Manufacturing method for L10 type FeNi ordered alloy

Abstract

To provide a FeNi superlattice capable of reducing manufacturing costs by improving nitridation efficiency, and a manufacturing method thereof.SOLUTION: An L10 type FeNi ordered alloy has a regular structure of L10 type, and contains sulfur, the sulfur content is 0.01% by mass or more, and the sulfur content is 10% by mass or less. Further, a method for manufacturing an L10-type FeNi ordered alloy having an L10-type ordered structure includes a step of nitriding an S-containing FeNi alloy to obtain a nitride containing Fe and Ni.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an L10-type FeNi (iron-nickel) ordered alloy having an L10-type regular structure (hereinafter also referred to as an FeNi superlattice). )of

Background Art

[0002] FeNi superlattices are expected as magnet materials having high heat resistance and magnetic device materials such as magnetic recording. For example, Patent Document 1 discloses a method for manufacturing a high-quality FeNi superlattice. In the manufacturing method shown here, a high-quality FeNi superlattice is manufactured by using a nitridation and denitridation method in which an FeNi alloy is nitrided by nitridation treatment to obtain a nitride and then nitrogen is removed from the nitride by denitridation treatment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] To achieve the above objective, the invention described in claim 1 provides a method for producing an L10 type FeNi ordered alloy, which involves nitriding a sulfur-containing FeNi alloy to obtain sulfur-containing Fe and Ni nitrides, The aforementioned This includes forming a sulfur-containing L10 type FeNi ordered alloy by performing a denitrification treatment on the nitride.

[0010] In this way, the FeNi alloy containing sulfur is subjected to nitriding treatment. This makes it possible to obtain high nitriding efficiency.

[0011] The reference numerals in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described later. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing the lattice structure of an L10 type FeNi ordered structure. [Figure 2] This is a schematic diagram showing the lattice structure of FeNiN. [Figure 3] This is a flowchart showing the synthesis process of the FeNi superlattice according to the first embodiment. [Figure 4] This is a flowchart showing the synthesis process of the FeNi superlattice according to the second embodiment. [Figure 5] This chart shows the differences in manufacturing conditions for FeNi superlattices, the formation rate of FeNiN, and the ammonia efficiency for each example and comparative example. [Figure 6] This figure shows the measurement results of the powder X-ray diffraction (XRD) patterns for Comparative Example 2 and Example 3. [Figure 7] This figure shows the results of cross-sectional TEM observation and compositional imaging using a transmission electron microscope (TEM). [Figure 8] It is a figure showing the results of cross-sectional TEM observation and compositional image observation using TEM. [Figure 9] It is a chart showing the differences in the manufacturing conditions of the FeNi superlattice, the formation rate of FeNiN, the ammonia efficiency, etc. for each of the examples and comparative examples. [Figure 10] It is a chart showing the differences in the manufacturing conditions of the FeNi superlattice, the formation rate of FeNiN, the ammonia efficiency, etc. for each of the examples and comparative examples. [Figure 11] It is a figure showing the magnetic properties of FeNi superlattice magnetic powder obtained using FeNiN of Comparative Example 2, Example 3, and Example 7. [Figure 12] It is a figure showing the X-ray absorption near-edge structure (XANES) for each of the FeNi superlattice magnetic powders of Example 3 and Example 4.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are an example for embodying the technical idea of the present invention, and the present invention is not limited to the following. In this specification, the term "step" includes not only an independent step but also the case where it cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Also, the numerical range indicated using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. Also, in the following respective embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals and described.

[0014] <L10-type FeNi regular alloy> The L10-type FeNi ordered alloy of this embodiment has an L10-type ordered structure and contains sulfur. Here, an L10-type ordered alloy means that the degree of order is 0.1 or higher, preferably 0.5 or higher. The upper limit of the degree of order may be 1 or less. The L10-type FeNi ordered alloy according to this embodiment is suitably used as a magnetic powder and magnetic material. Examples of magnetic materials include sintered magnets, bonded magnets, and magnetic recording materials. Here, the degree of order S indicates the degree of ordering in the FeNi superlattice. The L10-type ordered structure is based on a face-centered cubic lattice and has a lattice structure as shown in Figure 1. In this figure, the uppermost layer in the (001) plane stacking structure of the face-centered cubic lattice is called the I site, and the intermediate layer located between the uppermost and lowermost layers is called the II site. In this case, if the proportion of metal A present in the I site is x and the proportion of metal B present is 1-x, then the proportion of metal A and metal B present in the I site is A x B 1-x It can be expressed as follows. Similarly, if x is the proportion of metal B present at site II and 1-x is the proportion of metal A present, then the proportion of metal A and metal B present at site II is A 1-x B x This can be expressed as follows. Note that x satisfies 0.5 ≤ x ≤ 1. In this case, the degree of regularity S is defined as S = 2x - 1.

[0015] The degree of order can be estimated using the following formula for estimating the degree of order S in an L10 type FeNi ordered alloy, shown in Equation 1.

[0016]

number

[0017] The lower limit of the sulfur (S) content in the L10-type FeNi ordered alloy can be, for example, 0.01 mass% or more, preferably 0.03 mass% or more, and more preferably 0.1 mass% or more. Also, the upper limit of the S content in the L10-type FeNi ordered alloy can be, for example, 10 mass% or less, preferably 2.0 mass% or less, more preferably 1.5 mass% or less, preferably 1.0 mass% or less, still more preferably 0.75 mass% or less, and particularly preferably 0.53 mass% or less. The S content can be measured by the method described in the examples below.

[0018] In the L10-type FeNi ordered alloy, the oxidation number of sulfur (S) may include S 2- or S 6+ or a mixed state thereof. Also, the oxidation number of sulfur (S) may be S 2- or S 6+ or a mixed state thereof. The oxidation number of sulfur can be measured by the XAFS measurement (i.e., partial fluorescence yield measurement) described below. The absorption peak that appears at 2482.0 ± 2 eV in the XAFS measurement is the peak attributed to S 6+ , and the absorption peak that appears at 2471.5 ± 2 eV is the peak attributed to S 2-These peaks can be considered to be caused by S. 2- and S 6+ It can be determined that each of these exists. Furthermore, if an improvement in ammonia efficiency is obtained, the oxidation state of sulfur contained in the FeNi superlattice is S 2- and S 6+ It doesn't have to be anything else.

[0019] An L10 type FeNi ordered alloy may be composed of particles 100 having an L10 type ordered structure, as shown in Figures 7 and 8 described later. When an L10 type FeNi ordered alloy is composed of particles 100 having an L10 type ordered structure, S may be present throughout the particles, segregated inside the particles, or segregated on the particle surface. The state of S can be measured by the method described in the examples described later.

[0020] When an L10-type FeNi ordered alloy is composed of particles having an L10-type ordered structure, the lower limit of the average particle size can be, for example, 10 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. The upper limit of the average particle size can be, for example, 5000 nm or less, preferably 1000 nm or less, and more preferably 500 nm or less. The average particle size can be measured from scanning electron microscope (SEM) images.

[0021] L10 type FeNi ordered alloys may be composed of secondary particles formed by the aggregation of primary particles. In this case, the lower limit of the average particle size of the primary particles can be, for example, 10 nm or more, preferably 30 nm or more, and more preferably 50 nm or more. The upper limit of the average particle size of the primary particles can be, for example, 1000 nm or less, and preferably 500 nm or less. The average particle size of the primary particles can be calculated by analyzing the XRD pattern using the Williamson-Hall method.

