insulating coating layer has already been formed, a gradual oxidation treatment is generally not required after drying.

[0174] The insulating properties of crystallized powder (alloy powder) are significantly improved by the insulating coating treatment. For example, the compact resistivity (applied pressure: 64 MPa) of iron-nickel alloy powder without the insulating coating treatment is usually 0.1 Ω·cm or less. However, when the iron-nickel alloy powder is subjected to the insulating coating treatment to form an insulating coating layer made of silicon dioxide (SiO2) with a thickness of about 0.015 μm (15 nm), the compact resistivity increases to 10 6 It is improved to more than Ω·cm.

[0175] <Crushing process> If necessary, a crushing process may be performed on the crystallized powder recovered in the recovery process, or on the crystallized powder before drying during recovery, or on the crystallized powder that has been insulated. When the alloy particles constituting the crystallized powder precipitate in the crystallization process, they may come into contact with each other and fuse to form agglomerates. Therefore, the crystallized powder obtained through the crystallization process may contain coarse agglomerates. As mentioned above, coarse agglomerates may have eddy currents flowing through them, increasing Joule heat loss or impairing the powder's packing ability. A crushing process can be performed after or during the recovery process to crush the agglomerates. Crushing can be performed using dry crushing methods such as spiral jet crushing and counter jet mill crushing, wet crushing methods such as high-pressure fluid impingement crushing, or other commonly used crushing methods. Dry crushing can be directly applied to the dry crystallized powder recovered in the recovery process. Furthermore, if the dry crystallized powder after the recovery process is made into a slurry, wet crushing can be applied to it. Furthermore, if the slurry crystallized powder obtained during the recovery process is not yet dried, wet crushing can be applied as is. These crushing methods utilize the collision energy of the particles to break down agglomerated particles. The collisions also smooth the surface during the crushing process, which also helps improve the packing ability of the powder.

[0176] In this manner, the iron (Fe)-nickel (Ni) alloy powder of this embodiment can be produced. This production method is characterized by the use of a specific nucleating agent (a water-soluble salt of a metal nobler than nickel) that has a particle size control effect and a specific complexing agent (e.g., hydroxycarboxylic acid) that has the effects of promoting reduction reactions, spheroidization, and surface smoothing. The method partially oxidizes a magnetic metal source containing divalent iron (Fe(II)), divalent nickel (Ni(II)), and, optionally, divalent cobalt (Co(II)). This not only provides the resulting alloy powder with excellent magnetic and powder properties, but also allows for a large particle size. Specifically, the average particle size of the produced alloy powder can be increased to over 0.6 μm or even 1 μm or greater. Furthermore, the resulting alloy powder has a narrow particle size distribution and a uniform particle size. Furthermore, the alloy powder is spherical and has a smooth surface. Therefore, it has excellent packing properties. Furthermore, although not limited thereto, the use of an amine compound that functions as a hydrazine self-decomposition inhibitor and a reduction reaction accelerator can reduce the amount of hydrazine used, which leads to a reduction in production costs and enables the powder properties of the alloy powder to be improved.

[0177] To the best of the inventors' knowledge, there is no known method for easily and inexpensively producing iron-nickel alloy powder having such a narrow particle size distribution and large particle size. For example, Patent Document 4 discloses a method for producing iron-nickel alloy powder by a wet process, but this method does not employ a magnetic metal source partial oxidation step in which a portion of the magnetic metal source is oxidized, and therefore the alloy powder produced has an average particle size of up to approximately 0.6 μm. In fact, the examples in Patent Document 4 only produce fine alloy powder with an average particle size of 0.27 μm to 0.48 μm.

[0178] <<2. Iron-nickel alloy powder>> The iron (Fe)-nickel (Ni) alloy powder of this embodiment has a narrow particle size distribution. Furthermore, the average particle size of this alloy powder can be increased to more than 0.6 μm, or even 1 μm or more. Furthermore, it is spherical, has high surface smoothness, and has excellent packing properties. Such alloy powder of this embodiment can be used in various electronic components such as noise filters, choke coils, inductors, and radio wave absorbers, and is particularly suitable as a material for dust cores for choke coils and inductors.

[0179] The alloy powder can be made larger in particle size by applying a magnetic metal source partial oxidation process in which a portion of the magnetic metal source is oxidized. Specifically, the average particle size can be made larger than 0.6 μm. The average particle size is preferably greater than 0.6 μm and not more than 3 μm, and more preferably 0.7 μm or more and not more than 3 μm.

[0180] 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 index of particle size variation, and the smaller the coefficient of variation, the narrower the particle size distribution. By keeping the coefficient of variation small, the number of coarse particles and excessively fine particles with large surface oxidation is reduced, making it possible to prevent an increase in eddy current loss while maintaining excellent magnetic properties. Furthermore, a small coefficient of variation is desirable, but from a practical standpoint, it may be 1% or more. The coefficient of variation (CV value) is calculated by determining the average particle size and standard deviation in the number particle size distribution of the alloy powder and using these according to the following formula (1).

[0181]

number

[0182] 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. Increasing the saturation magnetic flux density of the alloy powder can improve the magnetic properties (magnetic flux density) of the powder core. The coercive force 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. Reducing the coercive force of the alloy powder can prevent an increase in hysteresis loss. The alloy powder of this embodiment has a large average particle size of more than 0.6 μm and a small coefficient of variation of 25% or less, so the content of fine alloy particles that tend to deteriorate the coercive force is extremely small, and such magnetic properties can be obtained.

