JP2018182301A - Composite magnetic material and motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite magnetic material which includes an iron element, and which is high in aging stability.SOLUTION: A composite magnetic material 101 comprises: a soft magnetic material S; and a hard magnetic material H. The soft magnetic material S and the hard magnetic material H each include an iron element; 90 atom % or more and 100 atom % or less of the iron element included in the soft magnetic material S forms a first oxide or first composite oxide, and 90 atom % or more and 100 atom % or less of the iron element included in the hard magnetic material H forms a second oxide or second composite oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite magnetic material and a motor.

A neodymium magnet (composition: Nd ₂ Fe ₁₄ B, etc.) is known as a high-performance magnet. Neodymium magnets are widely used due to their high residual magnetic flux density and coercivity.

  The neodymium magnet contains neodymium, which is a rare earth element, as an essential component. Since rare earth elements are expensive and there is a possibility that the supply may become unstable, there is a demand to suppress the use amount of the rare earth elements. Therefore, attempts have been made to manufacture high-performance magnets while suppressing the amount of rare earth used.

Patent Document 1 discloses a core of a hard magnetic phase containing epsilon iron oxide (ε-Fe ₂ O ₃ ) and a shell of a soft magnetic phase containing alpha iron (α-Fe) and covering at least a part of the core. And a core-shell type magnetic material is described. In Patent Document 1, a nano-structure in which ε-Fe ₂ O _{3 is used} as a hard magnetic phase with high coercivity, and α-Fe is used as a soft magnetic phase with high saturation magnetic flux density, and both are magnetically coupled by exchange coupling action. Composite magnets are manufactured.

JP, 2011-35006, A

  In a magnetic material using an iron-based material containing an iron element, the iron-based material may be exposed on the surface of the magnetic material. This becomes particularly remarkable when iron-based materials are used as shells of core-shell type magnetic materials as described in Patent Document 1.

  When iron or an iron alloy is used as the iron-based material, the iron or iron alloy is easily oxidized by air or moisture. Therefore, if the iron or iron alloy constituting the magnetic material is exposed to the surface, it is oxidized by air or moisture, and the magnetic properties of the magnetic material are degraded. That is, the composite magnetic material containing an iron element has a problem that the stability over time is low.

  Then, in view of the above-mentioned subject, in the present invention, it is a composite magnetic material containing iron, and it aims at providing a magnetic material with high temporal stability.

  The composite magnetic material according to one aspect of the present invention is a composite magnetic material containing a soft magnetic material and a hard magnetic material, wherein the soft magnetic material and the hard magnetic material each contain an iron element, and the soft magnetic material 90 atomic% or more and 100 atomic% or less of the iron element contained in the first oxide or the first composite oxide, 90 atomic% or more and 100 atomic% or more of the iron element contained in the hard magnetic material The following is characterized in that a second oxide or a second composite oxide is formed.

  According to the present invention, it is possible to provide a composite magnetic material containing iron element and having high stability over time.

It is a figure which shows typically the structure of the composite magnetic material which concerns on 1st Embodiment. It is a figure which shows typically the structure of the composite magnetic material which concerns on 1st Embodiment.

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments, and appropriate modifications may be made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Those to which improvements and the like have been added are also included in the scope of the present invention.

First Embodiment
The composite magnetic material according to the present embodiment is a composite magnetic material containing a soft magnetic material and a hard magnetic material, and the soft magnetic material and the hard magnetic material each contain an iron element. Furthermore, 90 atomic% or more and 100 atomic% or less of the iron element contained in the soft magnetic material forms the first oxide or the first composite oxide, and 90 atomic% of the iron element contained in the hard magnetic material The above 100 at% or less forms the second iron oxide or the second composite oxide.

  Here, in the present specification, the “soft magnetic material” refers to a material having a small coercive force and a large saturation magnetic flux density. Further, in the present specification, “hard magnetic material” refers to a material having a large coercive force.

The composite magnetic material according to the present embodiment is fine in which two phases of a soft magnetic material phase (soft magnetic phase) and a hard magnetic material phase (hard magnetic phase) are adjacent to each other on the order of nm (nanometer). It has a mixed structure. By having such a fine mixed structure, an exchange coupling action can be exerted between the soft magnetic phase and the hard magnetic phase. When the exchange coupling action is working between the soft magnetic phase and the hard magnetic phase, the magnetization reversal of the soft magnetic phase is suppressed by the magnetization of the exchange-coupled hard magnetic phase when a reverse magnetic field is applied. At this time, the magnetization curve behaves as if it were a single phase magnet as if it were a soft magnetic phase and a hard magnetic phase by the exchange coupling action. Therefore, a magnetization curve having a large saturation magnetic flux density of the soft magnetic phase and a large coercivity of the hard magnetic phase is realized. As a result, high energy product (BH) _max can be realized. A magnet which exerts an exchange coupling action between the soft magnetic phase and the hard magnetic phase as described above is known as a nanocomposite magnet or a replacement spring magnet.

  FIG. 1 is a view schematically showing a structural example of the composite magnetic material according to the first embodiment. The composite magnetic material 101 according to the present embodiment is, as shown in FIG. 1A and FIG. 1B, an island having an island portion including the hard magnetic material H in a sea portion including the soft magnetic material S. It has a structure.

(Soft magnetic material S)
The soft magnetic material S is a material having a larger saturation magnetic flux density than the hard magnetic material H. The saturation magnetic flux density of the soft magnetic material S is not particularly limited, but is preferably 50 emu / g or more, and more preferably 70 emu / g or more.

  The soft magnetic material S contains an iron element, and 90 atomic% or more and 100 atomic% or less of the iron element contained in the soft magnetic material S form a first oxide or a first composite oxide. When the iron element contained in the soft magnetic material S forms iron or an iron alloy, the iron element is easily oxidized, and the temporal stability of the magnetic properties of the soft magnetic material S may be lowered. On the other hand, in the present embodiment, since 90 atomic% or more of the iron element contained in the soft magnetic material S forms the first oxide or the first composite oxide, the iron element is unlikely to be oxidized, and the soft magnetic material It can suppress that the magnetic characteristic of material S falls temporally.

