DE102022124393A1 - TYPE L10 ORDERED IRON-NICKEL ALLOY AND METHOD OF PRODUCTION OF TYPE L10 ORDERED IRON-NICKEL ALLOY - Google Patents

Abstract

An ordered L10-type iron-nickel (FeNi) alloy has an ordered L10-type structure and contains sulfur. The L10-type FeNi ordered alloy may have a sulfur content in a range of 0.01% to 10% by mass. A method for producing an ordered L10-type FeNi alloy comprises subjecting an FeNi alloy containing sulfur to a nitriding treatment to obtain a nitride containing Fe and Ni.

Description

The present disclosure relates to an ordered L1 ₀ type iron-nickel (FeNi) alloy (hereinafter also referred to as FeNi superlattice) having an ordered L1 ₀ type structure and a method for producing an ordered FeNi type alloy L1 ₀ .

FeNi superlattices are expected to be used as magnet materials with high heat resistance and materials for magnetic devices such as magnets. B. magnetic recording materials can be used. The Japanese Patent JP 6 332 359 B2 discloses, for example, a fabrication method for a high quality FeNi superlattice. In the manufacturing method, the high quality FeNi superlattice is manufactured using a nitriding and denitrating method 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 denitrating treatment.

However, in the conventional nitriding and denitrating method, a large amount of ammonia (NH ₃ ) is required for the nitriding treatment of the FeNi alloy as a raw material to synthesize FeNiN, which is a precursor of the FeNi superlattice, and the fact that the nitriding efficiency ( nitriding efficiency) is low is one of the factors increasing the production cost of the FeNi superlattice magnetic powder.

The inventors of the present invention repeatedly studied how to improve the nitriding efficiency and found that the nitriding efficiency is lowered because the nitride generated in the nitriding process is decomposed by heat.

In view of the above points, it is an object of the present disclosure to provide an ordered FeNi L1 ₀ type alloy and a manufacturing method for an ordered FeNi L1 ₀ type alloy, which can reduce production costs by improving nitriding efficiency.

According to an aspect of the present disclosure, an ordered L1 ₀ type FeNi alloy has an ordered L1 ₀ type structure and contains sulfur.

When the L1 ₀ type FeNi ordered alloy contains sulfur, that is, when the L1 ₀ type FeNi ordered alloy is formed using a sulfur-containing FeNi alloy as a raw material, high nitriding efficiency can be obtained.

According to another aspect of the present disclosure, a production method of an ordered L1 ₀ type FeNi alloy includes performing a nitriding treatment on an FeNi alloy containing sulfur to obtain a nitride containing Fe and Ni.

In this way, high nitriding efficiency can be obtained when the sulfur-containing FeNi alloy is subjected to nitriding treatment.

• 1 ein schematisches Diagramm, das eine Gitterstruktur einer geordneten FeNi-Struktur des Typs L1₀ zeigt;
• 2 ein schematisches Diagramm, das eine Gitterstruktur von FeNiN zeigt;
• 3 ein Flussdiagramm, das einen Syntheseprozess eines FeNi-Übergitters gemäß einer ersten Ausführungsform zeigt;
• 4 ein Flussdiagramm, das einen Syntheseprozess eines FeNi-Übergitters gemäß einer zweiten Ausführungsform zeigt;
• 5 ein Diagramm, das die Unterschiede in den Herstellungsbedingungen eines FeNi-Übergitters, der FeNiN-Bildungsrate, der Ammoniakeffizienz und dergleichen für jedes der Beispiele und Vergleichsbeispiele zeigt;
• 6 ein Diagramm, das die Messergebnisse eines Pulverröntgenbeugungsmusters (XRD) von Vergleichsbeispiel 2 und Beispiel 3 zeigt;
• 7A bis 7D Diagramme, die Ergebnisse einer Querschnitts-TEM-Betrachtung und einer Zusammensetzungsbildbetrachtung unter Verwendung eines Transmissionselektronenmikroskops (TEM) zeigen;
• 8A bis 8D Diagramme, die Ergebnisse der Querschnitts-TEM-Betrachtung und der Zusammensetzungsbildbetrachtung unter Verwendung des TEM zeigen;
• 9 ein Diagramm, das Unterschiede in den Herstellungsbedingungen eines FeNi-Übergitters, der FeNiN-Bildungsrate, der Ammoniakeffizienz und dergleichen für jedes der Beispiele und Vergleichsbeispiele zeigt;
• 10 ein Diagramm, das Unterschiede in den Herstellungsbedingungen eines FeNi-Übergitters, der FeNiN-Bildungsrate, der Ammoniakeffizienz und dergleichen für jedes der Beispiele und Vergleichsbeispiele zeigt;
• 11 ein Diagramm, das die magnetischen Eigenschaften eines FeNi-Übergitter-Magnetpulvers zeigt, das unter Verwendung von FeNiN aus Vergleichsbeispiel 2, Beispiel 3 und Beispiel 7 erhalten wurde; und
• 12 ein Diagramm, das Spektren einer Röntgen-Nahkanten-Absorptionsspektroskopie (XANES) für FeNi-Übergitter-Magnetpulver von Beispiel 3 und Beispiel 4 zeigt.

Other objects and advantages of the present disclosure will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawings. In the drawings is/are:

• 1 Fig. 12 is a schematic diagram showing a lattice structure of an L1 ₀ type FeNi ordered structure;
• 2 a schematic diagram showing a lattice structure of FeNiN;
• 3 14 is a flowchart showing a synthesis process of an FeNi superlattice according to a first embodiment;
• 4 14 is a flowchart showing a synthesis process of an FeNi superlattice according to a second embodiment;
• 5 Fig. 14 is a graph showing differences in FeNi superlattice manufacturing conditions, FeNiN formation rate, ammonia efficiency and the like for each of Examples and Comparative Examples;
• 6 Fig. 14 is a graph showing the measurement results of a powder X-ray diffraction (XRD) pattern of Comparative Example 2 and Example 3;
• 7A until 7D Diagrams showing results of cross-sectional TEM observation and compositional image observation using a transmission electron microscope (TEM);
• 8A until 8D charts showing results of cross-sectional TEM observation and compositional image observation using the TEM;
• 9 Fig. 14 is a graph showing differences in FeNi superlattice manufacturing conditions, FeNiN formation rate, ammonia efficiency and the like for each of Examples and Comparative Examples;
• 10 Fig. 14 is a graph showing differences in FeNi superlattice manufacturing conditions, FeNiN formation rate, ammonia efficiency and the like for each of Examples and Comparative Examples;
• 11 a graph showing magnetic properties of FeNi superlattice magnet powder obtained using FeNiN of Comparative Example 2, Example 3 and Example 7; and
• 12 Fig. 14 is a graph showing X-ray near-edge absorption spectroscopy (XANES) spectra for FeNi superlattice magnetic powders of Example 3 and Example 4.

Embodiments of the present disclosure are described in detail below. However, the embodiments described below are examples for implementing the technical idea 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 contained in another process as long as an intended purpose of the process is achieved, even if it cannot be clearly distinguished from the other process. In addition, the range of numbers indicated by the use of "to" denotes a range that includes the numerical value before or after "to" as the minimum value or maximum value, respectively. In the embodiments described below, the same or equivalent parts are denoted by the same reference numbers.