[0183] The alloy powder may contain cobalt (Co) as a magnetic metal if necessary. That is, the alloy powder may be an iron-nickel alloy powder containing only iron and nickel, or an iron-nickel-cobalt alloy powder containing iron, nickel, and cobalt. Iron, nickel, and cobalt are all ferromagnetic magnetic metals. Therefore, iron-nickel alloy powder and iron-nickel-cobalt alloy powder have high saturation magnetic flux density and excellent magnetic properties.

[0184] The proportions of iron (Fe), nickel (Ni), and cobalt (Co) contained in the alloy powder are not particularly limited. For example, the iron (Fe) content of the alloy powder may be 10 mol% to 95 mol%, the nickel (Ni) content may be 5 mol% to 90 mol%, and the cobalt (Co) content may be 0 mol% to 40 mol%. The iron content may be 25 mol% to 90 mol%, or 40 mol% to 80 mol%. The nickel content may be 10 mol% to 75 mol%, or 20 mol% to 60 mol%. The cobalt content may be 5 mol% to 20 mol%, provided that the total content of iron, nickel, and cobalt is 100 mol% or less.

[0185] Preferably, the saturation magnetic flux density of the alloy powder is 1 T (tesla) or more, and the coercive force is 2000 A / m or less. Increasing the saturation magnetic flux density of the alloy powder can improve the magnetic properties (magnetic flux density) of the dust core. Furthermore, reducing the coercive force of the alloy powder can prevent an increase in hysteresis loss. The saturation magnetic flux density is more preferably 1.2 T or more, even more preferably 1.5 T or more, particularly preferably 1.8 T or more, and most preferably 2.0 T or more. The coercive force is more preferably 1600 A / m or less, even more preferably 1200 A / m or less, and particularly preferably 800 A / m or less.

[0186] The alloy powder may have an insulating coating layer made of a metal oxide provided on the surface of the particles that make up the alloy powder. The provision of the insulating coating layer improves the insulation between the particles that make up the alloy powder. Similar to the increase in loss due to eddy currents in coarse agglomerated particles, in a powder core obtained by compression molding an iron-nickel alloy powder, contact between alloy particles can increase eddy currents that flow between particles. The provision of the insulating coating layer makes it possible to suppress the generation of eddy currents due to contact between alloy particles.

[0187] As the high-resistance metal oxide, those containing at least one selected from the group consisting of silicon dioxide (SiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), and titanium dioxide (TiO2) as a main component are preferred. In particular, those containing silicon dioxide (SiO2) as a main component are particularly preferred because they are inexpensive and have excellent insulating properties.

[0188] The thickness of the insulating coating layer is not limited to a specific value, as it depends on the required level of insulation. A thickness of 1 nm to 30 nm is preferred, with 2 nm to 25 nm being more preferred, and 3 nm to 20 nm being even more preferred. If the thickness is too high, the insulating properties will saturate, while the content of soft magnetic components will decrease, resulting in a deterioration of magnetic properties such as saturation magnetic flux density. If the thickness is within the above range, the insulating function of the insulating coating layer can be exhibited without significantly deteriorating magnetic properties and other characteristics.

[0189] The alloy powder of this embodiment may be used in any manner as long as it satisfies the above-mentioned requirements. The alloy powder may be used alone or in a mixture with other inorganic and / or organic materials. For example, a compact containing only the alloy powder may be produced. Alternatively, the alloy powder may be mixed with ferrite powder to produce a metal-ferrite composite material. In this case, the high saturation magnetic flux density of the alloy powder and the high electrical resistance of the ferrite can be utilized in a complementary manner. Alternatively, a metal-organic resin composite material may be produced by mixing and kneading the alloy powder with an organic resin. By using this composite material, a composite with excellent magnetic properties, high shape freedom, and high dimensional accuracy can be obtained.

[0190] Preferably, the alloy powder is applied to a green compact or a sheet. This green compact or sheet contains the above-mentioned alloy powder. The green compact is produced by subjecting the alloy powder or a mixture of the alloy powder and other components to pressure molding, such as press molding. The other components may include inorganic or organic materials other than the alloy powder, or additives such as lubricants. The green compact after pressure molding may also be heat-treated to remove strain imparted during molding. The sheet can be produced by adding a solvent and, if necessary, an additive such as a binder to the alloy powder to form a paste, and then forming or coating the resulting paste onto a substrate.

[0191] The alloy powder of this embodiment has excellent magnetic properties and is therefore suitable for magnetic devices. Examples of such magnetic devices include inductors, reactors, choke coils, noise filters, transformers, rotating machines, generators, and radio wave absorbers. The inductors, reactors, choke coils, noise filters, transformers, rotating machines, generators, and radio wave absorbers include the above-mentioned compacted powder and / or sheet. The magnetic device may also be a chip component such as a chip inductor.

[0192] FIG. 8 shows an example of an inductor (toroidal coil) made from a powder compact containing alloy powder. The inductor (10) is composed of a toroidal powder compact core (12) and a coil (14) wound around the powder compact core (12). Input / output terminals (16a, 16b) are provided at both ends of the coil (14). The powder compact core (12) can be fabricated by press-molding alloy powder and, if necessary, additives such as lubricants. The coil (14) can be fabricated by winding a conductor around the powder compact core (12). To prevent electrical continuity between the powder compact core (12) and the coil (14), it is desirable to fabricate the coil (14) using a coated conductor or to interpose an insulating sheet between the powder compact core (12) and the coil (14).

