A lightweight heat dissipating composite

Abstract

This invention discloses a lightweight heat dissipation composite material, characterized in that the lightweight heat dissipation composite material includes an outer shell layer, a weight reduction layer, and a bonding layer that bonds the outer shell layer and the weight reduction layer; wherein, the outer shell layer is a metal layer, and the weight reduction layer is a thermally conductive material; this invention adopts a structure combining thermally conductive material and metal, which has good thermal conductivity and can ensure that the heat source maintains a low temperature. At the same time, since the density of the composite material is lower than that of the metal material, it can effectively reduce the weight of metal devices or metal shells.

Description

Technical Field

[0001] This invention relates to a lightweight heat-dissipating composite material. Background Technology

[0002] Traditional chassis or motor housings are typically solid structures, which are too heavy. Weight reduction can be achieved by drilling holes or making them hollow, but this sacrifices heat dissipation. Patent CN201521032017.1 uses cast aluminum instead of steel to reduce weight and utilizes aluminum's thermal conductivity for heat dissipation, but aluminum's thermal conductivity is limited.

[0003] Therefore, it is necessary to develop new lightweight heat dissipation materials to achieve good heat dissipation while reducing weight. Summary of the Invention

[0004] The purpose of this invention is to provide a lightweight heat-dissipating composite material to solve the problem that it is difficult to achieve both weight reduction and heat dissipation in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A lightweight heat dissipation composite material includes an outer shell layer with a cavity, a weight-reducing layer disposed within the cavity of the outer shell layer, and a bonding layer connecting the outer shell layer and the weight-reducing layer; wherein the outer shell layer is a metal layer, and the weight-reducing layer is a thermally conductive material.

[0007] In the lightweight heat dissipation composite material of the present invention, the outer shell layer is on the outside and is made of metal, and its main function is to provide support; the bonding layer is in the middle and its function is to connect the weight reduction layer and the outer shell layer and reduce the interfacial thermal resistance; the weight reduction layer is on the inside and is made of thermally conductive material, and its main function is to reduce the overall density and increase the thermal conductivity.

[0008] In one embodiment of the lightweight heat-dissipating composite material according to the present invention, the thermally conductive material is a thermally conductive foam material and / or a thermally conductive carbon block; wherein the thermally conductive foam material is thermally conductive carbon foam or copper foam; in one embodiment, preferably, the thermally conductive carbon foam has a density of 0.1-1.2 g / cm³. 3 Thermal conductivity greater than 50 W / mK; thermally conductive copper foam density 0.5-1.8 g / cm³ 3 Thermal conductivity greater than 5 W / mK.

[0009] In one embodiment, the thermally conductive foam material is processed to the same size as the cavity; the thermally conductive foam material can be one or both of thermally conductive carbon foam and copper foam. In one embodiment, the thermally conductive foam material accounts for 30-80% of the total volume of the lightweight heat dissipation composite material; the medium in the pores of the thermally conductive foam material can be air.

[0010] In one embodiment, the bonding layer is a welding metal, thermally conductive silicone grease, or a combination of thermally conductive silicone grease and a high thermal conductivity graphite film. For example, to obtain a more uniform temperature distribution, a high thermal conductivity graphite film can be applied to both the upper and lower surfaces of the cavity, and then thermally conductive silicone grease can be further disposed between the high thermal conductivity graphite film and the weight-reducing layer. The bonding layer, located between the weight-reducing layer and the outer shell layer, serves to tightly connect the weight-reducing layer and the outer shell layer, reducing interfacial thermal resistance. The bonding layer accounts for less than 5% of the total volume of the lightweight heat dissipation composite material. Preferably, the thermal conductivity of the thermally conductive silicone grease is ≥5 W / mK. Preferably, the thickness of the high thermal conductivity graphite film is 12-20 μm, and the horizontal thermal conductivity is greater than 1200 W / mK. In this invention, when the weight-reducing layer is metal, the bonding layer can be manufactured by welding.

[0011] In one embodiment of the lightweight heat-dissipating composite material according to the present invention, the thermally conductive carbon block occupies 10%-80% of the total volume of the outer shell layer; when the carbon block does not fill the cavity of the metal outer shell layer, the remainder is air.

