L10-type iron-nickel ordered alloy and method for manufacturing L10-type iron-nickel ordered alloy

Abstract

The present application relates to an L10-type iron-nickel (FeNi) ordered alloy having an L10-type ordered structure and containing sulfur. The L10-type FeNi ordered alloy may have a sulfur content in the range of 0.01 mass% to 10 mass%. A method for manufacturing the L10-type FeNi ordered alloy includes subjecting a FeNi alloy containing sulfur to a nitriding treatment to obtain nitrides containing Fe and Ni.

Description

Technical Field

[0001] The present disclosure relates to an L10-type iron-nickel (FeNi) ordered alloy having an L10-type ordered structure (hereinafter, also referred to as an FeNi superlattice) and a method for manufacturing the L10-type FeNi ordered alloy. Background Art

[0002] FeNi superlattices are expected to be magnet materials and magnetic device materials such as magnetic recording materials having high heat resistance. For example, Japanese Patent No. 6332359 discloses a method for manufacturing a high-quality FeNi superlattice. In this manufacturing method, a nitriding and denitriding method is used to manufacture a high-quality FeNi superlattice, in which an FeNi alloy is nitrided by a nitriding treatment to obtain a nitride, and then nitrogen is desorbed from the nitride by a denitriding treatment. Summary of the Invention

[0003] However, in the conventional nitriding and denitriding methods, in the nitriding treatment using an FeNi alloy as a raw material, a large amount of ammonia (NH3) is required to synthesize the precursor FeNiN of the FeNi superlattice, and the fact that the nitriding efficiency is low is one of the factors increasing the production cost of FeNi superlattice magnetic powder.

[0004] The inventors of the present invention repeatedly studied to improve the nitriding efficiency and confirmed that the nitriding efficiency is reduced due to the thermal decomposition of the nitride generated in the nitriding process.

[0005] In view of the above points, an object of the present disclosure is to provide an L10-type FeNi ordered alloy and a method for manufacturing the L10-type FeNi ordered alloy, which can reduce the production cost by improving the nitriding efficiency.

[0006] According to one aspect of the present disclosure, the L10-type FeNi ordered alloy has an L10-type ordered structure and contains sulfur.

[0007] When the L10-type FeNi ordered alloy contains sulfur, that is, when an FeNi alloy containing sulfur is used as a raw material to form the L10-type FeNi ordered alloy, a high nitriding efficiency can be obtained.

[0008] According to another aspect of the present disclosure, a method for manufacturing an L10-type FeNi ordered alloy includes nitriding a sulfur-containing FeNi alloy to obtain a nitride containing Fe and Ni.

[0009] In this way, when the sulfur-containing FeNi alloy is nitrided, a high nitriding efficiency can be obtained. Brief Description of the Drawings

[0010] The above and other subjects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. In the figures:

[0011] Figure 1 is a schematic diagram showing the lattice structure of the L10-type FeNi ordered structure;

[0012] Figure 2 is a schematic diagram showing the lattice structure of FeNiN;

[0013] Figure 3 is a flow chart showing the synthesis process of the FeNi superlattice according to the first embodiment;

[0014] Figure 4 is a flow chart showing the synthesis process of the FeNi superlattice according to the second embodiment;

[0015] Figure 5 is a graph showing the differences in the manufacturing conditions of the FeNi superlattice, the FeNiN formation rate, the ammonia efficiency, etc. of each example and comparative example;

[0016] Figure 6 is a graph showing the measurement results of the powder X-ray diffraction (XRD) patterns of Comparative Example 2 and Example 3;

[0017] Figures 7A to 7D is a graph showing the results of cross-sectional TEM observation and compositional image observation using a transmission electron microscope (TEM);

[0018] Figures 8A to 8D is a graph showing the results of cross-sectional TEM observation and compositional image observation using a TEM;

[0019] Figure 9 is a graph showing the differences in the manufacturing conditions of the FeNi superlattice, the FeNiN formation rate, the ammonia efficiency, etc. of each example and comparative example;

[0020] Figure 10 is a graph showing the differences in the manufacturing conditions of the FeNi superlattice, the FeNiN formation rate, the ammonia efficiency, etc. of each example and comparative example;

[0021] Figure 11 is a graph showing the magnetic properties of the FeNi superlattice magnetic powder obtained from FeNiN of Comparative Example 2, Example 3, and Example 7; and

[0022] Figure 12 is a graph showing the X-ray absorption near-edge spectroscopy (XANES) of the FeNi superlattice magnetic powder of Example 3 and Example 4 respectively. DETAILED DESCRIPTION

[0023] In the following, embodiments of the present disclosure will be described in detail. However, the embodiments described below are examples for embodying the technical concept of the present disclosure, and the present disclosure is not limited to the following embodiments. In the present disclosure, the term "process" is used not only as an independent process but also as a process included in other processes, as long as the intended purpose of the process is achieved, even if it cannot be clearly distinguished from other processes. In addition, the numerical range represented by using "to" means a range including the values before and after "to" as the minimum value and the maximum value, respectively. In the embodiments described below, the same or equivalent parts will be denoted by the same reference numerals.

[0024] <L10-type FeNi ordered alloy>

[0025] The L10-type FeNi ordered alloy of this embodiment has an L10 ordered structure and contains sulfur. The L10-type ordered alloy mentioned here means that the degree of order is 0.1 or more, and may preferably be 0.5 or more. In addition, the upper limit of the degree of order may be 1 or less. The L10-type FeNi ordered alloy according to this embodiment is suitable for use as magnetic powder and magnetic materials. Examples of magnetic materials include magnetic materials such as sintered magnets, bonded magnets, and magnetic recording materials. The degree of order S reg represents the degree of order in the FeNi superlattice. The L10-type ordered structure has a structure based on a face-centered cubic lattice and has a lattice structure as shown in Figure 1 . In Figure 1 , the uppermost layer in the stacking structure on the (001) plane of the face-centered cubic lattice is defined as site I, and the intermediate layer disposed between the uppermost layer and the lowermost layer is defined as site II. In this case, the atomic fraction of metal A at site I is defined as x, and the atomic fraction of metal B at site I is defined as (1 - x). The atomic fraction of metal A and metal B at site I is expressed as A x B 1-x . Similarly, the atomic fraction of the metal at site II is defined as x, and the atomic fraction of metal A at site II is defined as (1 - x). The atomic fraction of metal A and metal B at site II is expressed as A 1-x B x . Here, x satisfies the relationship of 0.5 ≤ x ≤ 1. In this case, the degree of order S reg is defined as S reg = 2x - 1.

[0026] The degree of order S reg in the L10-type FeNi ordered alloy is evaluated using the evaluation equation of the degree of order S reg shown in Equation 1 below.

[0027] (Equation 1)

[0028]

[0029] Here, in Equation 1, "I sup " is the integrated intensity of a diffraction peak (superlattice diffraction peak) peculiar to the L10-type ordered alloy and is obtained from an X-ray diffraction (XRD) pattern observed by the XRD method. "I fund " is the integrated intensity of a diffraction peak (basic diffraction peak) that appears in both the FeNi alloy and the L10-type FeNi ordered alloy. "(I sup / I fund ) obs " is the ratio of the integrated intensity of the superlattice diffraction peak to the integrated intensity of the basic diffraction peak in the X-ray diffraction patterns measured in each of the examples and comparative examples. Further, "(I sup / I fund ) cal " is the ratio of the integrated intensity of the superlattice diffraction peak to the integrated intensity of the basic diffraction peak of the FeNi ordered alloy having an order degree of 1 evaluated by Rietbelt simulation. As shown in Equation 1, the order degree S reg is obtained by calculating the square root of these two ratios. As the XRD apparatus used here, a general apparatus such as SmartLab manufactured by Rigaku Co., Ltd. can be used, but the order degree S reg can be accurately evaluated by using Fe-kβ rays as the X-rays.

