JP2021089964A - Coating particle powder and preparation method thereof - Google Patents

Abstract

To provide a coating particle powder containing coating particles that has multiple layers of insulating film formed, is excellent in eddy current suppression performance, and has high-pressure resistance, and a preparation method thereof.SOLUTION: The coating particle powder contains coating particles 100 that include: soft magnetic particles 10 containing metal; a first inorganic insulating film 20 formed on the surface of the soft magnetic particles 10; and a second inorganic insulating film 30 formed on the surface of the first inorganic insulating film 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coated particle powder containing coating particles obtained by insulatingly coating soft magnetic particles, and a method for producing the same.

In recent years, with the spread of hybrid cars and the advent of electric vehicles, the importance of electric motors in the field of transportation is increasing more than ever. Further, the use of electric motors is expanding not only in means of transportation such as automobiles, ships, and airplanes, but also in industrial equipment and electric appliances in general households.

Further, soft magnetic materials are used not only for electric motors but also for iron cores of power electronics devices used for alternating current such as inverters, transformers, and reactors. When the iron core is excited at a high frequency, hysteresis loss and eddy current loss occur. Hysteresis loss is proportional to the exciting frequency. On the other hand, the eddy current loss is proportional to the square of the frequency. Therefore, in order to realize compact, high-efficiency, low-loss power electronics equipment that is expected from the market in the future, it is indispensable to reduce the eddy current of the iron core and increase the resistance by using a soft magnetic material.

As a technique for reducing the eddy current of the iron core and increasing the resistance, for example, Patent Document 1 describes a technique in which an insulating film is formed on the surface of iron powder, powder compaction is performed, and then heat treatment is performed in an oxidizing atmosphere. Is disclosed. In this technique, an oxidative influence layer containing an iron oxide and a Fe-Si oxide is formed at the interface between iron powders.

International Publication No. 2013/108643

In the technique disclosed in Patent Document 1, the iron powder surface is subjected to a phosphorylation treatment to form an Fe-P-based inorganic insulating film, and then an inorganic insulating film made of a silicone-based resin is formed. Is heat-treated. Therefore, a two-step insulating film forming step is required, which is not desirable from the viewpoint of the cost and productivity of insulating film formation. When the iron powder is amorphous, the iron powder is polycrystalline by heat treatment at a high temperature after compaction molding. As a result, the magnetic properties of the obtained magnetic material deteriorate. Further, although high pressure resistance is also required for soft magnetic materials, the actual situation is that coating particles having both high pressure resistance and eddy current suppression performance have not been obtained.

In view of the above problems, we provide a coating particle powder containing coating particles having excellent eddy current suppression performance and high pressure resistance, and a method for producing the coating particle powder by heat treatment at a low temperature with a small number of man-hours. The purpose.

The present disclosure provides the following coated particle powders.
Includes coating particles having soft magnetic particles, a first inorganic insulating film formed on the surface of the soft magnetic particles, and a second inorganic insulating film formed on the first inorganic insulating film. Coating particle powder.

The present disclosure also provides a method for producing the following coated particle powder.
A step of preparing soft magnetic particles having a first inorganic insulating film on the surface, a step of forming a third inorganic insulating film on the surface of the first inorganic insulating film, and a step of forming the third inorganic insulating film. A step of heat-treating the first inorganic insulating film and the third inorganic insulating film to form a second inorganic insulating film at the interface between the first inorganic insulating film and the third inorganic insulating film is included. A method for producing a coated particle powder.

The coating particle powder according to the present disclosure contains coating particles having excellent eddy current suppression performance and high pressure resistance. Further, according to the method for producing coated particle powder according to the present disclosure, coated particles can be produced with a small number of man-hours and heat treatment at a low temperature.