[0193] An example of applying a powder compact to a chip inductor is shown in Figure 9. The chip inductor (20) is composed of a powder compact core (22) and a coil (24) embedded in the powder compact core (22). The chip inductor (20) can be produced by first preparing the coil (24) and then pressurizing and molding the coil (24) together with alloy powder.

[0194] An example in which a powder compact is applied to a reactor is shown in Fig. 10. The reactor (30) includes a powder compact core (32), a first coil (34) provided so as to surround one end of the powder compact core (32), a second coil (36) provided so as to surround the other end of the powder compact core (32), and a connecting portion (38) that electrically connects the first coil (32) and the second coil (34).

[0195] FIG. 11 shows an example in which the powder compact is applied to the stator of a rotating machine (motor) or generator. In the figure, the direction of magnetic flux during operation is indicated by arrows. The stator (40) has a powder compact core (42) and windings (44). The windings (44) are provided inside the powder compact core (42) and are arranged to wrap around each of the multiple protrusions of the core (42).

[0196] An example in which the powder compact is applied to the rotor of a rotating machine (motor) or generator is shown in Figure 12. The rotor 50 has a powder compact core 52, windings 54, and an output shaft 56. The windings 54 are provided on the outside of the powder compact core 52 so as to surround each of a plurality of protrusions on the core 52. The output shaft 56 is fixed to the center of the powder compact core 52. [Example]

[0197] The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to the following examples.

[0198] (1) Preparation of iron-nickel alloy powder (iron-nickel-cobalt alloy powder) [Example 1] In Example 1, an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 70 mol % of iron (Fe), 10 mol % of nickel (Ni), and 20 mol % of cobalt (Co) was produced according to the procedure shown in Fig. 6. In Example 1, when preparing the reaction solution, a partially oxidized metal salt raw material solution at room temperature was added to and mixed with a reducing solution heated using a water bath.

[0199] <Preparation process> Ferrous sulfate heptahydrate (FeSO4·7H2O, molecular weight: 278.05, reagent manufactured by Wako Pure Chemical Industries, Ltd.) was prepared as a water-soluble iron salt of divalent iron (Fe(II)), nickel sulfate hexahydrate (NiSO4·6H2O, molecular weight: 262.85, reagent manufactured by Wako Pure Chemical Industries, Ltd.) was prepared as a water-soluble nickel salt of divalent nickel (Ni(II)), and cobalt sulfate heptahydrate (CoSO4·7H2O, molecular weight: 281.103, reagent manufactured by Wako Pure Chemical Industries, Ltd.) was prepared as a water-soluble cobalt salt of divalent cobalt (Co(II)). The following reagents were prepared: ammonium palladium(II) chloride (also known as ammonium tetrachloropalladate(II)) ((NH4)2PdCl4, molecular weight: 284.31, Wako Pure Chemical Industries, Ltd.), trisodium citrate dihydrate (Na3(C3H5O(COO)3)·2H2O, molecular weight: 294.1, Wako Pure Chemical Industries, Ltd.), commercial industrial grade 60% by mass hydrazine hydrate (Otsuka-MGC Chemical Co., Ltd.), reducing agent; and sodium hydroxide (NaOH, molecular weight: 40.0, Wako Pure Chemical Industries, Ltd.), pH adjuster. The 60% by mass hydrazine hydrate was prepared by diluting hydrazine hydrate (N2H4·H2O, molecular weight: 50.06) 1.67 times with pure water. Furthermore, ethylenediamine (EDA; H2NC2H4NH2, molecular weight: 60.1, reagent manufactured by Wako Pure Chemical Industries, Ltd.) was prepared as an amine compound.

[0200] <Magnetic metal source partial oxidation process> (a) Preparation of metal salt raw solution 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. Palladium (Pd) was weighed out to a molar ratio of 0.02 ppm by mass (0.01 ppm by mole) relative to the total amount of magnetic metals (Fe, Ni, and Co) in the resulting metal salt raw material solution. Trisodium citrate was also weighed out to a molar ratio of 0.290 (29.0 mol%) relative to the total amount of magnetic metals (Fe, Ni, and Co). Specifically, a metal salt raw material solution was prepared by dissolving 686.0 g of ferrous sulfate heptahydrate, 92.6 g of nickel sulfate hexahydrate, 198.1 g of cobalt sulfate heptahydrate, 10.7 μg of palladium (II) ammonium chloride, and 300.6 g of trisodium citrate dihydrate in 1835 mL of pure water. The oxidation-reduction potential (ORP vs. SHE) of this metal salt raw material solution was -40 mV.

[0201] (b) Partial oxidation of magnetic metal source (preparation of partially oxidized metal salt raw material solution) The resulting metal salt raw solution was subjected to aeration to obtain a partially oxidized metal salt raw solution. Specifically, a gas injection tube equipped with a porous sintered glass body with pores of 5 to 15 μm at its tip was used, and air bubbles were injected from this gas injection tube into the metal salt raw solution to oxidize a portion of the magnetic metal source (Fe(II)) to Fe(III)). The aeration treatment was carried out under the conditions of an air supply rate of 240 mL / min for 11 minutes. The aeration treatment increased the oxidation-reduction potential (ORP vs. SHE) of the solution from -40 mV to 78 mV.

