A method for preparing a graphene-based thermally / electrically conductive composite material

Abstract

The present application relates to the technical field of new materials and its application, and in particular to a preparation method of a graphene-based heat-conducting / conducting composite material. Open-cell foam metal with a three-dimensionally connected structure is laminated and pressed, and the pressed foam metal is annealed under suitable temperature and atmosphere conditions. A graphene layer is catalytically grown on the surface of the foam metal template by using a chemical vapor deposition process. After the metal substrate is removed, a foam graphene network skeleton with an open-cell close-packed structure is obtained. A polymer matrix is filled into the pores of the foam graphene network skeleton with the close-packed three-dimensionally connected structure by using a vacuum impregnation process, and solidification is completed by selecting a suitable process. The present application has a simple process and low production cost. The graphene-based composite material prepared has excellent heat-conducting and conducting properties, and has great application potential in the fields of heat conduction, electricity conduction, electromagnetic shielding, etc.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new materials and their applications, and particularly relates to a preparation method of a graphene-based heat-conducting / conducting composite material. BACKGROUND

[0002] With the development of science and technology, polymer heat-conducting / conducting composite materials have been more and more widely applied. Compared with traditional metal materials, polymer heat-conducting / conducting composite materials have the characteristics of light weight, flexibility, corrosion resistance, easy processing and low cost, etc. of the polymer matrix itself, and can realize heat conduction, electrical conductivity and other functions by adding fillers. Traditional polymer heat-conducting / conducting composite materials are generally prepared by directly mixing filler particles in a polymer material such as epoxy resin, and the corresponding functions (such as heat conduction, electrical conductivity, etc.) are realized by adding a large amount of fillers to form a tightly packed structure of fillers. However, in these composite materials, the filler particles are generally distributed randomly in the polymer matrix and are separated by the polymer matrix, which seriously restricts the performance of the fillers. The addition of a large amount of heat-conducting fillers not only increases the cost and weight, but also seriously affects the mechanical properties and processing properties of the material, but the heat-conducting and electrical conductivity of the material are difficult to be significantly improved. Carbon materials are one of the choices of high-performance heat-conducting / conducting composite material fillers due to their excellent heat-conducting / conducting properties, low density and stable chemical properties. Currently, commercially available high-performance carbon-based heat-conducting / conducting composite materials are mainly prepared by directly adding carbon fibers or highly conductive carbon black in the matrix material, and the heat conductivity is generally 40 W / m K, and the electrical conductivity is generally below 300 S / cm. On the one hand, the raw materials and products including high-performance carbon fiber fillers are monopolized by foreign companies, which poses a risk of neck blockage; on the other hand, the heat-conducting / conducting properties of the existing products are still not ideal, and due to the excessive amount of fillers, the mechanical properties of the composite materials are seriously affected.

[0003] Since graphene was discovered, it has been widely concerned for its excellent thermal conductivity (its thermal conductivity can reach 5300 W / mK, which is more than 10 times that of traditional copper and silver, and more than 100 times that of aluminum oxide), electrical conductivity, high strength, and currently the thinnest material known, and has great application potential in thermal and electrical composite materials. However, the development of high-performance graphene-based composites also faces many difficulties and challenges: the thermal and electrical conductivity of graphene is significantly affected by its crystalline quality. Currently, the process for mass production of graphene either produces graphene with many defects and poor crystalline quality (graphene prepared by oxidation method), or the number of layers and the surface inertness are difficult to control (graphene prepared by intercalation method); compared with traditional spherical thermal conductive fillers, the addition of conventional flaky graphene powder as filler is extremely difficult to achieve good dispersion in the matrix material, and the addition amount has a more significant impact on the viscosity and hardness of the composite material; unlike isotropic three-dimensional bulk materials, flaky graphene exhibits significant anisotropy, with a huge difference in thermal and electrical conductivity in different directions. Its in-plane thermal conductivity can be more than 500 times that of out-of-plane thermal conductivity; flaky graphene has a significant barrier and partition effect on the polymer matrix, which significantly affects the strength of the composite material. In summary, the crystalline quality, morphology, distribution, addition amount of graphene filler, and the order degree of graphene in the matrix greatly affect the thermal and electrical conductivity of the composite material and the use performance such as hardness and strength.

