Hard heat-conducting and wave-absorbing composite material and preparation method thereof

Abstract

The invention relates to the technical field of wave-absorbing materials, in particular to a hard heat-conducting wave-absorbing composite material and a preparation method thereof. The composite material is of a layered structure and comprises an upper surface layer coating, a transition layer, a middle functional layer and a substrate reinforcing layer, the upper surface layer coating comprises a compact copper film and a graphene thermal radiation coating, and the transition layer is formed by mixing and curing nickel-plated short carbon fibers and epoxy resin. The middle functional layer is formed by pitch-based carbon fibers and modified epoxy resin through hot press molding and is a continuous heat conduction network, and the substrate reinforcing layer is formed by curing PAN-based carbon fiber woven cloth and high-stability resin. The problem that electromagnetic clutter absorption and rapid heat dissipation in the device are difficult to take into account at the same time is solved, the hard composite material is directly applied to the electronic device packaging shell, the situation that a heat dissipation device and the like occupy the internal space of the device is avoided, an existing device internal material installation mode is not changed, and the cost is reduced. And the realization mode of thermal management and electromagnetic compatibility of the electronic device is fundamentally changed.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing materials, and more specifically, to a rigid heat-conducting microwave absorbing composite material and a preparation method thereof. Background Art

[0002] With the rapid development of electronic technology, modern electronic devices are evolving towards high integration and miniaturization. The power density of electronic components represented by semiconductor chips continues to climb, resulting in a sharp increase in the heat generated during device operation. At the same time, the electromagnetic interference (EMI) problem caused by high-frequency and high-speed circuits is becoming increasingly prominent, seriously affecting the reliability and signal integrity of electronic systems. To address this challenge, thermal interface materials such as flexible heat-conducting microwave absorbing patches and heat-conducting microwave absorbing silicone grease have emerged on the market. These products alleviate the contradiction between internal heat dissipation and electromagnetic compatibility of devices to a certain extent by combining the dual functions of heat conduction and microwave absorption.

[0003] The current mainstream flexible heat-conducting microwave absorbing materials mainly adopt the preparation route of polymer matrix (such as liquid silicone rubber, silicone gel, etc.) compounded with functional fillers: on the one hand, ceramic powders such as boron nitride and alumina are introduced to improve the heat conduction performance, and on the other hand, magnetic microwave absorbing agents such as ferrite and carbon-based materials are added to achieve electromagnetic wave absorption. However, this technical solution has inherent defects: 1 The dispersion compatibility of heat conduction fillers and microwave absorbing agents in the matrix is poor, and component segregation is likely to occur; 2 There is a threshold effect in the addition ratio of functional fillers. When the heat conduction performance is improved, the microwave absorption performance often decreases, and it is difficult to optimize them synergistically; 3 Limited by the mechanical strength of the flexible matrix, the material is prone to creep and aging during long-term use, and the interfacial thermal resistance increases significantly. More importantly, the existing technology has never been able to break through the process framework of traditional thermal interface materials and still stays in the fine-tuning stage of the types and particle size distributions of fillers, lacking fundamental innovations in material systems and preparation methods.

[0004] Therefore, developing a new composite material that can simultaneously achieve high heat conduction, broadband microwave absorption, and excellent mechanical properties has become the key breakthrough point for solving the problem of thermal-electromagnetic co-management of high-power electronic devices. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, an object of one aspect of the present invention is to provide a rigid heat-conducting microwave absorbing composite material. The composite material is a layered structure, including an upper surface layer coating, a transition layer, an intermediate functional layer, and a substrate reinforcing layer. The upper surface layer coating is a dense copper film and a graphene thermal radiation coating. The transition layer is formed by mixing and curing nickel-plated short carbon fibers and epoxy resin. The intermediate functional layer is formed by hot pressing asphalt-based carbon fibers and modified epoxy resin into a continuous heat conduction network. The substrate reinforcing layer is formed by curing PAN-based carbon fiber woven fabric and a high-stability resin.

[0006] Preferably, the thickness of the upper surface layer coating is 50 - 200 μm, the thickness of the transition layer is 0.20 - 0.50 mm, the thickness of the intermediate functional layer is 1 - 2 mm, and the thickness of the substrate reinforcing layer is 1 - 2 mm.

