Composite material

Abstract

The composite material comprises a dispersed material with a thermal conductivity of 100 W / K·m or higher, and an insulator between the dispersed materials. For example, the dispersed material is an aluminum-based metal powder. For example, the insulating system is an oxide or resin with a glass transition temperature lower than or equal to the melting point of the dispersed material. For example, the composite material has an electrical conductivity of 0.5 × 10⁶ S / m or lower.

Description

[Technical Field]

[0001] This invention relates to composite materials. Cross-reference to related applications: This application claims priority to Japanese Patent Application No. 2024-174351, filed with the Japan Patent Office on October 3, 2024, the entire contents of which are incorporated herein by reference. [Previous Technology]

[0002] Patent documents 1 and 2 describe a pressed powder magnetic core. The pressed powder magnetic core is made by compressing iron-based powder together with a binder containing resin or ceramic.

[0003] Patent document 1 is Japanese Patent Application Publication No. 2011-216745. Patent document 2 is Japanese Patent Application Publication No. 2016-12671. [Summary of the Invention]

[0004] In recent years, the development of motor-powered vehicles such as electric vehicles and remote-controlled airplanes has become increasingly popular. Consequently, the output power of motors is increasing while their weight is decreasing. With the increasing power of motors, the necessity of improving the thermal conductivity of the materials that make up the motors is growing. Currently, in order to achieve lightweighting, CFPR is sometimes used as a material for structural components such as motor housings, but materials with higher thermal conductivity are still needed.

[0005] Magnetic flux changes rapidly around a rotating motor. If a material with high conductivity is present around the motor, a large amount of induced current will be generated, which will hinder the rotation of the motor or cause heat generation, thus being a disadvantage. Therefore, it is preferable that the materials constituting the motor have low conductivity.

[0006] The pressed powder magnetic cores described in Patent Documents 1 and 2 are unsuitable for applications other than motor cores due to their low thermal conductivity. In one part of the present invention, it is preferable to provide a composite material with high thermal conductivity and low electrical conductivity.

[0007] Part of the present invention is a composite material comprising a dispersed material with a thermal conductivity of 100 W / K·m or higher, and an insulator between the dispersed materials. The composite material of this invention has high thermal conductivity and low electrical conductivity.

Implementation Method

[0009] Hereinafter, embodiments of the present invention will be described by way of example with reference to the drawings. <First Embodiment> 1. The composite material 1 is configured as shown in Figure 1, S-C, and the composite material 1 has a dispersion material 3 and an insulator 5. The insulator 5 is disposed between the dispersion materials 3. The thermal conductivity of the dispersion material 3 is 100 W / K·m or more.

[0010] The dispersion material 3 is, for example, a metal powder. The metal may be, for example, aluminum, copper, silver, gold, or an alloy of two or more of these metals. The dispersion material 3 may be, for example, an aluminum-based powder. Examples of aluminum-based powders include aluminum atomized powder and aluminum shaving powder. It is preferable that the average particle size of the dispersion material 3 is 10 μm or more and 500 μm or less. The average particle size is measured by a mesh sieve method.

[0011] The insulator 5 is, for example, a low-melting-point ceramic, oxide, silicone, or resin. The glass transition temperature of the insulator 5 is, for example, lower than or equal to the melting point of the dispersion material 3. The insulator 5 is, for example, a low-melting-point ceramic, oxide, silicone, or resin with a glass transition temperature lower than or equal to the melting point of the dispersion material 3.

[0012] The electrical conductivity of the composite material 1 is, for example, 0.5 x 10⁶ S / m or less. One method to reduce 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, preferably 10 W / K·m or more. One method to increase the thermal conductivity of the composite material 1 is to reduce the amount of insulator 5.

[0013] For example, the density of composite material 1 is 2.7 g / cm3 or less. As a method to reduce the density of composite material 1, there are methods to reduce the pressure during the manufacture of composite material 1 and methods to increase the diameter of the dispersed material 3.

[0014] When the mass of the dispersed material 3 is 100 parts by mass, it is preferable that the mass of the insulator 5 is 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 easily stabilized. For example, the composite material 1 can be used as a material for structural components of a motor. Examples of structural components include, for example, the cover plate of the motor assembly, the fixing plate of the stator, and the fixing plate of the rotor.