[0202] <Crystallization process> (c) Preparation of reducing agent solution A reducing agent solution containing sodium hydroxide (pH adjuster), hydrazine (reducing agent), and water was prepared. At this time, the hydrazine was weighed out so that the molar ratio of the amount of hydrazine to the total amount of magnetic metals (Fe, Ni, and Co) in the reaction solution prepared in the subsequent crystallization step would be 1.94. The sodium hydroxide was also weighed out so that the molar ratio of the amount of sodium hydroxide to the total amount of magnetic metals (Fe, Ni, and Co) would be 7.07. Specifically, 996 g of sodium hydroxide was dissolved in 2440 mL of pure water to prepare a sodium hydroxide solution, and 571 g of 60 mass% hydrazine hydrate was added to and mixed with this sodium hydroxide solution to prepare a reducing agent solution.

[0203] (d) Preparation of amine compound solution An amine compound solution containing ethylenediamine (amine compound) and water was prepared. At this time, the ethylenediamine was weighed so that the molar ratio of the ethylenediamine to the total amount of magnetic metals (Fe, Ni, and Co) in the reaction solution prepared in the subsequent crystallization step would be a very small amount, 0.02 (2.0 mol%). Specifically, 4.24 g of ethylenediamine was dissolved in 72 mL of pure water to prepare the amine compound solution.

[0204] (e) Preparation of reaction solution and precipitation of crystallized powder The prepared partially oxidized metal salt raw material solution was placed in a Teflon®-coated stainless steel vessel (reaction vessel) equipped with a stirring blade placed in a water bath and heated with stirring to a liquid temperature of 85°C. The partially oxidized metal salt raw material solution, which had a liquid temperature of 25°C, was then added to the reducing agent solution heated in the water bath and mixed for 10 seconds, yielding a reaction liquid with a liquid temperature of 69°C. The concentration of magnetic metals (Fe, Ni, and Co) in the reaction liquid was 35.0 g / L. This initiated the reduction reaction (crystallization reaction) (reaction initiation temperature: 69°C). The temperature of the reaction liquid continued to rise by heating in the water bath after the reaction began, and the liquid temperature was maintained at approximately 85°C for 45 minutes after the start of the reaction (reaction maintenance temperature: 85°C). The color of the reaction liquid was dark green immediately after the start of the reaction (preparation of the reaction liquid), but changed to dark gray after a few minutes. The reason why the color tone turned dark green immediately after the start of the reaction is thought to be because the reaction according to formula (10) above progressed and a coprecipitate of iron hydroxide (Fe(OH)2 and a small amount of Fe(OH)3), nickel hydroxide (Ni(OH)2), and cobalt hydroxide (Co(OH)2) was formed in the reaction solution. Furthermore, the reason why the color tone turned dark gray a few minutes after the start of the reaction is thought to be because nucleation occurred due to the action of the nucleating agent (palladium salt).

[0205] The amine compound solution was added dropwise to the reaction solution over a 10-minute period, from 3 to 13 minutes after the start of the reaction, to allow the reduction reaction to proceed. This resulted in the precipitation of iron-nickel-cobalt crystallized powder in the reaction solution. The reaction solution was black at this stage, but the supernatant liquid became transparent within 60 minutes of the start of the reaction. It is believed that the reduction reaction of the above formula (10) was completed, and all of the iron, nickel, and cobalt components in the reaction solution were reduced to metallic iron, metallic nickel, and metallic cobalt. After the reaction was complete, the reaction solution was a slurry containing iron-nickel-cobalt crystallized powder. The temperature change in the reaction tank during the crystallization step in Example 1 is shown in Figure 13.

[0206] <Recovery process> The slurry-like reaction solution obtained in the crystallization process was subjected to filtration, washing, and solid-liquid separation to recover a cake-like iron-nickel-cobalt 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 reached 10 μS / cm or less. The recovered cake-like crystallized powder was dried in a vacuum dryer set at 50°C. The dried crystallized powder was then cooled to 35°C in a vacuum, after which nitrogen gas containing 1.0% by volume of oxygen was supplied to the crystallized powder for gradual oxidation. In this way, an iron-nickel-cobalt alloy powder was obtained. The obtained alloy powder consisted of spherical particles with a smooth surface. The particle size distribution was sharp, and the average particle size was 0.77 μm.

[0207] [Example 2] In Example 2, the aeration treatment conditions in the magnetic metal source partial oxidation step were changed to an air supply rate of 240 mL / min for 15 minutes. The oxidation-reduction potential (ORP vs. SHE) of the resulting partially oxidized metal salt raw material solution was 88 mV. Otherwise, the preparation of the reaction solution and the precipitation of the crystallized powder were carried out in the same manner as in Example 1, producing an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 70 mol% iron (Fe), 10 mol% nickel (Ni), and 20 mol% cobalt (Co). The concentration of the magnetic metals (Fe, Ni, and Co) in the reaction solution was 35.0 g / L. The resulting alloy powder consisted of spherical particles with smooth surfaces. The particle size distribution was sharp, and the average particle size was 0.94 μm.