[0022] In the L10-type FeNi ordered alloy, the ratio of the number of moles of Fe to the total number of moles of Fe and Ni may be 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.48 to 0.52. The number of moles of Fe and Ni can be measured by, for example, inductively coupled plasma (ICP) emission spectrometry or energy-dispersive X-ray analysis (EDS) using an electron microscope.

[0023] <Manufacturing method of L10-type FeNi ordered alloy> The manufacturing method of the L10-type FeNi ordered alloy of the present embodiment includes nitriding an FeNi alloy containing sulfur (S) to obtain a nitride containing Fe and Ni. According to the present embodiment, since the FeNi alloy used in the nitriding step contains S, it is considered that the thermal decomposition of the FeNi nitride generated in the nitriding step can be suppressed, and thus the nitriding efficiency is improved. The L10-type FeNi ordered alloy manufactured by the present embodiment is suitably used as a magnetic powder and a magnetic material. Examples of the magnetic material include magnetic materials such as sintered magnets, bonded magnets, and magnetic recording materials.

[0024] [Nitriding step] In the nitriding process, an FeNi alloy containing S (hereinafter also referred to as FeNi-S) can be nitrided to obtain a nitride containing Fe and Ni (hereinafter referred to as FeNi nitride). The nitriding process is not particularly limited as long as FeNi nitride can be obtained from FeNi-S, but examples include gas nitriding with ammonia gas or nitrogen, plasma nitriding, and nitriding using metal amides. Specifically, the nitriding process is carried out by heat-treating a pre-fabricated FeNi-S under an ammonia gas flow. The flow rate of ammonia gas in the nitriding process can be 0.1 to 10 liters / min per 1 g of FeNi-S, preferably 0.5 to 5 liters / min. The heat treatment temperature can be, for example, 300 to 500°C, preferably 310 to 475°C, and more preferably 330 to 450°C. The heat treatment time can be, for example, 5 to 50 hours, preferably 10 to 20 hours. The FeNi nitride obtained in the nitriding process may be an FeNi nitride containing S (hereinafter also referred to as FeNi nitride-S).

[0025] FeNi alloys containing sulfur used in the nitriding process may have a disordered structure. A disordered structure here means that the arrangement of atoms is random and lacks regularity, or that when measured by X-ray diffraction, no L10 type ordered structure peak is observed.

[0026] FeNi-S used in the nitriding process can be produced by adding a predetermined amount of a sulfur-containing compound (hereinafter also referred to as a sulfur compound) to an FeNi alloy produced by a known method, as needed. It can also be produced by heat treatment after mixing the FeNi alloy and the sulfur compound, or by reacting the FeNi alloy and the sulfur compound. Furthermore, it can be produced by sulfiding a portion of the FeNi alloy with hydrogen sulfide gas or the like. The sulfur compound can be any compound that contains a sulfur element, such as sulfur, organic sulfur compounds, metal sulfides such as iron sulfide and nickel sulfide, and sulfates such as ammonium sulfate, iron sulfate and nickel sulfate.

[0027] FeNi-S used in the nitriding process may be synthesized during the process itself. Specifically, for example, the FeNi alloy can be heat-treated under a mixed gas flow of ammonia gas and hydrogen sulfide, allowing the synthesis of FeNi nitride-S and nitriding to occur in parallel (sulfur nitriding).

[0028] The ratio of the number of moles of Fe to the total number of moles of Ni in the FeNi-S used in the nitriding process may be 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.48 to 0.52.

[0029] The sulfur (S) content in the FeNi-S used in the nitriding process can be, for example, 0.01% to 10% by mass, preferably 0.02% to 2.0% by mass, more preferably 0.02% to 1.5% by mass, even more preferably 0.03% to 1.0% by mass, and particularly preferably 0.05% to 0.7% by mass. When the S content in the FeNi-S used in the nitriding process is within the above range, it tends to promote nitriding while suppressing a decrease in the magnetic performance of the final FeNi ordered alloy. The S content can be measured by the method described in the examples below.

[0030] Examples of FeNi nitrides obtained in the nitriding process include FeNiN and Fe2Ni2N, and a higher proportion of FeNiN is preferable to obtain an L10-type FeNi ordered alloy. FeNiN has a crystal structure as shown in Figure 2 and can be identified from the XRD diffraction pattern. The proportion of FeNi nitride after the nitriding process can be 90% by mass or more of the total material. The proportion of FeNiN in the FeNi nitride can be 50% by mass or more, preferably 80% by mass or more. The proportion of nitride and the proportion of FeNiN after the nitriding process can be calculated by analyzing the XRD diffraction pattern using the reference intensity ratio (RIR) method.

[0031] The ratio of the number of moles of Fe to the total number of moles of Fe and Ni in the FeNi nitride obtained in the nitriding process may be 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.48 to 0.52. The number of moles of Fe and Ni can be measured by inductively coupled plasma (ICP) emission spectroscopy or energy-dispersive X-ray analysis (EDS) using an electron microscope.

[0032] The FeNi nitride obtained in the nitriding process may contain sulfur (S). When the FeNi nitride contains S, the lower limit of the S content can be, for example, 0.01% by mass or more, preferably 0.03% by mass or more, and more preferably 0.05% by mass or more. Furthermore, the upper limit of the S content in the L10 type FeNi ordered alloy can be, for example, 10% by mass or less, preferably 2.0% by mass or less, more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.7% by mass or less. The S content can be measured by the method described in the examples below.

[0033] If the FeNi nitride obtained in the nitriding process contains sulfur (S), it may be composed of particles. When the FeNi nitride is composed of particles, S may be present throughout the particles, or it may be segregated within the particles. Alternatively, S may be segregated on the particle surface. The state of S can be measured by the method described in the examples below.

[0034] When the FeNi nitride obtained in the nitriding process is composed of particles, the lower limit of the average particle size can be, for example, 10 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. The upper limit of the average particle size can be, for example, 5000 nm or less, preferably 1000 nm or less, and more preferably 500 nm or less. The average particle size can be measured from scanning electron microscope (SEM) images.

[0035] The FeNi nitride obtained in the nitriding process may consist of secondary particles formed by the aggregation of primary particles. In this case, the lower limit of the average particle size of the primary particles can be, for example, 10 nm or more, preferably 30 nm or more, and more preferably 50 nm or more. The upper limit of the average particle size can be, for example, 1000 nm or less, and preferably 500 nm or less. The average particle size of the primary particles can be calculated by analyzing the XRD pattern using the Williamson-Hall method.

[0036] In the nitriding process, the FeNi-S is subjected to nitriding treatment. This makes it possible to obtain high nitriding efficiency, as shown in the examples described later. The nitriding efficiency in the nitriding process is 4.7 × 10⁻⁶. -5 It can be made larger, preferably 10 × 10 -5 It can be more than 20 × 10 -5 The above can be applied. In this specification, "nitriding efficiency" refers to the amount of FeNiN formed (g) by the nitriding treatment divided by the amount of nitrogen raw material consumed (g) in the nitriding treatment. Furthermore, when ammonia is used as the nitrogen raw material, the nitriding efficiency (hereinafter also referred to as ammonia efficiency) is the amount of FeNiN formed (g) divided by the amount of ammonia consumed (g), and indicates the amount of ammonia required to synthesize FeNiN. A higher ammonia efficiency value means that FeNiN can be synthesized with a smaller amount of ammonia.