[0004] Using a template to pre-construct a naturally connected and directional close-packed high-efficiency thermal and electrical conduction network of graphene, and then further compounding it with a polymer matrix, is an effective way to reduce the addition amount of graphene and improve the thermal and electrical conductivity and use performance of the composite. However, the current process for constructing a directional thermal network of graphene mainly uses easily dispersed graphene oxide to assemble and construct. The subsequent reduction and recrystallization process requires a slow heating and carbonization process of up to 10 hours and a subsequent super-high temperature graphitization process of more than 8 hours (the temperature generally needs to be above 2800℃, which is very energy-consuming). At the same time, the network constructed by using flaky graphene (including the use of graphene film deformation to prepare wrinkled graphene and other processes in addition to the graphene oxide ice template method) is basically a closed structure, and it is difficult for high molecular materials to be injected into the network pores, and the subsequent composite material preparation process is difficult. Therefore, it is of great practical value to overcome the drawbacks of the existing process and develop high-performance carbon-based thermal and electrical conduction composites with better performance. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a graphene-based thermal and electrical conduction composite material. The process of the present application is simple and the production cost is low. The prepared graphene-based composite material has excellent thermal and electrical conductivity. It has great application potential in the fields of thermal and electrical conduction, electromagnetic shielding, etc.

[0006] The technical scheme of the present application is:

[0007] A preparation method of a graphene-based thermal / electric conductive composite material, comprising the following steps:

[0008] (1) laminating open-cell foam metal with three-dimensional interconnected structure, and the compression rate is 90-99%;

[0009] (2) heating the annealing furnace cavity to a set temperature of 1000-1800 ℃ under a carrier gas protection atmosphere;

[0010] (3) putting the compressed foam metal substrate into the constant temperature zone of the annealing furnace cavity, introducing reducing gas, and keeping warm for 0-60 min, and then taking out the foam metal substrate after cooling under the carrier gas protection atmosphere, and annealing the compressed foam metal;

[0011] (4) heating the reaction furnace cavity to a set temperature of 600-1200 ℃ under a carrier gas protection atmosphere;

[0012] (5) introducing a mixed atmosphere of carbon source gas, reducing gas and carrier gas into the reaction furnace cavity, and catalytically growing graphene on the surface of the foam metal substrate after annealing; the flow rate ratio of the carbon source gas, the reducing gas and the carrier gas in the mixed atmosphere is 1:(0-80):(0-100), and the reaction time is 1-120 min;

[0013] (6) taking out the foam metal substrate after cooling under the carrier gas protection atmosphere, and obtaining a foam graphene network skeleton structure with close-packed structure grown on the foam metal substrate;

[0014] (7) removing the foam metal substrate by using a metal etching solution to obtain foam graphene with close-packed structure;

[0015] (8) filling a polymer matrix into the pores of the foam graphene network skeleton with close-packed structure by using a vacuum impregnation process, and completing solidification.

[0016] In the preparation method of the graphene-based thermal / electric conductive composite material, in step (1), the foam metal substrate is one of foam nickel, foam copper, foam iron, foam cobalt, foam silver, foam gold, foam platinum and foam titanium, or a foam alloy formed by two or more metals, the porosity of the foam metal substrate is distributed in 50-400 PPI, and the initial thickness is 0.5-15 mm.

[0017] In the preparation method of the graphene-based thermal / electric conductive composite material, in step (2), the carrier gas protection atmosphere is one or a mixture of two or more of argon, nitrogen and helium, the set temperature is 1050-1400 ℃, and in step (3), the annealing treatment of the compressed foam metal is performed at the set temperature.

