JP7243282B2 - FeNi ordered alloy, method for producing FeNi ordered alloy, and magnetic material containing FeNi ordered alloy - Google Patents

Description

The present invention provides an _L10 type FeNi (iron-nickel) ordered alloy having an _L10 type (Erwanzero type) ordered structure, a method for producing such an _L10 type FeNi ordered alloy, and furthermore, an _{L10 type FeNi} ordered alloy. It relates to magnetic materials comprising FeNi ordered alloys of the type.

The _L10 type FeNi ordered alloy is expected as a magnet material and a magnetic recording material that does not use rare earths or precious metals. Patent Document 1 discloses such an _L10 type FeNi ordered alloy. In Patent Document 1, a powder sample of an FeNi disordered alloy is subjected to a nitriding treatment, and then a denitrification treatment is performed to remove nitrogen from the nitrided FeNi disordered alloy. _{A 0} -type FeNi ordered alloy is obtained.

JP 2018-109238 A

However, in the method described in Patent Document 1, the surface of the particles of the obtained _L10 type FeNi ordered alloy is exposed, so the problems described in (1) to (4) below. was found to occur.

(1) The _L10 type FeNi ordered alloy is used as a magnetic material such as a magnet, and magnetic interaction is caused by the contact of the magnetic powder particles composed of the particles of the _L10 type FeNi ordered alloy. . This interaction causes a reduction in coercive force and causes a problem of degraded magnetic properties.

(2) In magnetic powder particles with high electric conductivity, when an electric conduction path is formed by contact between the magnetic powder particles, it becomes a cause of eddy current generation, which causes a problem of deteriorating the characteristics of the magnet.

(3) When particles of an _L10 type FeNi ordered alloy are used as magnetic powder and the magnetic powder is solidified with a composite material such as resin to form a bond magnet, the surface of the magnetic powder is is required to be in a state of good wettability to the composite material. For this reason, a surface treatment is performed to obtain such a surface state, but it is difficult to directly surface-treat the exposed surfaces of the particles of the FeNi disordered alloy.

(4) In order to expand the usage environment of magnets, it is desirable that the magnet surface has high weather resistance and high chemical stability against water, salt, and corrosive gases such as acids. However, the chemical stability of the _L10 type FeNi ordered alloy is not high.

The present invention has been made in view of the above problems, and is capable of suppressing deterioration of magnetic properties, and even when applied to a bonded magnet, exhibits good wettability with respect to composite materials and excellent chemical stability. It is an object of the present invention to provide an _L10 type FeNi ordered alloy having a sintering property, a method for producing the same, and a magnetic material containing the FeNi ordered alloy.

In order to achieve the above object, the FeNi ordered alloy according to claim 1 has _L10 type ordered structure particles (10), the particles are coated with insulating coatings (12, 13), The volume density of the FeNi ordered alloy in the whole particles and insulating coating is 80% or more .

In this way, the _L10 -type ordered structure particles are covered with an insulating coating. As a result, deterioration in magnetic properties can be suppressed, and even when applied to a bonded magnet, an FeNi ordered alloy having good wettability with respect to composite materials and excellent chemical stability can be obtained.

Further , in the method for producing an FeNi ordered alloy according to claim 7 , an insulating coating forming process is performed to cover the periphery of the FeNi disordered alloy powder particles (20) with insulating coatings (12, 13). , Nitriding treatment for nitriding the FeNi disordered alloy particles, followed by denitrification treatment for removing nitrogen from the nitrided FeNi disordered alloy particles, thereby covering the periphery with an insulating coating. obtaining particles (10) of an FeNi ordered alloy of _L10 type.

By these production methods, it is possible to produce an _L10 type FeNi ordered alloy having particles with an _L10 type ordered structure, the periphery of which is covered with an insulating coating.

It should be noted that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and specific components etc. described in the embodiments described later.

FIG. 2 is a cross-sectional view showing the appearance of particles of the FeNi ordered alloy described in the first embodiment; FIG. 2 is a flow chart showing a manufacturing process of the FeNi ordered alloy shown in FIG. 1. FIG. 1 is a chart showing a list of solvents used for forming an insulating coating, sources of materials for the insulating coating, and types of additives; FIG. 5 is a cross-sectional view showing the state of particles of the FeNi ordered alloy described in the second embodiment. 8 is a flow chart showing the manufacturing process of the FeNi ordered alloy described in the third embodiment. 6 is a cross-sectional view showing the particle cross-sectional structure corresponding to each step in FIG. 5; FIG.