[0037] In the nitriding process, an L10-type FeNi ordered alloy containing sulfur may be used as the FeNi alloy. In addition to the embodiments of this application, an L10-type FeNi ordered alloy containing sulfur can be produced by adding a predetermined amount of sulfur compound as needed to an L10-type FeNi ordered alloy produced by a known method. It can also be produced by mixing the L10-type FeNi ordered alloy and the sulfur compound and then heat-treating the mixture, or by reacting the L10-type FeNi ordered alloy with the sulfur compound. Furthermore, it can be produced by sulfiding a portion of the L10-type FeNi ordered alloy with hydrogen sulfide gas or the like. The sulfur compound is as described above. When using FeNi-S with an L10-type ordered structure, an improvement in the degree of order can be expected.

[0038] [Denitrification Process] In the denitrification process, the FeNi nitride obtained in the nitriding process described above can be denitrified to obtain an L10 type FeNi ordered alloy. Specifically, the FeNi nitride obtained in the nitriding process can be crushed and then heat-treated under a hydrogen atmosphere to perform the denitrification process. The hydrogen flow rate in the denitrification process can be 0.01 to 10 liters / min per 1g of FeNi nitride-S, preferably 0.1 to 5 liters / min. The heat treatment temperature can be, for example, 100 to 400°C, preferably 200 to 350°C. The heat treatment time can be, for example, 1 to 24 hours, preferably 2 to 10 hours. The L10 type FeNi ordered alloy obtained in the denitrification process may be an L10 type FeNi ordered alloy containing S.

[0039] The following describes an example of a method for manufacturing a sulfur-containing FeNi alloy used in the nitriding process. (First Embodiment) As shown in Figure 3, the first embodiment includes a reduction step to obtain FeNi-S by reducing an FeNi oxide containing S (hereinafter also referred to as FeNi oxide-S).

[0040] The reduction method in the reduction process is not particularly limited, but for example, FeNi-S can be obtained by heat-treating FeNi oxide containing S in a reducing gas atmosphere. The flow rate of the reducing gas can be 1 liter / min per 8.5 g of FeNi oxide-S, preferably 0.5 to 10.0 liters / min. The heat treatment temperature can be, for example, 300 to 700°C, preferably 450 to 700°C. The heat treatment time can be, for example, 1 to 10 hours, preferably 1.5 hours. Examples of reducing gases include hydrogen and carbon monoxide, but hydrogen is preferred from the viewpoint of reducing properties.

[0041] The ratio of the number of moles of Fe to the total number of moles of Fe and Ni in FeNi oxide-S may be 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.48 to 0.52.

[0042] The FeNi oxide-S used in the reduction process may contain Fe oxide or Ni oxide, or an oxide containing both Fe and Ni. Furthermore, Fe oxide, Ni oxide, and oxides containing both Fe and Ni may each contain S. Here, an oxide containing both Fe and Ni means that a single oxide particle contains both the element Fe and the element Ni.

[0043] FeNi oxide-S used in the reduction process can be prepared by adding a predetermined amount of sulfur compound as needed to FeNi oxide prepared by the embodiments of this application or by known methods. It can also be prepared by heat treatment after mixing FeNi oxide and sulfur compound, or by reacting FeNi oxide and sulfur compound. Furthermore, it can be prepared by sulfidizing a portion of the FeNi oxide with hydrogen sulfide gas or the like. The sulfur compound is as described above.

[0044] The FeNi oxide-S used in the reduction process may be synthesized during the reduction process itself. Specifically, for example, the synthesis and reduction of FeNi oxide-S can be carried out in parallel by heat treatment of FeNi oxide under a mixed gas flow of hydrogen gas and hydrogen sulfide.

[0045] Fe oxides are not particularly limited, but examples include FeO, Fe2O3, Fe3O4, and other oxides obtained by oxidizing iron metal, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron bromide, iron sulfate, iron nitrate, iron phosphate, and iron oxalate as raw materials. Among these, iron sulfate is preferred because it serves as a source of sulfur for sulfur-containing Fe oxides. S-containing Fe oxides may be prepared by the preparation method described above for FeNi oxide-S.

[0046] Ni oxides are not particularly limited, but examples include NiO, and other oxides obtained by oxidizing nickel metal, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel bromide, nickel sulfate, nickel nitrate, nickel phosphate, nickel oxalate, etc. Among these, nickel sulfate is preferred because it serves as a source of sulfur for sulfur-containing Ni oxides. S-containing Ni oxides may be produced by the production method described above for FeNi oxide-S.

[0047] An oxide containing Fe and Ni can be produced by a process of mixing a solution containing Fe and Ni with a precipitant to obtain a precipitate containing Fe and Ni (precipitation process), and then heat-treating the precipitate to obtain an oxide containing Fe and Ni (oxidation process). This method makes it easy to control the average particle size and particle size distribution of the resulting oxide containing Fe and Ni, and also makes it easier to achieve a uniform distribution of Fe and Ni elements in the oxide containing Fe and Ni.

[0048] [Precipitation process] In the precipitation process, Fe and Ni raw materials are dissolved in a strongly acidic solution to prepare a solution containing Fe and Ni.

[0049] The Fe and Ni raw materials are not limited as long as they can dissolve in an acidic solution. Examples of Fe raw materials include iron metal, iron oxide, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron sulfate, iron nitrate, iron phosphate, and iron oxalate. Iron metal, iron carbonate, iron sulfate, and iron chloride are preferred, and iron sulfate is more preferred because it serves as a source of sulfur in the precipitate containing sulfur. Examples of Ni raw materials include nickel metal, nickel oxide, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel sulfate, nickel nitrate, nickel phosphate, and nickel oxalate. Among these, nickel metal, nickel carbonate, nickel sulfate, and nickel chloride are preferred, and nickel sulfate is more preferred because it serves as a source of sulfur in the precipitate containing sulfur. Examples of acidic solutions include sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid. Among these, sulfuric acid is preferred because it serves as a source of sulfur in the precipitate containing sulfur, Fe, and Ni. The concentration of the solution containing Fe and Ni can be appropriately adjusted within the range in which the Fe and Ni raw materials are substantially soluble in the acidic solution.

[0050] In a solution containing Fe and Ni, the ratio of moles of Fe to the total number of moles of Fe and Ni may be 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.48 to 0.52.

[0051] A precipitate containing Fe and Ni is obtained by reacting a solution containing Fe and Ni with a precipitating agent. The reaction between the Fe and Ni solution and the precipitating agent can be carried out by adding the precipitating agent to the Fe and Ni solution, or by adding the Fe and Ni solution to the precipitating agent. Furthermore, the Fe and Ni solution referred to here only needs to be a solution containing Fe and Ni when reacted with the precipitating agent; the Fe and Ni raw materials can also be prepared as separate solutions, and each solution can be added and reacted with the precipitating agent. Even when preparing separate solutions, the solutions should be adjusted appropriately so that each raw material is substantially soluble in the acidic solution. The precipitating agent is not limited to those that react with the Fe and Ni solution to produce a precipitate, and examples include oxalic acid, alkaline solutions such as sodium hydroxide aqueous solution, sodium bicarbonate aqueous solution, potassium hydroxide aqueous solution, and lithium hydroxide aqueous solution. Alternatively, a precipitate can be obtained by blowing carbon dioxide into the Fe and Ni solution. Examples of precipitates produced include oxalates, carbonates, and hydroxides.