[0208] [Example 3] In Example 3, the aeration treatment conditions in the magnetic metal source partial oxidation step were changed to an air supply rate of 240 mL / min for 28 minutes. The oxidation-reduction potential (ORP vs. SHE) of the resulting partially oxidized metal salt raw material solution was 99 mV. Otherwise, the preparation of the reaction solution and the precipitation of the crystallized powder were carried out in the same manner as in Example 1, producing an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 70 mol% iron (Fe), 10 mol% nickel (Ni), and 20 mol% cobalt (Co). The concentration of the magnetic metals (Fe, Ni, and Co) in the reaction solution was 35.0 g / L. The resulting alloy powder consisted of spherical particles with smooth surfaces. The particle size distribution was sharp, and the average particle size was 1.31 μm.

[0209] [Example 4] In Example 4, the crystallized powder obtained in Example 1 was subjected to an insulating coating treatment to produce an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) coated with silicon dioxide (SiO2), an insulating metal oxide, containing 70 mol% of iron (Fe), 10 mol% of nickel (Ni), and 20 mol% of cobalt (Co). The insulating coating treatment was carried out as follows.

[0210] <Insulation coating process> 50.0 g of the crystallized powder (alloy powder) obtained in the recovery step of Example 1 was placed in a sealed polypropylene container, and 7.0 g of pure water and 50.0 g of ethyl alcohol (C2H5OH, molecular weight: 46.07, reagent manufactured by Wako Pure Chemical Industries, Ltd.) were added to disperse the crystallized powder (alloy powder) in a mixed solvent of water and ethyl alcohol. After that, 14.7 g of tetraethoxysilane (also known as tetraethyl orthosilicate, tetraethyl silicate) (abbreviation: TEOS) (Si(OC2H5)4, molecular weight: 208.33, reagent manufactured by Wako Pure Chemical Industries, Ltd.) as a silicon alkoxide was added and mixed thoroughly, and 3.6 g of 1 mass % ammonia water was added with stirring to serve as a base catalyst (alkali catalyst) for hydrolysis of the silicon alkoxide to form a uniform slurry. The 1% by mass ammonia water was prepared by diluting 28-30% by mass ammonia water (NH3, molecular weight: 17.03, manufactured by Wako Pure Chemical Industries, Ltd.) with pure water. The crystallized powder (alloy powder), water, ethyl alcohol, tetraethoxysilane, and 1% by mass ammonia water were all used at room temperature, and all addition and mixing were also performed at room temperature.

[0211] The slurry containing the crystallized powder (alloy powder), water, ethyl alcohol, tetraethoxysilane, and ammonia was kept at 40°C for two days in a rotating polypropylene sealed container. While stirring the slurry, hydrolysis and dehydration condensation polymerization of tetraethoxysilane proceeded, forming an insulating coating layer primarily composed of tetraethoxysilane hydrolysis polymer (composed almost entirely of silicon dioxide (SiO2) but containing a small amount of silanol groups (Si-OH)) on the surface of the crystallized powder (alloy powder). The slurry was then filtered, washed, and subjected to solid-liquid separation to recover the cake-like crystallized powder (alloy powder). The filtering and washing were performed first with ethanol containing 50% pure water, and then with ethanol. The remaining tetraethoxysilane hydrolysis polymer in the slurry that was not consumed in the insulating coating on the surface of the crystallized powder (alloy powder) particles is a very small molecular weight particle (silica sol) and is removed as filtrate during the filtering and washing process; therefore, it does not remain in the recovered cake-like crystallized powder (alloy powder).

[0212] The recovered cake-like crystallized powder (alloy powder) was dried in a vacuum dryer at 50°C and then heated in a vacuum at 150°C for 2 hours. This heat treatment caused the hydrolysis polymer of tetraethoxysilane that constituted the insulating coating layer to undergo further dehydration condensation polymerization, resulting in a harder and denser silicon dioxide (SiO2), further improving the insulating properties of the insulating coating layer. This insulating coating treatment resulted in iron-nickel alloy powder with a highly resistive insulating coating layer made of silicon dioxide (SiO2) formed on the particle surface. The resulting alloy powder consisted of spherical particles with a smooth surface. The particle size distribution was sharp, with an average particle size of 0.80 μm, and the thickness of the insulating coating layer was estimated to be approximately 0.015 μm (approximately 15 nm). Furthermore, the insulating coating treatment increased the green resistivity (applied pressure: 64 MPa) from 0.002 Ω·cm before the insulating coating treatment to exceed the measurement range (>10 7 The resistance increased significantly to Ω·cm.

[0213] [Comparative Example 1] In Comparative Example 1, the magnetic metal source partial oxidation step was not performed. That is, when preparing the reaction solution in the crystallization step, the metal salt raw material solution (oxidation-reduction potential: -40 mV) obtained in Example 1 was used instead of the partially oxidized metal salt raw material solution. Otherwise, the reaction solution was prepared and the crystallized powder was precipitated in the same manner as in Example 1, producing an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 70 mol% iron (Fe), 10 mol% nickel (Ni), and 20 mol% cobalt (Co). The concentration of the magnetic metals (Fe, Ni, and Co) in the reaction solution was 35.0 g / L. The obtained alloy powder was composed of spherical particles with smooth surfaces. The particle size distribution was sharp, and the average particle size was 0.37 μm.