[0012] In one embodiment, the thermally conductive carbon block has a density of 1.6-2.2 g / cm³. 3 The carbon content is greater than 90%, with a horizontal thermal conductivity of 300-600 W / mK and a vertical thermal conductivity of 10-80 W / mK. To effectively transfer heat, the horizontal thermal conductivity corresponds to the vertical direction of the thermally conductive carbon block array, i.e., aligning with the heat transfer direction of the carbon blocks (i.e., the direction of greatest temperature difference). It can be processed into independent cylinders, independent square columns, or grids. When the thermally conductive carbon blocks do not completely fill the cavity, the structure is not limited to these. In this invention, the thermally conductive carbon blocks can also completely fill the cavity.

[0013] In one embodiment of the lightweight heat-dissipating composite material according to the present invention, the weight-reducing layer is a combination of a thermally conductive carbon block and a thermally conductive foam material. The thermally conductive foam material has a low density, effectively reducing weight, while the thermally conductive carbon block has high thermal conductivity, enhancing thermal conductivity. Combining the two achieves two benefits simultaneously: weight reduction and pre-heat conduction. In one embodiment, the thermally conductive carbon block is partially filled within the thermally conductive foam material, and in this composite structure, the thermally conductive foam material accounts for 30%-70% of the volume of the thermally conductive framework. In this composite structure, the interface between the foam material and the thermally conductive carbon block can be carbon or metal. The weight-reducing layer in this composite structure accounts for 30%-80% of the total volume of the lightweight heat-dissipating composite material.

[0014] In one embodiment of the lightweight heat-dissipating composite material according to the present invention, thermally conductive carbon blocks are arranged in an array within a cavity, and thermally conductive foamed carbon and / or foamed copper are processed into a structure complementary to the array of thermally conductive carbon blocks to fill the cavity.

[0015] In this invention, the cavity can be sealed by welding, flanges, or other methods. The outer shell metal can be copper, aluminum, stainless steel, or an alloy, and it is a shell with a certain cavity. In one embodiment, the outer shell layer accounts for 20-70% of the total volume of the lightweight heat-dissipating composite material, that is, the metal volume of the outer shell layer accounts for 20-70% of the total volume of the outer shell layer.

[0016] In one embodiment of the lightweight heat-dissipating composite material according to the present invention, the thermally conductive material or thermally conductive foam material is thermally conductive carbon foam, and the preparation method of the thermally conductive carbon foam includes the following steps:

[0017] (1) Mix porous graphite with thermally conductive reinforcing material evenly, press and shape to obtain preform material;

[0018] (2) Dissolve the asphalt components in a solvent;

[0019] (3) Immerse the preform obtained in step (1) into the solution obtained in step (2) so that the asphalt component enters the preform and dry the solvent to obtain the impregnated material;

[0020] (4) The impregnated material obtained in step (3) is treated at 450-900℃ for more than 30 minutes under normal pressure and in a protective atmosphere to obtain the molding material;

[0021] (5) The molding material obtained in step (4) is subjected to high temperature treatment at a temperature above 1000°C under normal pressure and in a protective atmosphere to obtain foamed carbon material.

[0022] The impregnating material comprises 50%-70% porous graphite, 30%-50% asphalt component, and 0-20% thermally conductive reinforcing material; the asphalt component is mesophase asphalt.

[0023] In step (1), porous graphite is mixed uniformly with an optional thermally conductive reinforcing material. In one embodiment, the porous graphite and the optional thermally conductive reinforcing material are dry-mixed to achieve uniform mixing, for example, at room temperature. It should be understood that when the amount of thermally conductive reinforcing material is zero, mixing is not required, and subsequent molding processes are performed directly.

[0024] In step (1), the mixed raw materials are pressed and molded to obtain a preform, which serves as the basis for subsequent processing in this invention. In one embodiment, the density of the preform can be 0.3-0.6 g / cm³. 3For example, 0.35, 0.4, 0.45, 0.5, or 0.55 can help reduce the adverse foaming effects of subsequent steps, thereby facilitating the formation of hierarchical pores. In this invention, the molding pressure can be 5-20 MPa, such as 6, 8, 10, 15, or 18 MPa. In this invention, the holding time during molding can be 1-10 minutes, such as 2, 5, or 8 minutes.