An embodiment of the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, portions that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment will be described. The _L10 type FeNi ordered alloy, that is, the FeNi superlattice according to the present embodiment is applied to magnetic materials such as magnet materials and magnetic recording materials.

The _L10 -type regular structure is composed of a lattice structure based on a face-centered cubic lattice. A countless number of FeNi ordered alloy particles 10 having an _L10 type ordered structure as shown in FIG. 1 are collected and applied to a magnetic material.

The particles 10 have a particle size of about 200 to 500 nm and an average particle size of about 250 nm, for example. Each grain 10 may have any crystal structure, but is preferably composed of a single crystal and preferably composed of a single magnetic domain. It's good to be. When the particle size of the particles 10 is less than 200 nm, the coercive force is transferred due to the effect of thermal fluctuation, resulting in deterioration of the magnetic properties. Further, when the particle size of the particles 10 exceeds 500 nm, it is difficult to form a single magnetic domain, resulting in multiple magnetic domains. When multiple magnetic domains are formed, magnetization reversal occurs due to domain wall motion, so that the coercive force is reduced and the magnetic properties are deteriorated in the same manner as described above. Therefore, the particle size of the particles 10 is set to approximately 200 to 500 nm.

An insulating film 12 corresponding to an insulating coating is formed on the surface of the particle 10 . As a material constituting the insulating film 12, for example, oxides of III-VII group, XIII-XVI group elements such as silica, titania, zirconia, yttria and alumina can be used, and other insulating materials such as nitride films. You may use the film|membrane comprised by. Although the thickness of the insulating film 12 is arbitrary, it is preferably 1 nm or more, for example, 10 to 20 nm, in order to obtain sufficient insulation. On the other hand, if the insulating film 12 is too thick, the _L10 type FeNi ordered alloy grains 10 and the volume density of the FeNi ordered alloy in the insulating film 12 are reduced. As a result, the magnetic properties per weight or volume of the FeNi ordered alloy powder covering the surfaces of the particles 10 with the insulating film 12 are reduced. should set the upper limit of Preferably, the volume density of the FeNi ordered alloy in the particles 10 of the _L10 type FeNi ordered alloy and the insulating film 12 is 80% or more, that is, the volume density of the insulating film 12 is 20% or less.

By forming such an insulating film 12, the surface state of the particles 10 can be brought into a state capable of solving the problems (1) to (4) described above. This will be explained below.

First, since the non-magnetic insulating film 12 is formed on the surface of the particles 10, when the _L10 type FeNi ordered alloy of the present embodiment is used as a magnetic material such as a magnet, the magnetic powder composed of the particles 10 Direct contact between particles is suppressed. Therefore, magnetic interaction can be suppressed by the magnetic powder particles coming into contact with each other, so that the magnetic properties can be improved. This makes it possible to solve the problem (1).

Further, the FeNi ordered alloy particles 10 as in the present embodiment are magnetic powder particles with high electrical conductivity. For this reason, if an electrical conduction path is formed by contact between the magnetic powder particles composed of the particles 10, it becomes a cause of eddy current generation, resulting in deterioration of the characteristics of the magnet. contact is suppressed. Therefore, it is possible to solve the problem (2).

Next, when the _L10 type FeNi ordered alloy particles 10 are used as magnetic powder and the magnetic powder is solidified with a composite material such as resin to form a bonded magnet, the magnetic powder is It is required that the surface has good wettability to the composite material. Therefore, in the state where the surfaces of the particles 10 are covered with the insulating film 12 as in the present embodiment, it is sufficient that the insulating film 12 has good wettability with respect to the composite material. On the other hand, the insulating film 12 composed of oxides of group III to VII and group XIII to XVI elements has a surface state with many hydroxyl groups, and is in a chemical state that facilitates chemical modification. there is Therefore, the insulating film 12 has better wettability to commonly used composite materials such as polyamide and phenolic resin than the FeNi disordered alloy. Therefore, the process of directly surface-treating the exposed surfaces of the particles 10 of the FeNi disordered alloy can be omitted, and the problem (3) can be solved.

