Highly dense heat dissipation composite material and preparation method thereof

Abstract

The application relates to a high-density heat dissipation composite material and a preparation method thereof. The method comprises the following steps: preparing a high-thermal-conductivity carbon fiber preform; placing the high-thermal-conductivity carbon fiber preform in an atmosphere containing argon, hydrogen and methane gas, depositing a carbon nanosheet interface layer on the fiber surface of the high-thermal-conductivity carbon fiber preform through a chemical vapor deposition method to obtain an intermediate blank; the volume flow rate ratio of the argon, hydrogen and methane gas is (36-40):(1-2):(4-5), and the deposition temperature is 900-1000 DEG C; modifying the intermediate blank through an impregnation / solidification / pyrolysis PIP process by taking a carbon precursor solution as an impregnation liquid, and then performing graphitization treatment to obtain a carbon / carbon blank; and covering the carbon / carbon blank with a zirconium / hafnium / tantalum / silicon quaternary mixed powder to obtain the high-density heat dissipation composite material through a reaction infiltration method. The high-density heat dissipation composite material prepared by the application has the advantages of high density, high thermal conductivity and high mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite materials and preparation, and particularly relates to a high-density heat dissipation composite material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of aerospace technology, the temperature in the high-temperature region of the aircraft has reached the upper limit of the temperature resistance of some materials, and the performance requirements of the thermal management and heat dissipation of the thermal structural materials used are higher and higher. Compared with traditional metal heat dissipation materials, the heat dissipation composite material has excellent properties such as low density, high thermal conductivity, low thermal expansion coefficient, high strength and high modulus, and becomes the best high-thermal-conductivity candidate material. The current and future possible application fields include aerospace vehicle structural parts, aircraft heat exchangers, aircraft solar lenses, instrument cabin electronic components, etc.

[0003] The heat dissipation composite material needs to use high-thermal-conductivity mesophase pitch-based carbon fiber as a reinforcing body, and generally uses carbon or ceramic as a matrix. At present, the preparation period of the heat dissipation composite material is generally long, and there are many pores. In order to fill these pores, some additional preparation processes are added. Even so, although the large pores can be filled, there are still many pores between the fibers in the material, which will increase the scattering of phonons and significantly reduce the thermal conductivity of the material, resulting in the problems of low thermal conductivity and insufficient density of the heat dissipation composite material in the prior art. In addition, the heat dissipation composite material in the prior art also has the problem of poor mechanical properties.

[0004] Therefore, it is necessary to provide a high-density heat dissipation composite material and a preparation method thereof to provide material and technical support for later application. SUMMARY

[0005] In order to solve one or more technical problems in the prior art, the present application provides a high-density heat dissipation composite material and a preparation method thereof.

[0006] In a first aspect, the present application provides a preparation method of a high-density heat dissipation composite material, which comprises the following steps:

[0007] (1) preparing a high-thermal-conductivity carbon fiber preform;

[0008] (2) depositing a carbon nanosheet interface layer on the fiber surface of the high-thermal-conductivity carbon fiber preform by chemical vapor deposition in an atmosphere containing argon, hydrogen and methane to obtain an intermediate blank; wherein the volume flow rate ratio of argon, hydrogen and methane is (36-40):(1-2):(4-5), and the deposition temperature is 900-1000℃;

[0009] (3) modifying the intermediate blank by PIP process of impregnation / solidification / cleavage with carbon precursor solution as impregnation solution, and then graphitizing to obtain carbon / carbon blank; in the present application, the cleavage is carried out in inert atmosphere such as argon atmosphere;

[0010] (4) covering the carbon / carbon blank with zirconium hafnium tantalum silicon quaternary mixed powder to obtain high-density thermal-diffusion composite material by reactive infiltration method.

[0011] Preferably, in step (1), high-thermal-conductivity carbon fiber preform is prepared by mixing and weaving high-thermal-conductivity carbon fiber and polyacrylonitrile-based carbon fiber, and the high-thermal-conductivity carbon fiber preform has a three-dimensional orthogonal structure; the high-thermal-conductivity carbon fiber is mesophase pitch-based carbon fiber, and the high-thermal-conductivity carbon fiber has a thermal conductivity of >850 W / (m·K), a tensile strength of >2.4 GPa, and a tensile modulus of >950 GPa after graphitization; the density of the high-thermal-conductivity carbon fiber preform is 0.8-1.1 g / cm 3 .

[0012] Preferably, in step (1), the preparation of the high-thermal-conductivity carbon fiber preform comprises the following sub-steps:

[0013] (a) dispersing mesophase pitch-based carbon fiber bundle by mechanical vibration and / or ultrasonic vibration, and then fixing by hot melt wire to obtain unidirectional pitch-based carbon fiber cloth;

[0014] (b) stacking the unidirectional pitch-based carbon fiber cloth and sewing by polyacrylonitrile-based carbon fiber to obtain high-thermal-conductivity carbon fiber preform;

[0015] Preferably, the mesophase pitch-based carbon fiber in the mesophase pitch-based carbon fiber bundle has a diameter of 10-11 μm, a thermal conductivity of no less than 850 W / (m·K), a tensile strength of >2.4 GPa, and a tensile modulus of >950 GPa after graphitization, and / or the mesophase pitch-based carbon fiber bundle has a specification of 1K-4K;

[0016] Preferably, the width of the dispersed mesophase pitch-based carbon fiber bundle is 15-20 mm; the areal density of the unidirectional pitch-based carbon fiber cloth is 50-100 g / m 2 , and the thickness is 0.1-0.2 mm.

[0017] Preferably, in step (b), the unidirectional pitch-based carbon fiber cloth is stacked in one direction or two directions; the included angle between fibers in each layer of unidirectional pitch-based carbon fiber cloth is 0° or 90°; when the included angle between fibers is 90°, the ratio of fiber content in the two directions is (1-4):1; polyacrylonitrile-based carbon fiber is used for sewing in the direction perpendicular to the stacking direction, and the sewing interval is 1-2.5 mm.

[0018] Preferably, in step (2), the thickness of the carbon nanosheet interface layer is 300-500 nm.

[0019] Preferably, in step (3), the PIP process of 1-5 rounds of impregnation / solidification / cracking is carried out with a carbon precursor solution as the impregnation solution, the impregnation is vacuum impregnation first and then pressure impregnation, the pressure of the pressure impregnation is 2-3 MPa, the time of each vacuum impregnation is 1-2 h, the time of each pressure impregnation is 1-2 h, the temperature of the solidification is 280-400 ℃, the time of each solidification is 2-4 h, the cracking is hot isostatic pressing cracking, the temperature of the cracking is 900-1000 ℃, the pressure of the cracking is 60-90 MPa, and the time of each cracking is 2-4 h; the carbon precursor in the carbon precursor solution is resin and / or pitch; and / or the temperature of the graphitization treatment is 2700-3100 ℃, and the time of the graphitization treatment is 15-45 min.

