JP7742468B1 - composite materials - Google Patents

Abstract

To provide a composite material having high thermal conductivity and low electrical conductivity.
[Solution] The composite material includes a dispersed material having a thermal conductivity of 100 W/K·m or more and an insulator interposed between the dispersed materials. For example, the dispersed material is an aluminum-based metal powder. For example, the insulator is an oxide or resin whose glass transition point is equal to or lower than the melting point of the dispersed material. For example, the electrical conductivity of the composite material is equal to or lower than 0.5×10 ⁶ S/m.
[Selected Figure] Figure 1

Description

This disclosure relates to composite materials.

Patent documents 1 and 2 describe powder magnetic cores. Powder magnetic cores are made by compressing iron-based powder together with a binder containing resin or ceramics.

JP 2011-216745 A JP 2016-12671 A

In recent years, there has been active development of motor-powered mobility, such as electric vehicles and drones. This has led to advances in motors that are becoming more powerful and lighter in weight. As motors become more powerful, there is a growing need to improve the thermal conductivity of the materials that make up the motors. Currently, CFPR is sometimes used as a material for structural components such as motor casings to reduce weight, but materials with even higher thermal conductivity are needed.

In addition, magnetic flux changes drastically around a rotating motor. If a material with high electrical conductivity is placed around the motor, it is undesirable because it generates a large amount of induced current, which can cause resistance to the motor's rotation and lead to heat generation. For this reason, it is preferable for the material that makes up the motor to have low electrical conductivity.

The powder magnetic cores described in Patent Documents 1 and 2 have low thermal conductivity and are therefore unsuitable for applications other than motor cores. In one aspect of the present disclosure, it is preferable to provide a composite material with high thermal conductivity and low electrical conductivity.

One aspect of the present disclosure is a composite material comprising dispersed materials having a thermal conductivity of 100 W/K·m or more and an insulator interposed between the dispersed materials. The composite material of one aspect of the present disclosure has high thermal conductivity and low electrical conductivity.

1 is an explanatory diagram showing the structure of a composite material and a manufacturing method thereof. FIG. 1 is a perspective view showing the configuration of an apparatus for heating and compressing raw materials. FIG. 2 is a side cross-sectional view showing the configuration of the device when heat compression is being performed.

Exemplary embodiments of the present disclosure will now be described with reference to the drawings.
First Embodiment
1. Configuration of Composite Material 1 As shown in S_C in Fig. 1 , the composite material 1 includes dispersed materials 3 and insulators 5. The insulators 5 are interposed between the dispersed materials 3. The thermal conductivity of the dispersed materials 3 is 100 W/K m or more.

The dispersed material 3 is, for example, a metal powder. Examples of metals include aluminum, copper, silver, gold, and alloys of two or more of these. The dispersed material 3 is, for example, an aluminum-based metal powder. Examples of aluminum-based metal powder include aluminum atomized powder and aluminum cutting chips. The average particle size of the dispersed material 3 is preferably 10 μm or more and 500 μm or less. The average particle size is measured by the mesh passage method.

The insulator 5 is, for example, a low-melting-point ceramic, oxide, silicone, or resin. The glass transition point of the insulator 5 is, for example, lower than the melting point of the dispersion material 3. The insulator 5 is, for example, a low-melting-point ceramic, oxide, silicone, or resin whose glass transition point is lower than the melting point of the dispersion material 3.

The electrical conductivity of the composite material 1 is, for example, 0.5×10 ⁶ S/m or less. One method for decreasing the electrical conductivity of the composite material 1 is to increase the amount of insulator 5. The thermal conductivity of the composite material 1 is, for example, 8 W/K·m or more, and preferably 10 W/K·m or more. One method for increasing the thermal conductivity of the composite material 1 is to decrease the amount of insulator 5.

The density of the composite material 1 is, for example, 2.7 g/cm ³ or less. Methods for reducing the density of the composite material 1 include reducing the pressure used to produce the composite material 1 and increasing the diameter of the dispersed materials 3.