Ordered FeNi alloy of type L1 ₀

An ordered L1 ₀ type FeNi alloy of the present embodiment has an ordered L1 ₀ structure and contains sulfur. The L1 ₀ type ordered alloy mentioned here means that the regularity is 0.1 or more, and may preferably be 0.5 or more. In addition, the upper limit of regularity can be 1 or less. The L1 ₀ type ordered FeNi alloy according to the present embodiment can be used as magnetic powder and magnetic material. Examples of the magnetic material include magnetic materials such as sintered magnets, bonded magnets, and magnetic recording materials. The regularity S _reg indicates the degree of order in the FeNi superlattice. The ordered structure of type L1 ₀ has a structure based on a face-centered cubic lattice and has an as in 1 grid structure shown. In 1 an uppermost layer in a stacked structure on a (001) plane of the face-centered cubic lattice is defined as position I, and a middle layer located between the uppermost layer and an uppermost layer is defined as position II. In this case, the proportion of the metal A present at the I-position is defined as x and the proportion of the metal B present at the I-position is defined as (1-x). The proportion of metal A and metal B present at position I is expressed as A _x B _1-x . Likewise, the portion of metal B present at position II is defined as x and the portion of metal A present at position II is defined as (1-x). The proportion of metal A and metal B present at position II is expressed as A _1-x B _x . Here, x satisfies the relationship 0.5 ≤ x ≤1. In this case the regularity S _reg is defined as S _reg = 2x-1.

The estimation of the regularity S _reg is performed using an equation for estimating the regularity S _reg in the ordered FeNi alloy of the L1 ₀ type, which is shown in Equation 1 below. $$S_{\mathrm{right}eG}=\sqrt{\frac{{\left(I_{s\mathrm{and}p}/I_{f\mathrm{and}n\mathrm{i.e}}\right)}^{Obs}}{{\left(I_{s\mathrm{and}p}/I_{f\mathrm{and}n\mathrm{i.e}}\right)}^{cal}}}$$

Here, in Equation 1, “I _sup ” is an integrated intensity of a diffraction peak (superlattice diffraction peak) characteristic of the L1 ₀ type ordered alloy found in an X-ray diffraction (XRD) pattern observed by an XRD method. "If _and " is the integrated intensity of a diffraction peak (fundamental diffraction peak) appearing in both FeNi alloy and L1 ₀ type ordered FeNi alloy. "(I _sup /I _fund) ^obs " is the ratio of the integrated intensity of the superlattice diffraction peak and the integrated intensity of the fundamental diffraction peak in the X-ray diffraction pattern measured in each of Examples and Comparative Examples. Further, “(I _sup /I _fund ) ^cal ” is the ratio of the integrated intensity of the superlattice diffraction peak of the ordered FeNi alloy with a regularity of 1 estimated from the Rietbelt simulation and the integrated intensity of the ground diffraction peak. As shown in Equation 1, the regularity S _reg is obtained by taking the square root of these two ratios. A conventional device such as a SmartLab from Rigaku Co., Ltd. can be used as the XRD device. can be used, and the regularity S _reg can be accurately estimated by using Fe-kβ rays as X-rays.

The lower limit of the sulfur content (S content) in the ordered FeNi alloy of the type L1 ₀ z. B. 0.01% by mass or more, preferably 0.03% by mass or more and more preferably 0.1% by mass or more. The upper limit of the S content in the L1 ₀ type ordered FeNi 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, still more preferably 1. 0% by mass or less, more preferably 0.75% by mass or less, and more preferably 0.53% by mass or less. The S content can be measured by a method described in Examples below.

The oxidation number of sulfur (S) in the ordered L1 ₀ type FeNi alloy may comprise S ^2- or S ⁶⁺ or a mixed state of S ^2- and S ⁶⁺ . The oxidation number of sulfur can be measured by XAFS measurement (ie, fluorescence partial yield measurement) described later. The absorption peak appearing at 2482.0 ± 2 eV in the XAFS measurement can be regarded as the S ⁶⁺ peak, and the absorption peak appearing at 2471.5 ± 2 eV as the S ^2- peak. From the presence of these absorption peaks, it can be determined that S ^2- and S ⁶⁺ are present. In addition, the oxidation number of the sulfur contained in the FeNi superlattice can also be other than S ^2- and S ⁶⁺ as long as the effect of improving the ammonia efficiency can be obtained.

The ordered L1 ₀ type FeNi alloy may be composed of particles 100 having an ordered L1 ₀ type structure as in those described later 7 and 8th shown. In cases where the L1 ₀ type ordered FeNi alloy is composed of particles 100 having the L1 ₀ type ordered structure, S may be present throughout the particles, may be segregated within the particles, or may be present on the surfaces of the particles segregated. The state of the S can be measured by a method described in the following examples.

In cases where the L1 ₀ type ordered FeNi alloy is composed of particles having the L1 ₀ type ordered structure, the lower limit of the average particle size may be e.g. B. 10 nm or more, preferably 50 nm or more and more preferably 100 nm or more. In addition, the upper limit of the mean particle size z. B. 5000 nm or less, preferably 1000 nm or less and more preferably 500 nm or less. The mean particle size can be measured using scanning electron micrographs (SEM images).

The L1 ₀ type ordered FeNi alloy may consist of secondary particles in which primary particles are aggregated, and in this case the lower limit of the mean particle size of the primary particles may be e.g. B. 10 nm or more, preferably 30 nm and more preferably 50 nm or more. In addition, the upper limit of the mean particle size of the primary particles z. B. 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.

The proportion of the amount of Fe in the total amount of Fe and Ni in the ordered FeNi alloy of the _L10 type can be 0.4 to 0.6, preferably 0.45 to 0.55 and particularly preferably 0.48 to 0.52 be. The molar amount of Fe and Ni can be measured by inductively coupled plasma (ICP) emission spectroscopy, energy dispersive X-ray spectroscopy (EDS) using an electron microscope, or the like.

Manufacturing process for an ordered FeNi alloy of type L1 ₀

The manufacturing method for an ordered FeNi alloy of the L1 ₀ type according to the present embodiment comprises performing a nitriding treatment on an FeNi alloy containing sulfur (S) to obtain a nitride containing Fe and Ni. According to the present embodiment, the FeNi alloy used in the nitriding process contains S, so that the thermal decomposition of the FeNi nitrides generated in the nitriding process can be suppressed, which is intended to improve the nitriding efficiency. The L1 ₀ type ordered FeNi alloy produced according to the present embodiment is suitable for use as magnet powder and magnet material. Examples of the magnetic material are magnetic materials such as sintered magnets, bonded magnets and magnetic recording materials.

nitriding process

In the nitriding process, an FeNi alloy containing S (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 treatment using ammonia gas or nitrogen, plasma nitriding treatment, and nitriding treatment using metal amides. Specifically, the nitriding treatment is performed by heat treating prefabricated FeNi-S under an ammonia gas flow. The flow rate of the ammonia gas in the nitriding treatment may be 0.1 to 10 L/min, preferably 0.5 to 5 L/min based on 1 g of FeNi-S. The heat treatment temperature can e.g. 300 to 500°C, preferably 310 to 475°C and more preferably 330 to 450°C. The heat treatment time can e.g. B. 5 to 50 hours, preferably 10 to 20 hours. The FeNi nitride obtained in the nitriding process can have an S containing FeNi nitride (hereinafter also referred to as FeNi nitride-S).

The S-containing FeNi alloy used in the nitriding process can have a disordered structure. It may be a disordered structure in which the arrangement of atoms is random and has no regularity, or the peak of the ordered structure of the L1 ₀ type is not observed by X-ray diffraction.

The FeNi-S used in the nitriding process can be produced as needed by adding a compound containing a predetermined amount of the element sulfur (hereinafter also referred to as a sulfur compound) to an FeNi alloy prepared by a known method. The FeNi-S can also be produced by mixing the FeNi alloy and the sulfur compound and then heat-treating, or by reacting the FeNi alloy and the sulfur compound. The FeNi-S can also be produced by partially sulfurizing the FeNi alloy with hydrogen sulfide gas or the like. The sulfur compound should contain the element sulfur, 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.