[0020] Preferably, in step (4), the molar fraction of zirconium in the zirconium-hafnium-tantalum-silicon quaternary mixed powder is 10%-20%, the molar fraction of hafnium is 6%-10%, the molar fraction of tantalum is 4%-10%, and the molar fraction of silicon is 70%-80%; and / or the temperature of the reaction infiltration is 1500-1700 ℃, and the time is 2-3 h.

[0021] Preferably, the high-density heat-dissipation composite material prepared by the reaction infiltration method has a ZrC-HfC-TaC-SiC-C complex phase coating with a thickness of 50-100 μm formed on the surface of the material, the ceramic content in the complex phase coating is 95-100 wt%, the ceramic content gradually decreases from the ZrC-HfC-TaC-SiC-C complex phase coating to the inside of the material, and when the extension reaches 50-100 μm inside the surface of the material, the ceramic content is 5-10 wt%.

[0022] Preferably, the carbon precursor solution contains graphene nanosheets, and the carbon precursor solution is prepared by adding carbon precursors and graphene nanosheets into a solvent and then stirring and ultrasonic treatment; preferably, the mass ratio of the carbon precursors to the graphene nanosheets in the carbon precursor solution is (90-94):(6-10); and preferably, the flake diameter of the graphene nanosheets is 5-10 μm, and the thickness is 3-10 nm.

[0023] The application provides, in a second aspect, a high-density heat-dissipation composite material prepared by the preparation method described in the first aspect of the application.

[0024] Compared with the prior art, the application has at least the following beneficial effects:

[0025] (1) The preparation method in the present application has a short cycle, and the material is dense, so that even the tiny pores between fibers at the micro-nano level can be filled with the matrix, which significantly improves the thermal conductivity and other properties of the material. The reaction infiltration of the zirconium hafnium tantalum silicon quaternary complex alloy powder can further improve the material, especially the density near the outer surface of the material. The present application uses zirconium hafnium tantalum silicon quaternary complex alloy powder, and through one-time reaction infiltration, a ZrC-HfC-TaC-SiC-C complex coating is formed near the outer surface of the composite material. The ceramic content at the outer surface reaches 95-100%, and extends into the material, with the ceramic content gradually decreasing to form a composition gradient. When the extension reaches 50-100 μm inside the material, the ceramic content ranges from 5-10%, and the present application forms a ZrC-HfC-TaC-SiC-C thermal protection coating that synergistically resists high-temperature oxidation and ablation.

[0026] (2) The present application first forms a carbon nanosheet interface layer instead of an ordinary pyrolytic carbon interface layer on the surface of the high-thermal-conductivity carbon fiber preform by adjusting the chemical vapor deposition method. The present application finds that, compared with the pyrolytic carbon interface layer, the carbon nanosheet interface layer can more effectively transfer heat, which is conducive to increasing the overall thermal conductivity of the material and making it more suitable for heat dissipation applications. In addition, the present application finds that the carbon nanosheet interface layer can more effectively fill the micropores and cracks on the surface of the fiber than the pyrolytic carbon interface layer, which helps to improve the density of the material.

[0027] (3) In some preferred technical solutions of the present application, the molar fraction of zirconium in the zirconium hafnium tantalum silicon quaternary mixed powder is 10%-20%, the molar fraction of hafnium is 6%-10%, the molar fraction of tantalum is 4%-10%, and the molar fraction of silicon is 70%-80%. The high silicon content can act as the main component of the matrix during the reaction infiltration process, helping to fill the original pores and microcracks and thus improving the density of the material. The presence of appropriate amounts of zirconium, hafnium and tantalum can enhance the chemical bonding between the ceramic matrix and the carbon / carbon blank, thereby improving the interfacial strength and the mechanical properties of the material. The presence of appropriate amounts of zirconium, hafnium, tantalum and silicon can also improve the overall thermal conductivity of the material. The present application finds that an inappropriate component ratio in the zirconium hafnium tantalum silicon quaternary mixed powder can affect the uniformity of the reaction infiltration, resulting in pores or cracks in the material, which reduces the density, thermal conductivity and mechanical properties of the material. If the content of zirconium, hafnium and tantalum is too high, it can also cause the material to become more brittle, reduce the fracture toughness, and make it prone to cracking or breaking, which is not conducive to the toughness and impact resistance of the material. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present application.

[0029] The present application provides, in a first aspect, a method for preparing a high-density heat dissipation composite material, comprising the following steps:

[0030] (1) preparing a high-thermal-conductivity carbon fiber preform;

[0031] (2) placing the high-thermal-conductivity carbon fiber preform in an atmosphere containing argon, hydrogen and methane gas, depositing a carbon nanosheet interface layer on the fiber surface of the high-thermal-conductivity carbon fiber preform by chemical vapor deposition to obtain an intermediate blank; wherein the volume flow rate ratio of argon, hydrogen and methane gas is (36-40):(1-2):(4-5), and the deposition temperature is 900-1000℃;

[0032] (3) modifying the intermediate blank by the PIP process of impregnation / solidification / pyrolysis with a carbon precursor solution as the impregnation liquid, and then performing graphitization treatment to obtain a carbon / carbon blank; for example, the carbon precursor solution can use xylene as the solvent, and the solid content of the carbon precursor solution is, for example, 50-70wt%; in the present application, for example, the PIP process of 1-5 rounds of impregnation, solidification, hot isostatic pyrolysis is performed with a carbon precursor solution, until the weight gain is <1%, and then graphitization treatment is performed after the last round of pyrolysis to prepare a high-density high-thermal-conductivity carbon matrix to obtain a carbon / carbon blank; the present application does not specifically limit the amount of carbon precursor solution and intermediate blank, as long as the intermediate blank can be completely immersed in the carbon precursor solution;

[0033] (4) covering the carbon / carbon blank with a zirconium hafnium tantalum silicon quaternary mixed powder to prepare a high-density heat dissipation composite material by reaction infiltration; in the present application, the carbon / carbon blank is covered with a zirconium hafnium tantalum silicon quaternary mixed powder to prepare a high-density heat dissipation composite material by single reaction infiltration, and a coating (ZrC-HfC-TaC-SiC-C multi-phase coating) can be formed on the near-surface (outer surface) of the material; the high-density heat dissipation composite material prepared in the present application has a density range of preferably 2.1-2.6g / cm 3 , a porosity of preferably less than 3%, more preferably a porosity of not more than 2.2%, a high-thermal-conductivity carbon fiber used in the material, and a ceramic matrix that is gradiently distributed from the outer surface to the interior of the material; the high-density heat dissipation composite material has the characteristics of low density, high density, high thermal conductivity, high mechanical properties, etc.