[0007] Another object of this invention is to provide a preparation method of a hard thermal conductive and wave - absorbing composite material. The specific steps of the preparation method are as follows: S1. Preparation of the substrate reinforcing layer: Select a 3K PAN - based carbon fiber plain weave fabric that has been cleaned with distilled water and anhydrous ethanol. Uniformly spray a silane coupling agent on the surface of the PAN - based carbon fiber woven fabric, and dry it at room temperature to improve the resin wettability. Premix bisphenol A - type epoxy resin and a curing agent, and prepare it by resin impregnation using the hot - melt method. S2. Preparation of the intermediate functional layer: Use a pneumatic filament winding machine to achieve 0° / 90° orthogonal laying of pitch - based carbon fiber filaments, and let it stand for impregnation. Predisperse E - 44 epoxy resin, maleic anhydride, and silicon carbide powder in a stirring device to ensure that the silicon carbide is evenly distributed. Then, carry out impregnation and curing molding to form a continuous three - dimensional thermal conductive network. S3. Preparation of the transition layer: Short - cut nickel - plated carbon fibers are surface - modified in an aqueous solution of KH - 550, and then dried in an oven to remove the solvent. Premix epoxy resin (AG - 80) and the treated nickel - plated carbon fibers, mix them with a three - axis planetary mixer, carry out vacuum degassing, and scrape - coat it on the surface of the intermediate layer. S4. Overall hot - pressing and compounding: Clean the surfaces of the substrate reinforcing layer prepared in S1, the intermediate functional layer prepared in S2, and the transition layer prepared in S3. Remove surface impurities by solvent cleaning, and then carry out room - temperature drying treatment. Stack them in the order of substrate reinforcing layer - intermediate functional layer - transition layer, and then carry out hot - pressing and compounding to obtain an intermediate product. S5. Deposition of the upper surface layer coating: Deposit the upper surface layer coating on one side of the transition layer of the intermediate product prepared in S4. First, deposit a copper film; then spray a graphene thermal radiation coating to obtain a hard thermal conductive and wave - absorbing composite material.

[0008] Preferably, in S1, the moisture content of the PAN - based carbon fiber plain weave fabric is 0.05 - 0.2%, the areal density is 100 - 200 g / m², the silane coupling agent is KH550 or KH570, the spraying amount is 5 - 7 g / m², the room - temperature drying time is 1 - 2 h, the bisphenol A - type epoxy resin is E - 51 or E - 44, the curing agent is dicyandiamide, and the mass ratio of bisphenol A - type epoxy resin to the curing agent is 11:1; the thickness of the resin film for resin impregnation by the hot - melt method is 0.01 - 0.03 mm, the impregnation temperature is 60 - 80 °C, the resin content is 35 ± 3%, the rolling pressure is 0.2 - 0.5 MPa, and the lamination curing procedure is 120 °C / 2 h + 150 °C / 3 h.

[0009] Preferably, in S2, the mass ratio of E-44 epoxy resin, maleic anhydride and silicon carbide powder is 10:1-2:2-3, and the D50 of the silicon carbide powder is 2.5 μm.

[0010] Preferably, in S2, the volume content of carbon fiber filaments is 65-70%. Among them, for the hot pressing and curing process parameters, the heating temperature is 150-160 °C, the pressure is 8-10 MPa, the heating time is 30-45 min, and it is demolded after being kept under pressure and cooled to 80 °C.

[0011] Preferably, in S3, it is surface-modified in a 3-5 wt% KH-550 aqueous solution, dried in an oven at 40-60 °C for 2-4 h to remove the solvent, and the epoxy resin (AG-80) and the treated nickel-plated carbon fiber are premixed according to a mass ratio of 1:1-1:3.

[0012] Preferably, in S3, the mixing speed of the three-axis planetary mixer is 200 rpm / 30-60 min, the thickness is precisely controlled to be 0.2-0.5 mm through the scraper gap, and the step curing procedure is 60-80 °C / 1 h → 100-120 °C / 2 h → 140-160 °C / 1 h.

[0013] Preferably, in S4, the solvent is ethanol and distilled water, dried at room temperature for 3-5 h, the thermal compounding temperature is 180-190 °C, the pressure is 10-12 MPa, the time is 60-90 min, and the pressure-holding and cooling rate is 1-2 °C / min until it cools down to room temperature.

