A three-dimensional graphene thermal conductive film and preparation method thereof

Abstract

The present invention belongs to the field of graphene technology, and specifically discloses a three-dimensional graphene thermal conductive film and a preparation method thereof, comprising the following steps: (1) preparing a graphite oxide suspension, exfoliating the graphite oxide, and obtaining a single-layer graphene oxide dispersion; (2) adding a cross-linking agent, and continuously stirring at a high speed until the system forms a hydrogel; (3) freeze-drying to obtain a three-dimensional graphene oxide aerogel; (4) sequentially carbonizing and graphitizing the three-dimensional graphene oxide aerogel to obtain a three-dimensional graphene aerogel, and finally pressing to obtain a three-dimensional graphene thermal conductive film. The graphene thermal conductive film has an in-plane thermal conductivity of 935 to 1523 W / (m·K), a thermal conductivity in a direction perpendicular to the plane of 218 to 536 W / (m·K), and an adjustable thickness within 40 to 1000 μm, and also has good flexibility.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene, and in particular to a three-dimensional graphene thermal conductive film and a preparation method thereof. Background Art

[0002] With the rapid development of electronic information technology, the packaging density of electronic devices continues to increase and the size continues to be miniaturized. While improving powerful functions, it also leads to a sharp increase in heat generation. The heat dissipation of electronic equipment faces severe challenges. At present, artificial graphite film is the mainstream heat dissipation material in the market. It is a kind of carbon molecule highly crystalline graphite film made of highly oriented polyimide carbonized film under extremely high temperature environment. The in-plane thermal conductivity can reach 1500W / (m·K), but the thermal conductivity in the vertical direction is generally less than 20W / (m·K), which seriously limits the application field of graphite film.

[0003] Graphene is a single layer of carbon atoms that is formed by combining one carbon atom with three neighboring carbon atoms to form a honeycomb structure. It is the lightest and thinnest material known so far. It has excellent performance in light, electricity, heat, and force, and is known as the "best material" and "king of materials." The most important thing is that its thermal conductivity is as high as 5300W / (m·K), and its toughness is very good, and its density is much lower than that of metal copper and aluminum alloy. Therefore, graphene is expected to be assembled into a three-dimensional high-thermal conductivity heat dissipation film material, overcoming the problem of poor vertical thermal conductivity of artificial graphene, which has a very attractive prospect.

[0004] Prior art CN114214042A discloses an application of a graphene film as a high temperature resistant thermal interface material or a heat dissipation film material, which uses chemical vapor deposition to grow graphene on a three-dimensional porous metal substrate, uses a metal etching solution to remove the porous metal substrate, obtains three-dimensional porous graphene, and presses the obtained three-dimensional porous graphene to form a graphene film. The in-plane thermal conductivity of the obtained graphene film is 400-1500 W / m·K, and the perpendicular square thermal conductivity is 10-180 W / m·K. It can be seen that the vertical thermal conductivity of the obtained graphene thermal conductive film is not high, mainly because the density of the three-dimensional porous graphene is low, and the preparation method has environmental pollution problems. Summary of the invention

[0005] In order to obtain a flexible graphene film with high thermal conductivity both in the plane and in the vertical direction, a three-dimensional graphene thermal conductive film and a preparation method thereof are provided. The method of the present invention can obtain a flexible graphene high thermal conductive film with an adjustable thickness of 40 to 1000 μm, with an in-plane thermal conductivity of 935 to 1523 W / (m·K) and a thermal conductivity of 218 to 536 W / (m·K) in the vertical plane direction.

[0006] In order to achieve the above objectives, the present invention is implemented by the following technical solutions:

[0007] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0008] (1) dispersing a graphite oxide paste in water to prepare a graphite oxide suspension having a concentration of 10 to 50 g / L, stirring and dispersing the mixture evenly, adding ammonia water to adjust the pH to 5 to 7, and performing an exfoliation treatment to achieve a single-layer exfoliation of the graphite oxide to obtain a graphene oxide slurry;

[0009] (2) adding a crosslinking agent to the graphene oxide slurry, and dispersing at a high speed of 1000 to 3000 rpm for 10 to 60 min until the graphene oxide is fully crosslinked to obtain a uniform graphene oxide hydrogel;

[0010] (3) freeze-drying the graphene oxide hydrogel to obtain a three-dimensional graphene oxide aerogel;

[0011] (4) The three-dimensional graphene oxide aerogel is subjected to carbonization treatment and graphitization treatment in sequence to obtain a three-dimensional graphene aerogel, and finally pressed to obtain a three-dimensional graphene thermal conductive film.