[0034] The preparation method in the application has a short cycle, and the material is dense, so that even the micro-nano level small pores between fibers can be filled by the matrix, and the performance of the material, such as thermal conductivity, is significantly improved. The reaction infiltration of the zirconium hafnium tantalum silicon quaternary complex alloy powder can further improve the material, especially the density near the outer surface of the material. The application adopts the zirconium hafnium tantalum silicon quaternary complex alloy powder, and through one-time reaction infiltration, a ZrC-HfC-TaC-SiC-C complex coating is formed near the outer surface of the composite material. The ceramic content at the outer surface is 95-100%, and the ceramic content gradually decreases towards the inside of the material, forming a composition gradient. When the extension is 50-100 μm inside the material, the ceramic content ranges from 5-10%, and the application forms a ZrC-HfC-TaC-SiC-C thermal protection coating with synergistic high-temperature oxidation resistance and ablation resistance.

[0035] The application first forms a carbon nanosheet interface layer instead of an ordinary pyrolytic carbon interface layer on the fiber surface of a high-thermal-conductivity carbon fiber preform by adjusting the chemical vapor deposition method. The application finds that, compared with a pyrolytic carbon interface layer, a carbon nanosheet interface layer can more effectively transfer heat, which is conducive to increasing the overall thermal conductivity of the material and making it more suitable for heat dissipation applications. In addition, the application finds that a carbon nanosheet interface layer can more effectively fill the micropores and cracks on the fiber surface than a pyrolytic carbon interface layer, reducing the porosity of the material, which helps to improve the density of the material.

[0036] According to some preferred embodiments, in step (1): high-thermal-conductivity carbon fibers (mesophase pitch-based carbon fibers) and polyacrylonitrile-based carbon fibers (PAN-based carbon fibers) are mixed and woven into a high-thermal-conductivity carbon fiber preform, and the high-thermal-conductivity carbon fiber preform has a three-direction orthogonal structure. Specifically, for example, a three-direction orthogonal structure is adopted, the thermal conduction direction (X direction) adopts high-thermal-conductivity carbon fibers, and the other two directions (Y direction and Z direction) adopt high-thermal-conductivity carbon fibers or PAN-based carbon fibers for mixed weaving, or the thermal conduction directions (X direction and Y direction) adopt high-thermal-conductivity carbon fibers, and the thickness direction (Z direction) adopts PAN-based carbon fibers for mixed weaving. The application does not specifically limit the source of mesophase pitch-based carbon fibers and polyacrylonitrile-based carbon fibers, and products available on the market or synthesized by existing methods can be used. The high-thermal-conductivity carbon fibers are mesophase pitch-based carbon fibers, and the high-thermal-conductivity carbon fibers have a thermal conductivity > 850 W / (m·K), a tensile strength > 2.4 GPa, and a tensile modulus > 950 GPa after graphitization treatment. The fiber bundle specification of the high-thermal-conductivity carbon fibers is 1K, 2K, or 4K, and the fiber diameter ranges from 10 to 11 μm. The high-thermal-conductivity carbon fibers account for 60-100% of the volume fraction of carbon fibers in the high-thermal-conductivity carbon fiber preform. The density of the high-thermal-conductivity carbon fiber preform is 0.8-1.1 g / cm 3 .

[0037] According to some preferred embodiments, in step (1), the preparation of the high thermal conductivity carbon fiber preform includes the following sub-steps:

[0038] (a) Dispersing mesophase pitch-based carbon fiber bundles through mechanical vibration and / or ultrasonic vibration, and then fixing them with hot-melt wires, yields unidirectional pitch-based carbon fiber cloth; specifically, dispersing the mesophase pitch-based carbon fiber bundles into a planar structure through mechanical vibration and / or ultrasonic vibration, causing the mesophase pitch-based carbon fiber bundles to extend in the width direction and thin in the thickness direction, and fixing them with hot-melt wires, for example, by hot-melt wire sewing, to obtain a low areal density unidirectional pitch-based carbon fiber cloth; more specifically, dispersing the mesophase pitch-based carbon fiber bundles through mechanical vibration and / or ultrasonic vibration using a transmission device (e.g., a vibration transmission device), dispersing them into a planar structure of mesophase pitch-based carbon fiber cloth, and directly sewing the mesophase pitch-based carbon fiber cloth together with linear hot-melt wires, for example, sewing the perimeter of the mesophase pitch-based carbon fiber cloth together with hot-melt wires, which can provide a preliminary fixing effect. The residual carbon content of the hot-melt wire is low, and it essentially disappears during the subsequent preparation of the thermally conductive composite material at high temperatures. The stitching spacing can be, for example, 1–2.5 mm (e.g., 1.0, 1.5, 2.0, or 2.5 mm). This invention does not specifically limit the type of hot-melt wire; any commercially available product is acceptable. In some specific embodiments, the hot-melt wire can be, for example, nylon hot-melt wire. This invention does not specifically limit the conditions of mechanical vibration and ultrasonic vibration, as long as the mesophase pitch-based carbon fiber bundles are dispersed into a planar structure by mechanical vibration and / or ultrasonic vibration. In this invention, the frequency of the mechanical vibration can be, for example, 25–200 Hz, and the duration of the mechanical vibration can be, for example, 1–5 min; the frequency of the ultrasonic vibration can be, for example, 20–40 kHz, and the duration of the ultrasonic vibration can be, for example, 1–5 min.

[0039] (b) A high thermal conductivity carbon fiber preform is obtained by laminating unidirectional pitch-based carbon fiber cloth and then stitching it with polyacrylonitrile-based carbon fiber. It should be noted that "unidirectional" in this context refers to the carbon fibers being arranged in one direction within the same piece (same layer) of pitch-based carbon fiber cloth. Specifically, the unidirectional pitch-based carbon fiber cloth is laminated and placed in a weaving mold, and then stitched with polyacrylonitrile-based carbon fiber in the direction perpendicular to the lamination direction (Z-direction) to obtain the high thermal conductivity carbon fiber preform. During lamination, the angle between fibers in each layer of fiber cloth (adjacent layers) is 0° or 90°. °, when the included angle is 90°, the ratio range of fiber content in the two directions is, for example, (1~4):1, that is, when the included angle is 90°, the ratio of fiber volume fraction in the two directions is (1~4):1; In this invention, during lamination, unidirectional pitch-based carbon fiber cloth can be laminated in one direction or alternately laminated perpendicularly in two directions. Alternating perpendicular lamination in two directions means that the carbon fiber directions in two adjacent layers of unidirectional pitch-based carbon fiber cloth are perpendicular to each other. This allows the thermally conductive composite material to arrange mesophase pitch-based carbon fibers as thermal conductors and reinforcements in one direction (X) or two perpendicular directions (X, Y) in the plane.