In the first oxide or the first complex oxide formed by the iron element contained in the soft magnetic material S, part of Fe in Fe ₃ O ₄ or Fe ₃ O ₄ is Ga, Al, Ni, Co It is preferable to include a complex oxide substituted with at least one selected from the group consisting of Fe ₃ O ₄ (magnetite) has high stability in the air, and the soft magnetic material S containing Fe ₃ O ₄ can more effectively improve the temporal stability of the composite magnetic material 101. Further, since Fe ₃ O ₄ has a particularly high saturation magnetic flux density among iron-based oxide materials, the soft magnetic material S contains Fe ₃ O ₄ to increase the saturation magnetic flux density of the composite magnetic material 101. The energy product (BH) _max can be further increased.

In the first oxide or the first composite oxide formed by the iron element contained in the soft magnetic material S, part of Fe of γ-Fe ₂ O ₃ or γ-Fe ₂ O ₃ is Ga, Al It is preferable to include a complex oxide substituted by at least one selected from the group consisting of Ni and Co. γ-Fe ₂ O ₃ has high stability in the atmosphere, and the soft magnetic material S containing γ-Fe ₂ O ₃ can improve the temporal stability of the composite magnetic material 101 more effectively. .

In the first oxide or the first composite oxide formed by the iron element contained in the soft magnetic material S, part of Fe of α-Fe ₂ O ₃ or α-Fe ₂ O ₃ is Ga And the complex oxide substituted by at least one selected from the group consisting of Al, Ni and Co.

(Hard magnetic material H)
The hard magnetic material H is a material having a larger coercive force than the soft magnetic material S. The coercive force of the hard magnetic material H is not particularly limited, but is preferably 500 Oe or more, and more preferably 1000 Oe or more.

  The hard magnetic material H contains an iron element, and 90 atomic% or more and 100 atomic% or less of the iron element contained in the hard magnetic material H form a second oxide or a second composite oxide. When the iron element contained in the hard magnetic material H forms iron or an iron alloy, the iron element is easily oxidized, and the temporal stability of the magnetic characteristics of the hard magnetic material H may be lowered. On the other hand, in the present embodiment, since 90 atomic% or more of the iron element contained in the hard magnetic material H forms the second oxide or the second composite oxide, the iron element is not easily oxidized, and the hard magnetic material H is hard It can suppress that the magnetic characteristic of the material H falls with time.

In the second oxide or the second composite oxide formed by the iron element contained in the hard magnetic material H, part of ε-Fe ₂ O ₃ or ε-Fe ₂ O ₃ is Ga, Al, Ni It is preferable to include complex oxide substituted with at least one selected from the group consisting of ε-Fe ₂ O ₃ has high stability in the atmosphere, and the hard magnetic material H containing ε-Fe ₂ O ₃ can improve the temporal stability of the composite magnetic material 101 more effectively. . Further, since ε-Fe ₂ O ₃ has a particularly high coercive force among iron-based oxide materials, the hard magnetic material H contains ε-Fe ₂ O ₃ to make the coercivity of the composite magnetic material 101. The energy product (BH) _max can be further increased.

(Elements of composite magnetic material)
In the composite magnetic material 101 according to the present embodiment, when the total amount of the composite magnetic material 101 is 100% by mass, the content of Nd element is preferably 0% by mass or more and 3% by mass or less, and 0% by mass or more It is more preferable that it is 1 mass% or less. The composite magnetic material 101 particularly preferably contains substantially no Nd element. Thus, by reducing the content of the Nd element in the composite magnetic material 101, the cost of the composite magnetic material 101 can be reduced.

  The iron element contained in the composite magnetic material 101 according to the present embodiment is 90 atomic% or more and 100 atomic% or less of an oxide or complex oxide when the total amount of iron elements contained in the composite magnetic material 101 is 100 atomic%. It is preferable to form an object.

(Construction)
The composite magnetic material 101 according to the present embodiment has a sea-island structure having a sea part containing the soft magnetic material S and an island part containing the hard magnetic material H.

  In the present embodiment, although the sea portion includes the soft magnetic material S and the island portion includes the hard magnetic material H, the sea portion may include the hard magnetic material H and the island portion may include the soft magnetic material S. Good.

  The soft magnetic material S and the hard magnetic material H are preferably magnetically coupled by the exchange coupling action. Therefore, assuming that the distance at which the exchange coupling action works from the interface between the island and the sea (hereinafter referred to as “exchange coupling distance”) is a, in composite magnetic material 101, the average between two adjacent islands. The distance d preferably satisfies d ≦ 2a. That is, the average distance between two adjacent islands is preferably not more than twice the exchange coupling distance.

The average particle diameter of the particulate island containing the hard magnetic material H is preferably as large as possible so that the coercive force of the hard magnetic material H does not decrease. Also, if the hard magnetic material H comprises ε-Fe ₂ O _3, an average particle size of the particulate island portion comprising hard magnetic material H is the extent to which ε-Fe ₂ O ₃ it is possible to maintain the epsilon structure It is preferable to be small. Specifically, the average particle diameter of the particulate island including the hard magnetic material H is preferably 5 nm or more and 60 nm or less, and more preferably 10 nm or more and 40 nm or less.

(Method of manufacturing composite magnetic material)
The method for producing the composite magnetic material 101 according to the present embodiment is not particularly limited, and for example, the following method may be mentioned.

  The first method is a method in which particles of the soft magnetic material S and particles of the hard magnetic material H are prepared and mixed at an appropriate mixing ratio. After mixing and compression molding these, they may be heat treated.

