Preparation method of thickened graphene heat-conducting film

Abstract

The invention discloses a preparation method of a thickened graphene heat-conducting film. Before splicing, the graphene oxide thin film is clamped by two layers of tight polyester cloth and is soaked in deionized water, so that the surface roughness of the graphene oxide thin film can be improved, and the cohesiveness of the graphene oxide thin film in the subsequent splicing process is effectively improved by utilizing the swelling capacity of graphene oxide in water; and finally, the thickened graphene heat-conducting film with high shear breaking strength is obtained, and the defect of insufficient interlayer binding force in the preparation process of the thickened graphene heat-conducting film in the prior art is overcome.

Description

Technical Field

[0001] The invention belongs to the field of carbon materials, and in particular relates to a method for preparing a thickened graphene thermal conductive film. Background Art

[0002] As a new type of two-dimensional carbon-based material, graphene has high mechanical properties and high chemical stability in addition to high thermal conductivity. After graphene is stacked into a layered structure, it can form a flexible film with a low thermal expansion coefficient, which provides a good solution for the development of thermal conductive films in thermal management materials. Compared with graphene prepared by mechanical exfoliation, epitaxial growth, chemical vapor deposition (CVD) and other methods, graphene oxide (GO) has good dispersibility and can form a stable dispersion system, which is conducive to the construction of layered and highly oriented structures; after the reduction process, the prepared graphene has controllable structure and chemical properties, making it one of the important precursors for the manufacture of high thermal conductivity graphene films.

[0003] The Chinese patent with publication number CN112299404A, “A method for batch preparation of graphene oxide film and graphene oxide film obtained thereby” processes graphene oxide into graphene oxide slurry using vacuum stirring and shearing integrated equipment to obtain uniform bubble-free graphene oxide slurry, coats the uniform bubble-free graphene oxide slurry with a coating and heating device to form a film, and separates the dried graphene oxide film from the substrate film to obtain the graphene oxide film.

[0004] The Chinese patent "A graphene oxide film and its preparation method and application" with publication number CN111214959A mixes a graphene oxide dispersed aqueous solution with 1,2-dichloroethane to form an incompatible electrolyte solution interface, and the graphene oxide in the aqueous phase is adsorbed on the interface to form a graphene oxide film. However, its electrostatic adsorption time is 30 to 54 hours, the preparation time is long, the efficiency is low, and the graphene oxide film thickness is small.

[0005] The Chinese patent "Method for preparing graphene oxide film, OLED device and preparation method" with publication number CN111081904A adopts spin coating to prepare graphene oxide film. Although the preparation time is shortened, the thickness of the graphene oxide film prepared is small and it is not conducive to mass production. Summary of the invention

[0006] In the prior art, a thickened graphene thermally conductive film is usually prepared by physically calendering a multilayer graphene thermally conductive film, but the prepared graphene thermally conductive film has the defects of being easily delaminated and having poor interlayer bonding strength.

[0007] In order to solve the problems in the prior art, the present invention provides a method for preparing a thickened graphene thermal conductive film, comprising the following steps:

[0008] S1. providing a graphene oxide film;

[0009] S2, placing the graphene oxide film between two pieces of polyester cloth to form a graphene oxide film composite structure;

[0010] S3, placing the graphene oxide film composite structure into deionized water, soaking it, and then drying it;

[0011] S4, removing the polyester cloth from the dried composite structure, and subjecting the dried graphene oxide film to a second immersion treatment;

[0012] S5, stacking at least two graphene oxide films that have been soaked for the second time, overlapping and aligning the edges of the films, and performing a second drying process;

[0013] S6, graphitizing the stacked graphene oxide films that have undergone the second drying process to obtain the thickened graphene thermal conductive film.

[0014] According to a specific embodiment of the present invention, step S2 specifically includes: placing the graphene oxide film on a tight polyester cloth, and placing another layer of tight polyester cloth 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 the step S2, the mesh number of the polyester cloth is 100-500 mesh, preferably 300 mesh.