[0052] The precipitation step may include a step of separating and washing the precipitate. Methods for separating the precipitate include, for example, adding a solvent (preferably water) to the obtained precipitate and mixing, followed by filtration, decantation, or the like. Washing can be performed by repeating the same process on the precipitate that has already been separated.

[0053] After separating the precipitate, it is preferable to desolvent the separated material to prevent the precipitate from redissolving in the remaining solvent during the subsequent oxidation heat treatment and to suppress aggregation of the precipitate as the solvent evaporates. Specific desolvation methods include, for example, drying the material in an oven at 70°C to 200°C for 5 to 12 hours when water is used as the solvent. Furthermore, if necessary, crushing or grinding may be performed after drying to adjust the particle size.

[0054] Precipitates containing S, Fe, and Ni can be obtained by adding a predetermined amount of sulfur compound as needed during or after the reaction between the Fe and Ni solution and the precipitant, or by adding the sulfur compound during the separation and washing process. Alternatively, the precipitate can be prepared by adding a predetermined amount of sulfur compound as needed to the obtained precipitate, or by reacting the precipitate with the sulfur compound. The reaction between the precipitate and the sulfur compound can be carried out, for example, by mixing the precipitate and the sulfur compound and then heat-treating it. It can also be prepared by sulfidizing a portion of the precipitate with hydrogen sulfide gas or the like. The sulfur compounds are as described above.

[0055] [Oxidation process] The oxidation process involves heat-treating the precipitate containing Fe and Ni obtained in the precipitation process to obtain an oxide containing Fe and Ni. For example, the precipitate can be converted to an oxide by heat treatment. The heat treatment of the precipitate must be carried out in the presence of oxygen, for example, in an atmospheric environment. Furthermore, because it must be carried out in the presence of oxygen, it is preferable that the nonmetallic portion of the precipitate contains oxygen atoms. In the oxidation process, if a precipitate containing S, Fe, and Ni is used, FeNi oxide-S can be obtained. The obtained FeNi oxide-S may be crushed or pulverized to adjust its particle size as needed.

[0056] The heat treatment temperature in the oxidation process (hereinafter referred to as the oxidation temperature) is not particularly limited, but the heat treatment temperature can be, for example, 200 to 800°C, and preferably 350 to 450°C. The heat treatment time can be, for example, 4 to 24 hours, and preferably 8 hours.

[0057] The resulting oxides exhibit sufficient microscopic mixing of Fe and Ni within the oxide particles, and the shape and particle size distribution of the precipitate are reflected in the oxide particles.

[0058] The precipitate containing S, Fe, and Ni used in the oxidation process may be synthesized during the oxidation process. Specifically, for example, the synthesis and oxidation of the precipitate containing S, Fe, and Ni can be carried out in parallel by heat treatment of the precipitate containing Fe and Ni under a mixed gas flow of air and hydrogen sulfide.

[0059] (Second Embodiment) A second embodiment will now be described. This embodiment modifies the method of manufacturing FeNiN compared to the first embodiment, and is otherwise the same as the first embodiment. Therefore, only the differences from the first embodiment will be described. The method of manufacturing the FeNi superlattice of this embodiment will be described below with reference to the flowchart showing the synthesis process of the FeNi superlattice of this embodiment, which is shown in Figure 4.

[0060] First, as shown in Figure 4, an FeNi alloy with added sulfur is prepared. Specifically, FeNi powder is prepared first. Preferably, the FeNi powder has a composition ratio of Fe:Ni = 50:50, but it is acceptable if it is approximately 50:50. For example, the proportion of Fe should be 50±3%, and Ni should be the remaining {100-(50±3)}%. As such FeNi powder, for example, FeNi nanoparticles synthesized by the thermal plasma method manufactured by Nisshin Engineering Co., Ltd., or FeNi powder synthesized by the gas atomization method manufactured by Epson Atomics Co., Ltd. can be used.

[0061] Next, the FeNi powder is reacted in a mixed gas of H2S gas and nitrogen (N2) gas. This yields FeNi-S, an FeNi alloy with added sulfur. For example, a 3% H2S gas + 97% N2 gas mixture is used, and FeNi-S can be obtained by heat treatment at 200-500°C for 2-24 hours.

[0062] After this, FeNiN-S is synthesized by nitriding treatment using the same method as in the first embodiment, and then FeNi superlattice is obtained by further denitrification treatment. The FeNi superlattice obtained in this way also contains S. In this case as well, as shown in the examples described later, it is possible to obtain high ammonia efficiency. [Examples]

[0063] Below, we will describe examples in which FeNi-S was produced by various methods, including the manufacturing methods of each embodiment described above, and then subjected to nitriding denitrification treatment, in comparison with comparative examples using sulfur-free FeNi.

[0064] Figure 5 is a diagram showing how the manufacturing conditions for the FeNi superlattice, the formation rate of FeNiN, and the ammonia efficiency changed for each example and comparative example. In the figure, (1) refers to the manufacturing method of the first embodiment, and (2) refers to the manufacturing method of the second embodiment. Examples 1 to 5 will be described in detail later. Example 6 shows the case in which FeNi-S is synthesized by reacting ammonium sulfate with FeNi alloy particles prepared by the gas atomization method in the second embodiment. Example 7 shows the case in which FeNi-S is synthesized by reacting ammonium sulfate with FeNi alloy particles prepared by the thermal plasma method in the second embodiment. Comparative Examples 1 and 2 show the case in which FeNi prepared by the thermal plasma method is subjected to nitriding denitrification treatment without reacting it with ammonium sulfate.

[0065] The sulfur content (mass%) shown in Figure 5, that is, the mass ratio of S to the total mass of Fe, Ni, and S, was evaluated using commonly used elemental analysis methods. For example, the sulfur content can be identified by inductively coupled plasma (ICP) emission spectroscopy or energy-dispersive X-ray analysis (EDS) using an electron microscope. This sulfur content (mass%) is approximately the same before and after the nitriding denitrification treatment. The FeNiN formation rate is the ratio of the amount of FeNiN formed after nitriding to the amount of FeNi alloy before nitriding, and is calculated from the reference intensity ratio (RIR) method by measuring the powder XRD pattern. More specifically, the FeNiN formation rate is the ratio of the amount of FeNiN actually obtained to the ideal amount of FeNiN formed, assuming that the total amount of FeNi alloy contained in the raw material before nitriding was obtained as FeNiN by nitriding. For the analysis of the formation rate by the RIR method, the RIR values ​​of FeNiN, Fe2Ni2N, and FeNi alloy stored in the database of the analysis software (PDXL2) attached to the XRD instrument (Rigaku SmartLab) were used. Furthermore, the efficiency improvement rate shows the ratio of ammonia efficiency in Comparative Example 1 and Examples 1 to 7, with Comparative Example 2 as the baseline.

[0066] Examples 1-7, 9, 10, 12, and 13 are described in detail below. Unless otherwise specified, "%" refers to mass.