[0025] In this invention, the porous graphite can be one or more of graphene, expanded graphite, high thermal conductivity carbon felt, foamed graphite, and carbon nanotubes; in one embodiment, the bulk density of the porous graphite is not less than 100, such as 100, 200, 220, 250, 300, 330, 350, or 450; in another embodiment, the porous graphite is preferably one or more of graphene, expanded graphite, and carbon nanotubes, and the bulk density is preferably 200-400, which is beneficial for the mixing and dispersion of mesophase pitch and the generation of hierarchical pores.

[0026] In this invention, when the porous graphite in step (1) is a combination of multiple components, its bulkiness refers to the average bulkiness of the porous graphite composition, which is equal to the sum of the products of the weight parts of each component and the bulkiness divided by the sum of the weight parts of each component. For example, when the porous graphite is composed of expanded graphite and carbon nanotubes, its bulkiness is equal to (Z1*P1+Z2P2) / (Z1+Z2); where Z1 is the weight part of expanded graphite, Z2 is the weight part of carbon nanotubes, P1 is the bulkiness of expanded graphite, and P2 is the bulkiness of carbon nanotubes.

[0027] In step (2), the asphalt component is dissolved in a solvent; the solvent may be one or more of quinoline, heavy oil, tetrahydrofuran, solvent oil and carbon tetrachloride.

[0028] In one embodiment, the mesophase content of the mesophase pitch is not less than 80%, such as 90% or 100%; in another embodiment, the softening point of the mesophase pitch is 200-370°C, such as 210, 230, 250, 280, 300, 330 or 360°C, preferably 220-350°C; in this invention, the mass ratio of the mesophase pitch to the solvent in the solution obtained by dissolution can be 1:8-1:1, such as 1:5 or 1:2.

[0029] In step (3), the preform obtained in step (1) is immersed in the solution obtained in step (2) so that the asphalt component enters the preform and the solvent is dried. Those skilled in the art will understand that this process can be repeated once or multiple times until the content of asphalt component in the dried impregnated material reaches the target requirement.

[0030] In one embodiment, the impregnating material comprises 50-60% porous graphite by mass, such as 52%, 55%, or 58%; 30-45% bitumen component by mass, such as 32%, 35%, 40%, or 43%; and 5-20% thermally conductive reinforcing material by mass, such as 8%, 10%, 15%, or 18%. The thermally conductive reinforcing material, used to enhance the thermal conductivity of the thermally conductive carbon foam, is well-known in the art and can be one or more of natural graphite, high thermal conductivity carbon fiber, and boron nitride, wherein high thermal conductivity carbon fiber refers to carbon fiber with a thermal conductivity ≥2000 W / mK. It should be understood that in this invention, when the mass percentage of a component is 0, it means that the component is not present.

[0031] In step (4), the impregnated material obtained in step (3) is treated at 450-900°C for at least 30 minutes under normal pressure and a protective atmosphere to facilitate molding and greatly reduce foaming, thereby obtaining a molded material. In one embodiment, the treatment temperature is 500-800°C, such as 500, 520, 550, 600, 700, 750 or 780°C, and the treatment time can be 0.5-6 hours, such as 1, 2, 3 or 5 hours. Excessive time is not conducive to improving efficiency.

[0032] In step (5), the molding material obtained in step (4) is subjected to high-temperature treatment at a temperature above 1000°C under normal pressure and a protective atmosphere to obtain foamed carbon material. In one embodiment, the high-temperature treatment temperature is 1000-3200°C, such as 1200, 1500, 1600, 2000, 2500, 2800 or 3000°C. Different treatment temperatures can yield foamed carbon materials with different thermal diffusivity, so the corresponding treatment temperature can be selected according to the target thermal diffusivity. For example, to obtain a better thermal diffusivity, the high-temperature treatment temperature can be increased, such as to 2800°C or even 3000°C or 3200°C, to facilitate full graphitization. Alternatively, the foamed carbon material obtained by high-temperature treatment of the present invention (such as below 2000°C, 2500°C or even below 2800°C) can be further treated at a temperature above 2800°C, such as 3000°C or 3200°C, to facilitate full graphitization in order to improve the thermal diffusivity.