[0030] 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. 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, more preferably 1.0 mass% or less, 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 following examples.

[0031] The oxidation number of sulfur (S) in the L10-type FeNi ordered alloy can include S 2- or S 6+ or S 2- and a mixed state of S 6+ . The oxidation number of sulfur can be determined by XAFS measurement (i.e., partial fluorescence yield measurement) described later. The absorption peak that appears at 2482.0 ± 2 eV in the XAFS measurement can be considered as a peak due to S 6+ , and the absorption peak that appears at 2471.5 ± 2 eV can be considered as a peak due to S 2-and the existing peaks. Based on the existence of these absorption peaks, the presence of S can be determined 2- and S 6+ . In addition, the oxidation number of sulfur contained in the FeNi superlattice can be a value other than S 2- and S 6+ as long as the effect of improving ammonia efficiency can be obtained

[0032] The L10-type FeNi ordered alloy can be composed of particles 100 having an L10-type ordered structure, as shown in FIGS. 7 and 8 described later. In the case where the L10-type FeNi ordered alloy is composed of particles 100 having an L10-type ordered structure, S can be present throughout the particles, can be segregated inside the particles, or can be segregated on the surface of the particles. The state of S can be measured by the method described in the following examples

[0033] In the case where the 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, more preferably 100 nm or more. In addition, the upper limit of the average particle size can be, for example, 5000 nm or less, preferably 1000 nm or less, more preferably 500 nm or less. The average particle size can be measured from a scanning electron microscope (SEM) image

[0034] The L10-type FeNi ordered alloy can be composed of secondary particles in which primary particles are aggregated. 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, more preferably 50 nm or more. In addition, the upper limit of the average particle size of the primary particles can be, for example, 1000 nm or less, 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

[0035] The ratio of the number of moles of Fe to the total number of moles of Fe and Ni in the L10-type FeNi ordered alloy can be 0.4 to 0.6, preferably 0.45 to 0.55, more preferably 0.48 to 0.52. The number of moles of Fe and Ni can be measured by inductively coupled plasma (ICP) emission spectrometry or energy dispersive X-ray spectrometry (EDS) using an electron microscope, etc

[0036] <Manufacturing method of L10-type FeNi ordered alloy>

[0037] The manufacturing method of the L10 type FeNi ordered alloy according to the present embodiment includes subjecting a FeNi alloy containing sulfur (S) to a nitriding treatment to obtain a nitride containing Fe and Ni. According to the present embodiment, since the FeNi alloy used in the nitriding process contains S, thermal decomposition of the FeNi nitride generated in the nitriding process can be suppressed, which is considered to improve the nitriding efficiency. The L10 type FeNi ordered alloy manufactured according to the present embodiment is suitable for use as magnetic powder and magnetic materials. Examples of magnetic materials include magnetic materials such as sintered magnets, bonded magnets, and magnetic recording materials.

[0038] <Nitriding process>

[0039] In the nitriding process, a S-containing FeNi alloy (hereinafter also referred to as FeNi-S) is nitrided to obtain a nitride containing Fe and Ni (hereinafter referred to as FeNi nitride). The nitriding treatment is not particularly limited as long as FeNi nitride can be obtained from FeNi-S, but examples of the nitriding treatment include gas nitriding with ammonia gas or nitrogen gas, plasma nitriding, and nitriding with metal amides. In particular, the nitriding treatment is carried out by heat-treating the prefabricated FeNi-S under an ammonia gas flow. The flow rate of ammonia gas in the nitriding treatment can be 0.1 to 10 liters per minute relative to 1 g of FeNi-S, preferably 0.5 to 5 liters per minute. The heat treatment temperature can be, for example, 300 to 500 °C, preferably 310 to 475 °C, 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 can be a S-containing FeNi nitride (hereinafter also referred to as FeNi nitride-S).

[0040] The S-containing FeNi alloy used in the nitriding process may have a disordered structure. The disordered structure mentioned here can be a structure in which the arrangement of atoms is irregular and has no degree of order, or a structure in which peaks of the L10 type ordered structure are not observed when measured by X-ray diffraction.

[0041] The FeNi-S used in the nitriding process can be manufactured by adding a compound containing a predetermined amount of sulfur element (hereinafter also referred to as sulfur compound) to a FeNi alloy manufactured by a known method as needed. FeNi-S can also be manufactured by mixing a FeNi alloy and a sulfur compound and then performing a heat treatment, or by reacting a FeNi alloy and a sulfur compound. FeNi-S can also be manufactured by partially sulfiding a FeNi alloy with hydrogen sulfide gas or the like. The sulfur compound should contain sulfur element, and examples of the sulfur compound include sulfur, organic sulfur compounds, metal sulfides (such as iron sulfide and nickel sulfide), and sulfates (such as ammonium sulfate, iron sulfate, and nickel sulfate).

[0042] The FeNi-S used in the nitriding process can be synthesized during the nitriding process. In particular, for example, FeNi nitride forms a layer by heat-treating an FeNi alloy under a mixed gas flow of ammonia gas and hydrogen sulfide, so that the synthesis of FeNi nitride-S and nitriding (sulphonitriding) proceed in parallel.

[0043] The ratio of the number of moles of Fe to the total number of moles of Fe and Ni in the FeNi-S used in the nitriding process can be 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.48 to 0.52.

[0044] The sulfur (S) content in the FeNi-S used in the nitriding process can be, for example, 0.01% by mass to 10% by mass, preferably 0.02% by mass to 2.0% by mass, more preferably 0.02% by mass to 1.5% by mass, still more preferably 0.03% by mass to 1.0% by mass, and particularly preferably 0.05% by mass to 0.7% by mass. When the S content in the FeNi-S used in the nitriding process is within the above range, there is a tendency to promote nitriding while suppressing deterioration of the magnetic properties of the finally obtained FeNi ordered alloy. The sulfur content can be measured by the method described in the following examples.

[0045] Examples of the FeNi nitride obtained in the nitriding process include FeNiN, Fe2Ni2N, etc.; in order to obtain the L10-type FeNi ordered alloy, a larger proportion of FeNiN is preferred. FeNiN has a crystal structure as shown in Figure 2 and can be identified by an XRD diffraction pattern. The proportion of the FeNi nitride contained after the nitriding process can be 90% by mass or more of the whole product. The proportion of FeNiN in the FeNi nitride can be 50% by mass or more, preferably 80% by mass or more. The nitride proportion and the FeNiN proportion after the nitriding process can be calculated by analyzing the XRD diffraction pattern by the reference intensity ratio (RIR) method.

[0046] In the FeNi nitride obtained in the nitriding process, the ratio of the number of moles of Fe to the total number of moles of Fe and Ni can 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 spectrometry or energy-dispersive X-ray spectrometry (EDS) using an electron microscope, etc.

[0047] 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 may be, for example, 0.01% by mass or more, preferably 0.03% by mass or more, more preferably 0.05% by mass or more. The upper limit of the S content in the L10-type FeNi ordered alloy may be, for example, 10% by mass or less, preferably 2.0% by mass or less, more preferably 1.5% by mass or less, 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 following examples.

[0048] When the FeNi nitride obtained in the nitriding process contains S, the FeNi nitride may be composed of particles. When the FeNi nitride is composed of particles, S may be present throughout the particles or may segregate inside the particles. In addition, S may segregate on the surface of the particles. The state of S can be measured by the method described in the following examples.

[0049] When the FeNi nitride obtained in the nitriding process is composed of particles, the lower limit of the average particle size may be, for example, 10 nm or more, preferably 50 nm or more, more preferably 100 nm or more. In addition, the upper limit of the average particle size may be, for example, 5000 nm or less, preferably 1000 nm or less, more preferably 500 nm or less. The average particle size can be measured from a scanning electron microscope (SEM) image.