When Fe ₃ O ₄ is used as the soft magnetic material S, nanoparticles of iron oxide or iron hydroxide are formed using a chemical process in solution, and the generated nanoparticles are heat-treated in a reducing atmosphere. Fe ₃ O ₄ nanoparticles can be synthesized relatively easily. When the heat treatment is performed in a reducing atmosphere, if the temperature of the heat treatment is too high or the time is too long, the reduction may proceed too much and α-Fe and the like may be generated. Therefore, the temperature of the heat treatment is preferably 200 ° C. or more and 400 ° C. or less, and the time is preferably 2 hours or more and 5 hours or less.

When γ-Fe ₂ O ₃ is used as the soft magnetic material S, nanoparticles of iron oxide or iron hydroxide are produced using a chemical process in solution, and the produced nanoparticles are heat-treated in an oxidizing atmosphere Thus, γ-Fe ₂ O ₃ nanoparticles can be relatively easily synthesized. For example, the temperature of the heat treatment is preferably 200 ° C. or more and 400 ° C. or less, and the time is preferably 2 hours or more and 5 hours or less.

When ε-Fe ₂ O ₃ is used as the hard magnetic material H, iron oxide or iron hydroxide nanoparticles are formed using a chemical process in solution, and the generated nanoparticles are heated in an oxidizing atmosphere The ε-Fe ₂ O ₃ particles can be synthesized relatively easily. As a chemical process in a solution, for example, a reverse micelle method or a sol-gel method using iron nitrate hydrate as a starting material can be used. In the step of synthesizing the _ε-Fe 2 _{O 3} particles, the surface of the _ε-Fe 2 _{O 3} particles may be added step of coating with silica (SiO _2).

  The second method is to prepare either particles of the soft magnetic material S or particles of the hard magnetic material H, and treat the particles of the soft magnetic material S or the particles of the hard magnetic material H, It is a method of changing a part of one magnetic material to the other magnetic material.

For example, a _Fe 3 _{O 4} as a soft magnetic material S, when using a _ε-Fe 2 _{O 3} as a hard magnetic material H, after synthesizing the _ε-Fe 2 _{O 3} particles in the manner described above, _ε-Fe 2 O There is a method of heat treating ₃ particles in a reducing atmosphere. Thereby, a part of ε-Fe ₂ O ₃ is reduced to generate Fe ₃ O ₄ . In this case, a core-shell type composite magnetic material as in the second embodiment described later is generated.

  The third method is to prepare a dispersion in which particles of the other material are dispersed in a solution in which the raw material of one of the soft magnetic material S and the hard magnetic material H is dissolved. It is a method of depositing magnetic material particles or precursor particles thereof from the raw material. Thereafter, the powder of the obtained composite particles may be heat-treated.

  For example, particles of the hard magnetic material H (hard magnetic particles) are dispersed in a solution in which at least one transition metal element contained in the soft magnetic material S is ionized and dissolved to obtain a dispersion. Thereafter, while the dispersion is stirred, an additive such as a pH adjuster is added to the dispersion to precipitate particles containing the transition metal. At this time, the particles to be deposited may be particles of the target soft magnetic material S, or may be precursor particles that can be converted into the soft magnetic material S by subsequent heat treatment or the like. Since hard magnetic particles are dispersed in the dispersion, the ions are present around the hard magnetic particles in the dispersion so as to surround the hard magnetic particles. Ions react in this state, and particles or precipitates containing transition metal elements in the ions precipitate, so that particles or precipitates precipitate in a form surrounding the hard magnetic particles. Incidentally, even if the soft magnetic material S and the hard magnetic material H are interchanged, the composite magnetic material can be formed by the same method.

For example, ammonia which is a pH adjuster in an aqueous solution containing Fe ³⁺ ion obtained by dissolving a raw material containing trivalent iron such as iron (III) chloride, iron (III) sulfate or iron (III) nitrate in water By adding water to change the pH, iron hydroxide (Fe (OH) ₃ ) can be precipitated. According to this method, the average particle diameter of the precipitated iron hydroxide particles depends on the deposition conditions, but is approximately 5 nm to 15 nm. By reducing the iron hydroxide in the same manner as in the first method, Fe ₃ O ₄ as the soft magnetic material S can be obtained.

When the pH is changed by adding ammonia water, which is a pH adjuster, to an aqueous solution containing Fe ²⁺ ions obtained by dissolving a raw material containing divalent iron such as iron (II) chloride in water, Fe ₃ O ₄ particles can be deposited. According to this method, the average particle size of the precipitated Fe ₃ O ₄ particles depends on the precipitation conditions, but is approximately 13 nm to about 100 nm.

(magnet)
The composite magnetic material according to the present embodiment can be formed into a desired shape to be a nanocomposite magnet. The nanocomposite magnet according to this embodiment contains a soft magnetic material and a hard magnetic material, the quality magnetic material contains iron or an iron alloy, and the surface of the soft magnetic material is coated with crystalline iron oxide. The nanocomposite magnet according to the present embodiment may be a sintered magnet or a bonded magnet.

[1] Sintered Magnet A sintered magnet can be obtained by forming the composite magnetic material according to the present embodiment into a desired shape, and heat treating the obtained molded body in an inert atmosphere or under vacuum. A sintered magnet can also be obtained by sintering a compact by plasma activated sintering (PAS) or spark plasma sintering (SPS). Also, by molding in a magnetic field, an anisotropic sintered magnet can be obtained.

[2] Bonded Magnet A bonded magnet can be obtained by blending and molding the composite magnetic material according to the present embodiment and a binder (binder). As the binder, a resin material such as a thermoplastic resin or a thermosetting resin, or a low melting metal such as Al, Pb, Sn, Zn, or Mg, or an alloy composed of these low melting metals can be used. The composite magnetic material can be formed into a desired shape by compression molding or injection molding a mixture of the composite magnetic material and the binder. Also, by molding the composite magnetic material in a magnetic field, an anisotropic bonded magnet can be obtained.

(motor)
The composite magnetic material according to the present embodiment can be suitably used as a material for forming a rotor in a motor. That is, the motor according to the present embodiment has a magnet, and the magnet contains the composite magnetic material according to the present embodiment.