[0015] 2. Method for manufacturing composite material 1 Composite material 1 can be manufactured, for example, by the following method. First, raw material 21 shown in Figure 1 (S_A) is prepared. Raw material 21 includes dispersion material 3 and insulating powder 4. Insulating powder 4 becomes insulator 5 after melting. Insulating powder 4 acts as a binder. Insulating powder 4 is, for example, a low-melting-point ceramic, oxide, silicone, or resin powder. For example, the glass transition temperature of insulating powder 4 is lower than the melting point of dispersion material 3. The average particle size of insulating powder 4 is, for example, 1 μm or less and 30 μm or less.

[0016] The raw material 21 may be in the form of a powder, for example. For example, the raw material 21 may be prepared by mixing the dispersion material 3 and the insulating powder 4. For example, a mortar and pestle may be used for mixing. For example, the dispersion material 3 and the insulating powder 4 may be uniformly dispersed in the raw material 21.

[0017] Next, the raw material 21 is heated and compressed. When the raw material 21 is heated and compressed, as shown by S_B and S_C in Figure 1, the insulating powder 4 melts and becomes liquid insulator 5. When the raw material 21 is heated and compressed, for example, the dispersion material 3 does not melt. The liquid insulator 5 fills the spaces between the dispersion materials 3.

[0018] As a method for heating and compressing the raw material 21, for example, the apparatus 11 shown in FIG. 2 and FIG. 3 and a hot pressing apparatus not shown are used. The apparatus 11 includes a cylindrical mold 13, a first cylindrical punch 15, a second cylindrical punch 17 and a third cylindrical punch 19.

[0019] The cylindrical mold 13 is a hollow cylindrical component. The cylindrical mold 13 consists of an inner peripheral portion 13A and an outer peripheral portion 13B. The outer peripheral portion 13B is located on the outer peripheral side of the inner peripheral portion 13A. The inner peripheral portion 13A is made of graphite. The outer peripheral portion 13B is made of SKD61 steel.

[0020] The first cylindrical punch 15, the second cylindrical punch 17, and the third cylindrical punch 19 are each cylindrical components. The diameter D of the first cylindrical punch 15, the second cylindrical punch 17, and the third cylindrical punch 19 is close to the inner diameter of the cylindrical mold 13, and slightly smaller than the inner diameter of the cylindrical mold 13. The first cylindrical punch 15 and the second cylindrical punch 17 are made of graphite. The third cylindrical punch 19 is made of SKD61 steel.

[0021] The method for heating and compressing the raw material 21 using the apparatus 11 and the hot pressing apparatus is as follows. First, as shown in FIG3, the cylindrical mold 13 is configured so that its axial direction is aligned with the vertical direction. Next, the first cylindrical punch 15 is housed inside the cylindrical mold 13. The thickness direction of the first cylindrical punch 15 is aligned with the vertical direction.

[0022] Next, the raw material 21 is placed on the first cylindrical punch 15. Next, the second cylindrical punch 17 is placed on the raw material 21. The thickness direction of the second cylindrical punch 17 is aligned with the vertical direction. The raw material 21 is sandwiched between the first cylindrical punch 15 and the second cylindrical punch 17 in the vertical direction. Furthermore, the outer periphery of the raw material 21 is opposite to the inner periphery 13A.

[0023] Next, the third cylindrical punch 19 is placed on top of the second cylindrical punch 17. The thickness direction of the third cylindrical punch 19 is aligned with the vertical direction. At this time, the first cylindrical punch 15, the raw material 21, and the second cylindrical punch 17 are housed inside the cylindrical mold 13. The lower portion of the third cylindrical punch 19 is housed inside the cylindrical mold 13, while the other portion protrudes upwards from the cylindrical mold 13.

[0024] Next, the device 11 is housed in a hot press. The heating device 11 is heated while the third cylindrical punch 19 is pressed downwards using the hot press, thereby heating and compressing the raw material 21. Heating and compression can be performed under vacuum or atmospheric pressure. When the raw material 21 is heated and compressed, as shown by S_B and S_C in Figure 1, the insulating powder 4 melts and becomes liquid insulator 5. When the raw material 21 is heated and compressed, the dispersed material 3 does not melt. The liquid insulator 5 fills the spaces between the dispersed materials 3.

[0025] Next, the apparatus 11 is cooled. At this time, the insulator 5 solidifies, and the composite material 1 is completed. Cooling can be performed under vacuum or atmospheric pressure. For example, natural cooling can be used. Next, the apparatus 11 is removed from the hot press, and then the composite material 1 is further removed from the apparatus 11. Through the above steps, the composite material 1 shown in S_C in Figure 1 can be obtained.