[0067] Example 1 [Precipitation process] To 3 liters of a 10% by mass oxalic acid aqueous solution that was being stirred, 0.34 liters of a 5% by mass iron sulfate aqueous solution and 0.2 liters of a 9% by mass nickel sulfate aqueous solution were added, respectively, so that the molar ratio of iron to nickel was 50:50. This yielded an oxalate slurry containing Fe, Ni, and S. The obtained slurry was washed with pure water by decantation, and then the oxalate containing Fe and Ni was separated into solid and liquid. The separated oxalate containing Fe and Ni was dried in an oven at 100°C for 10 hours. The sulfur contained in the oxalate is thought to be due to sulfate ions from the raw materials, iron sulfate or nickel sulfate.

[0068] [Oxidation process] 50 g of the oxalate containing Fe, Ni, and S was heat-treated at 400°C for 8 hours in air. After cooling, an oxide containing Fe, Ni, and S was obtained.

[0069] [Reduction Process] 8.5 g of an oxide containing Fe, Ni, and S was heat-treated at 450°C for 1.5 hours in a hydrogen gas atmosphere (hydrogen flow rate 1 liter / min). After cooling, an FeNi alloy containing S was obtained. The sulfur content in the alloy was 0.03 mass%. The sulfur content was measured by dissolving in hydrochloric acid and using the ICP-AES method (instrument name: Optima8300), and was expressed as the mass ratio of S to the total mass of Fe, Ni, and S.

[0070] [Nitriding process] FeNiN was obtained by heat-treating 0.4 g of a sulfur-containing FeNi alloy at 335°C for 40 hours in an ammonia gas atmosphere (ammonia flow rate 1 liter / min). The FeNiN formation rate was 95%. The FeNiN formation rate was measured by X-ray diffraction using Fe's kβ rays (wavelength: 1.75653 Å) (instrument name: Smartlab, tube current 200 mA, tube voltage 45 kV), and was defined as the ratio of the integrated intensity of the FeNiN peak to the sum of the integrated intensity of the FeNiN peak (40°) and the integrated intensity of the Fe2Ni2N peak (41.5°). The FeNiN formation rate was calculated using the reference intensity ratio (RIR) method, taking into account the mass of the raw FeNi alloy, the mass of the obtained FeNi nitride, and the measurement of the powder XRD pattern.

[0071] [Denitrification Process] The obtained FeNiN was heat-treated at 250°C for 20 hours in a hydrogen gas atmosphere (hydrogen flow rate of 1 liter / min) to obtain an L10 type ordered FeNi alloy. The sulfur content in the L10 type ordered alloy was 0.03 mass%, which was confirmed to be approximately the same as that of the S-containing FeNi alloy obtained in the reduction process. The sulfur content was measured by dissolving the obtained FeNi alloy in hydrochloric acid and using the ICP-AES method, and was expressed as the mass ratio of S to the total mass of Fe, Ni, and S.

[0072] Example 2 The procedure was the same as in Example 1, except that the heat treatment temperature in the nitriding process was changed to 415°C.

[0073] Example 3 The procedure was the same as in Example 2, except that the oxalate containing Fe, Ni, and S obtained in Example 1 was heat-treated with ammonium sulfate. The amount of ammonium sulfate added was 0.02% by mass relative to the oxalate. As a result, the sulfur content in the alloy particles was 0.05% by mass.

[0074] Example 4 The procedure was the same as in Example 2, except that the oxalate containing Fe, Ni, and S obtained in Example 1 was heat-treated with ammonium sulfate. The amount of ammonium sulfate added was 0.11% by mass relative to the oxalate. As a result, the sulfur content in the alloy particles was 0.14% by mass.

[0075] Example 5 The procedure was the same as in Example 2, except that the oxalate containing Fe, Ni, and S obtained in Example 1 was heat-treated with ammonium sulfate. The amount of ammonium sulfate added was 0.45% by mass relative to the oxalate. As a result, the sulfur content in the alloy particles was 0.48% by mass.

[0076] First, in Comparative Examples 1 and 2, since FeNi superlattices were manufactured using a conventional method without adding sulfur to FeNi, the doping method and sulfur content (mass%) are marked with "-", meaning "none". In Comparative Example 2, when nitriding was performed at 300°C for 40 hours with an NH3 amount of 5 liters / min, the FeNiN formation rate was 99%, which is almost 100%, and the ammonia efficiency at this time was 4.7 (×10 -5 ) is used as the standard. In contrast, if the amount of NH3 is reduced to 1 liter / min, as in Comparative Example 1, which is less than in Comparative Example 2, the FeNiN formation rate drops to only 15%. The ammonia efficiency also drops to 3.6 (×10 -5 This yielded only 0.76, and the efficiency improvement rate was significantly lower than that of the baseline comparative example 2.

[0077] From this, it can be seen that when nitriding denitrification treatment is performed on FeNi without added sulfur, the amount of NH3 cannot be reduced, and unless the amount of NH3 is kept to about 5 liters / min, the FeNiN formation rate cannot be increased and the ammonia efficiency will be poor.

[0078] Although the nitriding temperature is set at 300°C, in the case of FeNi without added sulfur, the FeNiN formation rate does not stabilize at temperatures exceeding 300°C, and similarly, the ammonia efficiency decreases. Also, although the nitriding treatment is set for 40 hours, shortening this time tends to result in a unstable FeNiN formation rate and similarly, a lower ammonia efficiency. Furthermore, although the sample amount is set at 400 mg, increasing the amount of FeNi nitrided at one time also results in a unstable FeNiN formation rate and similarly, a lower ammonia efficiency. For this reason, as described above, reducing the amount of NH3, shortening the nitriding treatment time, or increasing the amount of FeNi nitrided at one time will worsen the ammonia efficiency and make it impossible to obtain pure FeNiN.

[0079] On the other hand, in Examples 1 to 7, nitridation denitrification treatment was performed on FeNi to which sulfur had been added, and in all cases of Examples 1 to 7, ammonia efficiency higher than the standard was obtained.

[0080] In Example 1, although the sulfur content was low at 0.03 (mass%), even when the NH3 amount was reduced to 1 liter / min under nitriding treatment conditions of 335°C for 40 hours, the FeNiN formation rate was a high 95%, and the ammonia efficiency was 22.9 (×10). -5 The efficiency improvement rate also reached a high value of 4.8.

[0081] In Example 2, using the same amount of sulfur as in Example 1, the nitriding treatment temperature was increased to 415°C. Although the FeNiN formation rate decreased to 43%, the ammonia efficiency increased to 10.4 (×10). -5 The value was higher than the standard. The efficiency improvement rate was also high at 2.2.

[0082] In Example 3, when the sulfur content was increased to 0.05 (mass%) compared to Example 1, even with a reduced NH3 amount of 1 liter / min under nitriding treatment conditions of 415°C for 40 hours, the FeNiN formation rate was a high 97%, and the ammonia efficiency was 23.6 (×10). -5 The value was high. The efficiency improvement rate was also high at 4.9. As will be described later, it has been confirmed that the FeNiN formation rate can be increased by changing the nitriding treatment temperature according to the amount of sulfur, and in Example 3, the nitriding treatment temperature was set to 415°C in order to further increase the FeNiN formation rate. As a result, the FeNiN formation rate was particularly high, and a higher ammonia efficiency was obtained.