It is a schematic cross-sectional view which shows the cross-sectional structure of the coating particle which concerns on Embodiment 1 of this disclosure. It is schematic cross-sectional view which shows the cross-sectional structure of the precursor of the coating particle which concerns on Embodiment 1 of this disclosure. It is a schematic cross-sectional view which shows the cross-sectional structure of the coating particle which concerns on Embodiment 2 of this disclosure. This is an example of a transmission electron microscope (TEM) photograph showing a cross section of coating particles according to the first embodiment of the present disclosure. It is an EDX profile of the cross section of the coating particle which concerns on 1st Example of this disclosure. The dielectric strength of the molded product produced by using the coating particles according to the first embodiment of the present disclosure was compared with the dielectric strength of the molded product produced by using the coating particles having a silicon oxide film as the insulating film. It is a graph.

Hereinafter, the coated particle powder and the method for producing the same will be described with reference to the drawings. The embodiments of the present disclosure are not limited to the embodiments described below, and can be changed to various other embodiments.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing a cross-sectional structure of the coating particles according to the first embodiment before heat treatment. The coating particle powder according to the first embodiment of the present disclosure includes the soft magnetic particle 10, the first inorganic insulating film 20 that covers the surface of the soft magnetic particle 10, and the second inorganic insulating film 20 that covers the surface of the soft magnetic particle 10. A coating particle 100 including an inorganic insulating film 30 and a third inorganic insulating film 40 for coating the second inorganic insulating film 30 is included. In addition to the coating particles 100, the coating particle powder may appropriately contain other components as long as the object and effect of the present disclosure are not impaired.

When the coating particle 100 has a plurality of layers of insulating films, the eddy current suppression performance of the coating particle powder is improved. Further, in the coating particle 100, when a plurality of insulating films are laminated, the pressure resistance is improved as compared with the case where the insulating film is composed of one layer.

That is, according to the coating particle powder according to the first embodiment, the coating particle 100 has a laminated insulating film (first inorganic insulating film 20, second inorganic insulating film 30, and third inorganic insulating film 40). Therefore, a soft magnetic material having a high withstand voltage and excellent eddy current suppression performance can be obtained.

The average particle size of the coating particles 100 in the coating particle powder is preferably 0.1 to 100 μm, more preferably 5 to 50 μm. The average particle size is a value measured by a laser diffraction / scattering method. When the average particle size of the coating particles 100 is in the above range, the coating particle powder can be easily applied to various uses.
The components constituting the coated particle powder (coating particles 100) will be described below.

<Soft magnetic particle 10>
The soft magnetic material particles 10 may be particles mainly containing a soft magnetic material, and the material may be iron or an iron-containing alloy such as pure iron powder, Fe-Si alloy, sendust, permalloy, or permendur. be able to. Further, the material of the soft magnetic particles 10 may be amorphous particles containing Fe and Si, nanocrystal particles and the like. Amorphous particles and nanocrystal particles may contain elements other than Fe and Si, and examples of other elements include B, C, P, Cu, Co, Ni, Nb, Al, Cr, Ti, Nb, Ta, Zr and the like are included. The soft magnetic particle 10 may contain only one kind of these, or may contain two or more kinds of these.

The crystal structure of the soft magnetic particles 10 is not particularly limited, and may have a nanocrystal structure, an amorphous structure, or a mixed structure thereof. By appropriately heat-treating the soft magnetic particles 10 having an amorphous structure at a temperature of 500 ° C. or lower, a nanocrystal structure having a crystal size of about 10 nm to 20 nm is formed in a part thereof. According to the soft magnetic particles 10 having a nanocrystal structure as a part of the amorphous structure, it is possible to reduce the coercive force of the soft magnetic particles 10.

The average particle size of the soft magnetic particles 10 is preferably 0.1 to 100 μm, more preferably 5 to 50 μm. The average particle size is a value measured by a laser diffraction / scattering method. When the average particle size of the soft magnetic particles 10 is in the above range, the coated particle powder can be easily applied to various uses.