[0033] In the above preparation method, the protective atmosphere can be a nitrogen atmosphere or an inert gas atmosphere.

[0034] In this invention, the thermally conductive foam carbon prepared according to the above preparation method has a multi-level pore size distribution. Specifically, the pore size distribution in the range of 0.01-50 μm (excluding 50 μm) is not less than 20%, preferably 25-50%, such as 30%, 35%, 40%, or 45%; the pore size distribution in the range of 50-250 μm is not less than 30%, preferably 35-55%, such as 40%, 45%, 47%, 50%, or 52%; and the pore size distribution in the range of 250-1000 μm (excluding 250 μm) is not less than 10%, preferably 10-30%, such as 13%, 15%, 20%, 25%, or 28%. In one embodiment, the density of the thermally conductive foam carbon is 0.2-0.6 g / cm³, for example 0.25-0.5 g / cm³. 3 For example, 0.25, 0.3, 0.4, 0.45, 0.48, 0.5, 0.55, or 0.58 g / cm³. 3 In one embodiment, the thermally conductive foam carbon is composed of graphite and amorphous carbon components, wherein the graphite content can be 40%-100%, such as 60%, 80%, 90%, or 95%, and the amorphous carbon content can be 0-60%. In another embodiment, the graphite content of the thermally conductive foam carbon is 90% or even 95% or higher, so as to have a relatively higher thermal diffusivity at its low density level.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] (1) The lightweight heat dissipation composite material or structure of the present invention can reduce weight by 30%-80% compared with solid metal materials, and transfer heat faster. The heat dissipation structure of the same size has a temperature difference of 5-15℃ compared with solid metal materials.

[0037] (2) Unlike existing technologies, the novel foamed carbon proposed by the foamed carbon preparation method of the present invention has a non-porous structure, which is different from the pore structure formed by traditional foaming. By preforming porous graphite and then impregnating it to disperse asphalt in the porous graphite, foaming can be effectively reduced during subsequent heating. The asphalt material and the porous graphite material are bonded together to form a low-density hierarchical pore structure with a multi-level distribution of pore size, especially with abundant distribution below 50 micrometers. At the same time, the fine thermally conductive skeleton of the foamed carbon can also make the entire composite material have high thermal conductivity. In addition, the foamed carbon preparation method of the present invention successfully produces thermally conductive foamed carbon using an atmospheric pressure preparation process. The atmospheric pressure process route is simple and has low process cost. Attached Figure Description

[0038] Figure 1A schematic diagram of one embodiment of a lightweight heat dissipation composite material: the weight reduction layer 2 is foamed carbon or foamed copper, with air filling the pores of the foamed carbon or foamed copper; the bonding layer 3 is thermally conductive silicone grease; to obtain a more uniform temperature distribution, high thermal conductivity graphite films can be applied to the upper and lower surfaces of the square cavity of the outer shell layer 1; or when it is foamed copper, the bonding layer can also be welded with metal.

[0039] Figure 2 A schematic diagram of one embodiment of the lightweight heat dissipation composite material: the weight reduction layer 2 is a thermally conductive carbon block; the carbon block structure consists of a carbon block array and a grid structure, with the remainder being air 4; the thermally conductive carbon block has directional thermal conductivity, with high thermal conductivity in the horizontal direction and low thermal conductivity in the vertical direction. By aligning the horizontal thermal conductivity with the vertical direction of the carbon block array, the optimal heat transfer effect is achieved; the bonding layer 3 is thermally conductive silicone grease; to obtain a more uniform temperature distribution, a high thermal conductivity graphite film can be applied to the upper and lower surfaces of the cavity of the outer shell layer 1;

[0040] Figure 3 A schematic diagram of one embodiment of the lightweight heat dissipation composite material: The weight reduction layer is a combination of thermally conductive foam material 2-1 (foamed carbon or foamed copper) and thermally conductive carbon blocks 2-2; the thermally conductive carbon blocks have directional thermal conductivity, with high thermal conductivity in the horizontal direction and low thermal conductivity in the vertical direction. By aligning the horizontal thermal conductivity with the vertical direction of the carbon block array, the optimal heat transfer effect is achieved; to obtain a more uniform temperature distribution, high thermal conductivity graphite films can be applied to the upper and lower surfaces of the cavity of the outer shell layer 1, and the bonding layer 3 is a combination of thermally conductive silicone grease and high thermal conductivity graphite film. Detailed Implementation

[0041] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the present invention is not limited to the listed embodiments and drawings.