[0018] The preparation method of the graphene-based thermal / electric conductive composite material, in step (4), the carrier gas protective atmosphere is one or more than two kinds of mixture of argon, nitrogen and helium, and the set temperature is 900-1100 DEG C, and the reaction in step (5) grows graphene, that is, it is carried out at the set temperature.

[0019] The preparation method of the graphene-based thermal / electric conductive composite material, in step (5), the carbon source gas is one or more than two kinds of mixture of methane, ethane, ethylene and acetylene, the reducing gas is one or more than two kinds of mixture of hydrogen and ammonia, and the carrier gas is one or more than two kinds of mixture of argon, nitrogen and helium; preferably, the flow rate of the mixed gas is 800-2400 sccm, the flow rate ratio of the carbon source gas, the reducing gas and the carrier gas in the mixed gas atmosphere is 1:20-60:30-90, and the reaction time is 30 min-90 min.

[0020] The preparation method of the graphene-based thermal / electric conductive composite material, in step (7), the metal etching solution is one or more than two kinds of mixture of hydrochloric acid, sulfuric acid, nitric acid, ammonium persulfate and ferric chloride in water or water-alcohol mixed solution.

[0021] The preparation method of the graphene-based thermal / electric conductive composite material, in step (8), the polymer matrix includes but is not limited to one or more than two kinds of mixture of epoxy resin, phenolic resin, polymethyl methacrylate and polyimide.

[0022] The preparation method of the graphene-based thermal / electric conductive composite material, by selecting different foam metal matrices and / or adjusting the temperature and the reaction gas atmosphere growth parameters in the reaction, the thickness, the porosity and the morphology of the prepared foam graphene network skeleton can be adjusted; the thickness of the prepared graphene-based thermal / electric conductive composite material ranges from 0.2 to 15 mm, and the density ranges from 1.0 to 2.5 g / cm 3 .

[0023] The preparation method of the graphene-based thermal / electric conductive composite material, in the prepared graphene-based thermal / electric conductive composite material, the mass fraction of the graphene network skeleton ranges from 15% to 70%.

[0024] The preparation method of the graphene-based thermal / electric conductive composite material, the composite material has excellent thermal conductivity and electrical conductivity in the in-plane and perpendicular-to-plane directions, wherein the thermal conductivity ranges from 80 to 400 W / mK, and the electrical conductivity ranges from 300 to 8000 S / cm.

[0025] The design mechanism of the present application is as follows:

[0026] The present application laminates open-cell foam metal with three-dimensional interconnected structure, and anneals the laminated foam metal at a suitable temperature and atmosphere. A graphene layer is catalytically grown on the surface of the foam metal template by chemical vapor deposition. After removing the metal substrate, a foam graphene network framework with open-cell close-packed structure is obtained. A polymer matrix is filled into the pores of the foam graphene network framework with close-packed three-dimensional interconnected structure by vacuum impregnation, and the polymer matrix is cured by a suitable process.

[0027] The laminating of the foam metal forms an ordered close-packed structure of the foam metal framework under stress induction. Annealing the laminated foam metal by a specific process promotes the fusion and interconnection between the laminated metal layers at high temperature, so as to form a long-range interconnected network structure in all directions of the foam metal framework.

[0028] The present application has the following advantages and beneficial effects:

[0029] 1. The present application uses three-dimensional interconnected ordered close-packed foam metal as a substrate template to catalytically grow graphene. By adjusting the type, compression amount and growth parameters of the foam metal, the morphology and thickness of the prepared close-packed foam graphene heat-conductive network can be adjusted to meet different application requirements.