When the mass of the dispersed material 3 is 100 parts by mass, the mass of the insulator 5 is preferably 30 parts by mass or more and 100 parts by mass or less. When the mass ratio of the dispersed material 3 to the insulator 5 is within this range, the shape of the composite material 1 is more likely to be stable. The composite material 1 can be used, for example, as a material for structural components of mobility motors. Examples of structural components include the cover for the entire motor, the stator fixing plate, and the rotor fixing plate.

2. Manufacturing Method of Composite Material 1 The composite material 1 can be manufactured, for example, by the following method. First, a raw material 21 shown as S_A in FIG. 1 is prepared. The raw material 21 includes a dispersion material 3 and an insulator powder 4. When later melted, the insulator powder 4 becomes the insulator 5. The insulator powder 4 functions as a binder. The insulator powder 4 is, for example, a powder of low-melting-point ceramic, oxide, silicone, or resin. For example, the glass transition point of the insulator powder 4 is lower than the melting point of the dispersion material 3. The average particle size of the insulator powder 4 is, for example, 1 μm or more and 30 μm or less.

The raw material 21 may be in the form of, for example, a powder. For example, the raw material 21 may be prepared by mixing the dispersing material 3 and the insulating powder 4. A mortar or the like may be used for mixing. For example, the dispersing material 3 and the insulating powder 4 are uniformly dispersed in the raw material 21.

Next, the raw material 21 is heated and compressed. When the raw material 21 is heated and compressed, the insulator powder 4 melts and becomes liquid insulator 5, as shown by S_B and S_C in Figure 1. When the raw material 21 is heated and compressed, for example, the dispersed material 3 does not melt. The liquid insulator 5 fills the spaces between the dispersed material 3.

One method for heating and compressing raw material 21 is to use, for example, the apparatus 11 shown in Figures 2 and 3 and a hot press apparatus (not shown). The apparatus 11 includes a cylindrical die 13, a first cylindrical bunch 15, a second cylindrical bunch 17, and a third cylindrical bunch 19.

The cylindrical die 13 is a hollow cylindrical member. The cylindrical die 13 is composed of an inner peripheral portion 13A and an outer peripheral portion 13B. The outer peripheral portion 13B is located further outward than the inner peripheral portion 13A. The inner peripheral portion 13A is made of graphite. The outer peripheral portion 13B is made of SKD61 steel.

The first cylindrical bunch 15, the second cylindrical bunch 17, and the third cylindrical bunch 19 are each cylindrical members. The diameter D of the first cylindrical bunch 15, the second cylindrical bunch 17, and the third cylindrical bunch 19 is close to, but slightly smaller than, the inner diameter of the cylindrical die 13. The first cylindrical bunch 15 and the second cylindrical bunch 17 are made of graphite. The third cylindrical bunch 19 is made of SKD61 steel.

The method for heating and compressing raw material 21 using apparatus 11 and a hot press is as follows. First, as shown in Figure 3, cylindrical die 13 is positioned so that its axial direction coincides with the vertical direction. Next, first cylindrical bunch 15 is placed inside cylindrical die 13. The thickness direction of first cylindrical bunch 15 coincides with the vertical direction.

Next, the raw material 21 is placed on top of the first cylindrical bunch 15. Next, the second cylindrical bunch 17 is placed on top of the raw material 21. The thickness direction of the second cylindrical bunch 17 coincides with the vertical direction. The raw material 21 is sandwiched vertically between the first cylindrical bunch 15 and the second cylindrical bunch 17. Furthermore, the outer periphery of the raw material 21 faces the inner periphery 13A.

Next, the third cylindrical bunch 19 is placed on top of the second cylindrical bunch 17. The thickness direction of the third cylindrical bunch 19 coincides with the vertical direction. At this time, the first cylindrical bunch 15, raw material 21, and second cylindrical bunch 17 are entirely contained inside the cylindrical die 13. A lower portion of the third cylindrical bunch 19 is contained inside the cylindrical die 13, while the other portion protrudes above the cylindrical die 13.

Next, the device 11 is placed in a hot press. The device 11 is heated while the third cylindrical bunch 19 is pressed downward using the hot press, thereby heat-compressing the raw material 21. Heat-compression can be performed under vacuum or atmospheric pressure. When the raw material 21 is heat-compressed, the insulator powder 4 melts and becomes liquid insulator 5, as shown by S_B and S_C in Figure 1. When the raw material 21 is heat-compressed, the dispersed material 3 does not melt. The liquid insulator 5 fills the spaces between the dispersed material 3.