[0042] like Figure 1-3 As shown, the lightweight heat-dissipating composite material of the present invention includes an outer shell layer 1 with a cavity, a weight-reducing layer 2 disposed within the cavity of the outer shell layer, and a bonding layer 3 connecting the outer shell layer and the weight-reducing layer; wherein, the outer shell layer is a metal layer, and the weight-reducing layer is a thermally conductive material. The thermally conductive material is a thermally conductive foam material and / or a thermally conductive carbon block; wherein, the thermally conductive foam material is thermally conductive carbon foam or copper foam. The outer shell layer is on the outside, is metal, and its main function is support; the bonding layer is in the middle, and its function is to connect the weight-reducing layer and the outer shell layer, reducing the interfacial thermal resistance; the weight-reducing layer is on the inside, is a thermally conductive material, and its main function is to reduce the overall density and increase the thermal conductivity.

[0043] In such Figure 1 In the embodiment shown, the weight-reducing layer 2 is foamed carbon or foamed copper, with air filling the pores of the foamed carbon or foamed copper; the bonding layer 3 is thermally conductive silicone grease and a high thermal conductivity graphite film (attached to the upper and lower surfaces of the square cavity); or when the weight-reducing layer is foamed copper, the bonding layer can also be welded metal.

[0044] In such Figure 2 In the embodiment shown, the weight-reducing layer 2 is a thermally conductive carbon block; the carbon block structure consists of a carbon block array and a grid structure, with the remainder being air 4; the thermally conductive carbon block has directional thermal conductivity, with high thermal conductivity in the horizontal direction and low thermal conductivity in the vertical direction. By aligning the horizontal thermal conductivity with the vertical direction of the carbon block array, the optimal heat transfer effect is achieved; the bonding layer 3 is a thermally conductive silicone grease; to obtain a more uniform temperature distribution, a high thermal conductivity graphite film can be further attached to the upper and lower surfaces of the square cavity.

[0045] In such Figure 3 In the illustrated embodiment, the weight-reducing layer 2 is a combination of thermally conductive foam material 2-1 (foamed carbon or foamed copper) and thermally conductive carbon blocks 2-2, with the carbon blocks evenly distributed within the foam material. The carbon blocks exhibit directional thermal conductivity, with high thermal conductivity in the horizontal direction and low thermal conductivity in the vertical direction. Aligning the horizontal thermal conductivity with the vertical direction of the carbon block array achieves optimal heat transfer. To obtain a more uniform temperature distribution, high thermal conductivity graphite films can be applied to the upper and lower surfaces of the square cavity. The bonding layer 3 consists of thermally conductive silicone grease and the high thermal conductivity graphite film. Thus, the low density of the thermally conductive foam material effectively reduces weight, while the high thermal conductivity of the carbon blocks enhances thermal conductivity.

[0046] Example 1

[0047] 50 parts of expanded graphite (300 bulk) and 5 parts of high thermal conductivity carbon fiber (thermal conductivity approximately 2000 W / mK, the same below) were mixed evenly and then pressed into a mold with a molding density of 0.4 g / cm³. 3 Asphalt with a softening point of 230℃ and a mesophase content of 60% was dissolved in solvent oil. The preform was then vacuum-impregnated in the solvent oil containing the mesophase asphalt for 30 minutes. After drying, the weight gain was 45 parts. The above material was then subjected to constant temperature at 600℃ for 60 minutes under normal pressure and nitrogen atmosphere. The removed sample was then treated at 3000℃. This yielded a thermally conductive carbon foam material with a density of 0.35 g / cm³. 3 Thermal diffusivity 25mm 2 / s. The pore size distribution is as follows: 0.01-50μm (excluding 50 μm) accounts for 30%, 250-1000μm accounts for 45%, and 250-1000μm (excluding 250 μm) accounts for 25%.