Second Embodiment
FIG. 2: is a figure which shows typically the structural example of the composite magnetic material which concerns on 2nd Embodiment. As shown in FIG. 2, the composite magnetic material 201 according to the present embodiment has a core shell having a core portion including a hard magnetic material H and a shell portion including a soft magnetic material S covering at least a part of the core portion. It has a structure. Furthermore, the composite magnetic material 201 has crystalline iron oxide O covering at least a part of the surface of the soft magnetic material S. The description similar to that of the first embodiment, such as the hard magnetic material H, the soft magnetic material S, and the crystalline iron oxide O which the composite magnetic material 201 has, is appropriately omitted.

(Construction)
The composite magnetic material 201 according to the present embodiment has a core-shell structure having a core portion including the hard magnetic material H and a shell portion including the soft magnetic material S covering at least a part of the core portion. The composite magnetic material 201 may be an aggregate of a plurality of core-shell particles, as shown in FIG.

  The soft magnetic material S and the hard magnetic material H are preferably magnetically coupled by the exchange coupling action. Therefore, assuming that the distance at which the exchange coupling action works from the interface between the core portion and the shell portion (hereinafter referred to as “exchange coupling distance”) is a, the thickness t of the shell portion satisfies t ≦ a. preferable. That is, the thickness of the shell portion is preferably equal to or less than the exchange coupling distance.

The average particle diameter of the core portion containing the hard magnetic material H is preferably as large as the coercivity of the hard magnetic material H does not decrease. Also, if the hard magnetic material H comprises ε-Fe ₂ O _3, an average particle diameter of the core part including the hard magnetic material H, it ε-Fe ₂ O ₃ be small enough to be able to keep the epsilon structure preferable. Specifically, the average particle diameter of the core portion containing the hard magnetic material H is preferably 5 nm or more and 60 nm or less, and more preferably 10 nm or more and 40 nm or less.

  Hereinafter, the present invention will be described in more detail using examples, but the technical scope of the present invention is not limited to the following examples. In addition, unless otherwise indicated, "%" used below is a mass reference | standard.

Example 1
In Example 1, Fe ₃ O ₄ nanoparticles and ε-Fe ₂ O ₃ particles are prepared, and these are mixed and heat-treated to obtain a composite containing Fe ₃ O ₄ and ε-Fe ₂ O ₃ A magnetic material was produced.

(Preparation of Fe ₃ O ₄ nanoparticles)
Fe ₃ O ₄ nanoparticles, which are soft magnetic materials, were produced by the following procedure.

First, 6 g of iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) was weighed and dissolved in 75 mL of pure water to obtain an iron nitrate aqueous solution. An aqueous iron nitrate solution was added to aqueous ammonia while stirring 75 mL of 28% aqueous ammonia to precipitate iron hydroxide (Fe (OH) ₃ ). The precipitated iron hydroxide was recovered by filter filtration, thoroughly washed with pure water, and then vacuum dried to obtain iron hydroxide nanoparticles. As a result of measuring the particle size of the obtained iron hydroxide nanoparticles by dynamic light scattering (DLS), the volume-based average particle size was 8 nm.

Next, the obtained iron hydroxide nanoparticles were put into an alumina crucible, and the iron hydroxide nanoparticles were heat-treated in a reducing atmosphere to obtain Fe ₃ O ₄ nanoparticles. A mixed gas of 2% hydrogen and 98% nitrogen was used as an atmosphere gas at the time of heat treatment, and the flow rate of the mixed gas was set to 300 sccm. The temperature during the heat treatment was 350 ° C., held at 350 ° C. for 3 hours, and cooled to room temperature. As a result of measuring the particle size of the obtained Fe ₃ O ₄ nanoparticles by dynamic light scattering (DLS), the volume-based average particle size was 18 nm. Moreover, as a result of evaluating the crystal structure of the obtained Fe ₃ O ₄ nanoparticles by X-ray diffraction (XRD), a diffraction peak of magnetite (Fe ₃ O ₄ ) is confirmed, and a diffraction peak derived from other crystal structures Was not confirmed.

(Preparation of ε-Fe ₂ O ₃ Particles)
The ε-Fe ₂ O ₃ particles as the hard magnetic material, was prepared by the following procedure.

  (1) First, two types of micelle solutions (micellar solution (A) and micelle solution (B)) were prepared as follows.

(1-1) In a reaction vessel, 30 mL of pure water, 92 mL of n-octane, and 19 mL of 1-butanol were added and mixed. Thereto, 6 g of iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) was added and sufficiently dissolved with stirring. Next, cetyltrimethylammonium bromide as a surfactant is added in an amount such that the molar ratio represented by (the number of moles of pure water) / (the number of moles of the surfactant) is 30, and stirring is performed. It was dissolved. Thus, a micelle solution (A) was obtained.

  (1-2) In another reaction vessel, 10 mL of 28% aqueous ammonia was mixed with 20 mL of pure water and stirred, and then 92 mL of n-octane and 19 mL of 1-butanol were added and stirred well. In the solution, cetyltrimethylammonium bromide as a surfactant is used, and the molar ratio represented by (number of moles of ((pure water + water in ammonia)) / (number of moles of surfactant) is 30. The amount was added and dissolved by stirring. Thus, a micelle solution (B) was obtained.

  (2) The micelle solution (B) was dropped to the micelle solution (A) while well stirring the micelle solution (A). After the addition was completed, stirring was continued for 30 minutes.

  (3) While stirring the obtained mixture, 7.5 mL of tetraethoxysilane (TEOS) was added to the mixture, and stirring was continued for 1 day. In this step, a silica layer was formed on the surface of the iron-containing particles in the mixed solution.

  (4) The obtained solution was set in a centrifuge and centrifuged for 30 minutes at a rotational speed of 4500 rpm to collect a precipitate. The collected precipitate was washed several times with ethanol.

  (5) After drying the obtained precipitate, it was put in a baking furnace of an air atmosphere and heat-treated at 1150 ° C. for 4 hours.