[0050] The FeNi nitride obtained in the nitriding process may be composed of secondary particles in which primary particles are aggregated. In this case, the lower limit of the average particle size of the primary particles may be, for example, 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more. In addition, the upper limit of the average particle size may be, for example, 1000 nm or less, 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.

[0051] In the nitriding process, FeNi-S is nitrided. Therefore, as shown in the examples described later, a high nitriding efficiency can be obtained. The nitriding efficiency in the nitriding process can be greater than 4.7×10 -5 , preferably greater than 10×10 -5 , more preferably greater than 20×10 -5。The term "nitriding efficiency" used in the present disclosure refers to the number obtained by dividing the amount (g) of FeNiN formed by nitriding treatment by the amount (g) of nitrogen raw material consumed in the nitriding treatment. The nitriding efficiency (hereinafter referred to as ammonia efficiency) in the case where ammonia is used as the nitrogen source refers to the value obtained by dividing the amount of FeNiN formed (g) by the amount of ammonia consumed (g), and is 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.

[0052] In the nitriding step, an L10-type FeNi ordered alloy containing S can be used as the FeNi alloy. The L10-type FeNi ordered alloy containing S can be obtained, in addition to the L10-type FeNi ordered alloy containing S described in the present embodiment, by adding a predetermined amount of sulfur compound as needed to the L10-type FeNi ordered alloy manufactured by a known method. The L10-type FeNi ordered alloy containing S can also be manufactured by mixing the L10-type FeNi ordered alloy with a sulfur compound and then performing heat treatment, or by reacting the L10-type FeNi ordered alloy with a sulfur compound. The L10-type FeNi ordered alloy containing S can also be manufactured by partially sulfiding the L10-type FeNi ordered alloy with hydrogen sulfide gas or the like. The sulfur compound is as described above. When FeNi-S having an L10-type ordered structure is used, an improvement in the degree of order can be expected.

[0053] [Denitriding step]

[0054] In the denitriding step, the FeNi nitride obtained in the above nitriding step is denitrided to obtain an L10-type FeNi ordered alloy. In particular, after the FeNi nitride obtained in the nitriding step is pulverized, the denitriding treatment can be performed by heat-treating it in a hydrogen atmosphere. The flow rate of hydrogen in the denitriding treatment can be 0.01 to 10 liters per minute with respect to 1 g of FeNi nitride-S, preferably 0.1 to 5 liters per minute. 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 denitriding step can be an L10-type FeNi ordered alloy containing S.

[0055] Examples of the method for manufacturing the S-containing FeNi alloy used in the nitriding step will be described below.

[0056] (First embodiment)

[0057] As Figure 3 shown, the manufacturing method according to the first embodiment includes a reduction step of reducing an FeNi oxide containing S (hereinafter, also referred to as FeNi oxide-S) to obtain FeNi-S.

[0058] The reduction method in the reduction process is not particularly limited. However, for example, FeNi-S can be obtained by heat-treating an FeNi oxide containing S in a reducing gas atmosphere. The flow rate of the reducing gas can be 1 liter per minute relative to 8.5 g of FeNi oxide-S, preferably 0.5 to 10.0 liters per minute. 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 the reducing gas include hydrogen and carbon monoxide, and hydrogen is preferred from the viewpoint of reduction characteristics.

[0059] The ratio of the number of moles of Fe in FeNi oxide-S to the total number of moles of Fe and Ni can be 0.4 to 0.6, preferably 0.45 to 0.55, more preferably 0.48 to 0.52.

[0060] The FeNi oxide-S used in the reduction process may contain an Fe oxide, a Ni oxide, or an oxide containing Fe and Ni. In addition, the Fe oxide, the Ni oxide, and the oxide containing Fe and Ni may each contain S. The oxide containing Fe and Ni used herein means that an Fe element and a Ni element are contained in one oxide particle.

[0061] The FeNi oxide-S used in the reduction process can be produced by adding a predetermined amount of a sulfur compound to an FeNi oxide produced by this embodiment or a known method as needed. The FeNi oxide-S can also be produced by mixing an FeNi oxide and a sulfur compound and then performing a heat treatment, or by reacting an FeNi oxide and a sulfur compound. The FeNi oxide-S can also be produced by partially sulfiding an FeNi oxide with hydrogen sulfide gas or the like. The sulfur compound is as described above.

[0062] The FeNi oxide-S used in the reduction process can be synthesized during the reduction process. In particular, for example, an FeNi oxide is heat-treated under a mixed gas flow of hydrogen and hydrogen sulfide, so that the synthesis and reduction of FeNi oxide-S proceed in parallel.

[0063] The Fe oxide is not particularly limited. Examples of the Fe oxide include FeO, Fe2O3, Fe3O4, and 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. Among these substances, iron sulfate is preferred because it serves as a sulfur source for the S-containing Fe oxide. The S-containing Fe oxide can be produced by the above-described method for preparing FeNi oxide-S.

[0064] The Ni oxide is not particularly limited. Examples of the Ni oxide include NiO, and oxides obtained by oxidizing nickel metal, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel bromide, nickel sulfate, nickel nitrate, nickel phosphate, and nickel oxalate. Among these substances, nickel sulfate is preferred because it serves as a sulfur source for the S-containing Ni oxide. The S-containing Ni oxide can be produced by the above-described method for producing FeNi oxide-S.

[0065] The oxide containing Fe and Ni can be prepared by mixing a solution containing Fe and Ni with a precipitant to obtain a precipitate containing Fe and Ni (precipitation step), and subjecting the precipitate to heat treatment to obtain an oxide containing Fe and Ni (oxidation step). According to this method, it is easy to control the average particle diameter and particle size distribution of the obtained oxide containing Fe and Ni, and the distribution of Fe element and Ni element in the oxide containing Fe and Ni tends to be uniform.

[0066] [Precipitation step]

[0067] In the precipitation step, the Fe raw material and the Ni raw material are dissolved in a strong acidic solution to prepare a solution containing Fe and Ni.

[0068] The Fe raw material and the Ni raw material are not limited as long as they can be dissolved in an acidic solution. Examples of the Fe raw material include iron metal, iron oxide, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron sulfate, iron nitrate, iron phosphate, iron oxalate, etc. Iron metal, iron carbonate, iron sulfate, or iron chloride is preferably used, and iron sulfate is more preferably used because it serves as a sulfur source for the S-containing precipitate. Examples of the Ni raw material include nickel metal, nickel oxide, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel sulfate, nickel nitrate, nickel phosphate, and nickel oxalate. Nickel metal, nickel carbonate, nickel sulfate, or nickel chloride is preferably used, and nickel sulfate is more preferably used because it serves as a sulfur source for the S-containing precipitate. Examples of the acidic solution include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc. Among these substances, sulfuric acid is preferred because it serves as a sulfur source for the precipitate containing S, Fe, and Ni. The concentration of the solution containing Fe and Ni can be appropriately adjusted within the range in which the Fe raw material and the Ni raw material are substantially dissolved in the acidic solution.

[0069] In the solution containing Fe and Ni, the molar ratio of Fe to the total moles of Fe and Ni can be 0.4 to 0.6, preferably 0.45 to 0.55, and more preferably 0.48 to 0.52.