[0040] The present invention preferably obtains the high thermal conductivity carbon fiber preform through steps (a) and (b), which enables the method of the present invention to prepare large-area dispersed high-density thermally conductive composite materials with near-net-shape molding. The fiber ratio and matrix composition can be controlled. The thermally conductive composite material obtained by using the high thermal conductivity carbon fiber preform has lower density, thinner thickness, higher specific strength, more uniform and dense internal structure, rapid in-plane thermal conductivity, and better mechanical and thermal properties.

[0041] This invention employs a method of dispersing mesophase pitch-based carbon fiber bundles through mechanical and / or ultrasonic vibration, followed by fixing with hot-melt wires to obtain a unidirectional pitch-based carbon fiber cloth. This cloth is characterized by its ultra-thin thickness. Using this unidirectional pitch-based carbon fiber cloth allows for a thinner thermally conductive composite material with essentially the same density. In contrast, existing techniques involve impregnating mesophase pitch-based carbon fibers in an organic carbon solution (mesophase pitch), then placing them parallel in a mold and drying at low temperature to obtain unidirectional carbon fiber sheets. This method causes the carbon fibers to saturate and absorb the solution during impregnation, and the subsequent drying process leaves a layer of pitch-based material between the fibers, increasing the sheet thickness. Furthermore, the stacking of carbon fiber layers during the parallel placement in the mold to obtain the unidirectional structure (unidirectional sheet) also contributes to the final sheet thickness. Moreover, this invention discovers that the unidirectional pitch-based carbon fiber cloth obtained by mechanical and / or ultrasonic vibration dispersion followed by hot-melt wire fixing yields a more consistent and uniform carbon fiber arrangement with more uniform fiber directionality. This consistency helps improve the thermal conductivity of the composite material. The improved strength and stability of the composite material help resist bending stress. The thinner unidirectional pitch-based carbon fiber cloth obtained by this invention means that the overall performance of the material is better and more uniform. For example, when preparing a thermally conductive composite material with a total thickness of 3 mm, using a thicker carbon cloth results in fewer layers. For instance, using ordinary carbon cloth with a thickness of 0.5-1 mm, only 3-6 layers can be stacked. However, the thickness of the dispersed unidirectional pitch-based carbon fiber cloth in this invention can be as thin as 0.1-0.2 mm, and the unidirectional pitch-based carbon fiber cloth can be stacked in 15-30 layers, which is a relatively large number of layers. With smaller spacing, the resulting thermally conductive composite material exhibits better uniformity in the thickness direction, smaller overall performance differences, more uniform performance, and better material stability, especially during long-term application. For example, if a thermally conductive composite material composed of 6 layers of 0.5mm thick carbon cloth peels off during use, the material loss reaches 16.67% if only one layer is peeled off. In contrast, for a thermally conductive composite material composed of 20 layers of 0.15mm thick unidirectional pitch-based carbon fiber cloth, the material loss is only 5% even if one layer is peeled off.

[0042] According to some preferred embodiments, the mesophase pitch-based carbon fibers (high thermal conductivity carbon fibers) in the mesophase pitch-based carbon fiber bundles have a diameter of 10–11 μm, a thermal conductivity of not less than 850 W / (m·K) after graphitization treatment, a tensile strength > 2.4 GPa, a tensile modulus > 950 GPa, and / or the mesophase pitch-based carbon fiber bundle specifications are 1K–4K (e.g., 1K, 2K, 3K, or 4K); the high thermal conductivity carbon fibers account for 60–100% of the carbon fiber volume fraction in the high thermal conductivity carbon fiber preform, and the bulk density of the high thermal conductivity carbon fiber preform is 0.8–1.1 g / cm³. 3 .

[0043] According to some preferred embodiments, the width of the dispersed mesophase pitch-based carbon fiber bundles is 15–20 mm (e.g., 15, 16, 17, 18, 19, or 20 mm); the areal density of the unidirectional pitch-based carbon fiber cloth is 50–100 g / m². 2 (e.g., 50, 60, 70, 80, 90 or 100 g / m²) 2 The thickness is 0.1 to 0.2 mm (e.g., 0.1, 0.15 or 0.2 mm).

[0044] According to some preferred embodiments, in step (b): the unidirectional pitch-based carbon fiber cloth is stacked in one direction or two directions; the included angle between the fibers in each layer of unidirectional pitch-based carbon fiber cloth is 0° or 90°, that is, the included angle between the fibers in two adjacent layers of unidirectional pitch-based carbon fiber cloth is 0° or 90°; in this invention, when the unidirectional pitch-based carbon fiber cloth is stacked in one direction, a unidirectional high thermal conductivity carbon fiber preform is formed, and the carbon fibers in each layer of unidirectional pitch-based carbon fiber cloth are arranged in one direction, with an included angle between the carbon fibers of 0°; when the unidirectional pitch-based carbon fiber cloth is stacked in two directions... When the layers are stacked in alternating directions, a bidirectional high thermal conductivity carbon fiber preform is formed. The carbon fibers in the pitch-based carbon fiber cloth are arranged in two directions, and the included angle between the carbon fibers in two adjacent unidirectional pitch-based carbon fiber cloth layers is 90°. When the included angle between the fibers is 90°, the ratio of fiber content (fiber volume fraction) in the two directions is (1-4):1 (e.g., 1:1, 2:1, 3:1 or 4:1). Polyacrylonitrile-based carbon fibers are used for stitching in the direction perpendicular to the stacking direction, and the stitching spacing is 1-2.5 mm (e.g., 1.0, 1.5, 2.0 or 2.5 mm).

[0045] According to some preferred embodiments, in step (2): the thickness of the carbon nanosheet interface layer is 300-500 nm;

[0046] This invention does not impose a specific limitation on the deposition time of the carbon nanosheet interface layer. Those skilled in the art can adjust the deposition time until the preset thickness is achieved. Unless otherwise specified, the deposition pressure during chemical vapor deposition is, for example, 5 to 10 kPa.