[0083] In Example 4, the sulfur content was increased to 0.14 (mass%) compared to Example 3, and the nitriding treatment conditions were the same as in Example 3. As a result, the FeNiN formation rate remained high at 90%, and the ammonia efficiency was 21.8 (×10). -5 ) was maintained at a high value. The efficiency improvement rate also reached a high value of 4.6. In Examples 5 to 7, the amount of sulfur was increased even further than in Example 4, and the same nitriding treatment conditions as in Examples 3 and 4 were used. In Example 5, the amount of sulfur was 0.48 (mass%), the FeNiN formation rate was 94%, and the ammonia efficiency was 22.8 (×10). -5 ), and the efficiency improvement rate was 4.8, both of which were high values. In Example 6, the sulfur content was 1.05 (mass%), the FeNiN formation rate was 92%, and the ammonia efficiency was 22.1 (×10). -5 ), and the efficiency improvement rate was 4.7, both of which were high values. In Example 7, the sulfur content was 2.26 (mass%), the FeNiN formation rate was 88%, and the ammonia efficiency was 21.2 (×10). -5 ), and the efficiency improvement rate was a high 4.5 in both cases.

[0084] For reference, Figure 6 shows the XRD pattern measurement results for Comparative Example 2 and Example 3. The "O" shown in this figure represents the XRD diffraction peak caused by FeNiN. It can be seen that high-purity FeNiN was obtained in both Comparative Example 2 and Example 3.

[0085] Examples 1 to 7 show that when FeNi superlattices are manufactured by adding sulfur to FeNi before nitriding denitrification, the FeNiN formation rate can be increased and ammonia efficiency can be improved compared to the conventional method without sulfur. Specifically, by setting the sulfur content to 0.03 (mass%) or more, ammonia efficiency can be more than doubled compared to the conventional method. Therefore, in the FeNi superlattices of this embodiment, by increasing ammonia efficiency, it is possible to reduce the amount of NH3, shorten the nitriding treatment time, and increase the amount of material treated at one time, thereby reducing manufacturing costs.

[0086] Furthermore, as shown in Examples 1 to 5, cross-sectional TEM observation and compositional image observation were performed on FeNi superlattices manufactured by the manufacturing method of the first embodiment using TEM, and the results shown in Figure 7 were obtained. In this figure, Image 1 shows the results of cross-sectional TEM observation, and Images 2 to 4 show the compositional images of S, Fe, and Ni, respectively.

[0087] When the FeNi superlattice particles 100 in Figure 7 are distributed as shown in Image 1, FeNi is evenly distributed, as shown in the Fe and Ni compositional images in Images 3 and 4, indicating that the FeNi superlattice is formed in a good state. Furthermore, as shown in Image 2, it can be seen that S is distributed throughout the FeNi superlattice particles 100, corresponding to their overall distribution. The fact that S is present throughout the FeNi superlattice particles 100 suggests that S is also present throughout the FeNi alloy and FeNiN particles 100 during the manufacturing process of the FeNi superlattice. Thus, when S is present throughout the superlattice particles 100, in other words, when S is present throughout the FeNi alloy and FeNiN particles 100 during the manufacturing process of the FeNi superlattice, it can be seen that high ammonia efficiency can be obtained.

[0088] As shown in Figure 7, the particle size of the FeNi superlattice in Examples 1-5 is approximately 100 nm. However, this particle size can be appropriately changed depending on the purpose for which the FeNi superlattice is applied, and can be changed within a range of, for example, 100 nm to several μm. Experiments have confirmed that the particle size of the FeNi superlattice changes depending on the firing temperature when obtaining FeNi oxide and the reduction temperature when obtaining FeNi alloy, and that the particle size tends to increase as the temperature rises. Since changes in particle size affect magnetic properties and environmental resistance, the firing temperature and reduction temperature should be set according to the purpose for which the FeNi superlattice is applied to obtain the desired magnetic properties and environmental resistance.

[0089] On the other hand, as in Examples 6 and 7, cross-sectional TEM observation and compositional image observation were also performed on FeNi superlattices manufactured by the manufacturing method of the second embodiment, and when those with large particle sizes were extracted, the results shown in Figure 8 were obtained. In this figure, Image 1 shows the results of cross-sectional TEM observation, and Images 2 to 4 show the compositional images of S, Fe, and Ni, respectively.

[0090] As shown in Image 1 in Figure 8, even when FeNi superlattices with large particle sizes are observed, FeNi is uniformly distributed within particle 100, as shown in the Fe and Ni compositional images in Images 3 and 4, indicating that the FeNi superlattice is formed in a good state. Furthermore, as shown in Image 2, it can be seen that S is segregated on the surface of FeNi superlattice particle 100. The fact that S is segregated on the surface of FeNi superlattice particle 100 suggests that S is also segregated on the surface of FeNi alloy and FeNiN particles during the manufacturing process of the FeNi superlattice. Thus, it can be seen that even if S is segregated on the surface of FeNi superlattice particle 100, or in other words, even if S is segregated on the surface of FeNi alloy and FeNiN particles during the manufacturing process of the FeNi superlattice, high ammonia efficiency can be obtained.

[0091] Next, the FeNiN formation rate, ammonia efficiency, and efficiency improvement rate were investigated by changing the temperature during the nitriding treatment while keeping the sulfur content constant. Specifically, the experiment was conducted by changing the temperature of the nitriding treatment when the sulfur content was 0.14 (mass%) as in Example 4 described above. Similar experiments were also conducted for the conventional manufacturing method as comparative examples. Figure 9 is a chart showing the results. In this figure, Example 4 is the same as Example 4 in Figure 5, while Examples 9 and 10 and Comparative Examples 9 and 10 show the case where only the temperature of the nitriding treatment was changed compared to Example 4. Comparative Example 2 is the same as Comparative Example 2 in Figure 5, and Comparative Examples 3 to 6 show the case where only the temperature of the nitriding treatment was changed compared to Comparative Example 2, with the NH3 flow rate remaining at 5 liters / min.

[0092] As shown in Examples 9 and 10, when the heat treatment temperature for nitriding was 375°C and 450°C, the FeNiN formation rates were 76% and 80%, respectively, but the ammonia efficiency was 18.4 (×10⁻⁶). -5 ), 19.2 (×10 -5 The values ​​were high. The efficiency improvement rates were also high, at 3.9 and 4.1, respectively. Furthermore, as in Example 4, when the nitriding treatment temperature was set to 415°C, which is between the temperatures of Example 9 and Example 10, the ammonia efficiency and efficiency improvement rates were also high.

[0093] Furthermore, as shown in Comparative Examples 9 and 10, when the heat treatment temperature for nitriding was 325°C and 500°C, the FeNiN formation rate was 12% and 3%, respectively, and the ammonia efficiency was 2.9 (×10) -5 ), 0.72 (×10 -5 The results were as follows: The efficiency improvement rates were 0.61 and 0.15, respectively. From these results, it can be seen that when 0.14 mass% of S is added, it is possible to increase ammonia efficiency and efficiency improvement rates by setting the nitriding temperature in a range higher than 325°C and lower than 500°C. More preferably, it can be seen that it is possible to increase ammonia efficiency and efficiency improvement rates by setting the nitriding temperature in a range of 375 to 450°C.

[0094] In contrast, Comparative Examples 2 and 4 showed relatively high values ​​for FeNiN formation rate, ammonia efficiency, and efficiency improvement rate, while Comparative Examples 3, 5, and 6 showed low or zero values ​​for FeNiN formation rate, ammonia efficiency, and efficiency improvement rate.