[0070] Precipitates containing Fe and Ni are obtained by reacting a solution containing Fe and Ni with a precipitant. In the reaction between the solution containing Fe and Ni and the precipitant, the precipitant can be added to the solution containing Fe and Ni, or the solution containing Fe and Ni can be added to the precipitant. The solution containing Fe and Ni mentioned here can be a solution containing Fe and Ni when reacting with the precipitant. The raw materials containing Fe and Ni can be prepared into separate solutions, and these solutions can be added to react with the precipitant. Even in the case where they are prepared into separate solutions, adjustment is made as appropriate within the range where each raw material is substantially dissolved in an acidic solution. The precipitant is not limited as long as it reacts with the solution containing Fe and Ni to obtain a precipitate. Examples of the precipitant include oxalic acid and alkaline solutions such as aqueous sodium hydroxide solution, aqueous sodium bicarbonate solution, aqueous potassium hydroxide solution, and aqueous lithium hydroxide solution. The precipitate can also be obtained by blowing carbon dioxide into the solution containing Fe and Ni. Examples of the precipitate include oxalate, carbonate, hydroxide, etc.

[0071] The precipitation process can include processes for separating and washing the precipitate. As a method for separating the precipitate, for example, after adding a solution (preferably water) to the obtained precipitate and mixing them, a filtration method or a decantation method can be used, etc. In addition, the washing can be carried out by repeating the same process for the precipitate that has been separated once.

[0072] After separating the precipitate, in order to prevent the precipitate from redissolving in the residual solvent during the heat treatment in the subsequent oxidation process and to prevent the precipitate from aggregating when the solvent evaporates, it is preferable to remove the solvent from the precipitate. As a specific example of the method for removing the solvent, for example, when water is used as the solvent, the precipitate can be dried in an oven at a temperature in the range of 70 to 200 °C for 5 to 12 hours. After drying, if necessary, the particles can be crushed or pulverized to adjust the particle size.

[0073] Precipitates containing S, Fe, and Ni can be obtained by adding a predetermined amount of a sulfur compound during or after the reaction between the solution containing Fe and Ni and the precipitant as needed, and can also be obtained by adding a sulfur compound in the separation and washing processes. Precipitates containing S, Fe, and Ni can also be prepared by adding a predetermined amount of a sulfur compound to the obtained precipitate, or by reacting the precipitate with a sulfur compound as needed. 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 the mixture. Precipitates containing S, Fe, and Ni can also be manufactured by sulfiding a part of the precipitate with hydrogen sulfide gas, etc. The sulfur compound is as described above.

[0074] [Oxidation process]

[0075] The oxidation process is a process of obtaining oxides containing Fe and Ni by heat-treating the precipitate containing Fe and Ni obtained in the precipitation process. The oxidation process can convert the precipitate into an oxide, for example, by heat treatment. When heat-treating the precipitate, the heat treatment must be carried out in the presence of oxygen and can be carried out, for example, in an air atmosphere. In addition, since the heat treatment must be carried out in the presence of oxygen, it is preferred that the non-metallic part of the precipitate contains oxygen atoms. When using a precipitate containing S, Fe, and Ni in the oxidation process, FeNi oxide-S can be obtained. If necessary, the obtained FeNi oxide-S can be crushed or pulverized to adjust the particle size.

[0076] The heat treatment temperature (hereinafter referred to as the oxidation temperature) in the oxidation process is not particularly limited, but the heat treatment temperature can be, for example, 200 to 800 °C, preferably 350 to 450 °C. The heat treatment time can be, for example, 4 to 24 hours, preferably 8 hours.

[0077] The obtained oxide is oxide particles in which Fe and Ni are sufficiently mixed microscopically and reflects the shape, particle size distribution, etc. of the precipitate.

[0078] The precipitate containing S, Fe, and Ni used in the oxidation process can be synthesized during the oxidation process. In particular, for example, the precipitate containing Fe and Ni is heat-treated under a mixed gas flow of air and hydrogen sulfide, so that the synthesis and oxidation of the precipitate containing S, Fe, and Ni are carried out in parallel.

[0079] (Second Embodiment)

[0080] The second embodiment is described below. The difference between this embodiment and the first embodiment lies in the manufacturing method of FeNiN, and other parts are similar to the first embodiment. Therefore, only the parts different from the first embodiment will be described below. Hereinafter, the manufacturing method of the FeNi superlattice according to this embodiment will be described with reference to Figure 4 the flowchart shown in

[0081] First, as Figure 4As shown in , an FeNi alloy added with S is manufactured. In particular, first, FeNi powder is prepared. It is preferable to prepare FeNi powder having a composition ratio of Fe:Ni = 50:50. The composition ratio of Fe:Ni may be approximately 50:50. For example, it is sufficient that the ratio of Fe is 50 ± 3% and the ratio of Ni is the remaining {100 - (50 ± 3)}%. As such FeNi powder, for example, FeNi nanoparticles synthesized by a thermal plasma method manufactured by Nisshin Engineering Co., Ltd., FeNi powder synthesized by a gas atomization method manufactured by Epson Atmix, etc. can be used.

[0082] Next, the FeNi powder is reacted in a mixed gas of H2S gas and nitrogen (N2) gas. As a result, FeNi-S, which is an FeNi alloy added with S, is obtained. For example, 3% H2S gas + 97% N2 gas is used as the mixed gas, and heat treatment is performed at 200 to 500 °C for 2 to 24 hours to obtain FeNi-S.

[0083] After that, nitriding treatment is performed in the same manner as in the first embodiment to synthesize FeNiN-S, and then denitriding treatment is further performed to obtain an FeNi superlattice. The FeNi superlattice obtained as described above also contains S. Also in this case, as shown in the examples described later, high ammonia efficiency can also be obtained.

[0084] Hereinafter, examples in which FeNi-S is manufactured by various methods including the manufacturing method of the above-described embodiment and then nitriding and denitriding treatments are performed are compared with comparative examples using FeNi without sulfur.

[0085] Figure 5 is a graph showing how the differences in the manufacturing conditions of the FeNi superlattice, the formation rate of FeNiN, the ammonia efficiency, etc. in each example and comparative (COMP) example change. In Figure 5 the S doping method, (1) represents the manufacturing method of the first embodiment, (2) represents the manufacturing method of the second embodiment, and the details of Examples 1 to 5 will be described later. Example 6 shows a case where FeNi-S is synthesized by reacting FeNi alloy particles manufactured by the gas atomization method of the second embodiment with ammonium sulfate. Example 7 shows a case where FeNi-S is synthesized by reacting ammonium sulfate with FeNi alloy particles manufactured by the thermal plasma method in the second embodiment. Comparative Examples 1 and 2 show cases where FeNi manufactured by the thermal plasma method is nitrided and denitrided without reacting with ammonium sulfate.

[0086] Note that Figure 5The sulfur content (% by mass) shown in [Fig. 0] (i.e., the mass ratio of S to the total mass of Fe, Ni, and S) is evaluated by using a commonly used elemental mass analysis method. For example, the sulfur content can be determined by inductively coupled plasma (ICP) emission spectrometry or energy-dispersive X-ray spectroscopy (EDS) using an electron microscope, etc. The sulfur content (% by mass) before and after the nitriding and denitriding treatments is substantially the same. The FeNiN formation rate is the ratio of the amount of FeNiN formed after the nitriding treatment to the amount of the FeNi alloy before the nitriding treatment, and is calculated by the reference intensity ratio (RIR) method by measuring the powder XRD pattern. More specifically, the FeNiN formation rate is: the ratio of the actually obtained amount of FeNiN to the ideal FeNiN formation amount when it is considered that the total amount of the FeNi alloy contained in the raw material before the nitriding treatment is obtained as FeNiN by the nitriding treatment. The RIR values of FeNiN, Fe2Ni2N, and the FeNi alloy stored in the database of the analysis software (PDXL2) attached to the XRD apparatus (SmartLab manufactured by Rigaku Corporation) are used to analyze the formation rate by the RIR method. In addition, the efficiency improvement rate represents the ratio of the ammonia efficiency in Comparative Example 1 and Examples 1 to 7, respectively, when Comparative Example 2 is used as a reference (REF).