[0047] According to some preferred embodiments, in step (3): a PIP process of impregnation / curing / pyrolysis is performed 1 to 5 times using a carbon precursor solution as the impregnation liquid. The impregnation is first vacuum impregnation, with a vacuum impregnation pressure of, for example, -0.1 to -0.05 MPa, followed by pressure impregnation at a pressure of 2 to 3 MPa. The duration of each vacuum impregnation is 1 to 2 hours, and the duration of each pressure impregnation is 1 to 2 hours. The curing temperature is 280 to 400°C (e.g., 280°C, 300°C, 320°C, 350°C, 380°C, or 400°C), and the curing time is 2 to 4 hours (e.g., 2, 3, or 4 hours). The pyrolysis is thermal isostatic pyrolysis, with a pyrolysis temperature of 900 to 1000°C. The pyrolysis temperature is 0℃, the pyrolysis pressure is 60-90 MPa (e.g., 60, 70, 80 or 90 MPa), and the pyrolysis time is 2-4 h (e.g., 2, 3 or 4 h). Preferably, the hot isostatic pressing (HIP) pyrolysis is performed at a temperature of 900-1000℃ and a pressure of 60-90 MPa. This invention has found that, compared to atmospheric pressure pyrolysis, HIP pyrolysis promotes a tighter bond between carbon precursors, helps to make the prepared carbon / carbon preform more compact, reduces structural defects, and improves the density and thermal conductivity of the material. It can also more effectively conduct heat. Furthermore, HIP pyrolysis under high pressure can form stronger interfacial bonding, improving the mechanical properties of the material, such as tensile strength, flexural strength, and impact resistance.

[0048] According to some preferred embodiments, the carbon precursor in the carbon precursor solution is a resin and / or pitch, such as phenolic resin, and the pitch is one or more of mesophase coal tar pitch, mesophase petroleum pitch, and petroleum pitch; and / or the graphitization treatment temperature is 2700–3100°C (e.g., 2700°C, 2800°C, 2900°C, 3000°C, or 3100°C), and the graphitization treatment time is 15–45 min (e.g., 15, 20, 25, 30, 35, 40, or 45 min).

[0049] According to some preferred embodiments, in step (4): the molar fraction of zirconium in the zirconium-hafnium-tantalum-silicon quaternary mixed powder is 10% to 20% (e.g., 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%), the molar fraction of hafnium is 6% to 10% (e.g., 6%, 7%, 8%, 9%, or 10%), and the molar fraction of tantalum is 4% to 10% (e.g., 4%, 5%, 6%, 7%). The molar fraction of silicon is 70% to 80% (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%). In this invention, the sum of the molar fractions of zirconium, hafnium, tantalum, and silicon in the zirconium-hafnium-tantalum-silicon quaternary mixed powder is 100%. Preferably, the molar fraction of zirconium in the zirconium-hafnium-tantalum-silicon quaternary mixed powder is 10% to 20%, and the molar fraction of hafnium is 70% to 80% (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%). The molar fraction of zirconium, hafnium, tantalum, and silicon is 6%–10%, 4%–10%, and 70%–80%, respectively. The high silicon content allows it to act as a major component of the matrix during the reaction infiltration process, helping to fill existing pores and microcracks, thereby increasing the material's density. The presence of appropriate amounts of zirconium, hafnium, tantalum, and silicon can enhance the chemical bonding between the ceramic matrix and the carbon / carbon preform, thereby improving interfacial strength and increasing the material's mechanical properties. Furthermore, the presence of appropriate amounts of zirconium, hafnium, tantalum, and silicon can improve the overall thermal conductivity of the material. This invention has found that an inappropriate component ratio in the zirconium-hafnium-tantalum-silicon quaternary mixed powder can affect the uniformity of the reaction infiltration, leading to pores or cracks within the material. This reduces the material's density, thermal conductivity, and mechanical properties. Moreover, excessively high contents of zirconium, hafnium, and tantalum can increase the material's brittleness and reduce its fracture toughness, making it prone to cracking or fragmentation, which is also detrimental to the material's toughness and impact resistance.

[0050] According to some preferred embodiments, the reaction melting temperature is 1500–1700°C (e.g., 1500°C, 1550°C, 1600°C, 1650°C or 1700°C), and the time is 2–3 hours (e.g., 2, 2.5 or 3 hours).

[0051] According to some preferred embodiments, a high-density thermally conductive composite material prepared by reactive infiltration has a ZrC-HfC-TaC-SiC-C multiphase coating with a thickness of 50-100 μm formed on its surface. The ceramic content in this multiphase coating is 95-100 wt%. The ceramic content gradually decreases as the ZrC-HfC-TaC-SiC-C multiphase coating extends into the material, reaching 5-10 wt% when it extends 50-100 μm into the material surface. That is, in this invention, after reactive infiltration... A ZrC-HfC-TaC-SiC-C multiphase coating with a thickness of 50-100 μm is formed near the outer surface of the material. The ceramic content at the outer surface reaches 95-100%. As it extends into the material, the ceramic content gradually decreases, forming a compositional gradient. When it extends 50-100 μm, the ceramic content ranges from 5-10%. In this invention, since reactive infiltration can cause the ceramic content to gradually decrease from the outer surface of the material to the interior of the material, the high-density thermally conductive composite material can also be referred to as a high-density gradient thermally conductive composite material.

[0052] According to some preferred embodiments, the carbon precursor solution contains graphene nanosheets. The carbon precursor solution is prepared by adding a carbon precursor and graphene nanosheets to a solvent, followed by stirring and ultrasonic treatment. Specifically, in this invention, the stirring speed is, for example, 400–800 rpm, and the stirring time is, for example, 20–40 min; the ultrasonic treatment frequency is 20–40 kHz, and the ultrasonic treatment time is, for example, 20–40 min. In this invention, the carbon precursor and graphene nanosheets are subjected to stirring and ultrasonic treatment. The graphene nanosheets are uniformly dispersed in the solvent to ensure that they are evenly distributed throughout the carbon precursor solution. This improves the uniformity of the high-density thermally conductive composite material and helps to ensure the material's performance. In this invention, the solvent may be xylene, for example, and the carbon precursor solution contains a total mass fraction of carbon precursor and graphene nanosheets of, for example, 50-70%. Preferably, the mass ratio of carbon precursor to graphene nanosheets in the carbon precursor solution is (90-94):(6-10) (e.g., 94:6, 92:8, or 90:10).