The FeNi-S used in the nitriding process can be synthesized during the nitriding process. Specifically, FeNi nitride is formed, for example, by heat-treating the FeNi alloy under a mixed gas flow of ammonia gas and hydrogen sulfide, so that the synthesis and nitriding of FeNi nitride-S are performed in parallel (sulfonitriding).

The proportion of the molar amount of Fe to the total molar amount 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.

The content of sulfur (S) in FeNi-S used in the nitriding process may be, for example, 0.01% to 10% by mass, preferably 0.02% to 2.0% by mass, more preferably 0 .02% by mass to 1.5% by mass, 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 content of S in FeNi-S used in the nitriding process is within the above range, there is a tendency that nitriding can be promoted while suppressing the deterioration in magnetic performance of the ordered FeNi alloy finally obtained. The sulfur content can be measured by the method described in the examples below.

Examples of FeNi nitride obtained in the nitriding process are FeNiN, Fe ₂ Ni ₂ N and the like, and it is preferable that the proportion of FeNiN is large in order to obtain the L1 ₀ type ordered FeNi alloy. FeNiN has a crystal structure as in 2 shown on and can be identified from an XRD diffraction pattern. The proportion of FeNi nitride contained after the nitriding process can be 90% by mass or more of the entire product. The content of FeNiN in the FeNi nitride may be 50% by mass or more, and preferably 80% by mass or more. The content of nitrides and the content of FeNiN after the nitriding process can be calculated by analyzing the XRD diffraction pattern by the reference intensity ratio (RIR) method.

The molar ratio of Fe to the total molar quantity of Fe and Ni in the FeNi nitride obtained by 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 molar ratio of Fe and Ni can be measured by inductively coupled plasma (ICP) emission spectroscopy, energy dispersive X-ray spectroscopy (EDS) using an electron microscope, or the like.

The FeNi nitride obtained in the nitriding process may contain sulfur (S). In cases where 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, and more preferably 0.05% by mass or more be. The upper limit of the S content in the L1 ₀ type ordered FeNi 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, still more preferably 1. 0% by mass or less, and more preferably 0.7% by mass or less. The S content can be measured by the method described in the examples below.

In cases where the FeNi nitride obtained in the nitriding process contains S, the FeNi nitride may be particulate. In cases where the FeNi nitride consists of particles, S may be present throughout the particles or may be segregated inside the particles. In addition, S may be segregated on the surface of the particles. The state of the S can be measured by the method described in the examples below.

In cases where the FeNi nitride obtained in the nitriding process is particulate, the lower limit of the average particle size may be, for example, 10 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. Furthermore, the upper limit of the mean particle size z. B. 5000 nm or less, preferably 1000 nm or less and more preferably 500 nm or less. The mean particle size can be measured using scanning electron micrographs (SEM images).

The FeNi nitride obtained in the nitriding process may consist of secondary particles in which primary particles are aggregated, and in this case, the lower limit of the mean particle size of the primary particles may be e.g. B. 10 nm or more, preferably 30 nm or more and more preferably 50 nm or more. Furthermore, the upper limit of the mean particle size z. B. 1000 nm or less, preferably 500 nm or less. The mean particle size of the primary particles can be calculated by analyzing the XRD pattern by the Williamson-Hall method.

In the nitriding process, the nitriding treatment is performed on FeNi-S. Accordingly, it is possible to obtain high nitriding efficiency as shown in Examples described later. The nitriding efficiency in the nitriding process can be greater than 4.7×10 ^-5 , preferably greater than 10×10 ^-5 , and even more preferably greater than 20×10 ^-5 . The term "nitriding efficiency" means the number obtained by dividing the amount of FeNiN formed in the nitriding treatment (g) by the nitrogen raw material consumed in the nitriding treatment (g). The nitration efficiency in a case where ammonia is used as a nitrogen source (hereinafter referred to as ammonia efficiency) is the figure obtained when the amount (g) of FeNiN formed is divided by the amount (g) of ammonia consumed, and is the amount of ammonia required for the synthesis of FeNiN. A higher ammonia efficiency number means that FeNiN can be synthesized with a smaller amount of ammonia.

In the nitriding process, an ordered FeNi alloy of the L1 ₀ type containing S can be used as the FeNi alloy. The L1 ₀ -type FeNi ordered alloy containing S can be obtained by adding a predetermined amount of a sulfur compound as needed to the L1 ₀ -type FeNi ordered alloy prepared by a known method, in addition to that L1 ₀ -type S-containing ordered FeNi alloy described in the present embodiment. The S-containing L1 ₀ -type FeNi ordered alloy can be further prepared by mixing an L1 ₀ -type FeNi ordered alloy and a sulfur compound, followed by heat treatment, or by reacting an L1 ₀ -type FeNi ordered alloy with a sulfur compound. Further, the L1 ₀ -type FeNi ordered alloy containing S can be produced by partially sulfurizing an L1 ₀ -type FeNi ordered alloy with hydrogen sulfide gas or the like. The sulfur compound is as described above. In cases where FeNi-S having the L1 ₀ type ordered structure is used, an improvement in regularity can be expected.

denitration process

In the denitration process, the FeNi nitride obtained in the nitriding process described above is denitrated to obtain an ordered L1 ₀ type FeNi alloy. Specifically, after the FeNi nitride obtained in the nitriding process is pulverized, a denitration treatment can be performed by subjecting it to a heat treatment in a hydrogen atmosphere. The flow rate of hydrogen in the denitration treatment may be 0.01 to 10 l/min, preferably 0.1 to 5 l/min based on 1 g of FeNi nitride-S. The temperature of the heat treatment can e.g. 100 to 400°C, preferably 200 to 350°C. The heat treatment time can e.g. B. 1 to 24 hours, preferably 2 to 10 hours. The L1 ₀ type FeNi ordered alloy obtained in the denitration process may be an L1 ₀ type FeNi ordered alloy containing S.

Examples of a method for producing the S-containing FeNi alloy used in the nitriding process are described below.

First embodiment

As in 3 1, a manufacturing method according to a first embodiment includes a reduction process for reducing an S-containing FeNi oxide (hereinafter also referred to as FeNi-Oxid-S) to obtain an FeNi-S.

The reduction method in the reduction process is not particularly limited, but, for example, the FeNi-S can be obtained by heat-treating the FeNi oxide containing S in a reducing gas atmosphere. The throughput of the reducing gas can be 1 l/min, preferably 0.5 to 10.0 l/min, based on 8.5 g of the FeNi oxide S. The heat treatment temperature can e.g. 300 to 700°C, preferably 450 to 700°C. The heat treatment time can e.g. B. 1 to 10 hours, preferably 1.5 hours. Examples of reducing gases are hydrogen and carbon monoxide, with hydrogen being preferred from the viewpoint of reducing properties.

The proportion of the amount of Fe in the total number of moles of Fe and Ni in the FeNi oxide S can be 0.4 to 0.6, preferably 0.45 to 0.55 and particularly preferably 0.48 to 0.52.

The FeNi-Oxide-S used in the reduction process may contain an Fe oxide, a Ni oxide, or an oxide containing Fe and Ni. Further, each of the Fe oxide, the Ni oxide, and the oxide containing Fe and Ni may contain S. The oxide containing Fe and Ni as used herein means that element Fe and element Ni are contained in an oxide particle.

The FeNi oxide-S used in the reduction process can be produced by adding a predetermined amount of a sulfur compound to the FeNi oxide produced by the present embodiment or a known method as needed. Furthermore, the FeNi oxide-S can be produced by mixing the FeNi oxide and the sulfur compound and then heat-treating, or by reacting an FeNi oxide and a sulfur compound. Furthermore, the FeNi oxide-S can be produced by partially sulfurizing the FeNi oxide with hydrogen sulfide gas or the like. The sulfur compound is as described above.