[0026] 3. Effects of Composite Material 1 (1A) Composite Material 1 has high thermal conductivity and low electrical conductivity. Due to the low electrical conductivity of Composite Material 1, even if Composite Material 1 is placed in a place where the magnetic flux changes rapidly, such as around a rotating motor, it is not easy to generate induced current in Composite Material 1. Since it is not easy to generate induced current in Composite Material 1, energy loss can be suppressed.

[0027] (1B) For example, the density of composite material 1 can be reduced. If the density of composite material 1 is low, composite material 1 can be used for moving objects. Examples of moving objects include HAPS (Habitat Assisted Systems), eVTOL (Electronic Vehicle-to-Everything), electric vehicles, and remote-controlled aircraft.

[0028] <Example> 1. Preparation of Samples S1 to S7 Samples S1 to S7 were prepared according to the following method. First, raw material 21 was prepared. In sample S1, raw material 21 was made only of aluminum powder. In samples S2 to S6, raw material 21 was a mixture of aluminum powder and low-melting-point ceramic powder. The mass ratios of aluminum powder and low-melting-point ceramic powder in samples S2 to S6 are shown in Table 1.

[0029] Table 1: Sample No. Raw material mixing ratio Aluminum (g): Ceramics (g) Powder pressing and forming density (g / cm 3 ) conductivity (MS / m) thermal conductivity (W / K‧m) S1 10:0 No - 0.64 - S2 10:1 No - 0.73 - S3 10:2 No - 0.7 - S4 10:3 Can 2.6 <0.5 38 S5 10:5 Can 2.6 <0.5 twenty three S6 10:10 Can 2.6 <0.5 12 S7 0:10 No - - - S8 A1050 rolled steel plate - 2.7 34 237 S9 Acrylic sheet - 1.2 <0.5 0.21

[0030] In samples S2 to S6, raw material 21 was prepared by mixing aluminum powder and low-melting-point ceramic powder in a mortar for about 5 minutes. Through mixing, the low-melting-point ceramic powder fully covers the surface of the aluminum powder. After mixing, the silver color of the aluminum powder and the white color of the low-melting-point ceramic powder are uniformly mixed in raw material 21, without any separated parts. This indicates that the aluminum powder and the low-melting-point ceramic powder have been fully mixed.

[0031] In sample S7, raw material 21 is made solely from low-melting-point ceramic powder. The purity of the aluminum powder contained in raw material 21 of samples S1 to S6 is 99% or higher. Furthermore, the particle size of the aluminum powder is 300µm or less. Furthermore, the thermal conductivity of the aluminum powder is 200 W / K·m. Furthermore, the melting point of the aluminum powder is 660.3°C. Additionally, the aluminum powder corresponds to dispersion material 3.

[0032] The low-melting-point ceramic powder contained in the raw material 21 of samples S2 to S7 is TMS-490 manufactured by TOMATEC. In addition, the low-melting-point ceramic powder corresponds to the insulator powder 4.

[0033] Next, using the apparatus 11 shown in Figures 2 and 3 and the vacuum hot pressing apparatus manufactured by Daiya Vacuum (a Japanese company), the raw material 21 is heated and compressed in the manner described above. The cylindrical mold 13 has 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 punch 15, the second cylindrical punch 17, and the third cylindrical punch 19 is 70 mm. Furthermore, the thickness of the first cylindrical punch 15, the second cylindrical punch 17, and the third cylindrical punch 19 is 15 mm.

[0034] When heating and compression are performed, the temperature in the vacuum hot press device rises to 550°C within 30 minutes and is maintained at 550°C for 1 hour. When heating and compression are performed, a pressure of 1 ton is applied to the device 11 for 1.5 hours. When heating and compression are performed, the low-melting-point ceramic powder melts in samples S2 to S7 and becomes insulator 5.

[0035] Next, the apparatus 11 in the vacuum hot pressing apparatus is allowed to cool naturally under vacuum. During cooling, the previously melted insulator 5 solidifies in the samples S2 to S7. Then, the apparatus 11 is moved into the atmosphere, and samples S1 to S7 are further removed from the apparatus 11. Samples S1 to S7 are obtained through the above steps.

[0036] Regarding sample S1, after being pressed into powder, it easily collapses when removed from device 11. Furthermore, pressing into powder refers to heating and compressing, followed by cooling. Regarding samples S2-S3, the molded bodies after pressing into powder cannot maintain their shape and collapse. Regarding samples S4-S6, the molded bodies after pressing into powder do not collapse and maintain their shape. Samples S4-S6 correspond to composite material 1. Regarding sample S7, since it breaks into fragments when removed from device 11, a molded body cannot be obtained.