Furthermore, in order to expand the usage environment of magnets, it is desirable that the magnet surface has high weather resistance and high chemical stability against water, salt, and corrosive gases such as acids. , _L10 type FeNi ordered alloys are not highly chemically stable. On the other hand, if the surface of the particle 10 is covered with the insulating film 12 having high weather resistance and high chemical stability as in the present embodiment, the insulating film 12 prevents the particle 10 itself from being exposed to water, salt, and corrosion-resistant gas. As a result, the chemical stability of the particles 10 can be enhanced. Therefore, the problem (4) can be solved.

Thus, the particles 10 are covered with the insulating film 12 which is non-magnetic, insulating, in a chemical state that facilitates chemical modification, and has high chemical stability. As a result, it is possible to suppress the deterioration of the magnetic properties, and even if it is applied to a bonded magnet, it is possible to obtain an FeNi disordered alloy that has good wettability with respect to composite materials and excellent chemical stability. Therefore, the FeNi ordered alloy having an _L10 type ordered structure with good magnetic properties can be obtained, and can be used as a magnetic material with good magnetic properties.

That is, if countless particles 10 of such an FeNi ordered alloy with an _L10 type ordered structure are collected and sintered, or mixed with a composite material such as resin and solidified by molding to produce a magnet body, It can be a magnet having strong magnetic properties.

For such an _L10 type FeNi ordered alloy, for example, after performing a nitriding treatment for nitriding the FeNi disordered alloy, a denitrification treatment for removing nitrogen from the nitrided FeNi disordered alloy is performed, and then particles It is obtained by covering the circumference of 10 with an insulating film 12 .

The method for producing the _L10 type FeNi ordered alloy will be described below with reference to the flowchart showing the production steps shown in FIG.

First, as shown in step S100 in FIG. 2, powder of an FeNi ordered alloy having an _L10 type ordered structure is prepared. An FeNi ordered alloy with an _L10 type ordered structure can be produced using a known method as disclosed in Patent Document 1.

For example, first, a FeNi disordered alloy powder is prepared by a thermal plasma method, a flame spray method, a coprecipitation method, or the like. The particles of the FeNi disordered alloy powder preferably have a particle diameter of about 200 to 500 nm, like the _L10 type FeNi ordered alloy to be finally obtained.

Next, nitriding denitrification treatment is performed. This nitriding and denitrifying method can be performed using a nitriding and denitrifying treatment apparatus or the like, as disclosed in Patent Document 1 mentioned above, for example. Although not shown, the nitriding and denitrification treatment apparatus includes a tubular furnace as a heating furnace heated by a heater, and a glove box for placing a sample in the tubular furnace. In addition, the nitriding and denitrifying apparatus includes a gas introduction part for switching between Ar (argon) as a purge gas, NH ₃ for nitriding, and H ₂ (hydrogen) for denitrifying, and introducing it into the tubular furnace. ing. Using such a nitriding and denitrifying treatment apparatus, the nitriding and denitrifying treatment is performed as follows.

First, a prepared FeNi disordered alloy powder sample is placed in a tubular furnace. Then, nitriding treatment is performed. In this nitriding treatment, NH ₃ gas is introduced into the tubular furnace to create an NH ₃ atmosphere in the tubular furnace, and the FeNi disordered alloy is heated at a prescribed temperature for a prescribed period of time for nitriding. At this time, N is taken into FeNi by the nitriding treatment, and crystal ordering occurs. Preferably, when FeNiN, which is an FeNi compound, is generated, the metal element arrangement structure of the FeNi ordered alloy can be obtained at the stage of the nitriding treatment.

After that, denitrification treatment is performed. In the denitrification treatment, H ₂ gas is introduced into the heating furnace to create an H ₂ atmosphere in the tubular furnace, and the nitrided FeNi disordered alloy is heated at a predetermined temperature for a predetermined time to remove nitrogen. By removing nitrogen in this way, powder of an _L10 type FeNi ordered alloy can be obtained. Then, in steps S110 to S140, an insulating coating forming process is performed.

