Method for preparing large-size graphene heat-conducting film

Abstract

The application discloses a preparation method of a large-size graphene heat-conducting film. Before splicing, two layers of tight polyester cloth are used to clamp the graphene oxide film, the graphene oxide film is placed in deionized water for immersion, and the swelling capacity of the graphene oxide in the water is used to effectively increase the adhesion of the graphene oxide film in the subsequent splicing process, so that the large-size graphene heat-conducting film with high tensile fracture strength is finally obtained, and the size and equipment limitations in the preparation process of the graphene heat-conducting film in the prior art are overcome.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials, specifically relating to a method for preparing a large-size graphene thermally conductive film. Background Technology

[0002] Graphene, as a novel two-dimensional carbon-based material, possesses high thermal conductivity, high mechanical properties, and high chemical stability. When graphene is stacked into a layered structure, it can form flexible films with a low coefficient of thermal expansion, providing an excellent solution for the development of thermally conductive films in thermal management materials. Compared to graphene prepared by methods such as mechanical exfoliation, epitaxial growth, and chemical vapor deposition (CVD), graphene oxide (GO) exhibits good dispersibility, forming a stable dispersion system, which is beneficial for constructing layered and highly oriented structures. After a reduction process, the prepared graphene possesses controllable structure and chemical properties, making it one of the important precursors for manufacturing high thermal conductivity graphene films.

[0003] Chinese patent CN112299404A, entitled "A method for mass production of graphene oxide film and graphene oxide film obtained therefrom", describes a method for processing graphene oxide slurry using a vacuum stirring and shearing integrated device to obtain a uniform, bubble-free graphene oxide slurry. The uniform, bubble-free graphene oxide slurry is then coated and formed into a film using a coating and heating device. The dried graphene oxide film is then separated from the substrate film to obtain the graphene oxide film.

[0004] Chinese patent CN111214959A, entitled "A graphene oxide film and its preparation method and application," describes mixing an aqueous dispersion of graphene oxide with 1,2-dichloroethane to form an immiscible electrolyte solution interface. The graphene oxide in the aqueous phase is adsorbed onto the interface to form a graphene oxide film. However, the electrostatic adsorption time is 30–54 hours, resulting in a long preparation time, low efficiency, and a thin graphene oxide film.

[0005] Chinese patent CN111081904A, entitled "Preparation method of graphene oxide film, OLED device and preparation method", uses spin coating to prepare graphene oxide film. Although it shortens the preparation time, the resulting graphene oxide film is thin and not conducive to mass production. Summary of the Invention

[0006] Current technologies typically involve coating graphene oxide into a thin film, followed by high-temperature treatment to obtain a graphene thermally conductive film. However, the size of the graphene thermally conductive film prepared by this method is limited by coating equipment and production costs.

[0007] To address the problems in the prior art, this invention provides a method for preparing a large-size graphene thermally conductive film, comprising the following steps:

[0008] S1. Provide graphene oxide film;

[0009] S2. Place the graphene oxide film between two pieces of polyester fabric to form a graphene oxide film composite structure.

[0010] S3. Immerse the graphene oxide film composite structure in deionized water, and then dry it.

[0011] S4. Remove the polyester fabric from the dried composite structure and perform a second immersion treatment on the dried graphene oxide film.

[0012] S5. Overlap the edges of at least two graphene oxide films that have undergone the second soaking treatment, and perform a second drying treatment.

[0013] S6. The overlapping graphene oxide film that has undergone a second drying process is graphitized to obtain the graphene thermal conductive film.

[0014] According to a specific embodiment of the present invention, step S2 specifically includes: placing a graphene oxide film on a taut polyester fabric, and placing another taut polyester fabric on top of the graphene oxide film to form a graphene oxide film composite structure.

[0015] According to a specific embodiment of the present invention, in step S2, the mesh count of the polyester fabric is 100-500 mesh, preferably 300 mesh.

[0016] This invention controls the mesh count of the polyester fabric within the range of 100-500 mesh. If the mesh count is too low, the adhesion of the graphene oxide film is poor, resulting in low tensile strength after splicing, but a high thermal conductivity. If the mesh count is too high, the adhesion of the graphene oxide film gradually increases, resulting in high tensile strength after splicing, but a low thermal conductivity.

[0017] According to a specific embodiment of the present invention, in step S3, the soaking time is 10 min to 25 min, preferably 18 min.

[0018] According to a specific embodiment of the present invention, in step S3, the drying temperature is 30-60°C, preferably 50°C.