[0030] 2. The prepared graphene heat-conductive network framework is a long-range interconnected close-packed structure formed in advance before being combined with a polymer matrix, which not only avoids the addition and dispersion problems of conventional graphene powder in the polymer matrix, but also ensures the ordered arrangement of graphene in the matrix and the construction of efficient heat-conductive / electrically-conductive paths, thereby realizing excellent heat-conductive / electrically-conductive performance of the composite material at a very low graphene addition amount.

[0031] 3. The prepared graphene heat-conductive / electrically-conductive network framework is an open-cell foam network structure, which effectively avoids the blocking and segmentation of conventional sheet-like graphene to the polymer matrix, and ensures that the composite material has excellent heat-conductive / electrically-conductive performance and good strength and other use properties.

[0032] 4. Existing carbon-based heat-conductive / electrically-conductive composite materials have poor heat-conductive and electrically-conductive performance, with a heat-conductive rate of generally 40 W / m K and an electrically-conductive rate of generally below 300 S / cm, which cannot meet the growing performance requirements. The prepared graphene-based high-performance heat-conductive / electrically-conductive composite material has a heat-conductive rate of up to 400 W / m K and an electrically-conductive rate of up to 8000 S / cm, which is much better than existing products.

[0033] 5. Due to the catalytic effect of the metal substrate, the present invention can ensure that the prepared graphene has good crystallinity and thus has good thermal / electrical conductivity without going through the time-consuming and energy-intensive carbonization and graphitization process (the carbonization process generally requires a slow heating for more than ten hours, and the subsequent graphitization process requires a temperature of more than 2800℃ and takes more than eight hours).

[0034] 6. The process of this invention is simple, easy to scale up for mass production, and has low production costs.

[0035] 7. The graphene-based high-performance thermally / conductively conductive composite material described in this invention has not appeared in the prior art, and has positive technical effects and applications. As a new type of thermally / conductively conductive composite material, it has great application potential. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the compression process.

[0037] Figure 2 Microscopic image of a close-packed foamed graphene network framework.

[0038] Figure 3 Microscopic images of graphene-based high-performance graphene-based thermally / electrically conductive composite materials.

[0039] Figure 4 Macroscopic photograph of graphene-based high-performance graphene-based thermally / electrically conductive composite materials. Detailed Implementation

[0040] In the specific implementation process, the present invention used the LFA467 flash thermal conductivity meter from NETZSCH GmbH, Germany (this instrument is currently widely used in domestic electronic product manufacturers and research institutions, and the test is carried out in accordance with the ASTM E 1461 standard) to test the thermal / electrical conductivity of the prepared graphene film.

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] Example 1:

[0043] In this embodiment, 20 sheets of copper foam with an initial porosity of 100 PPI and an initial thickness of 3 mm are pressed along the stacking direction to a thickness of 6 mm. The pressed copper foam is then annealed. The annealing furnace chamber is heated to a set temperature of 1050°C under an argon protective atmosphere. The pressed copper foam substrate is placed into the constant temperature zone of the annealing furnace chamber, hydrogen is introduced, and the temperature is maintained for 17 minutes. The copper foam substrate is then cooled under an argon protective atmosphere and removed.

[0044] The reactor chamber was heated to 1030°C under an argon protective atmosphere. The aforementioned close-packed copper foam was added to the constant temperature zone of the reactor chamber, and hydrogen gas was introduced. The temperature was maintained for 10 minutes at a flow rate of 600 sccm. The purpose of introducing hydrogen gas first is to remove the oxide layer on the substrate surface. A mixture of methane, hydrogen, and argon gas was then introduced at a flow rate of 800 sccm. The flow rate ratio of methane, hydrogen, and argon gas in the mixture was 1:20:59. The reaction time was 40 minutes, and graphene was catalytically grown on the surface of the aforementioned close-packed copper foam substrate.