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

The Fe oxide is not particularly limited. Examples of Fe oxides are FeO, Fe ₂ O ₃ , Fe ₃ O ₄ 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 them, ferrous sulfate is preferable since it serves as a sulfur source for the Fe oxide containing S. The Fe oxide containing S can be produced by the method for producing FeNi oxide-S described above.

The Ni oxide is not particularly limited. Examples of the Ni oxide are 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 them, nickel sulfate is preferable since it serves as a sulfur source for the S-containing Ni oxide. The Ni oxide containing S can be produced by the method for producing the FeNi oxide-S described above.

The oxide containing Fe and Ni can be prepared by mixing a solution containing Fe and Ni with a precipitating agent to obtain a precipitate containing Fe and Ni (precipitation process) and heat-treating the precipitate to obtain the oxide containing Ni and Ni ( oxidation process). By this method, it is easy to control the mean particle size and the particle size distribution of the resulting Fe and Ni-containing oxide, and the distribution of the element Fe and the element Ni in the Fe and Ni-containing oxide tends to be uniform.

precipitation process

In the precipitation process, Fe raw material and Ni raw material are dissolved in a strongly acidic solution to prepare a solution containing Fe and Ni.

The Fe and Ni raw materials are not limited as long as they can be dissolved in an acidic solution. Examples of the Fe raw material are iron metal, iron oxide, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron sulfate, iron nitrate, iron phosphate, iron oxalate and the like. It is preferable to use ferrous metal, ferrous carbonate, ferrous sulfate or ferric chloride, and it is more preferable to use ferrous sulfate 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. Preferably, nickel metal, nickel carbonate, nickel sulfate, or nickel chloride is used, with nickel sulfate being more preferable because it serves as a sulfur source for the S-containing precipitate. Examples of the acidic solution are sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid and the like. Among them, sulfuric acid is preferred since 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 adjusted in a range where the Fe raw material and the Ni raw material are substantially dissolved in the acidic solution.

The ratio of the molar amount of Fe to the total molar amount of Fe and Ni in the solution containing 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 precipitate containing Fe and Ni is obtained by reacting the solution containing Fe and Ni with the precipitating agent. In the reaction between the Fe and Ni containing solution and the precipitating agent, the precipitating agent may be added to the Fe and Ni containing solution or the Fe and Ni containing solution may be added to the precipitating agent. The solution containing Fe and Ni mentioned here may be a solution containing Fe and Ni when reacted with the precipitating agent. Raw materials containing Fe and Ni can be prepared as separate solutions, and the solutions can be added to react with the precipitant. Even when prepared as separate solutions, appropriate adjustments are made within the range that each raw material is substantially dissolved in the acidic solution. The precipitating agent is not limited as long as it reacts with the solution containing Fe and Ni to obtain the precipitate. Examples of the precipitating agent are oxalic acid and alkaline solutions such as a sodium hydroxide aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution and a lithium hydroxide aqueous solution. Furthermore, 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 and the like.

The precipitation process may include a process for separating and washing the precipitate. As a method for separating the precipitate z. B. after adding a solvent (preferably water) to the obtained precipitate and mixing it, a filtration method, a decantation method or the like can be used. Moreover, the washing of the precipitate once separated can be carried out by repeating the same procedure.

After separating the precipitate, in order to prevent the precipitate from being redissolved in the remaining solvent in the heat treatment of the subsequent oxidation process and the precipitate from aggregating in the evaporation of the solvent, it is preferable to remove the solvent from the precipitate. As a specific example of a method for removing the solvent, the precipitate can be e.g. B. in cases where water is used as solvent, dried in an oven at a temperature ranging from 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.

The precipitate containing S, Fe and Ni can be obtained by adding a predetermined amount of a sulfur compound as needed during or after the reaction between the Fe and Ni containing solution and the precipitant, and can be obtained by adding a sulfur compound in the process of separation and washing . Furthermore, the precipitate containing S, Fe and Ni can be prepared by adding a predetermined amount of a sulfur compound to the obtained precipitate or by reacting the precipitate with the sulfur compound, as needed. The reaction between the precipitate and the sulfur compound can e.g. B. be done by mixing the precipitate and the sulfur compound and then heat treating the mixture. Furthermore, the precipitate containing S, Fe, and Ni can also be prepared by sulfurizing part of the precipitate with hydrogen sulfide gas or the like. The sulfur compound is as described above.

oxidation process

The oxidation method is a method of obtaining an oxide containing Fe and Ni by heat-treating the precipitate containing Fe and Ni obtained in the precipitation process. The oxidation process can, for example, convert the precipitate to the oxide by heat treatment. In the case of the heat treatment of 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 performed in the presence of oxygen, it is preferable that the nonmetallic portion of the precipitate contains an oxygen atom. When the precipitate containing S, Fe and Ni is used in the oxidation process, the FeNi oxide-S can be obtained. The obtained FeNi-Oxide-S can be pulverized or crushed as needed to adjust the particle size.

The heat treatment temperature in the oxidation process (hereinafter referred to as oxidation temperature) is not particularly limited, but may 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.

The oxide obtained is an oxide particle in which Fe and Ni are sufficiently mixed microscopically, and the shape of the precipitate, the size distribution of the particles, and the like are reflected.

The precipitate containing S, Fe, and Ni used in the oxidation process can be synthesized during the oxidation process. Specifically, 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 the oxidation of the precipitate containing S, Fe and Ni are performed in parallel.

Second embodiment

A second embodiment will be described below. The present embodiment differs from the first embodiment in the manufacturing method of FeNiN, and the other parts are similar to those of the first embodiment. Therefore, only the part that differs from the first embodiment will be described below. A manufacturing method of an FeNi superlattice according to the present embodiment will be described below with reference to FIG 4 illustrated flow chart described.

First, as in 4 shown, an FeNi alloy to which S is added is prepared. Specifically, FeNi powder is first prepared. It is preferable to prepare FeNi powder having a composition ratio of Fe:Ni = 50:50. The composition ratio of Fe:Ni can be about 50:50. For example, it is sufficient if the Fe content is 50±3% and the Ni content is the remaining {100-(50±3)}%. As such FeNi powders, for example, FeNi nanoparticles synthesized by the thermal plasma method manufactured by Nisshin Engineering Co. Ltd., FeNi powders synthesized by the gas atomization method manufactured by Epson Atmix, and the like can be used.

The FeNi powder is then reacted in a gas mixture of H ₂ S gas and nitrogen (N ₂ ). As a result, FeNi-S, which is the FeNi alloy to which S is added, is obtained. For example, 3% H ₂ S gas + 97% N ₂ 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.

Thereafter, a nitriding process is performed in the same manner as in the first embodiment to synthesize the FeNiN-S, and then a further denitration treatment is performed to obtain the FeNi superlattice. The FeNi superlattice obtained as described above also contains S. Furthermore, as shown in Examples described later, it is possible to obtain high ammonia efficiency.

In the following, examples in which FeNi-S is produced by various methods including the production methods of the above-described embodiments and then subjected to nitriding and denitration treatment are compared with comparative examples using FeNi containing no S.

5 FIG. 14 is a diagram showing how the differences in the manufacturing conditions of an FeNi superlattice, the formation rate of FeNiN, the ammonia efficiency, and the like change in each example and comparative example. In an S-doping process in 5 (1) means the production method of the first embodiment, (2) means the production method of the second embodiment, and the details of Examples 1 to 5 will be described later. Example 6 shows a case where the FeNi-S is synthesized by reacting the FeNi alloy particles produced by the gas atomizing method of the second embodiment with ammonium sulfate. Example 7 shows a case where the FeNi-S is synthesized by reacting ammonium sulfate with FeNi alloy particles produced by the thermal plasma method of the second embodiment. Comparative Examples 1 and 2 show cases where the FeNi produced by the thermal plasma method is subjected to the nitriding and denitrating treatments without being reacted with ammonium sulfate.