<First inorganic insulating film 20>
The first inorganic insulating film 20 is a film made of an inorganic substance formed on the surface of the soft magnetic particles 10. Examples of the first inorganic insulating film 20 include a natural oxide film or a thermal oxide film of a metal (soft magnetic material) contained in the soft magnetic particle 10 described above. For example, when the soft magnetic particle 10 contains Fe, the first inorganic insulating film 20 may be _{FeO x, which is an oxide film of Fe.} The first inorganic insulating film 20 may contain not only the soft magnetic material and O contained in the soft magnetic particle 10 but also impurity elements such as P and B contained in the soft magnetic particle 10 and other elements. Further, the first inorganic insulating film 20 may partially contain an element (for example, Si) contained in the second inorganic insulating film 30 and the third inorganic insulating film 40, which will be described later.

The film thickness of the first inorganic insulating film 20 is about several nm to 100 nm. The film thickness of the first inorganic insulating film 20 can be confirmed, for example, by observing the cross section of the coating particles 100 with a transmission microscope.

<Second inorganic insulating film 30>
The second inorganic insulating film 30 is a film made of an inorganic substance that further covers the surface of the first inorganic insulating film 20 that covers the surface of the soft magnetic particles 10. The second inorganic insulating film 30 is a film mainly containing a compound of the soft magnetic metal contained in the soft magnetic particles 10 described above and the element contained in the third inorganic insulating film 40 described later. For example, when the third inorganic insulating film 40 described later is a silicon oxide film, the second inorganic insulating film 30 may be a silicate film of a soft magnetic metal contained in the soft magnetic particles 10.

More specifically, when the soft magnetic particle 10 contains Fe and the third inorganic insulating film 40 is a silicon oxide film, the second inorganic insulating film 30 is a film represented by the _{composition formula FeSiO x.} Can be done. The second inorganic insulating film 30 may further contain impurity elements such as P and B contained in the soft magnetic particle 10 and other elements.

The film thickness of the second inorganic insulating film 30 is usually 10 nm to several tens of nm. The film thickness of the second inorganic insulating film 30 can be confirmed, for example, by observing the cross section of the coating particles 100 with a transmission microscope.

<Third inorganic insulating film 40>
The third inorganic insulating film 40 is a film made of an inorganic substance that further covers the surface of the second inorganic insulating film 30. Examples of the third inorganic insulating film 40 include a silicon oxide film (SiO ₂ ), an aluminum oxide film (Al ₂ O ₃ ), a chromium oxide film (Cr ₂ O ₃ ), a titanium oxide film (TIO ₂ ), and a zinc oxide film. (ZnO) and the like are included. Among these, a silicon oxide film (SiO ₂ ) is preferable.

The third inorganic insulating film 40 may contain not only Si, Al, Cr, Ti, Zn and O, but also impurity elements such as P and B contained in the soft magnetic particle 10 and other metal elements. Good.

The film thickness of the third inorganic insulating film 40 is about 10 nm to 100 m. The film thickness of the third inorganic insulating film 40 can be confirmed, for example, by observing the cross section of the coating particles 100 with a transmission microscope.

<Manufacturing method of coating particles>
-Method of forming the soft magnetic particle 10 The method of forming the soft magnetic particle 10 is not particularly limited, and is appropriately selected depending on the type of the soft magnetic material, the desired average particle size, and the like. The soft magnetic particles 10 may be formed by, for example, an atomizing method, or may be formed by pulverization or the like. At this time, classification or the like may be performed as necessary.

-Method of forming the first inorganic insulating film 20 When the first inorganic insulating film 20 is a natural oxide film, the above-mentioned soft magnetic particles 10 are handled in an air atmosphere when they are produced by an atomizing method, a pulverization method, or the like. The first inorganic insulating film 20 may be formed. That is, the first inorganic insulating film 20 may be formed at the same time as the soft magnetic particles 10 are produced. Further, the first inorganic insulating film 20 may be formed by leaving the soft magnetic particles 10 in the air atmosphere for a certain period of time. The first inorganic insulating film 20 is formed by the reaction between oxygen in the atmosphere and the surface of the soft magnetic particles 10.