[0045] Under an argon protective atmosphere, a densely packed graphene network skeleton grown on a copper foam substrate was removed and placed in a 2 mol / L sulfuric acid aqueous solution (etching solution). The solution was then heated at 80°C for 180 minutes to completely remove the copper from the graphene network skeleton. After removal, cleaning, and drying, a densely packed, porous, hollow graphene network skeleton structure was obtained. The graphene network skeleton was then immersed in a container filled with epoxy resin, and the container was placed in a vacuum device and evacuated for 30 minutes. The epoxy-infused graphene composite material was placed in an oven and cured at 120°C for 30 minutes. The resulting high-performance graphene-based thermally / electrically conductive composite material had a thickness of 5 mm and a density of 1.05 g / cm³. 3 In the composite material, the mass fraction of the graphene network framework is 15%.

[0046] like Figure 1 The diagram illustrates the compression process of the foamed copper skeleton. Figure 2 The images show the microstructure of a close-packed graphene network framework grown on a substrate. The images reveal a three-dimensionally interconnected, densely packed, porous microstructure. This long-range connectivity and dense packing of the graphene network framework within the substrate ensures excellent thermal and electrical conductivity of the material.

[0047] like Figure 3 The image shows the microstructure of the prepared composite material. Figure 4 The image shows a macroscopic photograph of a graphene-based high-performance thermally / conductively conductive composite material. As can be seen from the image, due to the open-cell, porous structure of the graphene network framework, the polymer matrix also forms a three-dimensional interconnected network structure. This avoids the obstruction and segmentation of the polymer matrix by conventional sheet-like graphene, ensuring that the prepared composite material possesses excellent electrical conductivity while still exhibiting mechanical properties close to those of the polymer matrix material.

[0048] The prepared graphene-based composite material was tested and found to have a thermal conductivity of 110 W / mK and an electrical conductivity of 550 S / cm.

[0049] Since the graphene network skeleton and the composite material in the following examples have basically the same morphology as the embodiment, the details are not repeated.

[0050] Example 2:

[0051] The 20 pieces of nickel foam with an initial porosity of 230 PPI and an initial thickness of 2 mm were extruded to a thickness of 2 mm along the stacking direction by using a mold, and the extruded nickel foam was annealed. The annealing furnace cavity was heated to a set temperature of 1360°C under a nitrogen protective atmosphere, the extruded nickel foam matrix was placed into the constant temperature zone of the annealing furnace cavity, hydrogen was introduced, and the temperature was maintained for 23 min. The nickel foam matrix was cooled under a nitrogen protective atmosphere and then taken out.

[0052] The reaction furnace cavity was heated to 1100°C under a nitrogen protective atmosphere, the close-packed structure nickel foam was added into the constant temperature zone of the reaction furnace cavity, hydrogen was introduced, and the flow rate of hydrogen was 600 sccm. The hydrogen was first introduced to remove the surface oxide layer of the matrix. Then, a mixed gas of methane, hydrogen and argon was continuously introduced, and the flow rate of the mixed gas was 1210 sccm. The flow rate ratio of methane, hydrogen and argon in the mixed gas was 1:30:90, and the reaction time was 90 min. Graphene was catalytically grown on the surface of the above-mentioned close-packed nickel foam matrix.

[0053] The close-packed graphene network skeleton grown on the nickel foam matrix was taken out under a nitrogen protective atmosphere and placed into a 3 mol / L hydrochloric acid aqueous solution (etching solution) and maintained at 80°C for 150 min to completely remove the nickel in the graphene network skeleton. After the graphene network skeleton was taken out, washed and dried, a porous hollow graphene network skeleton structure was obtained. The graphene network skeleton was immersed in a container containing epoxy resin, and the container was placed in a vacuum device for 30 minutes. The graphene composite material filled with epoxy resin was placed in an oven and cured at 120°C for 30 minutes. The high-performance graphene-based thermal and electrical conductive composite material with a thickness of 2 mm and a density of 1.3 g / cm 3 was obtained. In the composite material, the mass fraction of the graphene network skeleton was 28%.

[0054] After testing, the prepared graphene-based composite material had a thermal conductivity of 240 W / mK and an electrical conductivity of 1550 S / cm.