[0214] Comparative Example 2 In Comparative Example 2, a metal salt raw solution was prepared by reducing the amount of palladium (Pd) used as a nucleating agent to 1 / 10 of that in Example 1. Specifically, the amount of Pd relative to the total amount of magnetic metals (Fe, Ni, and Co) was changed from 0.02 mass ppm (0.01 mol ppm) to 0.002 mass ppm (0.001 mol ppm). The oxidation-reduction potential (ORP vs. SHE) of the obtained metal salt raw solution was −42 mV. In addition, a magnetic metal partial oxidation step was not performed. That is, when preparing a reaction solution in the crystallization step, a metal salt raw solution was used instead of a partially oxidized metal salt raw solution. Otherwise, the reaction solution was prepared and the crystallized powder was precipitated in the same manner as in Example 1, to produce an iron-nickel alloy powder (iron-nickel-cobalt alloy powder) containing 70 mol% iron (Fe), 10 mol% nickel (Ni), and 20 mol% cobalt (Co). The concentration of magnetic metals (Fe, Ni, and Co) in the reaction solution was 35.0 g / L. The obtained alloy powder consisted of spherical particles with smooth surfaces. The particle size distribution was worse than that of each example and Comparative Example 1 (CV value: 15.9%), and the average particle size was 0.31 μm.

[0215] The manufacturing conditions for the alloy powders of Examples 1 to 4 and Comparative Examples 1 and 2 are summarized in Table 1 below.

[0216] [Table 1]

[0217] (2) Evaluation of iron-nickel alloy powder In Examples 1 to 4 and Comparative Examples 1 and 2, the oxidation-reduction potential of the partially oxidized metal salt raw material solution was measured, and the various properties of the obtained iron-nickel alloy powder were evaluated as follows.

[0218] <Measurement of the oxidation-reduction potential of partially oxidized metal salt raw material solution> The oxidation-reduction potential (ORP) of the partially oxidized metal salt raw material solution was measured using a portable ORP meter (MM-41DP (main unit) / MM4-ORP (probe) manufactured by DKK-TOA Corporation) as the potential value (mV) relative to a standard hydrogen electrode (SHE, or NHE) as the reference electrode. <Composition analysis> X-ray diffraction (XRD) measurements were carried out using an X-ray diffractometer, and the presence or absence of alloy powder generation was confirmed from the obtained XRD data.

[0219] <Analysis of metal impurities> The impurity content was analyzed. The oxygen content was measured by the inert gas fusion method using an oxygen analyzer (LECO Corporation, TC436), and the carbon and sulfur contents were measured by the combustion method using a carbon-sulfur analyzer (LECO Corporation, CS600). The chlorine content was measured using an X-ray fluorescence analyzer (Spectris, Magix), and the silicon and sodium contents were measured using an ICP emission spectrometer (Agilent Technologies, 5100).

[0220] <Particle size (average particle size, coefficient of variation)> The alloy powder was observed with a scanning electron microscope (SEM; JEOL Ltd., JSM-7100F) (magnification: 5000-80000 times). The observed images (SEM images) were analyzed, and the number-averaged average particle size and standard deviation of the particle size were calculated from the results. Furthermore, the coefficient of variation (CV value) was calculated according to the following formula (1), and the particle size (average particle size, coefficient of variation) of the alloy powder was determined.

[0221]

number

[0222] <Compressed powder resistivity> The compact resistivity of the alloy powder was measured using a powder resistivity measurement system (Mitsubishi Chemical Analytech, MCP-PD51) to evaluate the conductivity (insulation). Specifically, approximately 4 g of alloy powder was filled into the cylindrical sample chamber of the system, and a pressure of 64 MPa was applied using the press attached to the system to determine the compact resistivity (unit: Ω·cm).

[0223] <Magnetic properties (saturation magnetic flux density, coercive force)> The saturation magnetic flux density and coercive force of the alloy powder were evaluated. The saturation magnetic flux density (Bs) (T: Tesla) was calculated from the BH curve (magnetic hysteresis curve) obtained by measurement using a vibrating sample magnetometer (VSM). The coercive force (Hc) was measured using an automatic coercive force meter (Tohoku Steel Corporation, K-HC1000).

[0224] (3) Evaluation results The evaluation results obtained for Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in Table 2 below. SEM images of the alloy powders obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Figs. 14 to 19, respectively.

[0225] In all of Examples 1 to 3 and Comparative Example 1, the amount of palladium (Pd) as a nucleating agent in the reaction solution was 0.02 mass ppm (0.01 mol ppm) relative to the total amount of magnetic metals (Fe, Ni, and Co), and the reaction initiation temperature in the crystallization step was set to 69°C and the reaction holding temperature was set to 85°C, and iron-nickel-cobalt alloy powder was produced.

[0226] In Examples 1 to 3, which used a partially oxidized metal salt raw material solution in which the magnetic metal source was partially oxidized by the magnetic metal source partial oxidation step, the obtained alloy powders had large average particle sizes of 0.77 to 1.31 μm, small CV values, and sharp particle size distributions. Furthermore, the alloy powders were spherical and had smooth surfaces.

[0227] On the other hand, in Comparative Example 1, which used a metal salt raw material solution that had not undergone a magnetic metal source partial oxidation process, the average particle size of the obtained alloy powder was 0.37 μm, which was small compared to Examples 1 to 3, and it was difficult to increase the particle size.