Note that the in 5 shown sulfur content (mass %), ie the proportion of S in the total mass of Fe, Ni and S, is determined by a commonly used method of elementary mass analysis. For example, the sulfur content can be determined by inductively coupled plasma (ICP) emission spectroscopy, energy dispersive X-ray spectroscopy (EDS) using an electron microscope, or the like. The sulfur content (mass %) is substantially the same before and after the nitriding treatment and denitrating treatment. The FeNiN formation rate is the ratio of the amount of FeNiN formed after the nitriding treatment to the amount of FeNi alloy before the nitriding treatment, and is calculated by the reference intensity ratio (RIR) method by measuring the XRD powder pattern. Specifically, the FeNiN formation rate is a rate of actually obtained FeNiN amount with respect to the ideal FeNiN formation amount when it is assumed that the total amount of FeNi alloy contained in the raw material before the nitriding treatment is obtained as FeNiN by the nitriding treatment. For the analysis of the formation rate by the RIR method, the RIR values of FeNiN, Fe ₂ Ni ₂ N and FeNi alloy stored in the database of the analysis software (PDXL2) provided with the XRD device (SmartLab manufactured by Rigaku Corporation) is used. Further, the efficiency improvement rate indicates the rate of ammonia efficiency in each of Comparative Example 1 and Examples 1 to 7 when Comparative Example 2 is used as a reference (REF).

Examples 1 to 7, 9, 10, 12 and 13 are described in detail below. Unless otherwise stated, the "%" refers to the mass.

example 1

precipitation process

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

oxidation process

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

reduction process

Subsequently, 8.5 g of the 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 L/min). After cooling, an FeNi alloy containing S was obtained. The sulfur content in the alloy was 0.03% by mass. The sulfur content was determined by dissolving the S-containing FeNi alloy in hydrochloric acid and measuring the proportion of S in the total mass of Fe, Ni and S by the ICP-AES method with an Optima 8300 instrument.

nitriding process

Subsequently, 0.4 g of the S-containing FeNi alloy was heat-treated at 335° C. for 40 hours in an ammonia gas atmosphere (ammonia flow rate: 1 L/min) to obtain FeNiN. The FeNiN formation rate was 95%. The FeNiN formation rate was measured by an X-ray diffraction method (instrument name: Smartlab, tube current: 200 mA, tube voltage: 45 kV) using kβ rays of Fe (wavelength: 1.75653 Å) and as a proportion of the integrated intensity of FeNiN peak (40°) at the sum of the integrated intensity of the FeNiN peak and the integrated intensity of the Fe ₂ Ni ₂ N peak (41.5°). The FeNiN formation rate was calculated using the reference intensity ratio (RIR) method by measuring the powder XRD pattern in addition to the mass of the FeNi alloy as the raw material and the mass of the FeNi nitride obtained.

denitration process

The obtained FeNiN was heat-treated at 250°C for 20 hours in a hydrogen gas atmosphere (hydrogen flow rate: 1 L/min) to obtain an ordered L1 ₀ type FeNi alloy. It was confirmed that the sulfur content in the L1 ₀ type ordered FeNi alloy is 0.03% by mass, which is almost the same amount as in the S-containing FeNi alloy obtained through the reduction process. The sulfur content was measured by the ICP-AES method after dissolving the obtained FeNi alloy in hydrochloric acid and defined as the ratio of S to the total mass of Fe, Ni and S.

example 2

The same processes as in Example 1 were performed except that the heat treatment temperature in the nitriding process was changed to 415°C.

Example 3

The same processes as in Example 2 were carried out except that ammonium sulfate was added to the Fe-, Ni- and S-containing oxalate obtained in Example 1 and heat treatment was carried out. Ammonium sulfate was added in an amount of 0.02% by mass based on the oxalate. As a result, the sulfur content in the alloy particles was 0.05% by mass.

example 4

The same processes as in Example 2 were carried out except that ammonium sulfate was added to the Fe-, Ni- and S-containing oxalate obtained in Example 1 and heat treatment was carried out. Ammonium sulfate was added in an amount of 0.11% by mass based on the oxalate. As a result, the sulfur content in the alloy particles was 0.14% by mass.

Example 5

The same processes as in Example 2 were carried out except that ammonium sulfate was added to the Fe-, Ni- and S-containing oxalate obtained in Example 1 and heat treatment was carried out. Ammonium sulfate was added in an amount of 0.45% by mass based on the oxalate. As a result, the sulfur content in the alloy particles was 0.48% by mass.

In each of Comparative Examples 1 and 2, since the FeNi superlattice was produced by a conventional method in which sulfur was not added to FeNi, the doping method of sulfur (S doping method) and the sulfur content (mass %) are "-" stated what "no" means. In a case where the amount of NH ₃ was 5 L/min and the nitriding was performed at 300°C for 40 hours as in Comparative Example 2, the formation rate of FeNiN was 99%, which is nearly 100%, so that the ammonia efficiency of 4.7 (×10 ^-5 ) obtained at that time is used as a reference. On the other hand, as in Comparative Example 1, when the NH ₃ amount is 1 L/min, which is smaller than that in Comparative Example 2, the formation rate of FeNiN is only 15%. The ammonia efficiency was only 3.6 (×10 ^-5 ), and the efficiency improvement rate was 0.76, which is significantly lower than that of Comparative Example 2 serving as a reference.

From this, it is understood that in cases where FeNi to which sulfur is not added is subjected to nitriding treatment and denitration treatment, the amount of NH ₃ cannot be reduced unless the amount of NH ₃ is about 5 L/min , the FeNiN formation rate cannot be increased and the ammonia efficiency decreases.

The temperature during the nitriding treatment was set at 300°C. In the case of FeNi to which no sulfur is added, when the temperature exceeds 300°C, the FeNiN formation rate is not stabilized and the ammonia efficiency likewise decreases. The time for the nitriding treatment was set at 40 hours. If the time is shorter than 40 hours, the FeNiN formation rate will not be stabilized and the ammonia efficiency will decrease as well. The sample size was set at 400 mg. If the amount of FeNi to be nitrided at one time is increased, the FeNiN formation rate is not stabilized and the ammonia efficiency decreases as well. Therefore, as described above, if the amount of NH ₃ is reduced, the nitriding treatment is shortened, or the amount of FeNi to be nitrided simultaneously is increased, the ammonia efficiency decreases and pure FeNiN cannot be obtained.

On the other hand, in each of Examples 1 to 7, FeNi to which sulfur was added was subjected to the nitriding and denitration treatment, and in all cases of Examples 1 to 7, ammonia efficiency higher than the reference was obtained.

In Example 1, the sulfur was only 0.03 (mass %), but even when the NH ₃ amount was reduced to 1 L/min under the nitriding condition at 335°C for 40 hours, the FeNiN formation rate was at a high level of 95% and the ammonia efficiency at a high value of 22.9 (×10 ^-5 ). The efficiency improvement rate was also a high 4.8.

In example 2, with the same sulfur content as in example 1, only the nitration temperature was increased to 415°C. Although the FeNiN formation rate dropped to 43%, the ammonia efficiency was 10.4 (×10 ^-5 ), which is higher than the reference. The efficiency improvement rate was also at a high value of 2.2.