[0012] Furthermore, the stripping method described in step (1) is one of high-speed dispersion and high-pressure homogenization; the rotation speed of high-speed dispersion is 1000-3000 r / min, and the time is 0.5-5h; the pressure of high-pressure homogenization is 30-120 MPa, and the time is 5-30min.

[0013] Furthermore, the crosslinking agent described in step (2) is a linear aqueous crosslinking agent, including one of isocyanate, polycarbodiimide, acrylic acid, genipin, and polyvinyl pyrrolidone, preferably polycarbodiimide or genipin, and the amount used is 1 to 10% of the weight of graphite oxide.

[0014] Furthermore, the freeze-drying time in step (3) is 24 to 72 hours, the temperature is -55 to -45°C, and the vacuum degree is 5 to 20Pa.

[0015] Furthermore, the carbonization process described in step (4) is: placing the graphene oxide aerogel in an oven under an inert atmosphere, heating the temperature to 200-400° C. at a heating rate of 0.1-1° C. / min, and keeping the temperature for 0.5-2 h; the inert atmosphere is one or more of argon, nitrogen, and helium.

[0016] Furthermore, the graphitization process described in step (4) is: in an inert atmosphere, in a graphitization furnace, heating to 2800-3300°C at a heating rate of 10-50°C / min, keeping warm for 0.5-2h, and naturally cooling to obtain a three-dimensional graphene aerogel; the inert atmosphere is one or more of argon, nitrogen, and helium.

[0017] Furthermore, the pressing process described in step (4) is: using a vacuum flat pressing process, pressing for 10 to 60 minutes at a vacuum degree of 1 to 10 Pa and a pressure of 50 to 100 MPa to remove the gas generated between the graphene layers due to expansion.

[0018] The present invention provides a flexible graphene high thermal conductivity film obtained by the above method, with a film density of 1.8 to 2.2 g / cm3, a film thickness of 40 to 1000 μm, an in-plane thermal conductivity of 935 to 1523 W / (m·K), and a thermal conductivity in a direction perpendicular to the plane of 218 to 536 W / (m·K).

[0019] Compared with the prior art, the beneficial technical effects achieved by the present invention are:

[0020] First, the graphene oxide of the present invention forms a three-dimensional graphene network structure in the hydrogel through the action of a cross-linking agent, inhibits the nematic phase liquid crystalization of the graphene oxide, and forms a uniform hydrogel; secondly, in the drying stage, a mild freeze-drying method is used to maintain the three-dimensional network structure of the graphene oxide hydrogel to obtain a three-dimensional graphene oxide aerogel; finally, the present invention reduces and repairs the three-dimensional graphene through carbonization and graphitization, retains the three-dimensional graphene structure, and then uses a vacuum flat pressing process to obtain a dense graphene film. Since the graphene does not form an ordered structure during the entire processing process, a large amount of graphene is pressed in the graphene film structure obtained by pressing and running between the graphene layers, and the vacuum flat pressing process makes the film more compact, so the three-dimensional graphene film obtained has excellent thermal conductivity in both the in-plane and vertical directions, and also has good flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the three-dimensional graphene aerogel prepared in Example 3.

[0022] Figure 2 This is a cross-sectional SEM image of the final product, the three-dimensional graphene thermal conductive film, in Example 3. DETAILED DESCRIPTION

[0023] The graphite oxide paste used below has a solid content of 43±5wt%, a pH value of 1.8-2.3, a carbon content of 51±5wt%, and a sulfur content of ≤2wt%, and is SE2430W-N, a product of Changzhou Sixth Element Materials Technology Co., Ltd.

[0024] Example 1

[0025] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0026] (1) dispersing graphite oxide paste in deionized water to prepare 1 L of graphite oxide suspension with a concentration of 10 g / L, stirring evenly, adding ammonia water to adjust the pH to 5; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 120 MPa for 5 min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0027] (2) adding 0.1 g of acrylic acid to the graphene oxide slurry and dispersing at a high speed of 1000 rpm for 60 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0028] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 12 Pa and -47°C for 24 h to obtain a three-dimensional graphene oxide aerogel;

[0029] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 400°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 0.5 h;

[0030] Then, in a nitrogen atmosphere, the temperature was raised to 2850°C at a rate of 50°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0031] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 10Pa and a pressure of 100MPa for 15min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 1.8g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 150μm was obtained.