In step S110, a coating process is performed to coat the periphery of the _L10 type FeNi ordered alloy powder particles 10 with an insulating film 12 serving as an insulating coating. As the insulating film 12, as described above, for example, an oxide film of silica, titania, zirconia, yttria, alumina, or the like can be used. In addition, a film made of an insulating material such as a nitride film may be used. . As for the constituent material and formation of the insulating film 12, for example, the combination of the solvent, the material source of the insulating coating, and the additive shown in FIG. 3 may be applied.

Specifically, when the insulating film 12 is made of silica, a powder of an FeNi ordered alloy is mixed with a solvent such as water or ethanol to which tetraethoxysilane, which is a material source of the insulating coating, is added. Ammonia (NH ₃ ) aqueous solution is poured in. As a result, tetraethoxysilane and NH ₃ react with each other to produce silica, and the particles 10 of FeNi ordered alloy powder are coated with silica having a thickness of 10 to 20 nm, for example. In this manner, an insulating film 12 can be formed around the particles 10 .

Also, powder of FeNi ordered alloy is mixed with water, which is a solvent, added with sodium silicate, which is a material source of the insulating coating, and then hydrochloric acid (HCl), which is an additive, is poured. As a result, sodium silicate reacts with HCl to produce silica, and the periphery of the powder particles 10 of the FeNi ordered alloy is coated with silica having a thickness of, for example, 10 to 20 nm. In this way, the insulating film 12 can be formed around the particles 10 as well.

Similarly, when the insulating film 12 is composed of titania, ethanol can be used as a solvent, titanium tetraisopropoxide as a material source for the insulating coating, and NH ₃ as an additive. When the insulating film 12 is made of alumina, water can be used as a solvent, aluminum nitrate hexahydrate as a material source for the insulating coating, and NH ₃ as an additive. When the insulating film 12 is made of zirconia, water or ethanol can be used as the solvent, zirconium ethoxide can be used as the material source of the insulating coating, and NH ₃ can be used as the additive. When the insulating film 12 is made of yttria, water can be used as the solvent, yttrium chloride hexahydrate can be used as the material source of the insulating coating, and sodium hydroxide can be used as the additive.

In the case of forming the insulating film 12 from other materials, a general method known as a production method is applied, and powders of FeNi ordered alloys are mixed at the time of production to obtain various materials. can form the insulating film 12.

After that, in step S120, a cleaning process is performed. In the cleaning process, the unnecessary coating material formed at the same time as the insulating film 12 is formed to cover the particles 10 of the FeNi ordered alloy is removed. Here, centrifugation is performed after the reaction for forming the insulating film 12 to recover the solid content, and then the solvent at the time of reaction is added to the solid content and stirred, and then centrifuged again to recover the solid content. Unnecessary coating materials are removed by repeating this process multiple times. As a result, only the particles 10 of the FeNi ordered alloy covered with the insulating film 12 are sorted out.

Subsequently, a baking process is performed in step S130. For example, the insulating film 12 is baked by heating the FeNi ordered alloy covering the particles 10 with the insulating film 12 at a predetermined temperature for a predetermined time. When the particles 10 are only covered with the insulating film 12, the insulating film 12 may not have good crystallinity. For example, when it is desired to form the insulating film 12 with an oxide, the coating of the particles 10 may exist in the state of hydroxide only by the coating treatment in step S110, and it is possible to convert this into an oxide by firing. Then, the insulating film 12 has a more preferable crystal structure.

Thereafter, in step S140, evaluation processing is performed to select non-defective products and defective products. For example, evaluation of whether the insulating film 12 evenly covers the particles 10, whether the film thickness and crystallinity of the insulating film 12 are good, etc., by evaluating the workmanship using a scanning electron microscope (SEM) or X-ray diffraction (XRD). Then, those evaluated as non-defective products are used as magnetic materials. In this way, the insulating coating forming process is completed.

As described above, the _L10 type FeNi ordered alloy of the present embodiment can be produced. The particles 10 of the _L10 type FeNi ordered alloy thus produced are covered with an insulating film 12 which is non-magnetic, insulating, has a chemical state that facilitates chemical modification, and has high chemical stability. . Therefore, it is possible to suppress the deterioration of the magnetic properties, and even if it is applied to a bonded magnet, it is possible to obtain an FeNi disordered alloy that has good wettability with respect to composite materials and excellent chemical stability. Therefore, the FeNi ordered alloy having an _L10 type ordered structure with good magnetic properties can be obtained, and can be used as a magnetic material with good magnetic properties.