[0228] In Comparative Example 2, which did not undergo the magnetic metal source partial oxidation step as in Comparative Example 1 and used a metal salt raw material solution in which the amount of palladium (Pd) as a nucleating agent was 1 / 10 of that in Comparative Example 1 (reduced from 0.02 ppm by mass (0.01 mol ppm) to 0.002 ppm by mass (0.001 mol ppm) relative to the total amount of magnetic metals (Fe, Ni, and Co)), despite the reduced amount of nucleating agent, the resulting alloy powder had an average particle size of 0.31 μm, which was smaller than or equal to that in Comparative Example 1, and the particle size distribution was worse than in the other Examples and Comparative Example 1 (CV value: 15.9%). This is thought to be because reducing the amount of nucleating agent too much not only did not lead to an increase in particle size, but also caused the particle size control by the nucleating agent to become ineffective (initial nuclei formed on the reaction vessel wall surface and the stirring blade surface became dominant), adversely affecting the particle size distribution.

[0229] In Example 4, large-particle crystallized powder obtained as a dry powder through the crystallization and recovery processes was subjected to an insulating coating process to produce an iron-nickel alloy powder in which the particle surfaces were coated with highly resistive silicon dioxide (SiO2). This alloy powder has significantly improved interparticle insulation (significantly increased green resistivity), and is therefore expected to reduce eddy current loss between particles.

[0230] [Table 2]

[0231] From the above results, it can be seen that this embodiment provides large particle size iron-nickel alloy powder with excellent powder properties and magnetic properties, and a method for producing the same.

Claims

1. An iron (Fe)-nickel (Ni)-based alloy powder containing at least iron (Fe) and nickel (Ni) as magnetic metals, the alloy powder having an average particle size of more than 0.6 μm and a coefficient of variation (CV value) of 25% or less, which is calculated from the average particle size and standard deviation in a number particle size distribution according to the following formula (1): [Equation 1]

2. The alloy powder according to claim 1 , further comprising cobalt (Co) as a magnetic metal.

3. 3. The alloy powder according to claim 1, wherein the amount of iron (Fe) is 10 mol% or more and 95 mol% or less, the amount of nickel (Ni) is 5 mol% or more and 90 mol% or less, and the amount of cobalt (Co) is 0 mol% or more and 40 mol% or less.

4. 3. The alloy powder according to claim 1, which has a saturation magnetic flux density of 1 T (tesla) or more and a coercive force of 2000 A / m or less.

5. The alloy powder according to claim 1 or 2, further comprising an insulating coating layer made of a metal oxide provided on the surface of each particle constituting the alloy powder.

6. A green compact or sheet comprising the alloy powder according to claim 1 or 2.

7. An inductor, reactor, choke coil, noise filter, transformer, rotating machine, generator, or radio wave absorber comprising the powder compact and / or sheet according to claim 6.

8. A method for producing an iron (Fe)-nickel (Ni) based alloy powder containing at least iron (Fe) and nickel (Ni) as magnetic metals, the method comprising the following steps: a magnetic metal source partial oxidation step of obtaining a partially oxidized magnetic metal source containing a divalent magnetic metal and a trivalent magnetic metal by partial oxidation treatment of the magnetic metal source containing the magnetic metal; a crystallization step in which a crystallized powder containing the magnetic metal is crystallized by a reduction reaction in a reaction solution containing the partially oxidized magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, a pH adjuster, and water; and A recovery step of recovering the crystallized powder from the reaction solution, the magnetic metal source comprises a water-soluble iron salt and a water-soluble nickel salt; the nucleating agent is a water-soluble salt of a metal more noble 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 (N ２ H ４ ) and The method wherein the pH adjuster is an alkali hydroxide.

9. 9. The method according to claim 8, wherein the partial oxidation treatment is an addition treatment of adding an oxidized magnetic metal source containing a trivalent magnetic metal to a metal salt raw material solution in which a magnetic metal source containing a divalent magnetic metal is dissolved, or an aeration treatment of blowing an oxygen-containing gas into a metal salt raw material solution in which a magnetic metal source containing a divalent magnetic metal is dissolved.

10. The water-soluble iron salt is ferrous chloride (FeCl ２ ), ferrous sulfate (FeSO ４ ), and ferrous nitrate (Fe(NO ３ ) ２ 10. The method according to claim 8, wherein the at least one selected from the group consisting of:

11. The water-soluble nickel salt is nickel chloride (NiCl ２ ), nickel sulfate (NiSO ４ ), and nickel nitrate (Ni(NO ３ ) ２ 10. The method according to claim 8, wherein the at least one selected from the group consisting of:

12. The magnetic metal further comprises cobalt (Co), 10. The method of claim 8 or 9, wherein the magnetic metal source further comprises a water-soluble cobalt salt.

13. The water-soluble cobalt salt is cobalt chloride (CoCl ２ ), cobalt sulfate (CoSO ４ ), and cobalt nitrate (Co(NO ３ ) ２ 13. The method according to claim 12, wherein the at least one selected from the group consisting of:

14. The method according to claim 8 or 9, wherein the nucleating agent is at least one selected from the group consisting of copper salts, palladium salts, and platinum salts.

15. The complexing agent is tartaric acid ((CH(OH)COOH) ２ ) and citric acid (C(OH)(CH ２ COOH) ２ 10. The method according to claim 8, wherein the hydroxycarboxylic acid is at least one selected from the group consisting of hydroxycarboxylic acids (C1H-COOH).

16. The method according to claim 8 or 9, wherein the pH adjuster is at least one selected from sodium hydroxide (NaOH) and potassium hydroxide (KOH).