[0055] Example 3:

[0056] The 25 pieces of foam iron with initial porosity of 270 PPI and initial thickness of 3 mm are extruded to a thickness of 2 mm along the stacking direction by using a mold, and the extruded foam iron is annealed. The annealing furnace cavity is heated to a set temperature of 1400°C under an argon protective atmosphere, the annealed foam iron substrate is placed into the constant temperature zone of the annealing furnace cavity, hydrogen is introduced, and the foam iron substrate is kept at the temperature for 12 min. The foam iron substrate is cooled under the argon protective atmosphere and then taken out.

[0057] The reaction furnace cavity is heated to 1000°C under an argon protective atmosphere, the close-packed structure foam iron is added into the constant temperature zone of the reaction furnace cavity, hydrogen is introduced at a flow rate of 500 sccm, the hydrogen is first introduced to remove the surface oxide layer of the substrate, and then a mixed gas of ethylene, hydrogen and argon is continuously introduced at a flow rate of 1510 sccm, the flow rate ratio of ethylene, hydrogen and argon in the mixed gas being 1:60:90, and the reaction time is 60 min. Graphene is catalytically grown on the surface of the close-packed foam iron substrate.

[0058] The close-packed graphene network skeleton grown on the foam iron substrate is taken out under an argon protective atmosphere and placed into a 3 mol / L hydrochloric acid aqueous solution (etching solution) for heat preservation at 80°C for 120 min to completely remove the iron in the graphene network skeleton. After the graphene network skeleton is taken out, washed and dried, a close-packed porous hollow graphene network skeleton structure is obtained. The graphene network skeleton is immersed in a container containing epoxy resin, and the container is placed in a vacuum device for vacuumizing for 40 min. The graphene composite material filled with the epoxy resin is placed in an oven for curing at 130°C for 30 min, and then taken out to obtain the high-performance graphene-based thermal and electrical conductive composite material, which has a thickness of 1.8 mm and a density of 1.45 g / cm 3 . In the composite material, the mass fraction of the graphene network skeleton is 42%.

[0059] It is tested that the graphene-based composite material has a thermal conductivity of 298 W / mK and an electrical conductivity of 4035 S / cm.

[0060] Example 4:

[0061] The 20 pieces of foam nickel with an initial porosity of 300 PPI and an initial thickness of 6 mm are extruded to a thickness of 3 mm along the stacking direction by using a mold, and the extruded foam nickel is annealed. The annealing furnace cavity is heated to a set temperature of 1270°C under a nitrogen protective atmosphere, the extruded foam nickel substrate is placed into the constant temperature zone of the annealing furnace cavity, hydrogen is introduced, and the foam nickel substrate is kept at the temperature for 40 min. The foam nickel substrate is cooled under the nitrogen protective atmosphere and then taken out.

[0062] The reaction furnace cavity is heated to 1140℃ under nitrogen atmosphere, the close-packed structure of the foam nickel above is added into the constant temperature zone of the reaction furnace cavity, hydrogen is introduced, and the temperature is kept for 20 minutes. The flow rate of hydrogen is 600sccm. Hydrogen is introduced first to remove the surface oxide layer of the substrate. Then, the mixed gas of methane, hydrogen and nitrogen is continuously introduced. The flow rate of the mixed gas is 2000sccm. The flow rate ratio of methane, hydrogen and nitrogen in the mixed gas is 1:40:90. The reaction time is 70 minutes. Graphene is catalytically grown on the surface of the close-packed foam nickel substrate above.