[0037] 2.2 Preparation of test materials S8 to S9: A1050 rolled sheet was used as test material S8. Acrylic sheet was used as test material S9.

[0038] 3. Evaluation of Samples S1 to S9: The density, electrical conductivity, and thermal conductivity of samples S4 to S6 were measured respectively. Furthermore, the density and electrical conductivity of samples S8 and S9 were measured respectively. Furthermore, the electrical conductivity of samples S1 to S3 was measured respectively. The measurement results are shown in Table 1. The thermal conductivity of samples S8 and S9 shown in Table 1 is the literature value.

[0039] The density is measured as follows. The mass of the sample is measured using an electronic balance. Furthermore, the diameter and thickness of the sample are measured using a micrometer, and the volume of the sample is calculated based on its diameter and thickness. Finally, the density of the sample is calculated based on its mass and volume.

[0040] Conductivity was measured using a conductivity measuring instrument (Sigmatest) manufactured by FOERSTER (Japan). The measurement frequency was 480kHz. The sample size used for measurement was φ25mm × 1.5mm. Thermal conductivity was measured using the laser flash method.

[0041] As shown in Table 1, samples S4 to S6 have low density, low electrical conductivity, and high thermal conductivity. The electrical conductivity of samples S4-S6 is below the measurement limit of 0.5 × 10⁶ S / M. It is speculated that the reason for the low electrical conductivity of samples S4-S6 is that there is ceramic between the aluminum particles constituting aluminum powder, thereby insulating the aluminum particles from each other.

[0042] The conductivity of the portions of samples S1 to S3 that barely maintained their shape was measured to be above 0.5 × 10⁶ S / m. This is presumably because the ceramic particles were not sufficiently dispersed among the aluminum particles, thus failing to provide adequate insulation. Sample S8 exhibited higher conductivity. Sample S9 showed lower thermal conductivity.

[0043] <Other Embodiments> The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and can take various forms.

[0044] (1) The insulating powder 4 contained in the raw material 21 can be in the form of a curtain or a non-woven fabric. (2) The function of one of the constituent elements in the above embodiments can be dispersed among a plurality of constituent elements. The functions of a plurality of constituent elements can also be integrated into one constituent element. In addition, the constituent parts of the above embodiments can also be omitted. In addition, at least a part of the constituent parts of the above embodiments can also be added to or replaced with respect to the constituent parts of other above embodiments.

[0045] (3) In addition to the above-mentioned composite material 1, the present invention can also be realized in various forms such as a system with the composite material 1 as a constituent element and a method for manufacturing the composite material 1.

[0046] The technical concept disclosed in this specification is as follows: [Item 1] A composite material comprising: a dispersed material with a thermal conductivity of 100 W / K·m or more; and an insulator between the dispersed materials. [Item 2] The composite material of Item 1, wherein the insulating system is an oxide or resin whose glass transition temperature is lower than or equal to the melting point of the dispersed material. [Item 3] The composite material of Item 1 or Item 2, wherein the electrical conductivity is 0.5 × 10⁶ S / m or less. [Item 4] The composite material of any one of Items 1 to 3, wherein the thermal conductivity is 8 W / K·m or more. [Item 5] The composite material of any one of Items 1 to 4, wherein the density is 2.7 g / cm³. [Simplified Explanation of the Diagram]

[0008] [Figure 1] An explanatory diagram showing the structure and manufacturing method of the composite material. [Figure 2] A perspective view showing the structure of the apparatus for heating and compressing the raw material. [Figure 3] A side sectional view showing the structure of the apparatus for performing heating and compression.

Claims

1. A composite material comprising: Dispersed materials with a thermal conductivity of 100 W / K·m or higher; The composite material has an electrical conductivity of less than 0.5 × 10⁶ S / m and a thermal conductivity of more than 8 W / K·m. The insulating system is a ceramic, an oxide, or a resin excluding the aforementioned ceramics, with a glass transition temperature lower than or equal to the melting point of the dispersed material.

2. The composite material as claimed in claim 1, wherein, The glass transition temperature of the insulating system is lower than or equal to the melting point of the oxide of the dispersed material.

3. The composite material as described in claim 1 or claim 2, wherein, Its density is 2.7 g / cm3.

Images