Next, the device 11 is cooled. At this time, the insulator 5 solidifies, and the composite material 1 is completed. Cooling may be performed under vacuum or atmospheric pressure. For example, cooling may be performed by natural cooling. Next, the device 11 is removed from the hot press device, and then the composite material 1 is removed from the device 11. Through the above steps, the composite material 1 shown as S_C in Figure 1 is obtained.

3. Effects of Composite Material 1 (1A) Composite material 1 has high thermal conductivity and low electrical conductivity. Because composite material 1 has low electrical conductivity, induced currents are unlikely to occur in composite material 1, even when composite material 1 is installed in a location where magnetic flux changes drastically, such as around a rotating motor. Because induced currents are unlikely to occur in composite material 1, energy loss can be suppressed.

(1B) For example, the density of composite material 1 can be reduced. When the density of composite material 1 is low, composite material 1 can be used for a mobile object. Examples of mobile objects include HAPS (Hyper-Aerial Photonics Station), eVTOL (Electric Vehicle Toll Free), electric vehicles, drones, etc.

<Example>
1. Production of Samples S1 to S7 Samples S1 to S7 were each produced as follows. First, raw material 21 was prepared. In the case of sample S1, raw material 21 consisted of aluminum powder alone. In the cases of samples S2 to S6, raw material 21 was a mixture of aluminum powder and low-melting-point ceramic powder. In the cases of samples S2 to S6, the mass ratio of aluminum powder to low-melting-point ceramic powder was as shown in Table 1.

For samples S2 to S6, aluminum powder and low-melting point ceramic powder were mixed in a mortar for approximately five minutes to prepare raw material 21. By mixing, the low-melting point ceramic powder was thoroughly coated on the surface of the aluminum powder. After mixing, raw material 21 had no separation between the silver color of the aluminum powder and the white color of the low-melting point ceramic powder, and they were uniformly mixed together. This indicated that the aluminum powder and low-melting point ceramic powder were thoroughly mixed.

In the case of sample S7, raw material 21 consisted only of low-melting-point ceramic powder. The purity of the aluminum powder contained in raw material 21 of samples S1 to S6 was 99% or higher. The particle size of the aluminum powder was 300 μm or less. The thermal conductivity of the aluminum powder was 200 W/K·m. The melting point of the aluminum powder was 660.3°C. The aluminum powder corresponds to dispersion material 3.

The low-melting-point ceramic powder contained in raw material 21 for samples S2 to S7 was TMS-490 manufactured by TOMATEC. The low-melting-point ceramic powder corresponds to insulator powder 4.

Next, the raw material 21 was heated and compressed using the apparatus 11 shown in Figures 2 and 3 and a vacuum hot press manufactured by Daiya Vacuum Co., Ltd., using the method described above. The cylindrical die 13 had an inner diameter of 25 mm, an outer diameter of 100 mm, and a height of 70 mm. The diameter D of the first cylindrical bunch 15, the second cylindrical bunch 17, and the third cylindrical bunch 19 was each 70 mm. The thickness of the first cylindrical bunch 15, the second cylindrical bunch 17, and the third cylindrical bunch 19 was each 15 mm.

When performing the hot compression, the temperature inside the vacuum hot press device was raised to 550°C over 30 minutes and maintained at 550°C for 1 hour. When performing the hot compression, a pressure of 1 ton was applied to the device 11 for 1.5 hours. When performing the hot compression, the low-melting-point ceramic powder in samples S2 to S7 melted and became insulator 5.

Next, device 11 inside the vacuum hot press was allowed to cool naturally under vacuum. When cooled, in the case of samples S2 to S7, the previously molten insulator 5 solidified. Next, device 11 was removed into the atmosphere, and samples S1 to S7 were then removed from device 11. Through the above process, samples S1 to S7 were obtained.

In the case of sample S1, after compacting, it easily crumbled when removed from device 11. Note that compacting refers to heated compression followed by cooling. In the cases of samples S2 and S3, the compact after compacting crumbled and lost its shape. In the cases of samples S4 to S6, the compact after compacting retained its shape without crumbling. Samples S4 to S6 correspond to composite material 1. In the case of sample S7, it broke into pieces when removed from device 11, and no compact could be obtained.