[0014] Preferably, in S5, the copper film deposition rate is 3-5 μm / min and the thickness is 10-50 μm; the wet film thickness of the graphene thermal radiation coating is 40-150 μm, the temperature is 60-80 °C, and the hot air drying and curing time is 10-30 min to form a continuous radiation layer.

[0015] The beneficial effects of the present invention are as follows: The present invention breaks through the technical limitations of traditional heat-conducting and wave-absorbing materials, abandons the improvement ideas of traditional flexible heat-conducting / wave-absorbing materials through material system innovation and process innovation, endows the wave-absorbing materials with good heat-conducting performance, changes the use mode of heat-conducting and wave-absorbing materials, fundamentally solves the problem that it is difficult to simultaneously take into account the absorption of internal electromagnetic clutter and rapid heat dissipation of devices, directly applies the hard composite material to the electronic device packaging shell, avoids occupying the internal space of the device by using heat dissipation devices, etc., and maintains the existing material installation method inside the device without changing the existing production process. Through the integration of the shell structure, heat management and electromagnetic compatibility are realized, and the realization modes of heat management and electromagnetic compatibility of electronic devices are fundamentally changed.

[0016] Through the design of a multi-layer composite structure of "substrate enhancement layer - intermediate functional layer - transition layer - upper surface layer", for the first time, hard materials are enabled to simultaneously possess high thermal conductivity and broadband microwave absorption characteristics, solving the problem of mutual restriction between thermal conductivity and microwave absorption performance in traditional hard packaging materials. By organically combining processes such as dipping and hot pressing, forming of functional layers, and coating and curing, a stepped composite process is developed. While maintaining the compatibility of traditional process equipment, a significant improvement in material density and interfacial bonding strength is achieved.

[0017] A three-dimensional thermal conduction network is constructed by axially arranging pitch carbon fibers and transversely reinforcing silicon carbide powder. The thermal resistance is reduced more compared with traditional materials. The in-plane thermal conductivity ≥ 50 W / m·K, meeting the heat dissipation requirements of high-power chips. The density ≤ 2.2 g / cm³, and the tensile strength ≥ 100 MPa, which can replace the traditional metal heat dissipation structure; adopting the structure of "high-reflection copper foil - impedance-gradient transition layer - low-impedance intermediate layer" and combining the multiple scattering mechanism of pitch carbon fibers, the electromagnetic wave absorption bandwidth reaches 2 - 18 GHz, with a high electromagnetic wave attenuation coefficient.

[0018] Adopting conventional composite material forming technology, it is suitable for large-scale production, can directly replace the metal shells of existing electronic devices without changing the internal structure design, and has excellent environmental adaptability. It provides a revolutionary thermal-electromagnetic synergy solution for high-end fields such as 5G base stations and aerospace electronics, filling the technical gap of hard multi-functional composite materials and having great industrial value.

[0019] The additional aspects and advantages of the present invention will become obvious in the following description or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein: Figure 1 is a schematic structural diagram of an embodiment of the present invention; Figure 2 is the electromagnetic wave attenuation coefficient curve of a sample in Embodiment 1 of the present invention; Figure 3 is the electromagnetic wave attenuation coefficient curve of a sample in Embodiment 2 of the present invention; Figure 4 is the electromagnetic wave attenuation coefficient curve of a sample in Embodiment 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0022] In the following description, many specific details are set forth to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0023] Example 1: Preparation of the base enhancement layer: Select a 3K PAN-based carbon fiber plain weave fabric (with a moisture content of 0.1% and a surface density of 120 g / m²) that has been cleaned with distilled water and anhydrous ethanol. Uniformly spray KH-550 silane coupling agent on the surface of the PAN-based carbon fiber woven fabric (spraying amount: 5 g / m²), and dry it at room temperature for 2 h to improve the resin wettability. Select E-51 epoxy resin and dicyandiamide curing agent (mass ratio 11:1) for premixing, and prepare it by resin impregnation using the hot melt method. The main process parameters are as follows: resin film thickness 0.02 mm, impregnation temperature 70 °C, resin content 35%. Roller pressing pressure 0.3 MPa, lamination curing program: 120 °C / 2 h + 150 °C / 3 h.