Further, the above-mentioned soft magnetic particles 10 may be heated at a temperature of about 100 ° C. to 300 ° C. to form a thermal oxide film, which may be used as the first inorganic insulating film 20. In either method, the first inorganic insulating film 20 having a desired thickness (about 10 nm to 100 nm) is formed.

Method for Forming Third Inorganic Insulating Film 40 When the coating particles 100 of the present embodiment are produced, a precursor of the coating particles in which the first inorganic insulating film 20 and the third inorganic insulating film 40 are laminated as shown in FIG. 100a is produced first. FIG. 2 shows the cross-sectional structure of the precursor 100a of the coating particles in which the third inorganic insulating film 40 is formed on the surface of the first inorganic insulating film 20.

The method for forming the third inorganic insulating film 40 is appropriately selected depending on the type of the third inorganic insulating film 40. For example, when the third inorganic insulating film 40 is a silicon oxide film, the alkoxy group of the alkoxysilane compound is hydrolyzed and dehydrated and condensed by the sol-gel method in the presence of the soft magnetic particles 10 forming the first inorganic insulating film 20. By carrying out the reaction, the third inorganic insulating film 40 can be formed on the surface of the first inorganic insulating film 20. Examples of the alkoxysilane compound include tetramethoxysilane and tetraethoxysilane.

Hereinafter, the method for forming the third inorganic insulating film 40 will be specifically described by taking the case of forming the _{SiO 2 film using TEOS (tetraethoxysilane) as an example.}

The soft magnetic particles 10 coated with the first inorganic insulating film 20 are immersed in a mixed solution containing TEOS, aqueous ammonia (catalyst), and ethanol (solvent). Then, after stirring, the solvent is dried to form a _{SiO 2} film as the third inorganic insulating film 40 on the surface of the first inorganic insulating film 20. The _{film thickness of the SiO 2} film can be adjusted by changing various conditions such as the amount of TEOS, the amount of ammonia water as a catalyst, and the stirring time, and can be, for example, 10 nm to 200 nm. The _{film thickness of the SiO 2} film is appropriately adjusted according to the desired thickness of the second inorganic insulating film 30 and the thickness of the third inorganic insulating film 40.

The solvent used for the hydrolysis / dehydration condensation reaction of TEOS in the sol-gel method is not limited to ethanol, and for example, 2-propanol (IPA) or the like can be used. Further, the catalyst is not limited to aqueous ammonia, and for example, hydrochloric acid, nitric acid, or the like can be used.

-Method of forming the second inorganic insulating film 30 The second inorganic insulating film 30 can be formed by heat-treating the above-mentioned precursor 100a in which the third inorganic insulating film 40 is formed on the surface of the first inorganic insulating film 20. When the first inorganic insulating film 20 and the third inorganic insulating film 40 are laminated and heat-treated, the elements are diffused from the first inorganic insulating film 20 side to the third inorganic insulating film 40 side at these interfaces, and the third insulating film is insulated. The element diffuses from the film 40 side to the first inorganic insulating film 20 side. That is, the elements diffuse with each other (hereinafter, also referred to as "mixing reaction"). Then, by changing the composition of these interfaces (for example, a part of the third inorganic insulating film 40), the second inorganic insulating film 30 is formed at the interface between the first inorganic insulating film 20 and the third inorganic insulating film 40. To. The heat treatment temperature for forming the second inorganic insulating film 30 is preferably 200 ° C. to 600 ° C., more preferably 250 ° C. to 500 ° C. The thickness of the second inorganic insulating film 30 can be adjusted by the heat treatment temperature or the like.

(Embodiment 2)
In the coating particles 100 of the first embodiment described above, three layers of inorganic insulating films were arranged on the soft magnetic particles 10. However, in the present disclosure, as shown in FIG. 3, a coating particle powder containing coating particles 200 in which only the first inorganic insulating film 20 and the second inorganic insulating film 30 are laminated on the soft magnetic particles 10 may be used. .. The first inorganic insulating film 20 and the second inorganic insulating film 30 of the coating particles 200 of the second embodiment are the same as the first inorganic insulating film 20 and the second inorganic insulating film 30 of the first embodiment.