[0087] Hereinafter, Examples 1 to 7, 9, 10, 12, and 13 will be described in detail. Unless otherwise specified, "%" is based on mass.

[0088] (Example 1)

[0089] [Precipitation step]

[0090] First, 0.34 liters of a 5 mass% iron sulfate aqueous solution and 0.2 liters of a 9 mass% nickel sulfate aqueous solution were added to 3 liters of a 10 mass% oxalic acid aqueous solution being stirred, so that the molar ratio of iron to nickel became 50:50. Thus, an oxalate slurry containing Fe, Ni, and S was obtained. After the obtained slurry was washed with pure water by decantation, the oxalate containing Fe and Ni was separated into a solid and a liquid. The separated oxalate containing Fe and Ni was dried in an oven at 100 °C for 10 hours. The S contained in the oxalate is considered to be brought about by the sulfate ions of iron sulfate or nickel sulfate as the raw material.

[0091] [Oxidation step]

[0092] Subsequently, 50 g of the obtained oxalate containing Fe, Ni, and S was heat-treated in air at 400 °C for 8 hours. After cooling, an oxide containing Fe, Ni, and S was obtained.

[0093] [Reduction step]

[0094] Subsequently, 8.5 g of oxides containing Fe, Ni, and S were heat-treated in a hydrogen atmosphere (hydrogen flow rate: 1 L / min) at 450 °C for 1.5 hours. After cooling, an FeNi alloy containing S was obtained. The sulfur content in the alloy was 0.03 mass%. The sulfur content was determined by dissolving the S-containing FeNi alloy in hydrochloric acid and measuring the mass ratio of S to the total mass of Fe, Ni, and S by ICP-AES method using an instrument named Optima 8300.

[0095] [Nitriding process]

[0096] Subsequently, 0.4 g of the S-containing FeNi alloy was heat-treated in an ammonia atmosphere (ammonia flow rate: 1 L / min) at 335 °C for 40 hours to obtain FeNiN. The formation rate of FeNiN was 95%. The FeNiN formation rate was measured by X-ray diffraction method using the kβ ray of Fe (wavelength: ) (instrument name: Smartlab, tube current: 200 mA, tube voltage: 45 kV), and it was defined as the ratio of the integrated intensity of the FeNiN peak (40°) to the sum of the integrated intensities of the FeNiN peak and the Fe2Ni2N peak (41.5°). In addition to the mass of the FeNi alloy as the raw material and the mass of the obtained FeNi nitride, the FeNiN formation rate was calculated by the reference intensity ratio (RIR) method using the measured powder XRD pattern.

[0097] [Denitriding process]

[0098] The obtained FeNiN was heat-treated in a hydrogen atmosphere (hydrogen flow rate: 1 L / min) at 250 °C for 20 hours to obtain an L10-type FeNi ordered alloy. It was confirmed that the sulfur content in the L10-type ordered alloy was 0.03 mass%, which was almost the same as the sulfur content in the S-containing FeNi alloy obtained in the reduction process. The sulfur content was determined by ICP-AES method after dissolving the obtained FeNi alloy in hydrochloric acid, and it was defined as the mass ratio of S to the total mass of Fe, Ni, and S.

[0099] (Example 2)

[0100] The same procedures as in Example 1 were carried out except that the heat treatment temperature in the nitriding process was changed to 415 °C.

[0101] (Example 3)

[0102] The same procedures as in Example 2 were carried out except that ammonium sulfate was added and the oxalate containing Fe, Ni, and S obtained in Example 1 was heat-treated. The addition amount of ammonium sulfate was 0.02 mass% relative to the oxalate. As a result, the sulfur content in the alloy particles was 0.05 mass%.

[0103] (Example 4)

[0104] The same procedures as in Example 2 were carried out, except that ammonium sulfate was added and the oxalate containing Fe, Ni, and S obtained in Example 1 was heat-treated. The addition amount of ammonium sulfate was 0.11% by mass relative to the oxalate. As a result, the sulfur content in the alloy particles was 0.14% by mass.

[0105] (Example 5)

[0106] The same procedures as in Example 2 were carried out, except that ammonium sulfate was added and the oxalate containing Fe, Ni, and S obtained in Example 1 was heat-treated. The addition amount of ammonium sulfate was 0.45% by mass relative to the oxalate. As a result, the sulfur content in the alloy particles was 0.48% by mass.

[0107] In each of Comparative Examples 1 and 2, since the FeNi superlattice was manufactured by a conventional manufacturing method in which sulfur was not added to FeNi, the sulfur doping method (S doping method) and the sulfur content (% by mass) were indicated by "-", which means "none". In the case where the amount of NH3 was 5 L / min and nitriding was carried out at 300 °C for 40 hours as in Comparative Example 2, the formation rate of FeNiN was 99% (which is almost 100%), and thus the ammonia efficiency was 4.7 (×10 -5 ), and this was used as a reference. On the other hand, when the amount of NH3 was 1 L / min as in Comparative Example 1 (which is less than that in Comparative Example 2), the formation rate of FeNiN was only 15%. The ammonia efficiency was only 3.6 (×10 -5 ), and the efficiency improvement rate was 0.76, which was significantly lower than the efficiency improvement rate of Comparative Example 2 that served as the reference.

[0108] From this, it can be seen that in the case of nitriding and denitriding FeNi without adding sulfur, the amount of NH3 cannot be reduced; unless the amount of NH3 is about 5 L / min, the FeNiN formation rate cannot be increased and the ammonia efficiency decreases.

[0109] The temperature during the nitriding treatment was set to 300 °C. In the case of FeNi without adding sulfur, when the temperature exceeded 300 °C, the FeNiN formation rate was unstable, and the ammonia efficiency decreased similarly. The nitriding treatment time was set to 40 hours. If the time was shorter than 40 hours, the FeNiN formation rate was unstable, and the ammonia efficiency decreased similarly. The sample amount was set to 400 mg. If the amount of FeNi to be nitrided at one time was increased, the FeNiN formation rate was unstable, and the ammonia efficiency decreased similarly. Therefore, as described above, if the amount of NH3 is reduced, the nitriding treatment time is shortened, or the amount of FeNi to be nitrided at one time is increased, the ammonia efficiency decreases, and pure FeNiN cannot be obtained.

[0110] On the other hand, in each of Examples 1 to 7, FeNi added with sulfur was subjected to nitriding and denitriding treatments, and in all cases of Examples 1 to 7, an ammonia efficiency higher than the reference was obtained.

[0111] In Example 1, the sulfur content was as low as 0.03 (mass %), but even when the amount of NH3 was reduced to 1 liter / minute under nitriding conditions of 335 °C for 40 hours, the FeNiN formation rate was a high value of 95%, and the ammonia efficiency was a high value of 22.9 (×10 -5 ). The efficiency improvement rate was also a high value of 4.8.

[0112] In Example 2, with the same sulfur content as in Example 1, only the nitriding temperature was raised to 415 °C. Although the FeNiN formation rate decreased to 43%, the ammonia efficiency was 10.4 (×10 -5 ), which was higher than the reference. The efficiency improvement rate was also a high value of 2.2.

[0113] In Example 3, the sulfur content was set to 0.05 (mass %) (higher than the sulfur content in Example 1), the FeNiN formation rate was as high as 97%, and the ammonia efficiency was a high value of 23.6 (×10 -5 ). The efficiency improvement rate was also a high value of 4.9. As will be described later, it has been confirmed that the FeNiN formation rate can be increased by changing the temperature of the nitriding treatment according to the sulfur content. In Example 3, the nitriding temperature was set to 415 °C in order to increase the FeNiN formation rate. Therefore, the FeNiN formation rate can be a particularly high value, and a higher ammonia efficiency was obtained.