In Example 3, the sulfur content was set at 0.05 (mass%), which was higher than in Example 1. The FeNiN formation rate was 97%, and the ammonia efficiency was as high as 23.6 (×10 ^-5 ). The efficiency improvement rate was also a high 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 depending on the sulfur content. In Example 3, the nitriding temperature was set at 415°C to increase the FeNiN formation rate. This allowed the FeNiN formation rate to reach a particularly high value, and higher ammonia efficiency was obtained.

In Example 4, the sulfur content was increased to 0.14 (mass%), which is higher than in Example 3, and the nitriding conditions were the same as in Example 3. The FeNiN formation rate was kept as high as 90%, and the Ammonia efficiency was at a high of 21.8 (×10 ^-5 ) held. Furthermore, the efficiency improvement rate was a high value of 4.6. In Examples 5 to 7, the sulfur content was increased more than in Example 4, and the same nitriding conditions as in Examples 3 and 4 were used. In Example 5, the sulfur content was adjusted 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 at 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 at 2.26 (mass%), the FeNiN formation rate was 88%, the ammonia efficiency was 21.2 (×10 ^-5 ), and the efficiency improvement rate was 4.5, all high values.

For reference shows 6 the XRD measurement results for Comparative Example 2 and Example 3. The in 6 Circles shown are XRD diffraction peaks assigned to FeNiN. It can be seen that in both Comparative Example 2 and Example 3, high-purity FeNiN was obtained.

It is clear from these Examples 1 to 7 that in cases where the FeNi superlattice is produced by adding sulfur to FeNi and then nitriding and denitrating treatment, the FeNiN formation rate can be increased and the ammonia efficiency compared to the conventional production method, in which no sulfur is added, can be increased. Specifically, by adjusting the sulfur content to 0.03 (mass%) or more, ammonia efficiency can be improved by a factor of 2 or more compared to the conventional production method. Therefore, in the FeNi superlattice of the present embodiment, by increasing the ammonia efficiency, at least one of the following can be performed: reducing the amount of NH ₃ , shortening the nitriding time, and increasing the amount of material to be nitrided at once, which reduces costs.

In addition, as in Examples 1 to 5, the FeNi superlattice produced by the method of the first embodiment was subjected to a cross-sectional TEM observation and a composition image observation using a TEM, and the ones shown in FIGS 7A until 7D results shown. 7A shows the result of the cross-sectional TEM observation, 7B shows an S composition image, 7C shows an Fe composition picture and 7D shows a Ni composition image.

In a case where the FeNi superlattice particles 100 as in 7A are distributed, FeNi is uniformly present as in the composition pictures of Fe and Ni in 7C and 7D is shown, and the FeNi superlattice is formed in good condition. As in 7B As can be seen, S is present in a continuously distributed state, which corresponds to the distribution of FeNi superlattice particles 100 . The fact that S is present throughout the FeNi superlattice particles 100 means that S is also present in the entire FeNi alloy or FeNiN particles 100 in the process of fabricating the FeNi superlattice. In this way, it can be seen that high ammonia efficiency can be obtained in the cases where S is present throughout the particles 100 of the superlattice, in other words, in the cases where S is present throughout the particles 100 in the FeNi alloy or the FeNiN is present in the process of making the FeNi superlattice.

As in 7A , 7C and 7D shown, the particle diameter of the FeNi superlattice was about 100 nm in each of Examples 1 to 5, however, the particle diameter can be suitably changed according to the purpose of application of the FeNi superlattice and can range from 100 nm to several µm, for example be changed. According to experiments, the particle diameter of the FeNi superlattice changes depending on the sintering temperature at which the FeNi oxide is obtained and the reduction temperature at which the FeNi alloy is obtained, and there is a tendency that the particle diameter increases with increasing temperature increases. Since changes in particle diameter affect magnetic properties and environmental resistance, the sintering temperature and reduction temperature should be determined according to the purpose of use of the FeNi superlattice so that desired magnetic properties and environmental resistance can be obtained.

On the other hand, the FeNi superlattice produced by the method of the second embodiment was also subjected to cross-sectional TEM observation and compositional image observation as in Examples 6 and 7. Then, the results with a large particle diameter were extracted and put into 8A until 8D shown. 8A shows the result of the cross-sectional TEM observation, 8B shows an S composition image, 8C shows an Fe composition picture and 8D shows a Ni composition image.

Even in a case where the FeNi superlattice having a large particle size is confirmed, as in 8A As shown, FeNi is present uniformly in the particles 100 as in the composition images of Fe and Ni in FIG 8C and 8D is shown, and the FeNi superlattice is formed in good condition. As in 8B 12, it can be seen that S is segregated and present on the surface of the FeNi superlattice particles 100. FIG. The fact that S is segregated on the surface of the FeNi superlattice particles 100 means that S is already segregated on the surface of the FeNi alloy or FeNiN particles in the process of fabricating the FeNi superlattice. Thus, in cases where S is segregated on the surface of the FeNi superlattice particles 100, in other words, even if S is segregated on the particle surface of the FeNi alloy or FeNiN in the process of manufacturing the FeNi superlattice, a high ammonia efficiency can be obtained.

Next, the FeNiN formation rate, the ammonia efficiency, and the efficiency improvement rate by changing the temperature during the nitriding treatment while the sulfur content was kept the same were examined. Specifically, in the case where the sulfur content was set at 0.14 (mass %) as in Example 4 described above, the experiment was conducted by changing the temperature of the nitriding treatment. In addition, as a comparative example, a similar experiment was conducted with respect to the conventional manufacturing method. 9 is a graph showing the results. In 9 example 4 is the same as example 4 in 5 . Examples 9 and 10 and Comparative Examples 9 and 10 show cases where only the nitriding treatment temperature is changed from Example 4. In addition, Comparative Example 2 corresponds to Comparative Example 2 in 5 . Comparative Examples 3 to 6 show cases where only the nitriding treatment temperature is changed from Comparative Example 2 and the NH ₃ flow rate is kept at 5 L/min.

In cases where the heat treatment temperatures of the nitriding treatment were 375°C and 450°C, as shown in Examples 9 and 10, the FeNiN formation rates were 76% and 80%, respectively, but the ammonia efficiencies were as high as 18, 4 (×10 ^-5 ) and 19.2 (×10 ^-5 ), respectively. In addition, the efficiency improvement rates were also high at 3.9 and 4.1, respectively. Even when the temperature of the nitriding treatment was set at 415°C, which is a temperature between Examples 9 and 10, as in Example 4, the ammonia efficiency and the efficiency improvement rate were high.

In the cases where the heat treatment temperature of the nitriding treatment was 325°C and 500°C as shown in Comparative Examples 9 and 10, the FeNiN formation rates were 12% and 3%, respectively, and the ammonia efficiencies were 2.9 (×10 ^-5 ) and 0.72 (×10 ^-5 ), respectively. The efficiency improvement rates were 0.61 and 0.15, respectively. From these results, it is understood that in cases where 0.14% by mass of S is added, the ammonia efficiency and the efficiency improvement rate are increased by adjusting the nitriding treatment temperature to a temperature range of more than 325°C and less than 500°C C is set. Preferably, it can be found that the ammonia efficiency and the efficiency improvement rate can be increased by setting the nitriding temperature in the temperature range of 375 to 450°C.

In contrast, in Comparative Examples 2 and 4, FeNiN formation rates, ammonia efficiencies, and efficiency improvement rates were relatively high, but in Comparative Examples 3, 5, and 6, FeNiN formation rates, ammonia efficiencies, and efficiency improvement rates were relatively low or zero.