[0053] Preferably, during the impregnation / curing / pyrolysis PIP process, the carbon precursor solution also contains an appropriate amount of graphene nanosheets. This invention has found that an appropriate amount of graphene nanosheets can act as a filler in the carbon precursor solution, filling potential pores and microcracks. This helps reduce porosity without affecting subsequent melting and infiltration reactions. Furthermore, the addition of graphene nanosheets can effectively improve the thermal conductivity of the material. In addition, the addition of graphene nanosheets can also effectively enhance the mechanical properties of the material, thus improving its overall performance.

[0054] According to some preferred embodiments, the graphene nanosheets have a diameter of 5–10 μm and a thickness of 3–10 nm.

[0055] The present invention provides, in a second aspect, a highly dense thermally conductive composite material prepared by the preparation method described in the first aspect of the present invention.

[0056] The present invention will be further described below with reference to the embodiments. These embodiments are merely illustrative examples of preferred implementations of the present invention, and the scope of protection of the present invention should not be construed as being limited to these embodiments.

[0057] Example 1

[0058] ① Weaving of the high thermal conductivity carbon fiber preform: A three-dimensional orthogonal structure is adopted. Mesophase pitch-based carbon fiber (high thermal conductivity carbon fiber) is used in the X and Y directions, while polyacrylonitrile-based carbon fiber (PAN-based carbon fiber) is used in the thickness direction (Z direction) for mixed weaving. The graphitized mesophase pitch-based carbon fiber has a thermal conductivity of 860 W / (m·K), a tensile strength of 2.5 GPa, a tensile modulus of 960 GPa, a fiber bundle specification of 2K, and a fiber diameter of 10.5 ± 0.2 μm. High thermal conductivity carbon fiber accounts for 80% of the carbon fiber volume fraction in the high thermal conductivity carbon fiber preform, and the bulk density of the high thermal conductivity carbon fiber preform is 0.9 g / cm³. 3 .

[0059] ② Preparation of carbon nanosheet interface layer: The high thermal conductivity carbon fiber preform obtained in step ① is placed in an atmosphere containing argon, hydrogen and methane gas at 950℃ and 6kPa to deposit a carbon nanosheet interface layer with a thickness of 400nm on the fiber surface of the high thermal conductivity carbon fiber preform by chemical vapor deposition to obtain an intermediate preform; wherein, the volume flow rate ratio of argon, hydrogen and methane gas is 40:1.5:4.5.

[0060] ③ Carbon / carbon preform preparation: The intermediate preform obtained in step ② is completely immersed in a carbon precursor solution. Using the carbon precursor solution as the impregnation liquid, the intermediate preform is modified through an impregnation / curing / pyrolysis PIP process, followed by graphitization treatment at 3000℃ for 30 minutes to obtain a carbon / carbon preform. The carbon precursor solution is prepared by uniformly mixing the carbon precursor (petroleum asphalt) with xylene to obtain a carbon precursor solution containing 60% petroleum asphalt by mass. The carbon precursor solution is used as the impregnation liquid for further processing. The PIP process involves four rounds of impregnation / curing / pyrolysis. Specifically, the impregnation process is as follows: first, vacuum impregnation is performed at a pressure of -0.05 MPa for 1.5 hours; then, pressure impregnation is performed at a pressure of 3 MPa for 2 hours; the curing temperature is 300°C for 3 hours; and the pyrolysis is performed under hot isostatic pressure (HIP) at a temperature of 1000°C and a pressure of 70 MPa for 2 hours.

[0061] ④ Reactive infiltration of zirconium-hafnium-tantalum-silicon quaternary mixed powder: The carbon / carbon preform obtained in step ③ is covered with zirconium-hafnium-tantalum-silicon quaternary mixed powder to prepare a high-density thermally conductive composite material by a one-time reactive infiltration method; wherein, the molar fraction of zirconium in the zirconium-hafnium-tantalum-silicon quaternary mixed powder is 10%, the molar fraction of hafnium is 6%, the molar fraction of tantalum is 4%, the molar fraction of silicon powder is 80%, the reactive infiltration temperature is 1600℃, and the reactive infiltration time is 2h.

[0062] In this embodiment, after melting and infiltration, a ZrC-HfC-TaC-SiC-C multiphase coating with a thickness of 75μm is formed near the outer surface of the material. After elemental energy dispersive spectroscopy analysis, the ceramic content at the outer surface reaches 98%. As it extends into the material, the ceramic content gradually decreases, forming a compositional gradient. When it extends to 75μm inside the material surface, after elemental energy dispersive spectroscopy analysis, the ceramic content decreases to 6%.

[0063] Example 2

[0064] Example 2 is basically the same as Example 1, except that:

[0065] ③ Carbon / carbon preform preparation: The intermediate preform obtained in step ② is completely immersed in a carbon precursor solution. Using the carbon precursor solution as the impregnation liquid, the intermediate preform is modified through an impregnation / curing / pyrolysis PIP process, followed by graphitization treatment at 3000℃ for 30 minutes to obtain a carbon / carbon preform. The carbon precursor solution is prepared by uniformly mixing the carbon precursor (petroleum asphalt) with xylene to obtain a carbon precursor solution containing 60% petroleum asphalt by mass. The PIP process, which involves four rounds of impregnation / curing / pyrolysis using a bulk solution as the impregnation liquid, is as follows: the impregnation is first performed under vacuum at a pressure of -0.05 MPa for 1.5 hours each time, followed by pressure impregnation at a pressure of 3 MPa for 2 hours each time; the curing temperature is 300°C for 3 hours each time; and the pyrolysis is performed at 1000°C under normal pressure for 2 hours each time.

[0066] Example 3

[0067] Example 3 is basically the same as Example 1, except that:

[0068] ④ Reactive infiltration of zirconium-hafnium-tantalum-silicon quaternary mixed powder: The carbon / carbon preform obtained in step ③ is covered with zirconium-hafnium-tantalum-silicon quaternary mixed powder to prepare a high-density thermally conductive composite material by a one-time reactive infiltration method; wherein, the molar fraction of zirconium in the zirconium-hafnium-tantalum-silicon quaternary mixed powder is 25%, the molar fraction of hafnium is 25%, the molar fraction of tantalum is 25%, the molar fraction of silicon powder is 25%, the reactive infiltration temperature is 1600℃, and the reactive infiltration time is 2h.