[0095] Specifically, as in Comparative Examples 2 and 4, when the nitriding treatment temperature was set to 300°C and 325°C, the FeNiN formation rates were 99% and 95%, respectively, and the ammonia efficiency was 4.7 (×10) -5 ), 4.6 (×10 -5 The efficiency improvement rates were 1 and 0.98, respectively.

[0096] Furthermore, as in Comparative Example 3, when the nitriding temperature was 275°C and below 300°C, the FeNiN formation rate was 0%, the ammonia efficiency was 0, and the efficiency improvement rate was 0. Similarly, as in Comparative Examples 5 and 6, when the nitriding temperature was 375°C and 415°C, the FeNiN formation rates were 9% and 0%, respectively, and the ammonia efficiency was 0.43 (×10) -5 The ammonia efficiency and efficiency improvement rate were low, at 0.09 and 0 respectively. These results indicate that, without the addition of sulfur, the desired ammonia efficiency and efficiency improvement rate cannot be obtained unless the nitriding temperature is within the range of 300-325°C.

[0097] As described above, when sulfur (S) is added, the desired ammonia efficiency and efficiency improvement rate can be obtained by setting the nitriding temperature to at least 375-450°C. In contrast, with the conventional manufacturing method without added S, the desired ammonia efficiency and efficiency improvement rate cannot be obtained unless the nitriding temperature is at least 300-325°C. Therefore, by adding S, it is possible to broaden the temperature range in which the desired ammonia efficiency and efficiency improvement rate can be obtained, and it is also possible to raise the process temperature and expand the process window. If the process temperature can be raised, FeNiN-S can be synthesized at a higher temperature, which improves the crystallinity of the FeNi superlattice. This makes it possible to improve the properties of the FeNi superlattice. Furthermore, if the process window can be expanded, the temperature of the nitriding treatment only needs to be set within the range of that process window, making temperature control easier.

[0098] In this example, when the sulfur content is 0.14 mass%, as in Example 4, the nitriding temperature was described as being at least in the range of 375 to 450°C, based on the results of Examples 4, 9, and 10. However, this is merely one example, and high ammonia efficiency and efficiency improvement can be obtained by setting the nitriding temperature to at least 335°C, as shown in Example 1. Therefore, when the sulfur content is between 0.03 mass% and 2.26 mass%, the nitriding temperature can be set to 335 to 450°C, thus expanding the process window.

[0099] Furthermore, the FeNiN formation rate, ammonia efficiency, and efficiency improvement rate were investigated by keeping the sulfur content constant and varying the nitriding treatment time. Specifically, as in Example 3 described above, the experiment was conducted by varying the nitriding treatment time when the sulfur content was 0.05 (mass%). Similar experiments were also conducted for a conventional manufacturing method as a comparative example. Figure 10 is a table showing the results. In this figure, Example 3 is the same as Example 3 in Figure 5, and Examples 12 and 13 show the case where only the nitriding treatment time was changed compared to Example 3. Comparative Example 2 is the same as Comparative Example 2 in Figure 5, and Comparative Examples 7 and 8 show the case where only the nitriding treatment time was changed compared to Comparative Example 2.

[0100] As shown in Examples 12 and 13, even when the nitriding treatment time was shorter than 10 hours, 20 hours, and 40 hours, the FeNiN formation rate was 88% and 93%, respectively, and the ammonia efficiency was 84.6 (×10) -5 ), 44.9 (×10 -5 The values ​​are high. In addition, the efficiency improvement rates were also high, at 17.9 and 9.5 respectively. Therefore, it can be said that when sulfur is added, it is possible to improve ammonia efficiency and efficiency improvement rates even when the nitriding treatment time is shortened.

[0101] In contrast, as in Comparative Examples 7 and 8, when the nitriding treatment time was 10 hours and 20 hours, the FeNiN formation rates were 5% and 40%, respectively, and the ammonia efficiency was 0.97 (×10) -5 ), 3.9 (×10 -5 The results were as follows: The efficiency improvement rates were 0.20 and 0.82, respectively. From these results, it can be seen that if sulfur is not added, the desired ammonia efficiency and efficiency improvement rate cannot be obtained unless the nitriding treatment time is extended to 40 hours or more.

[0102] Thus, by adding sulfur (S), it becomes possible to obtain high ammonia efficiency and efficiency improvement rates even when the nitriding treatment time is shortened to less than 40 hours.

[0103] For reference, the order and magnetic properties of FeNi superlattice magnetic powders obtained by denitrifying FeNiN from Comparative Example 2, Example 3, and Example 7 at 250°C for 4 hours were investigated. The order of the FeNi superlattice obtained by denitrifying FeNi nitride from Comparative Example 2 was 0.71, while the order of the FeNi superlattice obtained by denitrifying FeNi nitride from Example 3 was 0.68, which is almost equivalent. The order of Example 7 was 0.60. Figure 11 shows the hysteresis curves for each. The coercivity was 142 kA / m for Comparative Example 2. In contrast, it was 135 kA / m for Example 3 and 120 kA / m for Example 7. The saturation magnetization was 139 Am for Comparative Example 2. 2 / kg, Example 3 also 139Am 2 It was given as / kg. In Example 7, it was 91Am 2 The value was given as / kg. From this, it can be seen that the FeNi superlattice to which an appropriate amount of sulfur was added, as in Example 3, achieved performance equivalent to that of the FeNi superlattice to which no sulfur was added, as in Comparative Example 2. If the amount of sulfur is excessive, it causes a decrease in saturation magnetization as in Example 7, so from the viewpoint of magnetic performance, it is preferable that the amount is 2 mass% or less.

[0104] Based on these results and the XRD pattern measurements of Comparative Example 2 and Example 3 shown in Figure 5 above, no effect on the crystal structure or magnetic properties was observed due to the appropriate amount of sulfur doping. Therefore, it can be said that even with sulfur doping, the ammonia efficiency during FeNi superlattice fabrication can be improved without degrading performance, thereby increasing the efficiency of FeNi superlattice fabrication.

[0105] Furthermore, the inventors investigated the oxidation state of sulfur contained in the FeNi superlattice magnetic powder obtained in Example 3 and Example 4, respectively. Specifically, XAFS measurements (i.e., partial fluorescence yield measurements) were performed at BL6N1 of the Aichi Synchrotron Radiation Center using the following procedure.

[0106] (1) Energy calibration Before measuring the sample, an S K-edge XANES measurement was performed on the standard sample K2SO4. Energy calibration was performed so that the peak top of that measurement was 2481.70 eV. XANES is an abbreviation for X-ray Absorption Near Edge Structure.

[0107] (2) Sample preparation The sample was embedded in an indium sheet and attached to a sample holder using conductive carbon tape. The sample holder with the attached sample was introduced into a He atmospheric pressure chamber, and He replacement was performed for approximately 30 minutes before measurement.

[0108] (3) This measurement Partial fluorescence yield measurements were performed within the measurement range of 2440–2550 eV. The incident angle of the light was 20° relative to the sample plate.