[0048] Example 2

[0049] 30 parts expanded graphite (200 bulk), 20 parts graphene (200 bulk), 10 parts natural graphite, and 10 parts high thermal conductivity carbon fiber were mixed evenly and then pressed into a mold with a molding density of 0.5 g / cm³. 3Asphalt with a softening point of 270℃ and a mesophase content of 80% was dissolved in heavy oil. The preform was then vacuum-impregnated in the solvent oil of the mesophase asphalt for 30 minutes. It was then removed and dried. This process was repeated twice to increase the weight of the preform by 30 parts per cubic centimeter through impregnation. The above material was then subjected to constant temperature at 800℃ for 150 minutes under normal pressure and nitrogen atmosphere. The removed sample was then treated at 3000℃. This yielded a thermally conductive carbon foam material with a density of 0.48 g / cm³. 3 Thermal diffusivity 80 mm 2 / s. The pore size distribution is as follows: 0.01-50μm (excluding 50 μm) accounts for 35%, 250-1000μm accounts for 44%, and 250-1000μm (excluding 250 μm) accounts for 21%.

[0050] Example 3

[0051] 20 parts expanded graphite (50% bulk), 35 parts carbon nanotubes (400% bulk), 5 parts boron nitride, and 10 parts high thermal conductivity carbon fiber were mixed evenly and then pressed into a mold with a density of 0.35 g / cm³. 3 Asphalt with a softening point of 330℃ and a mesophase content of 100% was dissolved in heavy oil. The preform was then vacuum-impregnated in the solvent oil of the mesophase asphalt for 30 minutes. It was then removed and dried. This process was repeated 1-2 times to increase the weight of the preform to 30 parts per cubic centimeter. The above material was then subjected to constant temperature at 550℃ for 50 minutes under normal pressure and nitrogen atmosphere. The removed sample was then treated at 3000℃. This yielded a thermally conductive foamed carbon material with a density of 0.3 g / cm³. 3 Thermal diffusivity 80 mm 2 / s. The pore size distribution is as follows: 0.01-50μm (excluding 50 μm) accounts for 45%, 250-1000μm accounts for 42%, and 250-1000μm (excluding 250 μm) accounts for 13%.

[0052] Example 4

[0053] The difference from Example 1 is that the high-temperature treatment of the obtained impregnated material was performed at 1600°C. This resulted in a thermally conductive carbon foam material with a density of 0.38 g / cm³. 3 Thermal diffusion system 15mm 2 / s. The pore size distribution is as follows: 0.01-50μm (excluding 50 μm) accounts for 33%, 250-1000μm accounts for 47%, and 250-1000μm (excluding 250 μm) accounts for 20%.

[0054] Examples 5-6 and Comparative Examples 1-3

[0055] Example 5 uses the thermally conductive foamed carbon prepared in Example 1 (such as...). Figure 1 (Settings), wherein the carbon blocks of Comparative Examples 1-3 and Example 6 are provided with 12 blocks, such as Figure 2Distribution. Thermal conductivity testing was conducted (test environment temperature: room temperature; test equipment: temperature acquisition device (with thermocouples), constant power heat source (80W); test procedure: fix the heat source on the lower surface of the composite material, and evenly fix 4 thermocouples on the upper surface of the composite material. Turn on the heat source and test the temperature change of the upper surface over time. Without fins, air cooling, or other additional heat dissipation methods, a higher upper surface temperature indicates better performance), see Table 1 for details:

[0056] Table 1

[0057]

[0058]

Claims

1. A lightweight heat-dissipating composite material, characterized in that, The lightweight heat dissipation composite material includes an outer shell layer with a cavity, a weight-reducing layer disposed within the cavity of the outer shell layer, and a bonding layer connecting the outer shell layer and the weight-reducing layer; wherein, the outer shell layer is a metal layer, and the weight-reducing layer is a thermally conductive material; The thermally conductive material is thermally conductive carbon foam, or a combination of thermally conductive carbon foam and thermally conductive carbon blocks; The method for preparing the thermally conductive foamed carbon includes the following steps: (1) Mix porous graphite with thermally conductive reinforcing material evenly, press and mold to obtain preform material; (2) Dissolve the asphalt components in a solvent; (3) Immerse the preform obtained in step (1) into the solution obtained in step (2) so that the asphalt component enters the preform and dry the solvent to obtain the impregnated material; (4) The impregnated material obtained in step (3) is treated at 450-900℃ for more than 30 minutes under normal pressure and in a protective atmosphere to obtain the molding material; (5) The molding material obtained in step (4) is subjected to high temperature treatment at a temperature above 1000°C under normal pressure and in a protective atmosphere to obtain foamed carbon material. The impregnating material comprises 50%-70% porous graphite, 30%-50% asphalt component, and 0-20% thermally conductive reinforcing material; the asphalt component is mesophase asphalt.