As described above, the second inorganic insulating film 30 is formed by a mixing reaction between the first inorganic insulating film 20 and the third inorganic insulating film 40. For example, the metal element in the first inorganic insulating film 20 is heat-treated. Therefore, it diffuses outward into the third inorganic insulating film 40. Therefore, in the method for producing the coating particles 100 described above, all the third inorganic insulating film 40 is formed by controlling the film thickness of the third inorganic insulating film 40 and the heat treatment temperature when forming the second inorganic insulating film 30. The composition can be changed to the second inorganic insulating film 30, and the coating particles 200 of the present embodiment can be obtained.

Hereinafter, the present disclosure will be described with reference to examples. The scope of this disclosure is not construed as limited by the examples.

(First Example)
(1) Preparation Step for Soft Magnetic Particles 10 and First Inorganic Insulating Film 20 In the first embodiment, soft magnetic particles (Fe particles) 10 having an average particle diameter of 100 μm or less formed by pulverization are prepared. It was allowed to stand in the air atmosphere. _{After that, it was confirmed that a FeO x} film (first inorganic insulating film 20), which is a natural oxide film of iron having a diameter of several nm to several tens of nm, was formed on the surface of the soft magnetic particle 10.

(2) the third inorganic insulating film 40 soft magnetic particles 10 500 g for formation step first inorganic insulating film 20 is formed of, ethanol 1 kg, TEOS (tetraethoxysilane, _{Si (OC} 2 H ₅₎ 4) 50 g and 50 g of aqueous ammonia (ammonia content 28 to 30% by volume) were added, and the mixture was stirred for 2 hours. After stirring, the particles in the solution were separated and dried _{to obtain a coated particle powder in which a SiO 2} film (third inorganic insulating film 40) was formed on _{the surface of the FeO x} film (first inorganic insulating film 20). ..

(3) Forming Step of Second Inorganic Insulating Film 30 A two-layer insulating film of FeO _x film (first inorganic insulating film 20) and SiO ₂ film (third inorganic insulating film 40) is formed on the soft magnetic particle 10. The prepared particles were heat-treated at 250 ° C. in a heating furnace. As a result, _{the elements in the FeO x} film (first inorganic insulating film 20) and the elements in the SiO ₂ film (third inorganic insulating film 40) undergo a mixing reaction, and a metal silicate film (second inorganic insulating film 40) is present at these interfaces. A film 30) was formed. As a result, the total film thickness of the obtained insulating film (total film thickness of the first inorganic insulating film 20, the second inorganic insulating film 30, and the third inorganic insulating film 40) was 70 nm.

(Evaluation)
As described above, the coating particles 100 having the three-layer inorganic insulating film on the surface of the soft magnetic particles 10 were produced. A transmission microscope (TEM) photograph of the cross section of the obtained coating particles 100 is shown in FIG. The EDX profile showing the composition ratio of the elements in this cross section is shown in FIG.

As shown in FIG. 4, the first inorganic insulating film 20 (FeO _x film) and the third inorganic insulating film 40 (SiO ₂ film) _{are formed by heat treatment after the formation of the SiO 2 film which is the third inorganic insulating film 40.} It can be confirmed _{that a metal silicate film (FeSiO x} film), which is the second inorganic insulating film 30, is formed at the interface.

FIG. 5 is an EDX line profile showing the composition ratio of the elements contained in the three-layer inorganic insulating film. From this result, it can be seen that the ratio of Fe contained in the inorganic insulating film decreases as the coating particles 100 move outward from the center. On the other hand, it can be seen that the ratio of Si contained in the inorganic insulating film decreases as the coating particles 100 proceed from the outside to the inside. Before the heat treatment, since was 2-layer structure of the first inorganic insulating film (FeO _x film) 20 and the third inorganic insulating film (SiO ₂ film) 40, and FeO _x is a first inorganic insulating film 20 by heat treatment It can be confirmed that the mixing reaction occurred at the interface with the _{SiO 2} which is the third inorganic insulating film 40, _{and the metal silicate film (FeSiO x film) which is the second inorganic insulating film 30 was formed.}

Further, the powder of the coating particles 100 was mixed with a binder, molded and cured to prepare a square sample. Then, a voltage was applied to the top and bottom of this sample using a digital ultra-high resistance / micro ammeter 5451 (manufactured by ADC), and the withstand voltage was measured. The measurement result of the dielectric strength is shown in FIG.