[0063] The close-packed graphene network skeleton grown on the foam nickel substrate is taken out under argon atmosphere, and is put into 3mol / L hydrochloric acid aqueous solution (etching solution) for 60 minutes at 80℃. The nickel in the graphene network skeleton is completely removed. After the graphene network skeleton is taken out, washed and dried, a close-packed porous hollow graphene network skeleton structure is obtained. The graphene network skeleton is immersed in a container containing phenolic resin, and the container is placed in a vacuum device for vacuumizing for 40 minutes. The graphene composite material filled with phenolic resin is put into an oven for curing at 140℃ for 30 minutes. The high-performance graphene-based thermal and electrical conductive composite material with a thickness of 3mm and a density of 1.8g / cm 3 is obtained. In the composite material, the mass fraction of the graphene network skeleton is 54%.

[0064] It is tested that the thermal conductivity of the prepared graphene-based composite material is 330W / mK, and the electrical conductivity is 5870S / cm.

[0065] Example 5:

[0066] The 30 pieces of foam nickel-cobalt alloy with an initial porosity of 360PPI and an initial thickness of 10mm are extruded to a thickness of 5mm along the stacking direction by using a mold. The extruded foam nickel-cobalt alloy is annealed. The annealing furnace cavity is heated to a set temperature of 1320℃ under argon atmosphere. The extruded foam nickel-cobalt alloy substrate is put into the constant temperature zone of the annealing furnace cavity. Hydrogen is introduced. The temperature is kept for 36 minutes. The foam nickel-cobalt alloy substrate is taken out after being cooled under argon atmosphere.

[0067] The reaction furnace cavity is heated to 1180℃ under argon atmosphere. The close-packed structure of the foam nickel-cobalt alloy above is added into the constant temperature zone of the reaction furnace cavity. Hydrogen is introduced. The flow rate of hydrogen is 700sccm. Hydrogen is introduced first to remove the surface oxide layer of the substrate. Then, the mixed gas of methane, hydrogen and argon is continuously introduced. The flow rate of the mixed gas is 2400sccm. The flow rate ratio of methane, hydrogen and argon in the mixed gas is 1:40:70. The reaction time is 80 minutes. Graphene is catalytically grown on the surface of the close-packed foam nickel-cobalt alloy substrate above.

[0068] The close-packed graphene network skeleton grown on the nickel-cobalt alloy foam substrate is taken out under an argon protective atmosphere, and is placed in a 3 mol / L hydrochloric acid aqueous solution (etching solution) and is preserved at 80°C for 240 min, so that the nickel-cobalt alloy in the graphene network skeleton is completely removed. After the graphene network skeleton is taken out, washed and dried, a close-packed porous hollow graphene network skeleton structure is obtained. The graphene network skeleton is immersed in a container containing phenolic resin, and the container is placed in a vacuum device and is vacuumized for 90 min. The graphene composite material filled with the phenolic resin is placed in an oven and is cured at 140°C for 30 min, and the high-performance graphene-based thermal / electric conductive composite material is obtained. The thickness of the high-performance graphene-based thermal / electric conductive composite material is 5 mm, and the density is 2.1 g / cm 3 The mass fraction of the graphene network skeleton in the composite material is 63%.

[0069] It is tested that the thermal conductivity of the prepared graphene-based composite material is 392 W / mK, and the electrical conductivity is 7630 S / cm.

[0070] In summary, the high-performance graphene-based thermal / electric conductive composite material has excellent thermal / electric conductivity and good mechanical properties, the preparation method is simple, mass production is easy, and the production cost is low. The raw materials and equipment used in the present application (material preparation process) are all domestic products, which can effectively avoid the risk of high-performance graphene-based thermal / electric conductive composite material. The high-performance graphene-based thermal / electric conductive composite material has excellent performance and great application potential, and has good application prospect in the fields of in-plane and perpendicular to the plane direction thermal / electric conductivity, electromagnetic shielding and the like.

[0071] The above provided examples are only illustrative, and should not be considered as limiting the scope of the present application. Any method of equivalent replacement or change according to the technical solutions and inventive concept of the present application should be covered within the protection scope of the present application.