[0032] Example 2

[0033] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0034] (1) dispersing graphite oxide paste in deionized water to prepare 1 L of graphite oxide suspension with a concentration of 10 g / L, stirring evenly, adding ammonia water to adjust the pH to 5; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 120 MPa for 5 min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0035] (2) adding 0.1 g of polypropylene pyrrolidone to the graphene oxide slurry, and dispersing at a high speed of 1000 rpm for 60 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0036] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 12 Pa and -47°C for 24 h to obtain a three-dimensional graphene oxide aerogel;

[0037] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 400°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 0.5 h;

[0038] Then, in a nitrogen atmosphere, the temperature was raised to 2850°C at a rate of 50°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0039] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 10Pa and a pressure of 100MPa for 15min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 1.8g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 150μm was obtained.

[0040] Example 3

[0041] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0042] (1) dispersing graphite oxide paste in deionized water to prepare 1 L of graphite oxide suspension with a concentration of 10 g / L, stirring evenly, adding ammonia water to adjust the pH to 5; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 120 MPa for 5 min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0043] (2) adding 0.1 g of polycarbodiimide to the graphene oxide slurry, and dispersing at a high speed of 1000 rpm for 60 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0044] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 12 Pa and -47°C for 24 h to obtain a three-dimensional graphene oxide aerogel;

[0045] (4) placing the obtained three-dimensional graphene oxide aerogel in an oven, heating it to 400° C. at a heating rate of 1° C. / min under a nitrogen atmosphere, and keeping it at that temperature for 0.5 h;

[0046] Then, in a nitrogen atmosphere, the temperature was raised to 2850°C at a rate of 50°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0047] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 10Pa and a pressure of 100MPa for 15min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 1.8g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 150μm was obtained.

[0048] Example 4

[0049] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0050] (1) dispersing graphite oxide paste in deionized water to prepare 1 L of graphite oxide suspension with a concentration of 10 g / L, stirring evenly, adding ammonia water to adjust the pH to 5; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 120 MPa for 5 min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0051] (2) adding 0.1 g of genipin to the graphene oxide slurry, and dispersing at a high speed of 1000 rpm for 60 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0052] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 12 Pa and -47°C for 24 h to obtain a three-dimensional graphene oxide aerogel;

[0053] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 400°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 0.5 h;

[0054] Then, in a nitrogen atmosphere, the temperature was raised to 2850°C at a rate of 50°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0055] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 10Pa and a pressure of 100MPa for 15min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 1.8g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 150μm was obtained.

[0056] Example 5

[0057] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0058] (1) dispersing graphite oxide paste in deionized water to prepare 1L of graphite oxide suspension with a concentration of 50g / L, stirring evenly, adding ammonia water to adjust the pH to 7; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 30MPa for 30min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0059] (2) adding 5 g of polypropylene pyrrolidone to the graphene oxide slurry, and dispersing at high speed at 3000 rpm for 10 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0060] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 11 Pa and -51°C for 72 h to obtain a three-dimensional graphene oxide aerogel;

[0061] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 200°C at a rate of 0.1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 2 h;

[0062] Then, in a nitrogen atmosphere, the temperature was raised to 2800°C at a rate of 20°C / min in a graphitization furnace, kept at that temperature for 2 hours, and cooled naturally to obtain expanded three-dimensional graphene aerogel;

[0063] Finally, the vacuum flat pressing process was used to press for 60 min at a vacuum degree of 8 Pa and a pressure of 50 MPa to compact the expanded graphene aerogel and remove the gas generated between the graphene layers due to expansion, resulting in a film density of 2.0 g / cm 3 , and finally a unit graphene high thermal conductive film with a thickness of 150μm was obtained.

[0064] Example 6

[0065] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0066] (1) dispersing graphite oxide paste in deionized water to prepare 1L of graphite oxide suspension with a concentration of 20g / L, stirring evenly, adding ammonia water to adjust the pH to 6; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 60MPa for 15min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0067] (2) adding 1 g of genipin to the graphene oxide slurry, and dispersing at a high speed of 2000 rpm for 30 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0068] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 9 Pa and -48°C for 24 h to obtain a three-dimensional graphene oxide aerogel;

[0069] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 300°C at a rate of 0.5°C / min under a nitrogen atmosphere, and keeping it at that temperature for 1 hour;

[0070] Then, in a nitrogen atmosphere, the temperature was raised to 3000°C at a heating rate of 30°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0071] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 8Pa and a pressure of 80MPa for 30min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 2.1g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 40μm was obtained.