(6) The heat-treated powder was dispersed in a 2 mol / L aqueous NaOH solution and stirred for 24 hours to remove the silica layer on the particle surface. Then, filtration, water washing and drying were carried out to obtain ε-Fe ₂ O ₃ particles. Moreover, as a result of evaluating the crystal structure of the obtained ε-Fe ₂ O ₃ particles by XRD, a diffraction peak of ε-Fe ₂ O ₃ was confirmed, and no diffraction peak derived from other crystal structures was confirmed. .

(Preparation of composite magnetic material)
0.31 g and 0.2 g of Fe ₃ O ₄ nanoparticles and ε-Fe ₂ O ₃ particles respectively produced by the above-mentioned method were weighed and mixed under a nitrogen gas atmosphere using a planetary ball mill. Next, this mixed powder was processed by a pressure molding machine to obtain a molded body.

The resulting set to molded an electric furnace, hydrogen and a mixed gas of nitrogen _{(2% H 2 -98% N} 2) atmosphere for 5 hours of heat treatment at 270 ° C.. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. Set to powder again electric furnace obtained by coarse grinding, the hydrogen mixed gas _{(2% H 2 -98% N} 2) atmosphere of nitrogen, and 3 hours of heat treatment at 270 ° C., the composite magnetic material 1 Obtained.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 1 by XRD, the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of magnetite (Fe ₃ O ₄ ) can be confirmed, respectively, and they are derived from other crystal structures. No diffraction peak was confirmed.

In addition, as a result of observing the cross section of the particulate composite magnetic material 1 by TEM, it is possible to confirm a sea-island structure in which a plurality of islands composed of ε-Fe ₂ O ₃ exist in the sea (continuous phase) composed of Fe ₃ O ₄ The

(Magnetic characterization of composite magnetic materials)
The temporal stability of the magnetic characteristics of the obtained composite magnetic material 1 was evaluated. Immediately after the preparation of the composite magnetic material, the residual magnetic flux density and the coercive force were measured using a vibrating sample magnetometer, and after storing for 30 days at room temperature in the air atmosphere, the residual magnetic flux density and the coercive force were measured again in the same manner. . The temporal stability of the magnetic characteristics was evaluated by the ratio (retention ratio) of the residual magnetic flux density and the coercive force after 30 days to the residual magnetic flux density and the coercive force immediately after the preparation. The results are shown in Table 1.

Example 2
In Example 2, reducing the surface of the _ε-Fe 2 _{O 3} particles by heating the _ε-Fe 2 _{O 3} particles in a reducing atmosphere, and the core of the _ε-Fe 2 _{O 3} particles, covering the core A core-shell particulate composite magnetic material having an Fe ₃ O ₄ shell was produced.

(Preparation of ε-Fe ₂ O ₃ Particles)
Ε-Fe ₂ O ₃ particles were produced in the same manner as in Example 1.

(Preparation of composite magnetic material)
Set the fabricated _ε-Fe 2 _{O 3} particles in an electric furnace, a gas mixture _{(2% H 2 -98% N} 2) under an atmosphere of hydrogen and nitrogen, was heated at 250 ° C. 30 min. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. Set to powder again electric furnace obtained by coarse grinding, the gas mixture _{(2% H 2 -98% N} 2) under an atmosphere of hydrogen and nitrogen, and heated for 30 minutes at 250 ° C., a composite magnetic material 2 Obtained.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 2 by XRD, it is possible to confirm the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of magnetite (Fe ₃ O ₄ ) respectively, which are derived from other crystal structures. No diffraction peak was confirmed.

Moreover, as a result of observing the cross section of the particulate-form composite magnetic material 2 by TEM, it could be confirmed that a magnetite (Fe ₃ O ₄ ) layer was formed on the surface layer of ε-Fe ₂ O ₃ particles.

(Magnetic characterization of composite magnetic materials)
The temporal stability of the magnetic properties of the composite magnetic material 2 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
The atmosphere gas for heat treatment at the time of "preparation of Fe ₃ O ₄ nanoparticles" in Example 1 and the atmosphere gas for heat treatment at the time of "preparation of composite magnetic material" are mixed gases of 2% hydrogen and 98% nitrogen. A composite magnetic material 3 was produced in the same manner as in Example 1 except that hydrogen gas was used.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 3 by XRD, the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of magnetite (Fe ₃ O ₄ ) can be confirmed, respectively, and they are derived from other crystal structures. No diffraction peak was confirmed.

In addition, as a result of observing the cross section of the particulate composite magnetic material 3 by TEM, it is possible to confirm a sea-island structure in which a plurality of islands consisting of ε-Fe ₂ O ₃ exist in the sea (continuous phase) consisting of Fe ₃ O ₄ The

(Magnetic characterization of composite magnetic materials)
The temporal stability of the magnetic properties of the composite magnetic material 3 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
Example 3 except that the temperature of the heat treatment at the time of “preparation of Fe ₃ O ₄ nanoparticles” of Example 3 and the temperature of the heat treatment at “preparation of the composite magnetic material” were changed from 350 ° C. to 370 ° C. A composite magnetic material 4 was produced in the same manner as in the above.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 4 by XRD, the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of magnetite (Fe ₃ O ₄ ) can be confirmed respectively, and they are derived from other crystal structures. No diffraction peak was confirmed.

In addition, as a result of observing the cross section of the particulate composite magnetic material 4 by TEM, it is possible to confirm a sea-island structure in which a plurality of islands consisting of ε-Fe ₂ O ₃ exist in the sea (continuous phase) consisting of Fe ₃ O ₄ The

(Magnetic characterization of composite magnetic materials)
The temporal stability of the magnetic properties of the composite magnetic material 4 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 5]
In Example 5, γ-Fe ₂ O ₃ nanoparticles and ε-Fe ₂ O ₃ particles are prepared respectively, and these are mixed and heat-treated to obtain γ-Fe ₂ O ₃ and ε-Fe ₂ O _3. And a composite magnetic material containing

(Preparation of γ-Fe ₂ O ₃ nanoparticles)
The γ-Fe ₂ O ₃ nanoparticles of a soft magnetic material, was prepared by the following procedure.