17. The reaction solution contains two or more primary amino groups (-NH ２ ), one primary amino group (—NH ２ 10. The method of claim 8 or 9, further comprising an amine compound containing one or more secondary amino groups (—NH—) and one or more secondary amino groups (—NH—) in the molecule.

18. 18. The method of claim 17, wherein the amine compound is at least one of an alkyleneamine and an alkyleneamine derivative.

19. The method according to claim 18, wherein the alkyleneamine and / or alkyleneamine derivative has at least a structure represented by the following (A) in which nitrogen atoms of amino groups in the molecule are bonded via a carbon chain having two carbon atoms: 【Chemistry 1】

20. The amine compound is ethylenediamine (H ２ NC ２ H ４ NH ２ ), diethylenetriamine (H ２ NC ２ H ４ NHC ２ H ４ NH ２ ), triethylenetetramine (H ２ N (C ２ H ４ NH) ２ C ２ H ４ NH ２ ), tetraethylenepentamine (H ２ N (C ２ H ４ NH) ３ C ２ H ４ NH ２ ), pentaethylenehexamine (H ２ N (C ２ H ４ NH) ４ C ２ H ４ NH ２ ), and propylenediamine (CH ３ CH(NH ２ ) CH ２ NH ２ ), and / or tris(2-aminoethyl)amine (N(C ２ H ４ NH ２ ) ３ ), N-(2-aminoethyl)ethanolamine (H ２ NC ２ H ４ NHC ２ H ４ OH), N-(2-aminoethyl)propanolamine (H ２ NC ２ H ４ NHC ３ H ６ OH), 2,3-diaminopropionic acid (H ２ NCH ２ CH(NH)COOH), ethylenediamine-N,N'-diacetic acid (HOOCCH ２ NHC ２ H ４ NHCH ２ COOH), and 1,2-cyclohexanediamine (H ２ NC ６ H10NH ２ 18. The method of claim 17, wherein the alkyleneamine derivative is at least one selected from the group consisting of:

21. 18. The method according to claim 17, wherein the amount of the amine compound to be blended is 0.01 mol % or more and 5.00 mol % or less relative to the total amount of the magnetic metal.

22. 10. The method according to claim 8 or 9, wherein in the crystallization step, a partially oxidized metal salt raw material solution containing a partially oxidized magnetic metal source, a nucleating agent, and a complexing agent dissolved in water, a reducing agent solution containing a reducing agent dissolved in water, and a pH adjusting solution containing a pH adjusting agent dissolved in water are each prepared, the partially oxidized metal salt raw material solution and the pH adjusting solution are mixed to form a mixed solution, and the mixed solution and the reducing agent solution are mixed to prepare a reaction solution.

23. 23. The method according to claim 22, wherein the partially oxidized magnetic metal source is obtained by at least one partial oxidation treatment selected from the group consisting of an addition treatment of adding an oxidized magnetic metal source containing a trivalent magnetic metal to a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent, and an aeration treatment of blowing an oxygen-containing gas into a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent.

24. The method according to claim 22, wherein, when preparing the reaction solution, the pH adjusting solution and the reducing agent solution are added to and mixed with the partially oxidized metal salt raw material solution in that order.

25. The method according to claim 22, wherein the time required for mixing the mixed solution and the reducing agent solution is 1 second or more and 180 seconds or less.

26. The method according to claim 22, wherein an amine compound is blended into at least one of the partially oxidized metal salt raw material solution, the reducing agent solution, the pH adjusting solution, and the reaction solution.

27. 10. The method according to claim 8 or 9, wherein in the crystallization step, a partially oxidized metal salt raw material solution containing a partially oxidized magnetic metal source, a nucleating agent, and a complexing agent dissolved in water, and a reducing agent solution containing a reducing agent and a pH adjuster dissolved in water are prepared, and the partially oxidized metal salt raw material solution and the reducing agent solution are mixed to prepare a reaction solution.

28. 28. The method according to claim 27, wherein the partially oxidized magnetic metal source is obtained by at least one partial oxidation treatment selected from the group consisting of an addition treatment of adding an oxidized magnetic metal source containing a trivalent magnetic metal to a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent, and an aeration treatment of blowing an oxygen-containing gas into a metal salt raw material solution containing a magnetic metal source containing a divalent magnetic metal, a nucleating agent, and a complexing agent.

29. 28. The method according to claim 27, wherein, when preparing the reaction solution, the reducing agent solution is added to the partially oxidized metal salt raw material solution and mixed, or conversely, the partially oxidized metal salt raw material solution is added to the reducing agent solution and mixed.

30. 28. The method according to claim 27, wherein the time required for mixing the partially oxidized metal salt raw material solution and the reducing agent solution is 1 second or more and 180 seconds or less.

31. The method according to claim 27, wherein an amine compound is blended into at least one of the partially oxidized metal salt raw material solution, the reducing agent solution, and the reaction solution.

32. 10. The method according to claim 8, wherein in the crystallization step, an additional raw material solution obtained by dissolving at least one of the water-soluble nickel salt and the water-soluble cobalt salt in water is further added to the reaction solution and mixed before completion of the reduction reaction.

33. 10. The method according to claim 8 or 9, wherein the temperature of the reaction solution at the start of crystallization of the crystallized powder (reaction initiation temperature) is 40°C or higher and 90°C or lower, and the temperature of the reaction solution maintained during crystallization after the start of crystallization (reaction maintenance temperature) is 60°C or higher and 99°C or lower.

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