_{FIG. 6 shows a natural oxide film (FeO x} film) which is the first inorganic insulating film 20 according to the first embodiment _{, a metal silicate film (FeSiO x} film) which is the second inorganic insulating film 30, and a third inorganic insulating film. Insulation withstand voltage of a molded product using powder of coating particles 100 having three layers of an inorganic insulating film of 40 SiO _{2 films, and as a comparative example, coating particles having only one layer of SiO 2} films as an insulating film. It is a graph which shows the ratio of the insulation withstand voltage of the molded body produced using powder. In FIG. 6, the pressure resistance of the comparative example (when the insulating film is _{only a SiO 2} film) is set to 1, and the ratio to the pressure resistance is shown.

The _{conditions for forming the SiO 2} film are the same for both, and the film thickness for both is about 70 nm. Figure 6
As shown in the above, when the three-layer inorganic insulating film is formed as in the first embodiment, the dielectric strength increases about five times as compared with the case where the _{one-layer SiO 2 film is formed.} You can see that there is. The dielectric strength can be adjusted by appropriately adjusting the film thickness of the _{SiO 2} film and the temperature of the heat treatment according to the first embodiment. As a result, the dielectric strength required by the desired device can be realized.

According to the coating particle powder containing the coating particles coated with insulation according to the present disclosure, it is possible to reduce the eddy current and improve the dielectric strength in the device using the coating particle powder. In addition, the laminated and thickened insulating film can improve the rust prevention property of the soft magnetic particles. Therefore, even when the crushed powder is used as the soft magnetic particles of the coating particles, the coated particle powder is used for the soft magnetic material device that is required to achieve both improvement of magnetic properties and reduction of iron loss by reducing eddy current. It is possible. Further, according to the coating particle powder production method of the present disclosure, the coating particle powder can be produced with a small number of steps.

100, 200 Coated particles 100a Precursor of coated particles 10 Soft magnetic particles 20 First inorganic insulating film 30 Second inorganic insulating film 40 Third inorganic insulating film

Claims (8)

With soft magnetic particles,
The first inorganic insulating film formed on the surface of the soft magnetic particles and
A second inorganic insulating film formed on the surface of the first inorganic insulating film and
Coating particle powder, including coating particles having. The coating particles further have a third inorganic insulating film that covers the second inorganic insulating film.
The coating particle powder according to claim 1. The third inorganic insulating film is a silicon oxide film.
The coating particle powder according to claim 2. The soft magnetic particles contain metal and
The first inorganic insulating film is a natural oxide film or a thermal oxide film of the metal.
The coating particle powder according to any one of claims 1 to 3. The soft magnetic particles contain metal and
The second inorganic insulating film is a silicate film of the metal.
The coated particle powder according to any one of claims 1 to 4. The crystal structure of the soft magnetic particles is either a nanocrystal structure, an amorphous structure, or a mixed structure of a nanocrystal structure and an amorphous structure.
The coated soft magnetic particle powder according to any one of claims 1 to 5. The average particle size is 0.1 μm to 100 μm.
The coated particle powder according to any one of claims 1 to 6. The process of preparing soft magnetic particles having a first inorganic insulating film on the surface, and
A step of forming a third inorganic insulating film on the surface of the first inorganic insulating film, and
The particles forming the third inorganic insulating film are heat-treated, the first inorganic insulating film and the third inorganic insulating film are reacted, and the second inorganic is at the interface between the first inorganic insulating film and the third inorganic insulating film. The process of forming the insulating film and
A method for producing a coated particle powder, including.

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