[0024] Preparation of the intermediate functional layer: Use a pneumatic filament winding machine to achieve 0° / 90° orthogonal laying of pitch-based carbon fiber filaments, and wait for impregnation. Pre-disperse E-44 epoxy resin, maleic anhydride (mass ratio of resin to maleic anhydride 10:1.5), and silicon carbide powder (mass ratio of resin to silicon carbide powder 10:2.5, D50 = 2.5 μm) in a stirring device to ensure uniform distribution of silicon carbide. Then, carry out impregnation and curing molding. The volume content of carbon fiber filaments is 68%. The hot pressing and curing process parameters are set as follows: temperature 155 °C, pressure 9 MPa, time 40 min, keep pressure and cool to 80 °C for demolding to complete the preparation of the intermediate functional layer and form a continuous three-dimensional heat conduction network.

[0025] Preparation of the transition layer: Surface-modify the short-cut nickel-plated carbon fibers in a 4 wt% KH-550 aqueous solution, and dry them in an oven at 50 °C for 3 h to remove the solvent. Premix epoxy resin (AG-80) and the treated nickel-plated carbon fibers at a mass ratio of 1:2, mix them with a three-axis planetary mixer (rotation speed 200 rpm / 45 min), perform vacuum degassing, and scrape-coat it on the surface of the intermediate layer. Accurately control the thickness to 0.30 mm through the gap of the scraper. The stepwise curing program is: 70 °C / 1 h → 110 °C / 2 h → 150 °C / 1 h.

[0026] Overall hot pressing and compounding: The prepared base reinforcement layer, intermediate functional layer, and transition layer are subjected to surface cleaning treatment. The surface impurities are removed by washing with solvents (ethanol, distilled water), and then they are dried at room temperature for 4 h. The base reinforcement layer - intermediate functional layer - transition layer are stacked from bottom to top in sequence, and then hot pressing and compounding are carried out. The compounding parameters are as follows: temperature 185 °C, pressure 11 MPa, time 75 min, pressure holding and cooling rate 1.5 °C / min until the temperature drops to room temperature to obtain an intermediate product; Upper surface coating deposition: Upper surface coating deposition is carried out on one side of the transition layer of the prepared intermediate product. First, a copper film is deposited, and the deposition rate is controlled at 4 μm / min. The thickness of the copper film coating is controlled at 30 μm to reach the expected set thickness. Then, graphene thermal radiation coating is sprayed. A coating machine or a doctor blade that meets the accuracy requirements is used to carry out the graphene thermal radiation coating process on the intermediate material after the copper film is deposited. The wet film thickness is 80 μm, and it is dried and cured at 70 °C for 20 min with hot air to form a continuous radiation layer, and a hard thermal conductive and wave-absorbing composite material is prepared.

[0027] The accurate thicknesses of each component of the sample prepared in Example 1 are shown in the table. It can be used for the encapsulation cover plate of high-power electronic devices, with an in-plane thermal conductivity of 70 W / (m·K), a normal perpendicular thermal conductivity of 20 W / m·K, and the copper film adhesion (cross-cut method) ≥ 4B level.

[0028] As Figure 2 shown in Table 1, the product has excellent electromagnetic wave attenuation performance.

[0029] Table 1. Set thicknesses of each layer of the material prepared in Example 1 Example 2: Preparation of the base reinforcement layer: Select 3K PAN-based carbon fiber plain weave fabric (moisture content 0.05%, areal density 200 g / m²) that has been cleaned with distilled water and anhydrous ethanol. The surface of the PAN-based carbon fiber woven fabric is evenly sprayed with KH-570 silane coupling agent (spraying amount 6 g / m²) and dried at room temperature for 1 h to improve the resin wettability. Premix E-51 epoxy resin and dicyandiamide curing agent (mass ratio 11:1), and prepare it by resin impregnation using the hot melt method. The main process parameters are as follows: resin film thickness 0.03 mm, dipping temperature 80 °C, resin content 38%. The roll pressing pressure is 0.5 MPa, and the laminating and curing procedure is: 120 °C / 2 h + 150 °C / 3 h.

[0030] Preparation of the intermediate functional layer: The pneumatic filament winding machine is used to achieve the orthogonal laying of asphalt-based carbon fiber filaments at 0° / 90°, and then it is placed and waiting for impregnation. E-44 epoxy resin, maleic anhydride (the mass ratio of resin to maleic anhydride is 10:2), and silicon carbide powder (the mass ratio of resin to silicon carbide powder is 10:3, D50 = 2.5μm) are pre-dispersed in the stirring equipment to ensure the uniform distribution of silicon carbide, and then impregnation and curing molding are carried out. The volume content of carbon fiber filaments is 70%. The hot pressing and curing process parameters are set as follows: temperature 160°C, pressure 10 MPa, time 45 min, and keep the pressure until it cools to 80°C and then demold to complete the preparation of the intermediate functional layer, forming a continuous three-dimensional heat conduction network.