[0019] According to a specific embodiment of the present invention, in step S4, the second soaking treatment time is 8-12 minutes, preferably 10 minutes.

[0020] The present invention controls the first soaking time to 10-25 minutes and the second soaking time to 8-12 minutes. Within this range, the graphene oxide film obtained by swelling has the best adhesion.

[0021] This invention employs a two-stage soaking-drying process. During the first soaking, the surface roughness of the upper and lower surfaces of the graphene oxide increases under the action of the polyester cloth. Based on this, a second soaking is performed to allow the two graphene oxide films with larger roughness to swell and bond in water.

[0022] In the technical solution of the present invention, drying can be performed more than twice as needed, at least twice, and polyester cloth is only used during the first drying.

[0023] According to a specific embodiment of the present invention, the temperature for both soakings is room temperature. The temperature should not be too high, as excessively high temperatures can cause graphene oxide to agglomerate and induce the shedding of certain oxidized functional groups, thus reducing the water solubility of graphene oxide.

[0024] According to a specific embodiment of the present invention, in step S5, the pressure of the second drying process is 8-12 MPa, preferably 10 MPa.

[0025] The second drying process is carried out under a pressure of 8-12 MPa. By increasing the pressure, the interfacial density of the material can be increased, allowing excess moisture between the graphene oxide films to be removed, thereby maximizing the bonding force between the materials.

[0026] According to a specific embodiment of the present invention, in step S5, the graphene oxide films used for overlapping are of the same size.

[0027] According to a specific embodiment of the present invention, in step S5, the temperature of the second drying treatment is 30-60°C, preferably 50°C.

[0028] According to a specific embodiment of the present invention, in step S6, the graphitization treatment conditions are as follows: the dried graphene oxide film is carbonized at 900-1200°C for 1-3 hours under an inert atmosphere; then graphitized at 2800-3200°C for 4-6 hours under an inert atmosphere; and then compressed at 90-110 MPa using a vacuum flat press.

[0029] Preferably, the carbonization temperature is 1000℃ for 2 hours;

[0030] The graphitization conditions were 3000℃ for 5 hours.

[0031] The compression condition is 100 MPa.

[0032] According to a specific embodiment of the present invention, the inert atmosphere is preferably a nitrogen atmosphere.

[0033] Beneficial effects:

[0034] The technical solution of this invention involves sandwiching a graphene oxide film between two tightly stretched polyester fabrics before splicing, and then immersing it in deionized water. This improves the surface roughness of the graphene oxide film and utilizes the swelling capacity of graphene oxide in water (the graphene oxide film dissolves and becomes liquid after being immersed in water for a period of time. By using the state between solid and liquid, the edges of the two graphene oxide films are overlapped. The graphene oxide at the bonding position undergoes a self-assembly process as the water evaporates, connecting the graphene oxides together). This effectively increases the adhesion of the graphene oxide films during subsequent splicing, ultimately obtaining a large-size graphene thermal conductive film with high tensile strength, overcoming the limitations of existing technologies on the size and equipment in the preparation of graphene thermal conductive films. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the preparation process of the large-size graphene thermal conductive film of the present invention. Detailed Implementation

[0036] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention fall within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0037] The method for testing the tensile breaking strength of the graphene thermal conductive film of the present invention is as follows: the tensile breaking strength of the material is tested using a universal tensile testing machine. The thermal conductive film is cut into rectangular strips of 12cm×1cm, and both ends are clamped on the Instron universal tensile testing machine. The test is performed at a rate of 20mm / min.

[0038] The method for testing the thermal conductivity of the graphene thermal conductive film of the present invention is as follows: using the LFA467 equipment of Netzsch, Germany, the laser flare method is used to test the thermal diffusivity and thermal conductivity of the material, and the standard adopted is ASTM E1461.

[0039] The graphene oxide film used in this invention is a graphene oxide film prepared using patent CN112299404A.

[0040] Example 1

[0041] First, place two graphene oxide films, each 5cm long, 5cm wide, and 0.2mm thick, separately on two 100-mesh taut polyester fabrics. Then, place another taut polyester fabric on top of the graphene oxide films. Soak the sandwiched polyester fabric in deionized water for 18 minutes. Dry the soaked graphene oxide films in a forced-air drying oven at 50°C. After drying, remove the graphene oxide films (i.e., remove the polyester fabric).