[0109] (4) Analysis of measurement results The inventors used "Athena" as the analysis software to analyze the measurement results. Planarization and normalization were performed with the following settings: convergence edge E0 2471eV, pre-edge range 2440~2470eV, and normalization range 2508~2547eV. Then, by comparison with a standard sample, S 6+ Absorption peaks and S caused by this 2- The presence or absence of an absorption peak caused by [the noise level] was determined. The presence or absence of an absorption peak was determined by the rise in absorption intensity of 10 times or more the noise level (i.e., S / N ratio of 10 or more). This noise level is the average of the absolute values ​​of the signal deviation in the range of 2440 to 2460 eV within the pre-edge range. 6+ (NH4)2SO4 was used as the standard sample. 2- FeS was used as the standard sample. The absorption peak appearing at 2482.0±2eV is S 6+ This is a peak caused by S. The absorption peak that appears at 2471.5±2eV is S 2- These are peaks caused by absorption. The presence of these absorption peaks indicates that S 2- and S6+ It was determined that each of these states exists.

[0110] The results of the measurements and analysis are shown in Figure 12. Figure 12 shows the X-ray absorption near-edge spectra (XANES) for the FeNi superlattice magnetic powders of Example 3 and Example 4, respectively. Figure 12 also shows the X-ray absorption near-edge spectra of the standard samples (NH4)2SO4 and FeS. As shown in Figure 12, in both Example 3 and Example 4, the oxidation number of sulfur was S 2- and S 6+ It was in a mixed state. In Example 3, S was higher than in Example 4. 6+ It contained a large amount of S. In Example 4, S was more abundant than in Example 3. 2- It contained a large amount of [unclear]. Incidentally, although not shown in the figures, it has been confirmed that the oxidation number of sulfur before and after denitrification was almost the same in both Example 3 and Example 4.

[0111] The results shown in Figure 12 indicate that the sulfur contained in the FeNi superlattice is not in the state of elemental sulfur, but rather in a state combined with other elements. Furthermore, the results shown in Figure 12 and the ammonia efficiency results for Examples 3 and 4 shown in Figure 5 suggest that an improvement in ammonia efficiency can be obtained even if the oxidation state of sulfur is different. Note that in Examples 3 and 4, the oxidation state of sulfur was S 2- and S 6+ It was in a mixed state, but the oxidation state of sulfur was S 2- and S 6+ It is believed that an improvement in ammonia efficiency can be obtained even with only one of these. Furthermore, if an improvement in ammonia efficiency is obtained, the oxidation state of sulfur contained in the FeNi superlattice will be S 2- and S 6+ It doesn't have to be anything else.

[0112] (Other embodiments) This disclosure is written in accordance with the embodiments described above, but is not limited to those embodiments and includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

[0113] For example, in the first embodiment, S is doped into the FeNi oxide, and in the second embodiment, into the FeNi alloy, but the S doping can be done during the nitriding treatment. In the first embodiment, S may be doped into the Fe,Ni salt or FeNi alloy. Alternatively, S may be doped during the nitriding treatment. Furthermore, the method of S doping is not limited to the methods mentioned in the first and second embodiments, but can be any method. For example, ammonium sulfate may be added to the raw materials and then heat-treated, or H2S may be reacted with the raw materials. For example, FeNi-S can be synthesized by any method, such as adding ammonium sulfate to metallic FeNi, or performing immersion nitriding by mixing H2S with NH3 gas during the nitriding treatment.

[0114] Furthermore, in the second embodiment described above, an example of S segregation in an FeNi superlattice was given where S segregated on the surface of the FeNi superlattice particles, but it may also be segregated in places other than the surface. For example, S may be segregated inside the particles of the FeNi superlattice.

[0115] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the claims. Furthermore, it goes without saying that the elements constituting the embodiments in each of the embodiments are not necessarily essential unless explicitly stated to be particularly essential or unless they are clearly essential in principle. Also, if numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiments are mentioned in each of the embodiments, the invention is not limited to those specific numbers unless explicitly stated to be particularly essential or unless they are clearly limited to a specific number in principle.

[0116] [1] An L10 type FeNi ordered alloy having an L10 type ordered structure and containing sulfur.

[0117] [2] The L10 type FeNi ordered alloy according to [1], wherein the sulfur content is 0.01% by mass or more.

[0118] [3] The L10 type FeNi ordered alloy according to [1] or [2], wherein the sulfur content is 10% by mass or less.

[0119] [4] An L10 type FeNi ordered alloy according to any one of [1] to [3], comprising particles (100) having the L10 type ordered structure, wherein the sulfur is present throughout the particles.

[0120] [5] An L10 type FeNi ordered alloy according to any one of [1] to [3], comprising particles (100) having the L10 type ordered structure, wherein the sulfur is segregated on the particles.

[0121] [6] The L10 type FeNi ordered alloy according to [5], wherein the sulfur is segregated on the surface of the particles.

[0122] [7] The oxidation state of the sulfur is S 2- Or S 6+ Or a mixed state thereof, an L10 type FeNi ordered alloy as described in any one of [1] to [6].

[0123] [8] A method for producing an L10 type FeNi ordered alloy, comprising nitriding a sulfur-containing FeNi alloy to obtain a nitride containing Fe and Ni.

[0124] [9] A method for producing an L10 type FeNi ordered alloy according to [8], wherein the sulfur content in the FeNi alloy is 0.01% by mass or more.

[0125]

[10] A method for producing an L10 type FeNi ordered alloy according to [8] or [9], wherein the sulfur content in the FeNi alloy is 10% by mass or less.

[0126]

[11] A method for producing an L10 type FeNi ordered alloy according to any one of [8] to

[10] , comprising performing a heat treatment in the nitriding treatment at a temperature in the range of 300 to 500°C.

[0127]

[12] A method for producing an L10 type FeNi ordered alloy according to any one of [8] to

[11] , comprising performing a heat treatment in the nitriding treatment at a temperature in the range of 330 to 450°C.

[0128]

[13] In the nitriding treatment, the nitriding efficiency when obtaining a nitride containing Fe and Ni is 4.7 × 10 -5 A method for producing an L10 type FeNi ordered alloy according to any one of [8] to

[12] , including being larger. [Explanation of symbols]

[0129] 100 FeNi superlattice particles

Claims

1. The process involves nitriding a sulfur-containing FeNi alloy to obtain a sulfur-containing Fe and Ni nitride, By performing a denitrification treatment on the nitride, L1 containing sulfur is obtained. ０ Forming a type of FeNi ordered alloy, L1 including ０ A method for manufacturing a type of FeNi ordered alloy.

2. L1 according to claim 1, wherein the sulfur content in the alloy is 0.01% by mass or more. ０ A method for manufacturing a type of FeNi ordered alloy.

3. L1 according to claim 1 or 2, wherein the sulfur content in the alloy is 10% by mass or less. ０ A method for manufacturing a type of FeNi ordered alloy.

4. The L1 according to claim 1 or 2, wherein the nitriding treatment includes performing a heat treatment at a temperature in the range of 300 to 500°C. ０ A method for manufacturing a type of FeNi ordered alloy.

5. The L1 according to claim 1 or 2, wherein the nitriding treatment includes performing a heat treatment at a temperature in the range of 330 to 450°C. ０ A method for manufacturing a type of FeNi ordered alloy.

6. In obtaining the nitride, the nitriding treatment is performed on the alloy, which improves the nitriding efficiency compared to when it is performed on a sulfur-free FeNi alloy, as described in claim 1 or 2. ０ A method for manufacturing a type of FeNi ordered alloy.

7. In the nitriding treatment, the nitriding efficiency when obtaining the nitride is 4.7×10 －５ The method for producing an L1 ０ type FeNi regular alloy according to claim 6, including being greater than.

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