First, 6 g of iron nitrate hydrate (Fe (NO ₃ ) ₃ .9H ₂ O) was weighed and dissolved in 75 mL of pure water to obtain an iron nitrate aqueous solution. An aqueous iron nitrate solution was added to aqueous ammonia while stirring 75 mL of 28% aqueous ammonia to precipitate iron hydroxide (Fe (OH) ₃ ). The precipitated iron hydroxide was recovered by filter filtration, thoroughly washed with pure water, and then vacuum dried to obtain iron hydroxide nanoparticles. As a result of measuring the particle size of the obtained iron hydroxide nanoparticles by dynamic light scattering (DLS), the volume-based average particle size was 8 nm.

Next, the obtained iron hydroxide nanoparticles were put into an alumina crucible, and the iron hydroxide nanoparticles were heat-treated in an oxidizing atmosphere to obtain γ-Fe ₂ O ₃ nanoparticles. Air was used as an atmosphere gas at the time of heat treatment, and the flow rate of air was 300 sccm. The temperature during the heat treatment was 350 ° C., held at 350 ° C. for 3 hours, and cooled to room temperature. As a result of measuring the particle size of the obtained γ-Fe ₂ O ₃ nanoparticles by dynamic light scattering (DLS), the volume-based average particle size was 20 nm. Moreover, as a result of evaluating the crystal structure of the obtained γ-Fe ₂ O ₃ nanoparticles by X-ray diffraction (XRD), a diffraction peak of γ-Fe ₂ O ₃ is confirmed, and diffraction derived from other crystal structures No peaks were identified.

(Preparation of ε-Fe ₂ O ₃ Particles)
Ε-Fe ₂ O ₃ particles were produced in the same manner as in Example 1.

(Preparation of composite magnetic material)
0.32 g and 0.2 g of γ-Fe ₂ O ₃ nanoparticles and ε-Fe ₂ O ₃ particles respectively produced by the above-described method were weighed, and mixed under a nitrogen gas atmosphere using a planetary ball mill. Next, this mixed powder was processed by a pressure molding machine to obtain a molded body.

  The obtained molded body was set in an electric furnace, and was heat-treated at 270 ° C. for 5 hours in an air atmosphere. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. The powder obtained by the coarse pulverization was again set in an electric furnace, and heat treated at 270 ° C. for 3 hours in an air atmosphere to obtain a composite magnetic material 5.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 5 by XRD, a diffraction peak of ε-Fe ₂ O _{3 and} a diffraction peak of γ-Fe ₂ O ₃ can be confirmed respectively, and diffraction derived from other crystal structures is possible. No peaks were identified.

Observation of the cross section of the particulate composite magnetic material 5 in TEM, the composite structure of _{ε-Fe 2 O 3 γ-} Fe 2 O 3 was confirmed.

(Magnetic characterization of composite magnetic materials)
In the same manner as in Example 1, the temporal stability of the magnetic properties of the composite magnetic material 5 was evaluated. The results are shown in Table 1.

Comparative Example 1
In Comparative Example 1, α-Fe nanoparticles and ε-Fe ₂ O ₃ particles are prepared, and these are mixed and heat-treated to obtain a composite containing α-iron (α-Fe) and ε-Fe ₂ O _3. A magnetic material was produced.

(Preparation of α-Fe nanoparticles)
The soft magnetic material α-Fe nanoparticles were produced by the following procedure.

  First, iron hydroxide nanoparticles were obtained in the same manner as in Example 1. As a result of measuring the particle size of the obtained iron hydroxide nanoparticles by dynamic light scattering (DLS), the volume-based average particle size was 8 nm.

  Next, the obtained iron hydroxide nanoparticles were put into an alumina crucible, and the iron hydroxide nanoparticles were heat-treated in a reducing atmosphere to obtain α-Fe nanoparticles. A mixed gas of 2% hydrogen and 98% nitrogen was used as an atmosphere gas at the time of heat treatment, and the flow rate of the mixed gas was set to 300 sccm. The temperature during the heat treatment was 500 ° C., held at 500 ° C. for 5 hours, and cooled to room temperature. As a result of measuring the particle size of the obtained α-Fe nanoparticles by dynamic light scattering (DLS), the volume-based average particle size was 25 nm. Further, as a result of evaluating the crystal structure of the obtained α-Fe nanoparticles by XRD, a diffraction peak of α-Fe (alpha iron) was confirmed, and a diffraction peak derived from other crystal structures was not confirmed.

(Preparation of ε-Fe ₂ O ₃ Particles)
Ε-Fe ₂ O ₃ particles were produced in the same manner as in Example 1.

(Preparation of composite magnetic material)
0.48 g and 0.2 g of each of the α-Fe nanoparticles and the ε-Fe ₂ O ₃ particles produced by the above-mentioned method were weighed, respectively, and mixed under a nitrogen gas atmosphere using a planetary ball mill. Next, this mixed powder was processed by a pressure molding machine to obtain a molded body.

The resulting set to molded an electric furnace, hydrogen and a mixed gas of nitrogen _{(2% H 2 -98% N} 2) atmosphere for 5 hours of heat treatment at 260 ° C.. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. Set to powder again electric furnace obtained by coarse grinding, the hydrogen mixed gas _{(2% H 2 -98% N} 2) atmosphere of nitrogen, and 3 hours of heat treatment at 260 ° C., the composite magnetic material 6 Obtained.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 6 by XRD, the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of α-Fe can be confirmed respectively, and the diffraction peaks derived from other crystal structures are confirmed It was not done.

Observation of the cross section of the particulate composite magnetic material 6 in TEM, the composite structure of _ε-Fe 2 _{O 3} and αFe was confirmed. In addition, in the surface layer of α-Fe exposed to the particle surface, amorphous iron oxide was formed with a thickness of about 3 nm.