2. Production of Samples S8 and S9 A rolled A1050 plate was used as Sample S8, and an acrylic plate was used as Sample S9.

3. Evaluation of Samples S1 to S9 The density, electrical conductivity, and thermal conductivity were measured for each of Samples S4 to S6. The density and electrical conductivity were also measured for each of Samples S8 and S9. The electrical conductivity was also measured for each of Samples S1 to S3. The measurement results are shown in Table 1. The thermal conductivities of Samples S8 and S9 shown in Table 1 are literature values.

The density was measured as follows: The mass of the sample was measured using an electronic balance. The diameter and thickness of the sample were also measured using a micrometer, and the volume of the sample was calculated based on the diameter and thickness. Finally, the density of the sample was calculated from the mass and volume of the sample.

Electrical conductivity was measured using a conductivity meter (Sigma Test) manufactured by Nippon Foerster. The measurement frequency was 480 kHz. The size of the test piece used for measurement was φ25 mm x t1.5 mm. Thermal conductivity was measured using the laser flash method.

As shown in Table 1, samples S4 to S6 had low density, low electrical conductivity, and high thermal conductivity. The electrical conductivity of samples S4 to S6 was below the measurement limit of 0.5 x 10 ⁶ S/M. The reason for the low electrical conductivity of samples S4 to S6 is presumed to be that ceramic is present between the aluminum particles that make up the aluminum powder, insulating them from each other.

When the electrical conductivity of the parts of samples S1 to S3 that barely maintained their shape was measured, it was 0.5 x 10 ⁶ S/M or more. The reason for this is presumably that the ceramic did not spread sufficiently between the aluminum particles, resulting in insufficient insulation. Sample S8 had high electrical conductivity. Sample S9 had low thermal conductivity.

<Other Embodiments>
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

(1) The insulating powder 4 contained in the raw material 21 may be in the form of a bamboo blind or a nonwoven fabric.
(2) The function of one component in each of the above embodiments may be shared among multiple components, or the functions of multiple components may be performed by one component. Also, part of the configuration of each of the above embodiments may be omitted. Furthermore, at least part of the configuration of each of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

(3) In addition to the composite material 1 described above, the present disclosure can also be realized in various forms, such as a system that includes the composite material 1 as a component, a method for manufacturing the composite material 1, etc.

1...Composite material, 3...Dispersion material, 4...Insulator powder, 5...Insulator, 11...Device, 13...Cylindrical die, 13A...Inner circumference, 13B...Outer circumference, 15...First cylindrical bunch, 17...Second cylindrical bunch, 19...Third cylindrical bunch, 21...Raw material

[Technical idea disclosed in this specification]
[Item 1]
a dispersion material having a thermal conductivity of 100 W/K m or more;
an insulator interposed between the dispersed materials;
A composite material comprising:
[Item 2]
Item 1: The composite material according to item 1,
the insulator is an oxide or resin having a glass transition point lower than the melting point of the dispersion material;
Composite material.
[Item 3]
Item 1 or 2: The composite material according to item 1 or 2,
The electrical conductivity is 0.5×10 ⁶ S/m or less.
Composite material.
[Item 4]
The composite material according to any one of items 1 to 3,
The thermal conductivity is 8 W/K m or more.
Composite material.
[Item 5]
The composite material according to any one of items 1 to 4,
The density is 2.7 g/cm ³ or less.
Composite material.

Claims (3)

a dispersion material having a thermal conductivity of 100 W/K m or more;
an insulator interposed between the dispersed materials;
Equipped with
The electrical conductivity is 0.5×10 ⁶ S/m or less,
The thermal conductivity is 8 W/K m or more,
The insulator is a ceramic, an oxide (excluding the ceramic), or a silicone having a glass transition point equal to or lower than the melting point of the dispersed material.
Composite material. 2. The composite material according to claim 1,
the insulator is the oxide having a glass transition point equal to or lower than the melting point of the dispersion material;
Composite material. The composite material according to claim 1 or 2,
The density is 2.7 g/cm ³ or less.
Composite material.