[0031] Preparation of the transition layer: The short-cut nickel-plated carbon fibers are surface-modified in 5wt% KH-550 aqueous solution, and then dried in an oven at 60°C for 2 h to remove the solvent. Epoxy resin (AG-80) and the treated nickel-plated carbon fibers are pre-mixed at a mass ratio of 1:3, and then mixed by a three-axis planetary mixer (rotation speed 200 rpm / 60 min), followed by vacuum degassing. Then it is scrape-coated on the surface of the intermediate layer, and the thickness is accurately controlled at 0.20 mm through the gap of the scraper. The step curing procedure is: 80°C / 1 h → 120°C / 2 h → 160°C / 1 h.

[0032] Overall hot pressing and composite: The prepared base reinforcement layer, intermediate functional layer, and transition layer are subjected to surface cleaning treatment. The surface impurities are removed by washing with solvents (ethanol, distilled water), and then dried at room temperature for 3 h. Stack the base reinforcement layer - intermediate functional layer - transition layer in order from bottom to top, and then carry out hot pressing and composite. The composite parameters are: temperature 190°C, pressure 12 MPa, time 90 min, and the pressure-holding cooling rate is 1.0°C / min until it cools down to room temperature to obtain an intermediate product; Deposition of the upper surface coating: The upper surface coating is deposited on one side of the transition layer of the prepared intermediate product. First, deposit a copper film with a deposition rate controlled at 5μm / min and the copper film coating thickness controlled at 50μm to reach the expected set thickness; then spray the graphene thermal radiation coating. Use a coating machine or a scraping machine that meets the accuracy requirements to carry out the graphene thermal radiation coating process on the intermediate material after depositing the copper film. The wet film thickness is 150μm, and it is dried and cured at 80°C with hot air for 30 min to form a continuous radiation layer, thus obtaining the hard thermal conductive and wave-absorbing composite material.

[0033] The accurate thicknesses of each component of the sample prepared in Example 2 are shown in the table. It can be used for the encapsulation cover plate of high-power electronic devices, with an in-plane thermal conductivity of 80 W / (m·K), a normal perpendicular thermal conductivity of 25 W / m·K, and the copper film adhesion (cross-cut method) ≥ 4B level.

[0034] As Figure 3 shown in Table 2, the product has excellent electromagnetic wave attenuation performance.

[0035] Table 2. Set thickness of each layer of the material prepared in Example 2 Example 3: Preparation of the base enhancement layer: Select a 3K PAN-based carbon fiber plain weave fabric (water content 0.2%, surface density 100 g / m²) that has been cleaned with distilled water and anhydrous ethanol. Uniformly spray KH-570 silane coupling agent on the surface of the PAN-based carbon fiber woven fabric (spraying amount 7 g / m²), and dry it at room temperature for 1.5 h to improve resin wettability. Select E-51 epoxy resin and dicyandiamide curing agent (mass ratio 11:1) for premixing, and prepare it by hot melt resin impregnation. The main process parameters are: resin film thickness 0.01 mm, dipping temperature 60 °C, resin content 32%. The rolling pressure is 0.2 MPa, and the lamination curing procedure is: 120 °C / 2 h + 150 °C / 3 h.

[0036] Preparation of the intermediate functional layer: Use a pneumatic filament winding machine to achieve 0° / 90° orthogonal laying of pitch-based carbon fiber filaments, and place them waiting for impregnation. Pre-disperse E-44 epoxy resin, maleic anhydride (mass ratio of resin to maleic anhydride 10:1), and silicon carbide powder (mass ratio of resin to silicon carbide powder 10:2, D50 = 2.5 μm) in a stirring device to ensure uniform distribution of silicon carbide. Then carry out impregnation and curing molding. The volume content of carbon fiber filaments is 65%. The hot pressing and curing process parameters are set as: temperature 150 °C, pressure 8 MPa, time 30 min, keep pressure and cool to 80 °C for demolding to complete the preparation of the intermediate functional layer and form a continuous three-dimensional heat conduction network.