(Magnetic characterization of composite magnetic materials)
In the same manner as in Example 1, the temporal stability of the magnetic properties of the composite magnetic material 6 was evaluated. The results are shown in Table 1.

Comparative Example 2
In Comparative Example 2, a core of _ε-Fe 2 _{O 3} particles to reduce the surface of the _ε-Fe 2 _{O 3} particles by a heat treatment in a reducing atmosphere, _ε-Fe 2 _{O 3} particles, covering the core A core-shell particulate composite magnetic material having an α-Fe shell was produced.

(Preparation of ε-Fe ₂ O ₃ Particles)
Ε-Fe ₂ O ₃ particles were produced in the same manner as in Example 1.

(Preparation of composite magnetic material)
Set the fabricated _ε-Fe 2 _{O 3} particles in an electric furnace, a gas mixture _{(2% H 2 -98% N} 2) under an atmosphere of hydrogen and nitrogen, was heated at 500 ° C. 30 min. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. Set to powder again electric furnace obtained by coarse grinding, the gas mixture _{(2% H 2 -98% N} 2) under an atmosphere of hydrogen and nitrogen, and heated at 500 ° C. 30 minutes, a composite magnetic material 7 Obtained.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 7 by XRD, diffraction peaks of ε-Fe ₂ O ₃ and αFe can be confirmed, respectively, and diffraction peaks derived from other crystal structures are not confirmed.

Moreover, as a result of observing the cross section of the particulate-form composite magnetic material 7 by TEM, it could be confirmed that the α-Fe layer was formed so as to cover the ε-Fe ₂ O ₃ particles. Furthermore, in the surface layer of α-Fe exposed to the particle surface, amorphous iron oxide was formed with a thickness of about 3 nm.

(Magnetic characterization of composite magnetic materials)
The temporal stability of the magnetic properties of the composite magnetic material 7 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 6]
In Example 6, Fe (OH) ₃ particles are precipitated in a dispersion in which ε-Fe ₂ O ₃ particles are dispersed, and heat-treated to precipitate Fe ₃ O ₄ and ε-Fe ₂ O ₃ . A composite magnetic material was prepared.

(Preparation of dispersion)
6 g of iron nitrate hydrate (Fe (NO ₃ ) _3. 9H ₂ O) was weighed and dissolved in 75 mL of pure water to obtain an aqueous iron nitrate solution. Next, 0.36 g of ε-Fe ₂ O ₃ particles obtained in the same manner as in Comparative Example 1 was weighed, added to an aqueous iron nitrate solution, and sufficiently dispersed by an ultrasonic disperser to prepare a dispersion.

(Precipitate of precursor particles)
While stirring the prepared dispersion, 75 mL of 28% ammonia water is added to precipitate Fe (OH) ₃ particles as precursor particles of Fe ₃ O ₄ , and Fe (OH) ₃ particles and ε-Fe ₂ O _A composite particle containing _three particles was formed. It was 10 nm-20 nm when the particle size of Fe (OH) ₃ particle | grains in the obtained composite particle was observed by SEM.

(Preparation of composite magnetic material)
The Fe (OH) ₃ particles were reduced and converted to Fe ₃ O ₄ to prepare a composite magnetic material. 1 g of powder of composite particles of Fe (OH) ₃ particles and ε-Fe ₂ O ₃ particles was processed by a pressure molding machine to produce a molded body.

The resulting set in the molded body in an electric furnace, hydrogen and a mixed gas of nitrogen _{(2% H 2 -98% N} 2) atmosphere for 5 hours of heat treatment at 350 ° C.. The flow rate of the mixed gas was 300 sccm. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. The powder obtained by the coarse pulverization was again set in an electric furnace, and heat treated at 270 ° C. for 3 hours in an air atmosphere to obtain a composite magnetic material 8.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 8 by XRD, the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of magnetite (Fe ₃ O ₄ ) can be confirmed, respectively, and they are derived from other crystal structures. No diffraction peak was confirmed.

In addition, as a result of observing the cross section of the particulate composite magnetic material 8 by TEM, it is possible to confirm a sea-island structure in which a plurality of islands consisting of ε-Fe ₂ O ₃ exist in the sea (continuous phase) consisting of Fe ₃ O ₄ The

(Magnetic characterization of composite magnetic materials)
In the same manner as in Example 1, the temporal stability of the magnetic properties of the composite magnetic material 8 was evaluated. The results are shown in Table 1.

[Example 7]
In Example 7, Fe ₃ O ₄ particles were precipitated in a dispersion liquid in which ε-Fe ₂ O ₃ particles are dispersed, to prepare a composite magnetic material containing Fe ₃ O ₄ and ε-Fe ₂ O ₃ .

(Preparation of dispersion)
3 g of iron chloride hydrate (FeCl ₂ · 4 H ₂ O) was weighed and dissolved in 75 mL of pure water to obtain an iron chloride aqueous solution. Next, 0.36 g of ε-Fe ₂ O ₃ particles obtained in the same manner as in Comparative Example 1 was weighed, added to an aqueous iron chloride solution, and sufficiently dispersed by an ultrasonic disperser to prepare a dispersion.

(Precipitate of precursor particles)
The prepared dispersion was added with stirring 28% aqueous ammonia 75 mL, to precipitate the _Fe 3 _{O 4} particles to form composite particles with the _Fe 3 _{O 4} particles and _ε-Fe 2 _{O 3} particles. The particle size of the _Fe 3 _{O 4} particles obtained composite particles were observed by SEM, it was 50Nm～80nm.

(Preparation of composite magnetic material)
The powder of the obtained composite particles was heat-treated to prepare a composite magnetic material. 1 g of powder of composite particles of Fe ₃ O ₄ particles and ε-Fe ₂ O ₃ particles was processed by a pressure molding machine to produce a molded body.