(Second embodiment)
A second embodiment will be described. This embodiment is different from the first embodiment in the configuration of the insulating coating, and is otherwise the same as the first embodiment. Therefore, only the parts different from the first embodiment will be described.

In the above-described first embodiment, the insulating film 12 is used as an example of the insulating coating, but in this embodiment, a powdery material is used.

As shown in FIG. 4, in this embodiment, particles 10 of the FeNi ordered alloy having the _L10 type ordered structure are covered with an insulator 13 of a powdery material serving as an insulating coating. The particles 10 may be covered with the insulator 13 made of such a powdery material. In this case, the insulator 13 cannot completely cover the entire circumference of the particle 10, and the weather resistance and chemical stability of the part of the particle 10 exposed from the insulator 13 may be degraded. However, since the insulator 13 covers a wide area around the particles 10 even if not the entire area, the weather resistance and chemical stability are improved as compared with the case where the insulator 13 is not covered. becomes possible.

In order to cover the particles 10 with the insulator 13 made of powder, the following process may be performed as the coating process in the insulating coating forming process.

For example, powder of the FeNi ordered alloy prepared in step S100 of FIG. 3 described in the first embodiment is mixed in a solution in which the powder of the insulating coating material is mixed with the solvent. Thereby, the periphery of the particles 10 can be covered with the insulator 13 . In addition, even if the powder of the insulating coating material is not mixed with the solvent, the particles 10 can be covered with the insulator 13 by directly sprinkling the powder of the insulating coating material on the powder of the FeNi ordered alloy. .

After that, through the remaining processes of the insulating coating forming process, that is, the cleaning process in step S120, the firing process in step S130, and the evaluation process in step _S140 in FIG. Ordered alloys can be obtained.

(Third embodiment)
A third embodiment will be described. This embodiment is different from the first and second embodiments in the method of manufacturing the FeNi ordered alloy, and is otherwise the same as the first and second embodiments. Only parts different from the form will be described. Here, the case where the present embodiment is applied to the case where the insulating film 12 is applied as in the first embodiment will be described as an example, but the insulator 13 made of powder as in the second embodiment is applied. This embodiment can also be applied when applying.

In this embodiment, the insulating film 12 is formed at the stage of the FeNi disordered alloy used for producing the FeNi disordered alloy, and the FeNi disordered alloy is produced therefrom. A method for producing such an FeNi disordered alloy will now be described with reference to the flow chart showing the production steps shown in FIG. 5 and the diagrams showing grain cross-sectional structures corresponding to the steps in FIG. 5 shown in FIG. Although FIG. 6 shows the cross-sectional structure of the grains, some of the grains are not hatched in order to make it easier to see the crystal structure.

First, in step S200 of FIG. 5, as described in step S100 of FIG. 3, FeNi disordered alloy powder is prepared by a well-known method. As a result, the FeNi disordered alloy powder particles 20 can be obtained in the state shown in FIG. 6(a). The grain 20 is polycrystalline, and has many grain boundaries in the crystal. The particle size of the particles 20 is preferably about 200 to 500 nm, like the _L10 type FeNi ordered alloy to be finally obtained. However, since densification or the like is performed by heat treatment to be described later, etc., and the particle size may change, the particle size does not necessarily have to be 200 to 500 nm.

Next, as shown in step S210, an insulating coating forming process is performed. Specifically, as the insulating coating forming process, the processes of steps S110 to S140 in FIG. 3 explained in the first embodiment are sequentially performed. Thereby, as shown in the state (b) of FIG. 6, the periphery of the particles 20 can be covered with the insulating film 12 .

Subsequently, as shown in step S220, heat treatment is performed. For example, heat treatment is performed at a temperature of 200 to 800° C. for one hour using hydrogen as an atmosphere gas. At this time, each particle 20 is covered with the insulating film 12 in step S210 described above. Therefore, even if the heat treatment is performed, the adjacent particles 20 can be isolated from each other, and as shown in the state (c) of FIG. Particles 20 of a FeNi disordered alloy, preferably monocrystalline, can be obtained. Here, the term “isolated state” means that the particles 20 are physically independent and can be separated from each other without being stuck together and integrated. .