[0037] Preparation of the transition layer: Short-cut nickel-plated carbon fibers are surface-modified in an aqueous solution of 3 wt% KH-550, and dried in an oven at 40 °C for 4 h to remove the solvent. Epoxy resin (AG-80) and the treated nickel-plated carbon fibers are pre-mixed at a mass ratio of 1:1, and mixed with a three-axis planetary mixer (rotation speed 200 rpm / 30 min), then vacuum degassed, and scrape-coated on the surface of the intermediate layer. The thickness is precisely controlled to 0.50 mm through the gap of the scraper. The step curing procedure is: 60 °C / 1 h → 100 °C / 2 h → 140 °C / 1 h.

[0038] Overall hot pressing and compounding: Clean the surfaces of the prepared base enhancement layer, intermediate functional layer, and transition layer, remove surface impurities by washing with solvents (ethanol, distilled water), and then perform a 5 h room temperature drying treatment. Stack the base enhancement layer - intermediate functional layer - transition layer in order from bottom to top, and then carry out hot pressing and compounding. The compounding parameters are: temperature 180 °C, pressure 10 MPa, time 60 min, and the pressure-holding and cooling rate is 2.0 °C / min until it cools down to room temperature to obtain an intermediate product; Upper surface coating deposition: The upper surface coating is deposited on one side of the prepared intermediate product transition layer. First, a copper film is deposited with a deposition rate controlled at 3 μm / min and the thickness of the copper film coating is controlled at 10 μm to reach the expected set thickness. Then, a graphene thermal radiation coating is sprayed. Using a film coating machine or a scraping machine that meets the accuracy requirements, the graphene thermal radiation coating is applied to the intermediate material after the copper film is deposited. The wet film thickness is 40 μm, and it is dried and cured at 60 °C with hot air for 10 min to form a continuous radiation layer, thus obtaining a hard thermal conductive and wave-absorbing composite material.

[0039] The accurate thicknesses of each component of the sample prepared in Example 3 are shown in the table. It can be used for the encapsulation cover plate of high-power electronic devices, with an in-plane thermal conductivity of 50 W / (m·K), a normal perpendicular thermal conductivity of 12 W / m·K, and the adhesion of the copper film (cross-cut method) ≥ 4B level.

[0040] As Figure 4 shown in Table 3, the product has excellent electromagnetic wave attenuation performance.

[0041] Table 3. Set thicknesses of each layer of the material prepared in Example 3 The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hard thermal conductive and wave-absorbing composite material, characterized in that: The composite material is a layered structure, including an upper surface coating, a transition layer, an intermediate functional layer, and a substrate reinforcement layer. The upper surface coating is a dense copper film and a graphene thermal radiation coating. The transition layer is formed by mixing and curing nickel-plated short carbon fibers and epoxy resin. The intermediate functional layer is formed by hot pressing asphalt-based carbon fibers and modified epoxy resin into a continuous heat conduction network. The substrate reinforcement layer is formed by curing PAN-based carbon fiber woven fabric and a high-stability resin.

2. The hard thermal conductive and wave absorbing composite material according to claim 1, characterized in that: The thickness of the upper surface coating is 50 - 200 μm, the thickness of the transition layer is 0.20 - 0.50 mm, the thickness of the intermediate functional layer is 1 - 2 mm, and the thickness of the substrate reinforcement layer is 1 - 2 mm.