Claims

1. A method for preparing a graphene-based thermally / electrically conductive composite material, characterized by, The method comprises the following steps: (1) laminating open-cell foam metal with three-dimensional connected structure, compression ratio being 90-99%; when laminating the foam metal, under stress induction, the foam metal skeleton forms ordered close-packed structure; (2) heating the annealing furnace cavity to a set temperature of 1000-1800 DEG C under carrier gas protection atmosphere; (3) putting the compressed foam metal substrate into the constant temperature zone of the annealing furnace cavity, introducing reducing gas, keeping warm for 12-60 min, taking out the foam metal substrate after cooling under carrier gas protection atmosphere, and annealing the compressed foam metal; when annealing the compressed foam metal, high temperature is used to promote fusion and connection among the laminated metal layers, so that long-range connected network structure is formed in each direction of the foam metal skeleton; (4) heating the reaction furnace cavity to a set temperature of 600-1200 DEG C under carrier gas protection atmosphere; (5) introducing mixed atmosphere of carbon source gas, reducing gas and carrier gas into the reaction furnace cavity, and catalytically growing graphene on the surface of the foam metal substrate after annealing; the flow ratio of the carbon source gas, the reducing gas and the carrier gas in the mixed atmosphere is 1:20-60:30-90, the flow of the mixed gas is 800-2400 sccm, and the reaction time is 30-90 min; (6) taking out the foam metal substrate after cooling under carrier gas protection atmosphere, so that the foam graphene network skeleton structure with close-packed structure grown on the foam metal substrate is obtained; (7) removing the foam metal substrate by using metal etching solution, so that the foam graphene with close-packed structure is obtained; (8) filling polymer matrix into the pores of the foam graphene network skeleton with close-packed structure by using vacuum impregnation process, and completing solidification.

2. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, In step (1), the foam metal substrate is one of foam nickel, foam copper, foam iron, foam cobalt, foam silver, foam gold, foam platinum and foam titanium, or a foam alloy formed by two or more metals; the porosity of the foam metal substrate is 50-400 PPI, and the initial thickness is 0.5-15 mm.

3. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, In step (2), the carrier gas protection atmosphere is one or a mixture of two or more of argon, nitrogen and helium; the set temperature is 1050-1400 DEG C; and the annealing of the compressed foam metal in step (3) is performed at the set temperature.

4. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, In step (4), the carrier gas protection atmosphere is one or a mixture of two or more of argon, nitrogen and helium; the set temperature is 900-1100 DEG C; and the graphene growth in step (5) is performed at the set temperature.

5. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, In step (5), the carbon source gas is one or a mixture of two or more of methane, ethane, ethylene and acetylene; the reducing gas is one or both of hydrogen and ammonia; and the carrier gas is one or a mixture of two or more of argon, nitrogen and helium.

6. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, In step (7), the metal etching solution is one or a mixture of two or more of hydrochloric acid, sulfuric acid, nitric acid, ammonium persulfate and ferric chloride in aqueous solution or water-alcohol mixed solution.

7. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, The polymer matrix in step (8) includes, but is not limited to, one or more than two kinds of epoxy resin, phenolic resin, polymethyl methacrylate, polyimide.

8. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, The method can control the thickness, porosity and morphology of the prepared foam graphene network skeleton by selecting different foam metal substrates and / or regulating the temperature and reaction atmosphere in the reaction; the prepared graphene-based thermal / electricity-conducting composite material has a thickness ranging from 0.2 to 15 mm and a density ranging from 1.0 to 2.5 g / cm 3 .

9. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, The mass fraction of the graphene network skeleton in the prepared graphene-based thermal / electric conductive composite material is 15% to 70%.

10. The method for preparing the graphene-based thermally / electrically conductive composite material according to claim 1, characterized in that, The composite material has excellent thermal and electric conductivity in the in-plane and vertical plane directions, wherein the thermal conductivity is 80 to 400 W / mK, and the electric conductivity is 300 to 8000 S / cm.

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