[0072] The SEM image of the three-dimensional graphene obtained in this step is as follows: Figure 1 As shown by Figure 1 It can be seen that three-dimensional graphene oxide has an obvious three-dimensional network structure.

[0073] The cross-sectional SEM image of the three-dimensional graphene thermal conductive film finally obtained in this embodiment is as follows: Figure 2 As shown by Figure 2 It can be seen that a very dense graphene oxide film is formed, with a thickness of 40 μm.

[0074] Example 7

[0075] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0076] (1) dispersing graphite oxide paste in deionized water to prepare 1L of graphite oxide suspension with a concentration of 30g / L, stirring evenly, adding ammonia water to adjust the pH to 7; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 30MPa for 30min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0077] (2) adding 2 g of polycarbodiimide to the graphene oxide slurry, and dispersing at a high speed of 2000 rpm for 30 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0078] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 5 Pa and -55°C for 48 h to obtain a three-dimensional graphene oxide aerogel;

[0079] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 300°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 1 h;

[0080] Then, in a nitrogen atmosphere, the temperature was raised to 3100°C at a rate of 10°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0081] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 6Pa and a pressure of 100MPa for 60min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 2.2g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 1000μm was obtained.

[0082] Example 8

[0083] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0084] (1) dispersing graphite oxide paste in deionized water to prepare 1L of graphite oxide suspension with a concentration of 30g / L, stirring evenly, adding ammonia water to adjust the pH to 7; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 30MPa for 30min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0085] (2) adding 2 g of polycarbodiimide to the graphene oxide slurry, and dispersing at a high speed of 2000 rpm for 30 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0086] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 5 Pa and -55°C for 48 h to obtain a three-dimensional graphene oxide aerogel;

[0087] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 300°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 1 h;

[0088] Then, in an argon atmosphere, the temperature was raised to 3100°C at a rate of 10°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0089] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 6Pa and a pressure of 100MPa for 60min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 2.2g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 1000μm was obtained.

[0090] Example 9

[0091] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0092] (1) dispersing graphite oxide paste in deionized water to prepare 1L of graphite oxide suspension with a concentration of 30g / L, stirring evenly, adding ammonia water to adjust the pH to 7; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 30MPa for 30min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0093] (2) adding 2 g of polycarbodiimide to the graphene oxide slurry, and dispersing at a high speed of 2000 rpm for 30 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0094] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 5 Pa and -55°C for 48 h to obtain a three-dimensional graphene oxide aerogel;

[0095] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 300°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 1 h;

[0096] Then, in a helium atmosphere, the temperature was raised to 3100°C at a rate of 10°C / min in a graphitization furnace, kept at that temperature for 0.5h, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0097] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 6Pa and a pressure of 100MPa for 60min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 2.2g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 1000μm was obtained.

[0098] Example 10

[0099] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0100] (1) dispersing graphite oxide paste in deionized water to prepare 1L of graphite oxide suspension with a concentration of 30g / L, stirring evenly, adding ammonia water to adjust the pH to 7; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 30MPa for 30min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0101] (2) adding 3 g of polycarbodiimide to the graphene oxide slurry, and dispersing at a high speed of 1500 rpm for 40 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0102] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 20 Pa and -45°C for 48 h to obtain a three-dimensional graphene oxide aerogel;

[0103] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 400°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 1 h;

[0104] Then, in a nitrogen atmosphere, the temperature was raised to 3100°C at a heating rate of 40°C / min in a graphitization furnace, kept at that temperature for 2 hours, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0105] Finally, the vacuum flat pressing process was used to press the expanded graphene film at a vacuum degree of 1Pa and a pressure of 60MPa for 60min to compact the expanded graphene film and remove the gas generated between the graphene layers due to expansion. The film density was 2.0g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 80μm was obtained.

[0106] Comparative Example 1

[0107] A method for preparing a three-dimensional graphene thermal conductive film comprises the following steps:

[0108] (1) dispersing graphite oxide paste in deionized water to prepare 1L of graphite oxide suspension with a concentration of 30g / L, stirring evenly, adding ammonia water to adjust the pH to 7; then, high-pressure homogenization treatment was performed in a high-pressure homogenizer at a pressure of 30MPa for 30min to achieve monolayer exfoliation, thereby obtaining graphene oxide slurry;

[0109] (2) adding 3 g of polycarbodiimide to the graphene oxide slurry, and dispersing at a high speed of 1500 rpm for 40 min until the graphene oxide is fully cross-linked to obtain a uniform graphene oxide hydrogel;

[0110] (3) freeze-drying the graphene oxide hydrogel at a vacuum degree of 20 Pa and -45°C for 48 h to obtain a three-dimensional graphene oxide aerogel;