[0069] Example 4

[0070] Example 4 is basically the same as Example 1, except that:

[0071] ④ Reactive infiltration of zirconium-hafnium-tantalum-silicon quaternary mixed powder: The carbon / carbon preform obtained in step ③ is covered with zirconium-hafnium-tantalum-silicon quaternary mixed powder to prepare a high-density thermally conductive composite material by a one-time reactive infiltration method; wherein, the molar fraction of zirconium in the zirconium-hafnium-tantalum-silicon quaternary mixed powder is 25%, the molar fraction of hafnium is 15%, the molar fraction of tantalum is 15%, the molar fraction of silicon powder is 45%, the reactive infiltration temperature is 1600℃, and the reactive infiltration time is 2h.

[0072] Example 5

[0073] Example 5 is basically the same as Example 1, except that:

[0074] ① Weaving of high thermal conductivity carbon fiber preforms: Mesophase pitch-based carbon fiber bundles are dispersed into a planar structure by mechanical vibration and then fixed by hot-melt wire stitching with a stitching spacing of 1.5 mm to obtain unidirectional pitch-based carbon fiber cloth; the frequency of the mechanical vibration is 100 Hz and the vibration time is 3 min; the fiber diameter in the mesophase pitch-based carbon fiber bundles is 10.5 ± 0.2 μm, the thermal conductivity after graphitization is 860 W / (m·K), the fiber bundle specification is 2K, the tensile strength is 2.5 GPa, the tensile modulus is 960 GPa, the width of the dispersed mesophase pitch-based carbon fiber bundles is 20 mm, and the areal density of the prepared unidirectional pitch-based carbon fiber cloth is 80 g / m³. 2 The thickness of a single layer of unidirectional pitch-based carbon fiber cloth is 0.15 mm. Ten layers of unidirectional pitch-based carbon fiber cloth are alternately stacked in two directions (alternating stacking in 0° / 90° directions) and placed in a weaving mold. Polyacrylonitrile-based carbon fiber is used for sewing in the vertical direction (Z) to obtain a high thermal conductivity carbon fiber preform with a thickness of 1.5 mm. The high thermal conductivity carbon fiber preform is a bidirectional vertical high thermal conductivity carbon fiber preform. The angle between fibers in two adjacent layers of unidirectional pitch-based carbon fiber cloth is 90°, the fiber content ratio (fiber volume fraction ratio) in the two directions is 1:1, the spacing between fibers in the Z direction (sewing spacing) is 1.5 mm, and the density of the high thermal conductivity carbon fiber preform is 0.9 g / cm³. 3 .

[0075] Example 6

[0076] Example 6 is basically the same as Example 1, except that:

[0077] ③ Carbon / carbon preform preparation: The intermediate preform obtained in step ② is completely immersed in a carbon precursor solution. Using the carbon precursor solution as the impregnation liquid, the intermediate preform is modified through an impregnation / curing / pyrolysis PIP process, followed by graphitization treatment at 3000℃ for 30 min to obtain a carbon / carbon preform. The carbon precursor solution is prepared by adding carbon precursor (petroleum pitch) and graphene nanosheets with a sheet size distribution range of 5-10 μm and a thickness distribution range of 3-10 nm to xylene. The mixture is then stirred at 400 rpm for 40 min, followed by ultrasonic treatment at 20 kHz for 40 min to obtain the carbon precursor solution. The carbon precursor solution contains petroleum... The sum of the mass percentages of asphalt and graphene nanosheets is 60%, and the mass ratio of carbon precursor to graphene nanosheets is 92:8. A four-round PIP process of impregnation / curing / pyrolysis is performed using a carbon precursor solution as the impregnation liquid. Specifically, the impregnation process involves: first, vacuum impregnation at a pressure of -0.05 MPa for 1.5 hours; then, pressure impregnation at 3 MPa for 2 hours; curing at 300°C for 3 hours; and pyrolysis at 1000°C and 70 MPa for 2 hours.

[0078] Example 7

[0079] Example 7 is basically the same as Example 1, except that:

[0080] ① Weaving of high thermal conductivity carbon fiber preforms: Mesophase pitch-based carbon fiber bundles are dispersed into a planar structure by mechanical vibration and then fixed by hot-melt wire stitching with a stitching spacing of 1.5 mm to obtain unidirectional pitch-based carbon fiber cloth; the frequency of the mechanical vibration is 100 Hz and the vibration time is 3 min; the fiber diameter in the mesophase pitch-based carbon fiber bundles is 10.5 ± 0.2 μm, the thermal conductivity after graphitization is 860 W / (m·K), the fiber bundle specification is 2K, the tensile strength is 2.5 GPa, the tensile modulus is 960 GPa, the width of the dispersed mesophase pitch-based carbon fiber bundles is 20 mm, and the areal density of the prepared unidirectional pitch-based carbon fiber cloth is 80 g / m³. 2The thickness of a single layer of unidirectional pitch-based carbon fiber cloth is 0.15 mm. Ten layers of unidirectional pitch-based carbon fiber cloth are alternately stacked in two directions (alternating stacking in 0° / 90° directions) and placed in a weaving mold. Polyacrylonitrile-based carbon fiber is used for sewing in the vertical direction (Z) to obtain a high thermal conductivity carbon fiber preform with a thickness of 1.5 mm. The high thermal conductivity carbon fiber preform is a bidirectional vertical high thermal conductivity carbon fiber preform. The angle between fibers in two adjacent layers of unidirectional pitch-based carbon fiber cloth is 90°, the fiber content ratio (fiber volume fraction ratio) in the two directions is 1:1, the spacing between fibers in the Z direction (sewing spacing) is 1.5 mm, and the density of the high thermal conductivity carbon fiber preform is 0.9 g / cm³. 3 .

[0081] ③ Carbon / carbon preform preparation: The intermediate preform obtained in step ② is completely immersed in a carbon precursor solution. Using the carbon precursor solution as the impregnation liquid, the intermediate preform is modified through an impregnation / curing / pyrolysis PIP process, followed by graphitization treatment at 3000℃ for 30 min to obtain a carbon / carbon preform. The carbon precursor solution is prepared by adding carbon precursor (petroleum pitch) and graphene nanosheets with a sheet size distribution range of 5-10 μm and a thickness distribution range of 3-10 nm to xylene. The mixture is then stirred at 400 rpm for 40 min, followed by ultrasonic treatment at 20 kHz for 40 min to obtain the carbon precursor solution. The carbon precursor solution contains petroleum... The sum of the mass percentages of asphalt and graphene nanosheets is 60%, and the mass ratio of carbon precursor to graphene nanosheets is 92:8. A four-round PIP process of impregnation / curing / pyrolysis is performed using a carbon precursor solution as the impregnation liquid. Specifically, the impregnation process involves: first, vacuum impregnation at a pressure of -0.05 MPa for 1.5 hours; then, pressure impregnation at 3 MPa for 2 hours; curing at 300°C for 3 hours; and pyrolysis at 1000°C and 70 MPa for 2 hours.