2. The lightweight heat-dissipating composite material according to claim 1, characterized in that, The bonding layer is thermally conductive silicone grease or a combination of thermally conductive silicone grease and a highly thermally conductive graphite film.

3. The lightweight heat-dissipating composite material according to claim 1, characterized in that, The metal volume of the outer shell layer accounts for 20-70% of the total volume of the outer shell layer; the metal of the outer shell layer is copper, aluminum, stainless steel or alloy.

4. The lightweight heat-dissipating composite material according to claim 3, characterized in that, The thermally conductive carbon foam has a density of 0.1-1.2 g / cm³. 3 Thermal conductivity greater than 50 W / mK; The density of the thermally conductive carbon block is 1.6-2.2 g / cm³. 3 The carbon content is greater than 90%, the horizontal thermal conductivity is 300-600 W / mK, and the vertical thermal conductivity is 10-80 W / mK; when setting the thermally conductive carbon block, the horizontal thermal conductivity is set to correspond to the vertical direction of the thermally conductive carbon block column.

5. The lightweight heat-dissipating composite material according to any one of claims 1-4, characterized in that, The thermally conductive material is a combination of thermally conductive carbon blocks and thermally conductive foam material; wherein, the thermally conductive carbon blocks are arranged in an array within the cavity, and the thermally conductive foam material is processed into a structure complementary to the array of thermally conductive carbon blocks to fill the cavity.

6. The lightweight heat-dissipating composite material according to claim 1, characterized in that, The porous graphite has a bulk density of not less than 100; the porous graphite is one or more of graphene, expanded graphite, high thermal conductivity carbon felt, foamed graphite and carbon nanotubes.

7. The lightweight heat-dissipating composite material according to claim 1, characterized in that, The porous graphite has a bulk density of not less than 200; the porous graphite is one or more of graphene, expanded graphite, and carbon nanotubes.

8. The lightweight heat-dissipating composite material according to claim 6 or 7, characterized in that, The thermally conductive enhancement material includes one or more of natural graphite, high thermal conductivity carbon fiber, and boron nitride.

9. The lightweight heat-dissipating composite material according to any one of claims 1, 6, and 7, characterized in that, The mesophase pitch has a mesophase content of 80-100% and a softening point of 230-370℃.

10. The lightweight heat-dissipating composite material according to claim 9, characterized in that, The solvent is one or more of quinoline, heavy oil, tetrahydrofuran, solvent oil, and carbon tetrachloride.

11. The lightweight heat-dissipating composite material according to any one of claims 1, 6-7, and 10, characterized in that, The impregnating material contains 50%-60% porous graphite, 30%-45% asphalt components, and 5%-20% thermally conductive reinforcing materials.

12. The lightweight heat-dissipating composite material according to claim 11, characterized in that, The density of the preform is 0.3-0.6 g / cm³. 3 .

13. The lightweight heat-dissipating composite material according to claim 12, characterized in that, The processing time in step (4) is 0.5-6 hours and the processing temperature is 500-800℃.

14. The lightweight heat-dissipating composite material according to any one of claims 1-4, 6-7, 10, and 12-13, characterized in that, The density of the thermally conductive foam carbon is 0.25-0.5 g / cm³. 3 ; The thermally conductive carbon foam has a multi-level pore size distribution, with the pore size ranging from 0.01 μm. The pore size distribution of 50μm is not less than 20%; the pore size distribution of 50-250μm is not less than 30%; and the pore size distribution of 250-1000μm is not less than 10%.

15. The lightweight heat-dissipating composite material according to claim 14, characterized in that, The thermally conductive carbon foam has a multi-level pore size distribution, with the pore size ranging from 0.01 mm to... The pore size distribution is 25-50% for 50μm; 35-55% for 50-250μm; and 10-30% for 250-1000μm.

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