[0111] (4) placing the three-dimensional graphene oxide aerogel in an oven, heating it to 400°C at a rate of 1°C / min under a nitrogen atmosphere, and keeping it at that temperature for 1 h;

[0112] Then, in a nitrogen atmosphere, the temperature was raised to 3100°C at a heating rate of 40°C / min in a graphitization furnace, kept at that temperature for 2 hours, and cooled naturally to obtain a three-dimensional graphene aerogel;

[0113] Finally, the graphene film was rolled at a pressure of 60 MPa for 60 min to compact the expanded graphene film and remove the gas generated between the graphene layers. The film density was 1.7 g / cm 3 , and finally a three-dimensional graphene thermal conductive film with a thickness of 100 μm was obtained.

[0114] The graphene thermal conductive films prepared in Examples 1 to 10 and Comparative Example 1 were subjected to density, thickness, thermal conductivity and bending tests, and the test results are shown in Table 1 below; wherein, the test standard for the thermal conductivity test is T / GDASE0006.

[0115] Table 1 Graphene film properties of the examples

[0116]

[0117] The embodiments described above only express several preferred embodiments of the present invention, and the descriptions thereof are relatively specific and detailed, but are not intended to limit the present invention. It should be noted that for those skilled in the art, the present invention may also have various changes and modifications, and any modifications, equivalent substitutions, improvements, etc. made within the concept and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional graphene thermally conductive film, characterized in that: The steps include: (1) dispersing graphite oxide paste in water to prepare a graphite oxide suspension with a concentration of 10-50 g / L, stirring and dispersing the mixture evenly, adding ammonia water to adjust the pH to 5-7, and then performing an exfoliation treatment to obtain a graphene oxide slurry; (2) adding a crosslinking agent to the graphene oxide slurry, and dispersing the slurry at a high speed of 1000-3000 rpm for 10-60 min until the graphene oxide is fully crosslinked to obtain a uniform graphene oxide hydrogel; the crosslinking agent is one of polycarbodiimide and genipin, and the amount thereof is 1-10% of the weight of the graphene oxide; (3) freeze-drying the graphene oxide hydrogel to obtain a three-dimensional graphene oxide aerogel; (4) The three-dimensional graphene oxide aerogel is subjected to carbonization treatment and graphitization treatment in sequence to obtain a three-dimensional graphene aerogel, and finally pressed to obtain a three-dimensional graphene thermal conductive film; the pressing is performed by using a vacuum flat pressing process.

2. The method for preparing the three-dimensional graphene thermally conductive film according to claim 1, characterized in that: The stripping method described in step (1) is high-speed dispersion or high-pressure homogenization; the speed of high-speed dispersion is 1000~3000r / min, and the time is 0.5~5h; the pressure of high-pressure homogenization is 30~120MPa, and the time is 5~30min.

3. The method for preparing the three-dimensional graphene thermal conductive film according to claim 1, characterized in that: The cross-linking agent described in step (2) is isocyanate.

4. The method for preparing the three-dimensional graphene thermally conductive film according to claim 1, characterized in that: The freeze-drying time in step (3) is 24 to 72 hours, the temperature is -55 to -45°C, and the vacuum degree is 5 to 20 Pa.

5. The method for preparing the three-dimensional graphene thermal conductive film according to claim 1, characterized in that: The carbonization treatment described in step (4) is as follows: placing the graphene oxide aerogel in an oven under an inert atmosphere, heating the temperature to 200-400°C at a heating rate of 0.1-1°C / min, and keeping the temperature for 0.5-2h to obtain a carbonized graphene aerogel; the inert atmosphere is one or more of argon, nitrogen, and helium.

6. The method for preparing the three-dimensional graphene thermal conductive film according to claim 1, characterized in that: The graphitization treatment in step (4) is as follows: placing the carbonized graphene aerogel in a graphitization furnace under an inert atmosphere, heating the temperature to 2800-3300°C at a heating rate of 10-50°C / min, keeping the temperature for 0.5-2h, and cooling naturally to obtain the three-dimensional graphene aerogel; the inert atmosphere is one or more of argon, nitrogen, and helium.

7. The method for preparing the three-dimensional graphene thermally conductive film according to claim 1, characterized in that: The pressing in step (4) is performed by using a vacuum flat pressing process at a pressure of 50-100 MPa for 10-60 minutes.

8. A three-dimensional graphene thermally conductive film prepared according to the method according to any one of claims 1 to 7.

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