[0082] Comparative Example 1

[0083] Comparative Example 1 is basically the same as Example 1, except that:

[0084] After obtaining the carbon / carbon preform in step ③, step ④ is not performed.

[0085] Comparative Example 2

[0086] Comparative Example 2 is basically the same as Example 1, except that:

[0087] ② Preparation of pyrolytic carbon interface layer: The high thermal conductivity carbon fiber preform obtained in step ① is placed in an atmosphere containing argon and methane gas at 1050℃ and 6kPa and a pyrolytic carbon interface layer (carbon interface layer) with a thickness of 400nm is deposited on the fiber surface of the high thermal conductivity carbon fiber preform by chemical vapor deposition to obtain an intermediate preform; wherein, the volume flow rate ratio of argon and methane gas is 1:1.

[0088] Comparative Example 3

[0089] Comparative Example 3 is basically the same as Example 1, except that:

[0090] ④ Silicon powder reactive infiltration: The carbon / carbon preform obtained in step ③ is covered with silicon powder and a thermally conductive composite material is prepared by a one-time reactive infiltration method; wherein, the reactive infiltration temperature is 1600℃ and the reactive infiltration time is 2h.

[0091] The present invention conducted performance tests on the high-density thermally conductive composite materials prepared in each embodiment and the materials finally prepared in each comparative example. The test results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] In Table 1, the symbol "-" indicates that the performance metric was not tested.

[0096] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in each embodiment, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-density, thermally conductive composite material, characterized in that, The method includes the following steps: (1) Preparation of a high thermal conductivity carbon fiber preform; In step (1), the preparation of the high thermal conductivity carbon fiber preform includes the following sub-steps: (a) dispersing mesophase pitch-based carbon fiber bundles into a planar structure by mechanical vibration and / or ultrasonic vibration, so that the mesophase pitch-based carbon fiber bundles extend in the width direction and become thinner in the thickness direction, and then fixing them with hot melt wire to obtain a unidirectional pitch-based carbon fiber cloth; (b) laminating the unidirectional pitch-based carbon fiber cloth and then stitching it with polyacrylonitrile-based carbon fiber to obtain a high thermal conductivity carbon fiber preform; the width of the dispersed mesophase pitch-based carbon fiber bundles is 15-20 mm; the areal density of the unidirectional pitch-based carbon fiber cloth is 50-100 g / m³. 2 The thickness is 0.1–0.2 mm; (2) The high thermal conductivity carbon fiber preform is placed in an atmosphere containing argon, hydrogen and methane gas and carbon nanosheet interface layer is deposited on the fiber surface of the high thermal conductivity carbon fiber preform by chemical vapor deposition to obtain an intermediate preform; wherein, the volume flow rate ratio of argon, hydrogen and methane gas is (36~40):(1~2):(4~5) and the deposition temperature is 900~1000℃; (3) The intermediate preform is modified by impregnation / curing / pyrolysis PIP process using carbon precursor solution as impregnation liquid, and then graphitized to obtain carbon / carbon preform; the pyrolysis is hot isostatic pyrolysis, the pyrolysis temperature is 900-1000℃, the pyrolysis pressure is 60-90MPa, and the time for each pyrolysis is 2-4h; the carbon precursor solution contains graphene nanosheets, and the mass ratio of carbon precursor to graphene nanosheets in the carbon precursor solution is (90-94):(6-10); (4) A high-density thermally conductive composite material is prepared by covering the carbon / carbon preform with a zirconium-hafnium-tantalum-silicon quaternary mixed powder and reacting infiltration method. The zirconium-hafnium-tantalum-silicon quaternary mixed powder has a molar fraction of 10% to 20%, a molar fraction of 6% to 10%, a molar fraction of 4% to 10%, and a molar fraction of 70% to 80%. The high-density thermally conductive composite material prepared by reacting infiltration method has a ZrC-HfC-TaC-SiC-C multiphase coating with a thickness of 50 to 100 μm on the surface of the material. The ceramic content in the multiphase coating is 95 to 100 wt%. The ceramic content gradually decreases as the ZrC-HfC-TaC-SiC-C multiphase coating extends into the material. When it extends to 50 to 100 μm inside the material surface, the ceramic content is 5 to 10 wt%.

2. The preparation method according to claim 1, characterized in that: The mesophase pitch-based carbon fibers in the mesophase pitch-based carbon fiber bundle have a diameter of 10-11 μm, a thermal conductivity of not less than 850 W / (m·K) after graphitization treatment, a tensile strength > 2.4 GPa, a tensile modulus > 950 GPa, and / or the mesophase pitch-based carbon fiber bundle has a specification of 1K-4K.

3. The preparation method according to claim 2, characterized in that: In step (b): The unidirectional pitch-based carbon fiber cloth is laminated in one or two directions; The included angle between fibers in each layer of unidirectional pitch-based carbon fiber cloth is 0° or 90°. When the angle between fibers is 90°, the ratio of fiber content in the two directions is (1~4):1; Polyacrylonitrile-based carbon fibers are used for stitching in the direction perpendicular to the lamination, with a stitch spacing of 1–2.5 mm.

4. The preparation method according to claim 1, characterized in that, In step (2): The thickness of the carbon nanosheet interface layer is 300–500 nm.

5. The preparation method according to claim 1, characterized in that, In step (3): A PIP process using a carbon precursor solution as the impregnation liquid for 1 to 5 rounds of impregnation / curing / pyrolysis is described. The impregnation process involves first performing vacuum impregnation, followed by pressure impregnation. The pressure of the pressure impregnation is 2 to 3 MPa, and the time for each vacuum impregnation is 1 to 2 hours, and the time for each pressure impregnation is 1 to 2 hours. The curing temperature is 280 to 400°C, and the curing time for each curing is 2 to 4 hours. The carbon precursor in the carbon precursor solution is resin and / or asphalt; and / or The graphitization treatment temperature is 2700–3100℃, and the graphitization treatment time is 15–45 min.

6. The preparation method according to claim 1, characterized in that, In step (4): The reaction melting temperature is 1500-1700℃, and the time is 2-3 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The carbon precursor solution was prepared by adding a carbon precursor and graphene nanosheets to a solvent, followed by stirring and ultrasonic treatment.

8. The preparation method according to claim 7, characterized in that: The graphene nanosheets have a diameter of 5–10 μm and a thickness of 3–10 nm.

9. A highly dense thermally conductive composite material prepared by any one of claims 1 to 8.

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