[0114] In Example 4, the sulfur content was increased to 0.14 (mass %) (higher than the sulfur content in Example 3), and the nitriding conditions were the same as those in Example 3. The FeNiN formation rate remained at a high value of 90%, and the ammonia efficiency was maintained at a high value of 21.8 (×10 -5 ). The efficiency improvement rate was also a high value of 4.6. In Examples 5 to 7, the sulfur content was increased to more than that in Example 4, and the same nitriding conditions as in Examples 3 and 4 were used. In Example 5, the sulfur content was set to 0.48 (mass %), the FeNiN formation rate was 94%, the ammonia efficiency was 22.8 (×10 -5 ), and the efficiency improvement rate was 4.8, all of which were high values. In Example 6, the sulfur content was set to 1.05 (mass %), the FeNiN formation rate was 92%, the ammonia efficiency was 22.1 (×10 -5 ), and the efficiency improvement rate was 4.7, all of which were high values. In Example 7, the sulfur content was set to 2.26 (mass %), the FeNiN formation rate was 88%, the ammonia efficiency was 21.2 (×10 -5), and the efficiency improvement rate is 4.5, and these values are all high values.

[0115] For reference, Figure 6 shows the XRD pattern measurement results of Comparative Example 2 and Example 3. Figure 6 The circles shown in are XRD diffraction peaks attributable to FeNiN. It can be seen that high-purity FeNiN was obtained in both Comparative Example 2 and Example 3.

[0116] From these Examples 1 to 7, it can be seen that in the case where the FeNi superlattice is manufactured by adding sulfur to FeNi and then performing nitriding and denitriding treatments, compared with the conventional manufacturing method without adding sulfur, the FeNiN formation rate can be increased and the ammonia efficiency can be improved. In particular, by setting the sulfur content to 0.03 (mass%) or more, the ammonia efficiency can be increased to 2 times or more compared with the conventional manufacturing method. Therefore, in the FeNi superlattice of the present embodiment, by improving the ammonia efficiency, at least one of reducing the amount of NH3, shortening the nitriding time, and increasing the amount of material to be nitrided at one time can be implemented, which reduces the cost.

[0117] In addition, as in Examples 1 to 5, cross-sectional TEM observation and compositional image observation using TEM were performed on the FeNi superlattice manufactured by the manufacturing method of the first embodiment, and the results shown in 7A to 7D were obtained. Figure 7A shows the results of cross-sectional TEM observation, Figure 7B shows the S compositional image, Figure 7C is the Fe compositional image, and Figure 7D shows the Ni compositional image.

[0118] In the case where the particles 100 of the FeNi superlattice are distributed as shown in Figure 7A FeNi exists uniformly, as shown in the compositional images of Fe and Ni shown in Figure 7C and Figure 7D , and the FeNi superlattice is formed in a good state. Then, as shown in Figure 7B , it can be seen that S exists in a state of being distributed throughout, which corresponds to the distribution of the particles 100 of the FeNi superlattice. The fact that S exists in the entire particles 100 of the FeNi superlattice means that even during the manufacturing process of the FeNi superlattice, S exists in the entire FeNi alloy or FeNiN particles 100. In this way, it can be seen that in the case where S exists in the entire particles 100 of the superlattice (in other words, in the case where S exists in the entire particles 100 of the FeNi alloy or FeNiN during the manufacturing process of the FeNi superlattice), high ammonia efficiency can be obtained.

[0119] As shown in Figure 7A ,Figure 7C and Figure 7D As shown in Figure 7D , in each of Examples 1 to 5, the particle size of the FeNi superlattice is about 100 nm, but the particle size can be appropriately changed according to the purpose of applying the FeNi superlattice, and can be changed, for example, in the range of 100 nm to several μm. According to experiments, the particle size of the FeNi superlattice varies according to the sintering temperature for obtaining the FeNi oxide and the reduction temperature for obtaining the FeNi alloy, and has a tendency that the particle size tends to increase with the increase of temperature. Since the change in particle size affects the magnetic properties and environmental resistance, the sintering temperature and reduction temperature should be set according to the application purpose of the FeNi superlattice, so that the desired magnetic properties and environmental resistance can be obtained.

[0120] On the other hand, as in Examples 6 and 7, cross-sectional TEM observation and compositional image observation were also performed on the FeNi superlattice manufactured by the manufacturing method of the second embodiment. Then, the results with large particle sizes were extracted and shown in Figures 8A to 8D . Figure 8A The results of the cross-sectional TEM observation are shown, Figure 8B the S compositional image is shown, Figure 8C the Fe compositional image is shown, and Figure 8D the Ni compositional image is shown.

[0121] Even in the case of the FeNi superlattice in which a large particle size is confirmed as shown in Figure 8A , FeNi is uniformly present in the particles 100, as shown in the compositional images shown in Figure 8C and Figure 8D , and the FeNi superlattice is formed in a good state. Then, as shown in Figure 8B , it can be seen that S segregates and exists on the surface of the particles 100 of the FeNi superlattice. The fact that S segregates on the surface of the particles 100 of the FeNi superlattice means that even in the manufacturing process of the FeNi superlattice, S segregates on the surface of the FeNi alloy or FeNiN particles. Therefore, in the case where S segregates on the surface of the particles 100 of the FeNi superlattice (in other words, even if S segregates on the particle surface of the FeNi alloy or FeNiN during the manufacturing process of the FeNi superlattice), a high ammonia efficiency can be obtained.

[0122] Next, by changing the temperature during the nitriding treatment while maintaining the sulfur content, the FeNiN formation rate, ammonia efficiency, and efficiency improvement rate were examined. Specifically, in the case where the sulfur content was set to 0.14 (mass%) as in Example 4 above, experiments were carried out by changing the temperature of the nitriding treatment. In addition, as a comparative example, a similar experiment was carried out on the conventional manufacturing method. Figure 9 is a graph showing the results. InFigure 9 In Example 4, it is the same as Example 4 in Figure 5 . Examples 9 and 10 and Comparative Examples 9 and 10 show cases where only the temperature of the nitriding treatment is changed compared to Example 4. In addition, Comparative Example 2 is the same as Figure 5 Comparative Example 2 in. Comparative Examples 3 to 6 show cases where only the temperature of the nitriding treatment is changed compared to Comparative Example 2 and the NH3 flow rate is maintained at 5 L / min.

[0123] When the heat treatment temperatures of the nitriding treatment are 375°C and 450°C as shown in Examples 9 and 10, the FeNiN formation rates are 76% and 80% respectively, but the ammonia efficiencies are 18.4 (×10 -5 ) and 19.2 (×10 -5 ) respectively, which are high values. In addition, the efficiency improvement rates are also high values of 3.9 and 4.1 respectively. Moreover, even when the temperature of the nitriding treatment is set to 415°C (which is the temperature between Examples 9 and 10) as shown in Example 4, the ammonia efficiency and the efficiency improvement rate are also high.

[0124] In addition, when the heat treatment temperatures of the nitriding treatment are 325°C and 500°C as shown in Comparative Examples 9 and 10, the FeNiN formation rates are 12% and 3% respectively, and the ammonia efficiencies are 2.9 (×10 -5 ) and 0.72 (×10 -5 ) respectively. The efficiency improvement rates are 0.61 and 0.15 respectively. From these results, it can be seen that when 0.14 mass% of S is added, by setting the temperature of the nitriding treatment in the temperature range higher than 325°C and lower than 500°C, the ammonia efficiency and the efficiency improvement rate are improved. More preferably, it can be seen that by setting the nitriding temperature in the temperature range of 375 to 450°C, the ammonia efficiency and the efficiency improvement rate can be improved.