3. A preparation method of a hard thermal conductive and wave-absorbing composite material, characterized in that: The specific steps of the preparation method are as follows: S1. Preparation of the substrate reinforcement layer: Select 3K PAN-based carbon fiber plain weave fabric that has been cleaned with distilled water and anhydrous ethanol. Uniformly spray a silane coupling agent on the surface of the PAN-based carbon fiber woven fabric and dry it at room temperature. Premix bisphenol A-type epoxy resin and a curing agent, and prepare it by resin impregnation using the hot melt method. S2. Preparation of the intermediate functional layer: Use a pneumatic filament winding machine to achieve 0° / 90° orthogonal laying of asphalt-based carbon fiber filaments, place them for impregnation, pre-disperse E-44 epoxy resin, maleic anhydride, and silicon carbide powder in a stirring device to ensure uniform distribution of silicon carbide, and then perform impregnation and curing molding to form a continuous three-dimensional heat conduction network. S3. Preparation of the transition layer: Surface-modify the short nickel-plated carbon fibers in an aqueous solution of KH-550, and dry them in an oven to remove the solvent. Premix epoxy resin and the treated nickel-plated carbon fibers, mix them with a three-axis planetary mixer, perform vacuum degassing, and scrape and coat them on the surface of the intermediate layer. S4. Overall hot pressing and compounding: Perform surface cleaning treatment on the substrate reinforcement layer prepared in S1, the intermediate functional layer prepared in S2, and the transition layer prepared in S3. Remove surface impurities by solvent cleaning, and then perform room temperature drying treatment. Stack the substrate reinforcement layer - intermediate functional layer - transition layer in order from bottom to top, and then perform hot pressing and compounding to obtain an intermediate product. S5. Deposition of the upper surface coating: Deposit the upper surface coating on one side of the transition layer of the intermediate product prepared in S4. First deposit a copper film; then spray a graphene thermal radiation coating to obtain a hard heat conduction and wave absorption composite material.

4. The preparation method of a hard thermal conductive and wave-absorbing composite material according to claim 3, wherein: In S1, the moisture content of the PAN-based carbon fiber plain weave fabric is 0.05 - 0.2%, the areal density is 100 - 200 g / m², the silane coupling agent is KH550 or KH570, the spraying amount is 5 - 7 g / m², dry at room temperature for 1 - 2 h, the bisphenol A-type epoxy resin is E-51 or E-44, the curing agent is dicyandiamide, and the mass ratio of bisphenol A-type epoxy resin to the curing agent is 11:1; the thickness of the resin film for resin impregnation by the hot melt method is 0.0I - 0.03 mm, the impregnation temperature is 60 - 80 °C, the resin content is 35 ± 3%, the rolling pressure is 0.2 - 0.5 MPa, and the lamination and curing procedure is 120 °C / 2 h + 150 °C / 3 h.

5. The preparation method of a hard thermal conductive and wave - absorbing composite material according to claim 3, characterized in that: In S2, the mass ratio of E-44 epoxy resin, maleic anhydride, and silicon carbide powder is 10:1 - 2:2 - 3, and the D50 of the silicon carbide powder is 2.5 μm.

6. The preparation method of a hard thermal conductive and wave-absorbing composite material according to claim 3, wherein: In S2, the volume content of carbon fiber filaments is 65 - 70%. Among them, for the hot pressing and curing process parameters, the heating temperature is 150 - 160 °C, the pressure is 8 - 10 MPa, the heating time is 30 - 45 min, and it is demolded after holding pressure and cooling to 80 °C.

7. The preparation method of a hard thermal conductive and wave-absorbing composite material according to claim 3, characterized in that: In S3, it is surface - modified in a 3 - 5 wt% KH - 550 aqueous solution, dried in an oven at 40 - 60 °C for 2 - 4 h to remove the solvent, and epoxy resin (AG - 80) and the treated nickel - plated carbon fiber are premixed at a mass ratio of 1:1 - 1:

3.

8. The preparation method of a hard thermal conductive and wave - absorbing composite material according to claim 3, characterized in that: In S3, the mixing speed of the three - axis planetary mixer is 200 rpm for 30 - 60 min, the thickness is precisely controlled to be 0.2 - 0.5 mm through the scraper gap, and the step - curing procedure is 60 - 80 °C / 1 h → 100 - 120 °C / 2 h → 140 - 160 °C / 1 h.

9. The preparation method of a hard thermal conductive and wave - absorbing composite material according to claim 3, characterized in that: In S4, the solvent is ethanol and distilled water, dried at room temperature for 3 - 5 h, the thermal - compounding temperature is 180 - 190 °C, the pressure is 10 - 12 MPa, the time is 60 - 90 min, and the pressure - holding and cooling rate is 1 - 2 °C / min until it cools down to room temperature.

10. The preparation method of a hard thermal conductive and wave-absorbing composite material according to claim 3, characterized in that: In S5, the copper - film deposition rate is 3 - 5 μm / min and the thickness is 10 - 50 μm; the wet - film thickness of the graphene thermal - radiation coating spray is 40 - 150 μm, the temperature is 60 - 80 °C, and the hot - air drying and curing time is 10 - 30 min to form a continuous radiation layer.

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