Thereafter, as shown in step S230, a nitriding and denitrifying process is performed. This nitriding and denitrification method may be performed in the same manner as step S110 in FIG. 3 described in the first embodiment. By performing the nitriding and denitrification treatment in this way, powder of the _L10 type FeNi ordered alloy is obtained. That is, the particles 20 of the FeNi disordered alloy covered with the insulating film 12 are subjected to nitriding and denitrification treatment to form an _L10 type FeNi ordered alloy having the structure shown in FIG. 1, as shown in the state (d) of FIG. , that is, the particles 10 of the FeNi superlattice. In addition, since the particles 20 of the FeNi disordered alloy in an isolated state are subjected to the nitriding and denitrification treatment, the particles 10 of the _L10 type FeNi ordered alloy are also in a state in which adjacent particles 10 are isolated. Become.

As described above, the particles 20 of the FeNi disordered alloy may be covered with the insulating film 12 and then subjected to the nitriding and denitrification treatment to produce the _L10 type FeNi ordered alloy. Even in this way, the same effect as in the first embodiment can be obtained. Furthermore, since the FeNi disordered alloy is densified by heat treatment and then the nitriding and denitrification treatment is performed, it is possible to reduce the volume fraction of pores contained in the finished FeNi ordered alloy. It is possible to improve the magnetic properties.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the claims.

For example, in each of the above embodiments, an example of conditions for nitriding treatment, denitrification treatment, coating formation treatment, and heat treatment has been described. However, what has been described here is only an example of each condition.

Furthermore, the _L10 type FeNi ordered alloy according to the above embodiment is applied to magnetic materials such as magnet materials and magnetic recording materials, but the scope of application of this FeNi ordered alloy is not limited to magnetic materials. .

10 Particles 12 Insulating Film 13 Insulator 20 Particles

Claims (11)

It has particles (10) with an _L10 type ordered structure, the particles are covered with an insulating coating (12, 13), and the volume density of the FeNi ordered alloy in the whole of the particles and the insulating coating is 80 % or more FeNi ordered alloy. A FeNi ordered alloy according to claim 1, wherein said insulating coating is an insulating film (12). A FeNi ordered alloy according to claim 1, wherein said insulating coating is a powder insulator (13). 4. The FeNi ordered alloy according to claim 2, wherein said insulating coating has nitrogen permeability. The FeNi ordered alloy according to any one of claims 1 to 4, wherein said insulating coating is an oxide of group III-VII and group XIII-XVI elements. A magnetic material comprising the FeNi ordered alloy according to any one of claims 1 to 5. A method for producing an FeNi ordered alloy having an _L10 type ordered structure, comprising:
performing an insulating coating forming process of covering particles (20) of FeNi disordered alloy powder with insulating coatings (12, 13);
After performing a nitriding treatment for nitriding the particles of the FeNi disordered alloy, a denitrification treatment is performed to remove nitrogen from the particles of the FeNi disordered alloy subjected to the nitriding treatment, so that the surrounding area is covered by the insulating coating. obtaining coated _L10 type FeNi ordered alloy particles (10). 8. The method for producing an FeNi ordered alloy according to claim 7 , wherein in said insulating coating forming process, said particles are covered with said insulating coating having nitrogen permeability. 9. The method for producing an FeNi ordered alloy according to claim 7, further comprising densifying particles of said FeNi disordered alloy powder by heat treatment. 10. Production of the FeNi ordered alloy according to claim 9, wherein the nitriding treatment and the denitrifying treatment are performed after the densification, thereby reducing the volume fraction of pores contained in the FeNi ordered alloy. Method. L1 surrounded by the insulating coating ₀ 11. Any one of claims 7 to 10, wherein the volume density of said FeNi ordered alloy in the whole of said FeNi ordered alloy particles and said insulating coating is 80% or more in obtaining said particles of said FeNi ordered alloy of said type. The method for producing the FeNi ordered alloy according to 1.

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