[0125] On the other hand, in Comparative Examples 2 and 4, the FeNiN formation rate, the ammonia efficiency, and the efficiency improvement rate are relatively high values, but in Comparative Examples 3, 5, and 6, the FeNiN formation rate, the ammonia efficiency, and the efficiency improvement rate are relatively low or zero.

[0126] Specifically, when the temperatures of the nitriding treatment are 300°C and 325°C as in Comparative Examples 2 and 4, the FeNiN formation rates are 99% and 95% respectively, and the ammonia efficiencies are 4.7 (×10 -5 ) and 4.6 (×10 -5 ) respectively. The efficiency improvement rates are 1 and 0.98 respectively.

[0127] When the temperature of the nitriding treatment is 275 °C (which is lower than 300 °C) as in Comparative Example 3, the FeNiN formation rate is 0%, the ammonia efficiency is 0, and the efficiency improvement rate is 0. Similarly, when the temperature of the nitriding treatment is 375 °C and 415 °C as in Comparative Examples 5 and 6, the FeNiN formation rates are 9% and 0% respectively, and the ammonia efficiencies are 0.43 (×10 -5 ) and 0 respectively, and the efficiency improvement rates are low values of 0.09 and 0. These results indicate that in the case where S is not added, unless the temperature of the nitriding treatment is in the range of 300 to 325 °C, the required ammonia efficiency and efficiency improvement rate cannot be obtained.

[0128] As described above, in the case where S is added, by setting the temperature of the nitriding treatment to at least the temperature range of 375 to 450 °C, the required ammonia efficiency and efficiency improvement rate can be obtained. On the other hand, in the case of the conventional manufacturing method where S is not added, unless the temperature of the nitriding treatment is at least in the temperature range of 300 to 325 °C, the required ammonia efficiency and efficiency improvement rate cannot be obtained. Therefore, by adding S, the temperature range in which the required ammonia efficiency and efficiency improvement rate can be obtained can be expanded, and the process temperature can also be increased and the process window can be expanded. If the process temperature can be increased, FeNiN-S can be synthesized at a higher temperature, thereby improving the crystallinity of the FeNi superlattice. Therefore, the characteristics of the FeNi superlattice can be improved. In addition, if the process window can be expanded, the temperature of the nitriding treatment can be set within the range of the process window, which is beneficial for temperature control.

[0129] The above describes the example in which the sulfur content is 0.14 mass% as in Example 4, and based on the results of Examples 4, 9, and 10, the temperature of the nitriding treatment should be at least in the temperature range of 375 to 450 °C. However, this is only one example. For example, as shown in Example 1, by setting the temperature of the nitriding treatment to at least 335 °C or higher, a high ammonia efficiency and a high efficiency improvement rate can be obtained. Therefore, in the case where the sulfur content is 0.03 mass% or more and 2.26 mass% or less, the temperature of the nitriding treatment can be set in the range of 335 to 450 °C, thereby further expanding the process window.

[0130] In addition, while maintaining the sulfur content, the FeNiN formation rate, ammonia efficiency, and efficiency improvement rate were studied by changing the nitriding treatment time. Specifically, in the case where the sulfur content was set to 0.05 (mass%) as in Example 3 above, experiments were conducted by changing the nitriding treatment time. In addition, as a comparative example, similar experiments were conducted on the conventional manufacturing method. Figure 10 is a graph showing the results. In Figure 10 Example 3 is compared with Figure 5is the same as Example 3. Examples 12 and 13 show cases where only the nitriding treatment time is changed compared to Example 3. Additionally, Comparative Example 2 is the same as Figure 5 Comparative Example 2 therein. Comparative Examples 7 and 8 show cases where only the nitriding treatment time is changed compared to Comparative Example 2.

[0131] Even when the nitriding treatment times are 10 hours and 20 hours as shown in Examples 12 and 13 (which are shorter than 40 hours), the FeNiN formation rates are 88% and 93% respectively, and the ammonia efficiencies are 84.6 (×10 -5 ) and 44.9 (×10 -5 ), which are high values. In addition, the efficiency improvement rates are also high values of 17.9 and 9.5 respectively. Therefore, it can be said that in the case where S is added, even if the nitriding treatment time is shortened, the ammonia efficiency and the efficiency improvement rate can be increased.

[0132] On the other hand, when the nitriding treatment times are 10 hours and 20 hours as in Comparative Examples 7 and 8, the FeNiN formation rates are 5% and 40% respectively, and the ammonia efficiencies are 0.97 (×10 -5 ) and 3.9 (×10 -5 ). The efficiency improvement rates are 0.20 and 0.82 respectively. These results show that in the case where S is not added, unless the nitriding treatment time is 40 hours or longer, the required ammonia efficiency and efficiency improvement rate cannot be obtained.

[0133] As described above, in the case where S is added, even if the nitriding treatment time is shortened from 40 hours, a high ammonia efficiency and a high efficiency improvement rate can be obtained.

[0134] For reference, the degree of order and magnetic properties of the FeNi superlattice magnet powder obtained by denitriding the FeNiN of Comparative Example 2, Example 3, and Example 7 at 250 °C for 4 hours were examined. The degree of order of the FeNi superlattice obtained by denitriding the FeNi nitride of Comparative Example 2 is 0.71, while the degree of order of the FeNi superlattice obtained by denitriding the FeNi nitride of Example 3 is 0.68, and they are almost the same. The orderliness of Example 7 is 0.60. Figure 11 The respective hysteresis curves are shown. The coercive force of Comparative Example 2 is 142 kA / m. On the other hand, the coercive force of Example 3 is 135 kA / m, and the coercive force of Example 7 is 120 kA / m. The saturation magnetization of Comparative Example 2 is 139 Am 2 / kg, and the saturation magnetization of Example 3 is also 139 Am 2 / kg. The saturation magnetization of Example 7 is 91 Am 2 / kg. From these results, it can be seen that the FeNi superlattice with an appropriate amount of S added in Example 3 has the same performance as the FeNi superlattice without S added in Comparative Example 2. Since an excessive amount of sulfur in Example 7 led to a decrease in the saturation magnetization, the sulfur content is preferably 2 mass% or less from the viewpoint of magnetic properties.

[0135] From these results and Figure 5 the measurement results of the XRD patterns of Comparative Example 2 and Example 3 shown in

[0136] it can be seen that no influence of doping an appropriate amount of sulfur on the crystal structure and magnetic properties was observed. Therefore, it can be said that even when doping sulfur, the ammonia efficiency during the manufacture of the FeNi superlattice can be improved without deteriorating the performance, and the production efficiency of the FeNi superlattice can be increased.

[0137] (1) Energy calibration

[0138] Before measuring the sample, SK-edge XANES measurement of K2SO4 as a standard sample was performed. Energy calibration was carried out so that the peak at that time was 2481.70 eV.

[0139] (2) Sample preparation

[0140] The sample was embedded in an indium sheet, and the sample was fixed (attach) to the sample holder using a conductive carbon tape. The sample holder with the fixed sample was introduced into a He atmospheric pressure chamber, and He replacement was performed for about 30 minutes before the measurement.

[0141] (3) Main measurement

[0142] Partial fluorescence yield measurement was performed in the measurement range of 2440 to 2550 eV. The incident angle of the incident light with respect to the sample plate was 20°.