  The obtained molded body was set in an electric furnace, and was heat-treated at 410 ° C. for 5 hours in a nitrogen gas atmosphere. The flow rate of nitrogen gas was 300 sccm. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. The powder obtained by the coarse crushing was again set in an electric furnace, and heat treated at 270 ° C. for 3 hours in an air atmosphere to obtain a composite magnetic material 9.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 9 by XRD, the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of magnetite (Fe ₃ O ₄ ) can be confirmed, respectively, and they are derived from other crystal structures. No diffraction peak was confirmed.

In addition, as a result of observing the cross section of the particulate composite magnetic material 9 by TEM, it is possible to confirm a sea-island structure in which a plurality of islands consisting of ε-Fe ₂ O ₃ exist in the sea (continuous phase) consisting of Fe ₃ O ₄ The

(Magnetic characterization of composite magnetic materials)
In the same manner as in Example 1, the temporal stability of the magnetic properties of the composite magnetic material 9 was evaluated. The results are shown in Table 1.

[Example 8]
In Example 8, Fe ₃ O ₄ particles were precipitated in a dispersion liquid in which ε-Fe ₂ O ₃ particles are dispersed, to prepare a composite magnetic material containing Fe ₃ O ₄ and ε-Fe ₂ O ₃ . In Example 8, the particle size of Fe ₃ O ₄ particles to be deposited was made smaller than in Example 7, to prepare a composite magnetic material.

(Preparation of dispersion)
1.5 g of iron chloride hydrate (FeCl ₂ · 4 H ₂ O) was weighed and dissolved in 150 mL of pure water to obtain an iron chloride aqueous solution. Next, 0.18 g of ε-Fe ₂ O ₃ particles obtained in the same manner as in Comparative Example 1 was weighed, added to an aqueous iron chloride solution, and sufficiently dispersed by an ultrasonic disperser to prepare a dispersion.

(Precipitate of precursor particles)
The prepared dispersion was added with stirring 28% aqueous ammonia 75 mL, to precipitate the _Fe 3 _{O 4} particles to form composite particles with the _Fe 3 _{O 4} particles and _ε-Fe 2 _{O 3} particles. The particle size of the _Fe 3 _{O 4} particles obtained composite particles were observed by SEM, it was 10 nm to 30 nm.

(Preparation of composite magnetic material)
The powder of the obtained composite particles was heat-treated to prepare a composite magnetic material. 1 g of powder of composite particles of Fe ₃ O ₄ particles and ε-Fe ₂ O ₃ particles was processed by a pressure molding machine to produce a molded body.

  The obtained molded body was set in an electric furnace, and was heat treated at 400 ° C. for 5 hours in a nitrogen gas atmosphere. The flow rate of nitrogen gas was 300 sccm. After cooling to room temperature, it was roughly crushed under a nitrogen gas atmosphere using a planetary ball mill. The powder obtained by the coarse grinding was again set in an electric furnace, and heat treated at 270 ° C. for 3 hours in an air atmosphere to obtain a composite magnetic material 10.

(Structural analysis of composite magnetic materials)
As a result of evaluating the crystal structure of the obtained composite magnetic material 10 by XRD, the diffraction peak of ε-Fe ₂ O _{3 and} the diffraction peak of magnetite (Fe ₃ O ₄ ) can be confirmed respectively, and they are derived from other crystal structures. No diffraction peak was confirmed.

In addition, as a result of observing the cross section of the particulate composite magnetic material 10 by TEM, it is possible to confirm a sea-island structure in which a plurality of islands consisting of ε-Fe ₂ O ₃ exist in the sea (continuous phase) consisting of Fe ₃ O ₄ The

(Magnetic characterization of composite magnetic materials)
The temporal stability of the magnetic properties of the composite magnetic material 10 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

  As shown in Table 1, in all of the composite magnetic materials of Examples 1 to 8, the retention rate of residual magnetic flux density and coercivity was as high as 99% or more, and the temporal stability was high. On the other hand, in all of the composite magnetic materials of Comparative Examples 1 and 2, the retention ratio of residual magnetic flux density and coercivity was as low as about 80%, and the temporal stability was low.

S Soft magnetic material H Hard magnetic material

Claims (9)

A composite magnetic material comprising a soft magnetic material and a hard magnetic material,
The soft magnetic material and the hard magnetic material each contain an iron element,
90 atomic% or more and 100 atomic% or less of the iron element contained in the soft magnetic material forms a first oxide or a first composite oxide,
A composite magnetic material, wherein 90 atomic% or more and 100 atomic% or less of iron element contained in the hard magnetic material forms a second oxide or a second complex oxide. In the second oxide or the second composite oxide, at least a portion of Fe of ε-Fe ₂ O ₃ or ε-Fe ₂ O ₃ is selected from the group consisting of Ga, Al, Ni, and Co. The composite magnetic material according to claim 1, comprising a composite oxide substituted by one. In the first oxide or the first composite oxide, a part of Fe in Fe ₃ O ₄ or Fe ₃ O ₄ is substituted with at least one selected from the group consisting of Ga, Al, Ni, and Co The composite magnetic material according to claim 1, wherein the composite magnetic material comprises a composite oxide as described above. In the first oxide or the first composite oxide, at least a portion of Fe of γ-Fe ₂ O ₃ or γ-Fe ₂ O ₃ is selected from the group consisting of Ga, Al, Ni, and Co. The composite magnetic material according to any one of claims 1 to 3, comprising a composite oxide substituted by one.   The composite magnetic material according to any one of claims 1 to 4, having a sea-island structure having a sea part containing the soft magnetic material and an island part containing the hard magnetic material.   The core part containing the said hard magnetic material and the shell part which has the said soft magnetic material which coat | covers at least one part of the said core part in any one of the Claims 1 thru | or 4 characterized by the above-mentioned. Composite magnetic material as described.   The composite magnetic material according to any one of claims 1 to 6, wherein the soft magnetic material and the hard magnetic material are magnetically coupled.   The composite magnetic material according to any one of claims 1 to 7, wherein the content of the Nd element is 3% by mass or less. A motor having a magnet,
A motor, wherein the magnet contains the composite magnetic material according to any one of claims 1 to 8.

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