[0042] The dried graphene oxide film was re-immersed in deionized water for 10 minutes to allow it to fully swell. The film was then removed, and its edges were overlapped. It was dried in a forced-air drying oven at 50°C, with a pressure of 10 MPa applied above the overlapped film until completely dry. The film was then carbonized in a nitrogen-filled furnace at 1000°C for 2 hours. After removal, the film was graphitized in a nitrogen-filled graphitization furnace at 3000°C for 5 hours. Finally, the film was compressed using a 100 MPa vacuum flat press to obtain a large-size graphene thermally conductive film. The tensile strength of the graphene thermally conductive film prepared in Example 1 was tested to be 20 MPa, and its thermal conductivity was 1500 W / mK.

[0043] Example 2

[0044] Other conditions were the same as in Example 1, except that the polyester fabric was 300 mesh. The graphene thermally conductive film prepared in Example 2 was tested and found to have a tensile breaking strength of 25 MPa and a thermal conductivity of 1450 W / mK.

[0045] Example 3

[0046] Other conditions were the same as in Example 1, except that the polyester fabric was 500 mesh. The graphene thermally conductive film prepared in Example 3 was tested and found to have a tensile breaking strength of 33 MPa and a thermal conductivity of 1300 W / mK.

[0047] Comparative Example 1

[0048] Other conditions are the same as in Example 1, except that: no polyester cloth is used, and PET film is used as the base material (to support the graphene oxide film). After the graphene oxide film is overlapped and dried, the tensile breaking strength is 10 MPa, and the thermal conductivity of the prepared graphene thermal conductive film is 1500 W / mK.

[0049] Comparative Example 2

[0050] Other conditions were the same as in Example 1, except that the second drying process was carried out under normal pressure. After the graphene oxide film was dried, the tensile breaking strength was 2 MPa, and the thermal conductivity of the prepared graphene thermal conductive film was 1500 W / mK.

[0051] As can be seen from Example 1 and Comparative Examples 1-2, using polyester cloth in the first drying step and applying pressure in the second drying step can improve the tensile breaking strength of the graphene thermal conductive film under conditions of high thermal conductivity.

[0052] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0053] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A method for preparing a large-size graphene thermally conductive film, characterized in that, Includes the following steps: S1. Provide graphene oxide film; S2. Place the graphene oxide film between two pieces of polyester fabric to form a graphene oxide film composite structure. S3. Immerse the graphene oxide film composite structure in deionized water, and then dry it. S4. Remove the polyester fabric from the dried composite structure and perform a second immersion treatment on the dried graphene oxide film. S5. Overlap the edges of at least two graphene oxide films that have undergone the second soaking treatment, and perform a second drying treatment. S6. The overlapping graphene oxide film that has undergone a second drying process is graphitized to obtain the graphene thermal conductive film.

2. The preparation method according to claim 1, characterized in that, Step S2 specifically includes: placing a graphene oxide film on a taut polyester fabric, and then placing another taut polyester fabric on top of the graphene oxide film to form a graphene oxide film composite structure.

3. The preparation method according to claim 1, characterized in that, In step S2, the mesh count of the polyester fabric is 100-500 mesh.

4. The preparation method according to claim 3, characterized in that, The polyester fabric has a mesh count of 300.

5. The preparation method according to claim 1, characterized in that, In step S3, the soaking time is 10 min to 25 min.

6. The preparation method according to claim 5, characterized in that, The soaking time is 18 minutes.

7. The preparation method according to claim 1, characterized in that, In step S3, the drying temperature is 30-60°C.

8. The preparation method according to claim 7, characterized in that, The drying temperature is 50°C.

9. The preparation method according to claim 1, characterized in that, In step S4, the second soaking treatment takes 8-12 minutes.

10. The preparation method according to claim 9, characterized in that, The second soaking treatment lasted for 10 minutes.

11. The preparation method according to claim 1, characterized in that, In step S5, the pressure of the second drying process is 8-12 MPa.

12. The preparation method according to claim 11, characterized in that, The pressure for the second drying process is 10 MPa.

13. The preparation method according to claim 1, characterized in that, In step S5, the temperature of the second drying process is 30-60℃.

14. The preparation method according to claim 13, characterized in that, The temperature for the second drying process is 50°C.

15. The preparation method according to claim 1, characterized in that, In step S5, the graphene oxide films used for overlapping are of the same size.

16. The preparation method according to claim 1, characterized in that, In step S6, the graphitization treatment conditions are as follows: the dried graphene oxide film is carbonized at 900-1200℃ for 1-3 hours in an inert atmosphere; then graphitized at 2800-3200℃ for 4-6 hours in an inert atmosphere; and then compressed at 90-110MPa using a vacuum flat press to obtain the graphene thermal conductive film.

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