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

When the temperature in the nitriding treatment was 275°C, which is lower than 300°C, as in Comparative Example 3, the FeNiN formation rate was 0%, the ammonia efficiency was 0, and the efficiency improvement rate was 0. Similarly, in cases where the As in Comparative Examples 5 and 6, nitriding treatment temperatures were 375°C and 415°C, the FeNiN formation rates were 9% and 0%, and the ammonia efficiencies were 0.43 (×10 ^-5 ) and 0, respectively, and the efficiency improvement rates at low values of 0.09 and 0, respectively. These results show that in cases where no S is added, the desired ammonia efficiency and efficiency improvement rate can be obtained only when the nitriding treatment temperature is in the range of 300 to 325 ° C lies.

As described above, in cases where S is added, desired ammonia efficiency and efficiency improvement rate can be obtained by adjusting the temperature in the nitriding treatment to at least a temperature range of 375 to 450°C. On the other hand, in the conventional production method in which S is not added, the desired ammonia efficiency and efficiency improvement rate can be obtained only when the temperature in the nitriding treatment is at least in the temperature range is from 300 to 325 °C. Therefore, by adding S, it is possible to expand the temperature range in which the desired ammonia efficiency and efficiency improvement rate can be obtained, and further it is possible to increase the process temperature and expand the process window. If the process temperature can be increased, the FeNiN-S can be synthesized at a higher temperature, so that the crystallinity of the FeNi superlattice can be improved. Accordingly, the properties of the FeNi superlattice can be improved. If the process window can be widened, the nitriding treatment temperature can be adjusted within the process window range, which makes it easier to control the temperature.

Examples were described above in which the sulfur content is 0.14% by mass as in Example 4, and the temperature in the nitriding treatment should be at least in the temperature range of 375 to 450°C based on the results of Examples 4, 9 and 10. This is just an example, for example, as shown in Example 1, by setting the temperature in the nitriding treatment to at least 335°C or higher, high ammonia efficiency and high efficiency improvement rate can be obtained. Therefore, in cases where the sulfur content is 0.03% by mass or more and 2.26% by mass or less, the temperature in the nitriding treatment can be set in a range of 335 to 450°C, so that the process window is wider can be enlarged.

Further, the FeNiN formation rate, ammonia efficiency, and efficiency improvement rate by changing the nitriding treatment time with the sulfur content being the same were examined. Specifically, in a case where the sulfur content was set to 0.05 (mass %) as in Example 3 described above, the experiment in which the time of the nitriding treatment was changed was conducted. In addition, as comparative examples, a similar experiment was conducted with respect to the conventional manufacturing method. 10 is a graph showing the results. In 10 example 3 is the same as example 3 in 5 . Examples 12 and 13 show cases where only the nitriding treatment time is changed from Example 3. In addition, Comparative Example 2 corresponds to Comparative Example 2 in 5 . Comparative Examples 7 and 8 show cases where only the nitriding treatment time is changed from Comparative Example 2.

Even in cases where the duration of the nitriding treatment was shorter than 40 hours at 10 and 20 hours, as shown in Examples 12 and 13, the FeNiN formation rates were 88% and 93%, respectively, and the ammonia efficiency was as high as 84 .6 (×10 ^-5 ) and 44.9 (×10 ^-5 ), respectively. Furthermore, the efficiency improvement rates were high at 17.9 and 9.5, respectively. Therefore, it can be said that in cases where S is added, the ammonia efficiency and the efficiency improvement rate can be improved even if the nitriding treatment time is shortened.

On the other hand, in the cases where the nitriding treatment time was 10 and 20 hours, as in Comparative Examples 7 and 8, the FeNiN formation rates were 5 and 40%, respectively, and the ammonia efficiencies were 0.97 (×10 ^-5 ) and 3.9 (×10 ^-5 ). The efficiency improvement rates were 0.20 and 0.82, respectively. These results show that in cases where S is not added, the desired ammonia efficiency and efficiency improvement rate can be obtained only when the nitration treatment time is 40 hours or longer.

As described above, in cases where S is added, even if the nitration treatment time is shortened from 40 hours, high ammonia efficiency and high efficiency improvement rate can be obtained.

As a reference, the regularities and magnetic properties of the FeNi superlattice magnet powders obtained by denitrating the FeNiN of Comparative Example 2, Example 3 and Example 7 at 250°C for 4 hours were examined. The regularity of the FeNi superlattice obtained by denitrating the FeNi nitride of Comparative Example 2 was 0.71, while the regularity of the FeNi superlattice obtained by denitrating the FeNi nitride of Example 3 was 0.68 , which was almost the same. The regularity of Example 7 was 0.60. 11 shows the corresponding hysteresis curves. The coercive force of Comparative Example 2 was 142 kA/m. On the other hand, the coercive force of Example 3 was 135 kA/m, and the coercive force of Example 7 was 120 kA/m. The saturation magnetization of Comparative Example 2 was 139 Am ² /kg, and the saturation magnetization of Example 3 was also 139 Am ² /kg. The saturation magnetization of Example 7 was 91 Am ² /kg. From these results, it is understood that the FeNi superlattice to which an appropriate amount of S is added as in Example 3 has the same performance as that of the FeNi superlattice to which S is not added as in Comparative Example 2. Since an excessive amount of sulfur causes a decrease in saturation magnetization as in Example 7, the sulfur content is preferably 2% by mass or less from the viewpoint of magnetic performance.

From these results and the measurement results of the XRD samples of Comparative Example 2 and Example 3 shown in 5 are shown, no effect of doping with an appropriate amount of sulfur on the crystal structure and magnetic properties was observed. Therefore, it can be said that even if sulfur is doped, it is possible to improve the ammonia efficiency during the production of the FeNi superlattice without impairing the performance, and it is possible to increase the production efficiency of the FeNi superlattice.

In addition, the inventors examined the oxidation number of sulfur contained in the FeNi superlattice magnet powders obtained in Examples 3 and 4. Specifically, XAFS measurement (i.e., fluorescence partial yield measurement) was performed at the Aichi Synchrotron Light Center BL6N1 according to the following procedure.

(1) Energy Calibration

Before measuring the sample, an SK edge XANES measurement of K ₂ SO ₄ which is a standard sample was performed. The energy calibration was performed so that the peak value at that time was 2481.70 eV.

(2) sample preparation

The sample was embedded in an indium sheet and attached to a sample holder with conductive carbon tape. The sample holder to which the sample was attached was inserted into the He atmospheric pressure chamber, and He substitution was performed for about 30 minutes before the measurement.

(3) main measurement

The measurements of the partial fluorescence yield were carried out in the measuring range from 2440 to 2550 eV. The angle of incidence of the irradiated light was 20° with respect to the sample plate.

(4) Analysis of the measurement results

The inventors of the present application analyzed the results of the measurements using the "Athena" analysis software. Smoothing and normalization was performed by setting the final E0 to 2471 eV, the pre-edge range to 2440-2470 eV, and the normalization range to 2508-2547 eV. Then, the presence or absence of an absorption peak due to S ⁶⁺ and an absorption peak due to S ^2- were determined by comparison with standard samples. The presence or absence of the absorption peaks was determined by the increase in absorption intensity to 10 times or more the noise level (ie, an S/N ratio of 10 or more). This noise level is the mean of the absolute value of the deviation of the signal in the range from 2440 to 2460 eV in the pre-edge region. (NH ₄ ) ₂ S0 ₄ was used as the S ⁶⁺ standard sample. FeS was used as the S ² standard sample. The absorption peak appearing at 2482.0 ± 2 eV is the peak due to S ⁶⁺ . The absorption peak appearing at 2471.5 ± 2 eV is the peak due to S ^2- . From the presence of these absorption peaks, it was determined that the S ^2- and S ⁶⁺ states are present.