[0143] (4) Analysis of measurement results

[0144] The inventors of the present invention analyzed the measurement results using "Athena" as analysis software. Flattening and normalization were performed by setting the end E0 of 2471 eV, the pre-edge range of 2440 to 2470 eV, and the normalization range of 2508 to 2547 eV. Then, by comparing with the standard sample, it was determined whether there was due to S6+ The absorption peaks generated thereby and due to S 2- The absorption peaks generated thereby. The presence of the absorption peaks is determined by an increase in the absorption intensity that is 10 times or more the noise level (i.e., an S / N ratio of 10 or greater). The noise level is the average of the absolute values of the signal deviations in the range of 2440 to 2460 eV in the pre-edge range. Use (NH4)2SO4 as the S 6+ standard sample. Use FeS as the S 2- standard sample. The absorption peak that appears at 2482.0 ± 2 eV is due to S 6+ The peak generated thereby. The absorption peak that appears at 2471.5 ± 2 eV is due to S 2- The peak generated thereby. Based on the presence of these absorption peaks, the presence of S 2- and S 6+ states is determined.

[0145] As a result of the measurement and analysis, the results shown in Figure 12 were obtained. Figure 12 is a graph showing the X-ray absorption near-edge spectra (XANES) of the FeNi superlattice magnetic powders of Example 3 and Example 4, respectively. Figure 12 Also shown are the X-ray absorption near-edge spectra of (NH4)2SO4 and FeS as standard samples. As Figure 12 shown, in Examples 3 and 4, the oxidation numbers of sulfur are a mixture of S 2- and S 6+ . Compared with Example 4, Example 3 contains more S 6+ . Compared with Example 3, Example 4 contains more S 2- . Incidentally, although not shown, it has been confirmed that the oxidation numbers of sulfur are substantially the same before and after the denitrification treatment in each of Examples 3 and 4.

[0146] From Figure 12 the results shown, it can be seen that the sulfur contained in the FeNi superlattice is not in the state of elemental sulfur, but in a state of combination with other elements. Furthermore, from Figure 12 the results shown and Figure 5 the ammonia efficiency results of Examples 3 and 4 shown, it can be said that even if the oxidation numbers of sulfur are different, an effect of improving the ammonia efficiency can be obtained. In Examples 3 and 4, the oxidation numbers of sulfur are a mixed state of S 2- and S 6+ , but even if the oxidation number of sulfur is only one of S 2- and S 6+ , an effect of improving the ammonia efficiency can be obtained. Furthermore, the oxidation number of the sulfur contained in the FeNi superlattice can be S 2- and S 6+Values other than this are acceptable as long as they can achieve the effect of improving ammonia efficiency.

[0147] (Other embodiments)

[0148] Although the present disclosure has been described in accordance with the above embodiments, the present disclosure is not limited to these embodiments and includes various modifications and equivalent modifications. In addition, although various elements are shown in exemplary various combinations and configurations, other combinations and configurations including more, fewer, or only a single element are also within the spirit and scope of the present disclosure.

[0149] For example, in the first embodiment, S is doped into the FeNi oxide, and in the second embodiment, S is doped into the FeNi alloy, but the doping of S can also be carried out during the nitriding treatment. In the first embodiment, S can be doped at the stage of Fe, Ni salts, or FeNi alloy. S can be doped during the nitriding treatment. In addition, the doping method of S is not limited to the methods described in the first and second embodiments, and any method can be used. For example, ammonium sulfate can be added to the raw material and then heat treatment can be carried out, or H2S can be applied to the raw material. For example, FeNi-S can be synthesized by any method, such as by adding ammonium sulfate to metallic FeNi or by impregnation nitriding by mixing H2S with NH3 gas during nitriding.

[0150] In the above second embodiment, as an example of the case where S segregates in the FeNi superlattice, S segregates on the surface of the particles of the FeNi superlattice. However, S can segregate to parts other than the surface. For example, S can segregate inside the particles of the FeNi superlattice.

[0151] The present disclosure is not limited to the above embodiments and can be appropriately modified. In the above embodiments, unless it is clearly stated that the element or feature is necessary, or unless the element or feature is clearly necessary in principle, a single element or feature of a specific embodiment is not necessarily necessary. In addition, in the above embodiments, when referring to numerical values such as the number, quantity, and range of the constituent elements of the embodiments, unless the numerical values are clearly indispensable therein (in particular, when the numerical values are clearly limited to specific numbers in principle), the present disclosure is not limited to specific numbers.

[0152] Aspects of the present disclosure will be described below. According to the first aspect, the L10-type FeNi ordered alloy has an L10-type ordered structure and contains sulfur.

[0153] According to the second aspect, the sulfur content of the L10-type FeNi ordered alloy according to the first aspect is 0.01 mass% or more.

[0154] According to a third aspect, the sulfur content of the L10-type FeNi ordered alloy according to the first aspect or the second aspect is 10% by mass or less.

[0155] According to a fourth aspect, the L10-type FeNi ordered alloy according to any one of the first to third aspects is composed of particles 100 having an L10-type ordered structure, and the sulfur is present throughout the particles.

[0156] According to a fifth aspect, the L10-type FeNi ordered alloy according to any one of the first to third aspects is composed of particles 100 having an L10-type ordered structure, and the sulfur segregates to the particles.

[0157] According to a sixth aspect, in the L10-type FeNi ordered alloy according to the fifth aspect, the sulfur segregates on the surface of the particles.

[0158] According to a seventh aspect, in the L10-type FeNi ordered alloy according to any one of the first to sixth aspects, the oxidation number of the sulfur includes S 2- or S 6+ or S 2- and S 6+ in a mixed state.

[0159] According to an eighth aspect, a method for manufacturing an L10-type FeNi ordered alloy includes subjecting a sulfur-containing FeNi alloy to a nitriding treatment to obtain nitrides containing Fe and Ni.

[0160] According to a ninth aspect, in the method for manufacturing an L10-type FeNi ordered alloy according to claim 8, the sulfur content in the FeNi alloy is 0.01% by mass or more.

[0161] According to a tenth aspect, in the method for manufacturing an L10-type FeNi ordered alloy according to the eighth aspect or the ninth aspect, the sulfur content in the FeNi alloy is 10% by mass or less.

[0162] According to an eleventh aspect, in the method for manufacturing an L10-type FeNi ordered alloy according to any one of the eighth to tenth aspects, the nitriding treatment includes a heat treatment at a temperature in the range of 300 to 500 °C.

[0163] According to a twelfth aspect, in the method for manufacturing an L10-type FeNi ordered alloy according to any one of the eighth to eleventh aspects, the nitriding treatment includes a heat treatment at a temperature in the range of 330 to 450 °C.

[0164] According to a thirteenth aspect, in the method for manufacturing the L10-type FeNi ordered alloy according to any one of the eighth to twelfth aspects, the nitriding efficiency in the nitriding treatment for obtaining the nitride containing Fe and Ni is greater than 4.7×10 -5 .

Claims

1. A method for manufacturing an L10-type iron-nickel (FeNi) ordered alloy by promoting nitridation of an FeNi alloy during a nitriding treatment by adding sulfur, the method comprising: Preparing an FeNi alloy containing sulfur; Subjecting the sulfur-containing FeNi alloy to a nitriding treatment to obtain a sulfur-containing FeNi nitride; and Subjecting the sulfur-containing FeNi nitride to a denitriding treatment to obtain an L10-type FeNi ordered alloy, Among them, wherein the sulfur content in the sulfur-containing FeNi alloy is 0.01% by mass or more and 10% by mass or less, and the nitriding treatment includes heat treatment at a temperature in the range of 330 to 450 °C.

2. The manufacturing method according to claim 1, wherein the nitriding efficiency in the nitriding treatment for obtaining the sulfur-containing FeNi nitride is greater than 4.7×10 -5 .

3. The manufacturing method according to claim 1, wherein the sulfur content in the sulfur-containing FeNi alloy is 0.03% by mass or more and 2.0% by mass or less, and the sulfur in the sulfur-containing FeNi alloy suppresses deterioration of the magnetic properties of the finally obtained L10-type FeNi ordered alloy.

Images