As a result of the measurements and analyses, the in 12 results shown. 12 13 is a graph showing X-ray absorption near-edge spectra (XANES) for FeNi superlattice magnetic powders of Example 3 and Example 4, respectively. 12 also shows the X-ray absorption near-edge spectra of (NH ₄ ) ₂ SO ₄ and FeS as standard samples. As in 12 shown, the oxidation number of the sulfur in both Examples 3 and 4 was a mixture of S ^2- and S ⁶⁺ . Example 3 contained more S ⁶⁺ than Example 4. Example 4 contained more S ^2- than Example 3. Incidentally, although not shown, it was confirmed that the oxidation numbers of sulfur before and after the denitration treatment in each of Examples 3 and 4 were im are essentially the same.

from the in 12 From the results shown, it is clear that the sulfur contained in the FeNi superlattice is not in the state of elemental sulfur but in the state of compound with other elements. from the in 12 results shown and the in 5 Furthermore, from the ammonia efficiency results shown in Examples 3 and 4, it can be deduced that even if the oxidation numbers of sulfur are different, the effect of improving the ammonia efficiency can be obtained. In Examples 3 and 4, the oxidation number of sulfur was in the mixed state of S ^2- and S ⁶⁺ , but the effect of improving the ammonia efficiency is obtained even when the oxidation number of sulfur is only one of S ^2- and S ⁶⁺ is. Further, the oxidation number of sulfur in the FeNi superlattice can be other than S ^2- and S ⁶⁺ as long as the effect of improving the ammonia efficiency can be obtained.

Other embodiments

While the present disclosure has been described in accordance with the embodiments described above, the present disclosure is not limited to these embodiments and includes various ones Modifications and Equivalent Modifications. In addition, while the various elements are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are within the spirit and scope of the present disclosure.

For example, in the first embodiment, S is doped into the FeNi oxide and in the second embodiment, S into the FeNi alloy, but S can be doped during the nitriding treatment. In the first embodiment, S may be doped at the level of Fe, Ni salt or FeNi alloy. S can be doped during the nitriding treatment. In addition, the S-type doping method is not limited to the methods described in the first and second embodiments, but any method can be used. For example, ammonium sulfate may be added to the raw material and then heat treatment may be performed, or H ₂ S may be applied to the raw material. For example, FeNi-S can be synthesized by any method such as adding ammonium sulfate to the metal FeNi or performing dip nitriding by mixing H ₂ S with NH ₃ gas during nitriding.

In the second embodiment described above, as an example of the case that S segregates in the FeNi superlattice, S segregates on the surface of the particles of the FeNi superlattice. However, S can also segregate in a region other than the surface. For example, S can be segregated inside the FeNi superlattice particles.

The present disclosure is not limited to the above-described embodiments and can be modified as appropriate. In each of the embodiments described above, individual elements or features are not necessarily essential to a particular embodiment unless specifically stated that the elements or features are essential or unless the elements or features are in principle obviously essential. Further, in each of the above-described embodiments, when reference is made to numerical values such as the number, amount, range and the like of the constituent parts of the embodiment, the present disclosure is not limited to the specific number except for the case where the numerical values are expressly are indispensable in particular, the case where the numerical values are apparently principally limited to a certain numerical value, and the like.

Various aspects of the present disclosure are described below. According to a first aspect, an ordered L1 ₀ type FeNi alloy has an ordered L1 ₀ type structure and contains sulfur.

According to a second aspect, the sulfur content of the ordered FeNi alloy of the L1 ₀ type according to the first aspect is 0.01% by mass or more.

According to a third aspect, the sulfur content of the ordered FeNi alloy of the L1 ₀ type according to the first aspect or the second aspect is 10% by mass or less.

According to a fourth aspect, the L1 ₀ type FeNi ordered alloy according to any one of the first to third aspects consists of particles 100 having the L1 ₀ type ordered structure, and the sulfur is present throughout the particles.

According to a fifth aspect, the L1 ₀ type FeNi ordered alloy according to any one of the first to third aspects consists of particles 100 having the L1 ₀ type ordered structure, and the sulfur is segregated on the particles.

According to a sixth aspect, in the ordered FeNi alloy of the L1 ₀ type according to the fifth aspect, the sulfur is segregated on the surfaces of the particles.

According to a seventh aspect, in the ordered FeNi alloy of the L1 ₀ type according to any one of the first to sixth aspects, the oxidation number of sulfur includes S ^2- or S ⁶⁺ or a mixed state of S ^2- and S ⁶⁺ .

According to an eighth aspect, a method for producing an ordered FeNi alloy of the L1 ₀ type comprises performing a nitriding treatment on an FeNi alloy containing sulfur to obtain a nitride containing Fe and Ni.

According to a ninth aspect, in the method for producing the ordered FeNi alloy of the L1 ₀ type according to the eighth aspect, the sulfur content in the FeNi alloy is 0.01% by mass or more.

According to a tenth aspect, in the method for producing the ordered FeNi alloy of the L1 ₀ type according to the eighth or ninth aspect, the sulfur content in the FeNi alloy is 10% by mass or less.

According to an eleventh aspect, in the method for producing the ordered FeNi alloy L1 ₀ type according to any one of the eighth to tenth aspects, the nitriding treatment includes a heat treatment at a temperature in a range of 300 to 500°C.

According to a twelfth aspect, in the method for producing the ordered FeNi alloy L1 ₀ type according to any one of the eighth to eleventh aspects, the nitriding treatment includes a heat treatment at a temperature ranging from 330 to 450°C.

According to a thirteenth aspect, in the method for producing the ordered FeNi L1 ₀ type 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 more than 4.7×10 ^-5 .

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Patent Literature Cited

• JP 6332359 B2 [0002]

Claims (13)

Ordered L1 ₀ -type iron-nickel (FeNi) alloy having an ordered L1 ₀ -type structure and containing sulfur. Ordered FeNi alloy of type L1 ₀ after claim 1 , wherein the sulfur content is 0.01% by mass or more. Ordered FeNi alloy of type L1 ₀ after claim 1 or 2 , wherein the sulfur content is 10% by mass or less. Ordered FeNi alloy of type L1 ₀ according to one of Claims 1 until 3 , where the ordered L1 ₀ type FeNi alloy consists of particles (100) having the ordered L1 ₀ type structure and the sulfur is present throughout the particles. Ordered FeNi alloy of type L1 ₀ according to one of Claims 1 until 3 , where the ordered L1 ₀ type FeNi alloy consists of particles (100) having the ordered L1 ₀ type structure and the sulfur is segregated on the particles. Ordered FeNi alloy of type L1 ₀ after claim 5 , where the sulfur is segregated on the surfaces of the particles. Ordered FeNi alloy of type L1 ₀ according to one of Claims 1 until 6 , where the oxidation number of sulfur includes S ^2- or S ⁶⁺ or a mixed state of S ^2- and S ⁶⁺ . A method for producing an ordered L1 ₀ type iron-nickel alloy (FeNi alloy), which comprises subjecting a FeNi alloy containing sulfur to a nitriding treatment to obtain a nitride containing Fe and Ni. manufacturing process claim 8 , wherein the sulfur content in the FeNi alloy is 0.01% by mass or more. manufacturing process claim 8 or 9 , wherein the sulfur content in the FeNi alloy is 10% by mass or less. Manufacturing process according to one of Claims 8 until 10 , wherein the nitriding treatment includes a heat treatment at a temperature in a range of 300 to 500°C. Manufacturing process according to one of Claims 8 until 11 , wherein the nitriding treatment includes a heat treatment at a temperature in a range of 330 to 450 °C. Manufacturing process according to one of Claims 8 until 12 , wherein the nitriding efficiency in the nitriding treatment for obtaining the nitride containing Fe and Ni is more than 4.7×10 ^-5 .

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