[0016] The mesh number of the polyester cloth is controlled within the range of 100-500 meshes. If the mesh number is too low, the adhesion of the graphene oxide film is poor, and the shear fracture strength after the final splicing is low, but the final thermal conductivity is high; if the mesh number is too high, the adhesion of the graphene oxide film gradually increases, and the shear fracture strength after the final splicing is high, but the final thermal conductivity is reduced.

[0017] According to a specific embodiment of the present invention, in step S3, the soaking time is 10 min-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 immersion treatment time is 8-12 minutes, preferably 10 minutes.

[0020] In the present invention, the first immersion time is controlled within 10 minutes to 25 minutes, and the second immersion time is controlled within 8 minutes to 12 minutes. The graphene oxide film obtained by swelling within this range has the best adhesion.

[0021] The present invention adopts two immersion-drying treatments. During the first immersion process, under the action of the polyester cloth, the surface roughness of the upper and lower surfaces of the graphene oxide increases; on this basis, the second immersion is performed so that two graphene oxide films with larger roughness can swell and adhere in water.

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

[0023] According to a specific embodiment of the present invention, the temperature of the two immersions is room temperature. The temperature cannot be too high, because too high a temperature will cause the graphene oxide to agglomerate and cause certain oxidized functional groups to fall off, making the water solubility of the graphene oxide worse.

[0024] According to a specific embodiment of the present invention, in step S5, the pressure of the second drying process is 4-6 MPa, preferably 5 MPa.

[0025] The second drying process is carried out at a pressure of 4-6MPa. The pressure can increase the surface density of the material, remove excess water between the graphene oxide films, and maximize the bonding strength between the materials.

[0026] According to a specific embodiment of the present invention, in step S5, the temperature of the second drying treatment is 20-60°C, preferably 50°C.

[0027] According to a specific embodiment of the present invention, in step S5, the graphene oxide films used for overlapping are of the same size.

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

[0029] Preferably, the carbonization temperature is 1000°C for 2h;

[0030] The graphitization conditions were 3000 °C, 5 h;

[0031] The compression condition is 100 MPa.

[0032] Beneficial effects:

[0033] The technical solution of the present invention is to first sandwich the graphene oxide film with two layers of tight polyester cloth before splicing, and soak it in deionized water, which can improve the roughness of the surface of the graphene oxide film, and utilize the swelling ability of graphene oxide in water (graphene oxide film will dissolve and become liquid after being placed in water for a period of time. The edges of two graphene oxide films are overlapped together by utilizing the state between the solid state and the liquid state, and the graphene oxide at the fitting position will form a self-assembly process as the water evaporates, connecting the graphene oxide and the graphene oxide together) to effectively increase the adhesion of the graphene oxide film in the subsequent splicing process, and finally obtain a thickened graphene thermal conductive film with high shear fracture strength, which overcomes the defect of insufficient interlayer bonding force in the preparation process of thickened graphene thermal conductive film in the prior art. The interlayer bonding force of the graphene thermal conductive film is improved to prevent the film from delamination. A thicker (thickness 2mm-5mm) graphene thermal conductive film can be prepared. The thickened graphene thermal conductive film can provide greater heat flow and thermal path in temperature uniformity and heat conduction application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the preparation process of the thickened graphene thermal conductive film of the present invention;

[0035] Figure 2 The left picture is a SEM picture of a single layer of graphene oxide before splicing in Example 1; the right picture is a SEM picture of the thickened graphene thermal conductive film prepared in Example 1. DETAILED DESCRIPTION

[0036] The following further exemplifies the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples in a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

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

[0038] The thermal conductivity of the graphene thermal conductive film of the present invention is tested by the laser flash method using the LFA467 equipment of NETZSCH of Germany, and the thermal diffusion coefficient and thermal conductivity of the material are tested according to the standard: ASTM E1461.

[0039] The raw material graphene oxide film used in the present invention is a graphene oxide film prepared by using patent CN112299404A.

[0040] Example 1

[0041] First, two graphene oxide films with a length of 5 cm, a width of 5 cm, and a thickness of 0.2 mm were placed separately on two pieces of 100-mesh tight polyester cloth, and another layer of tight polyester cloth was placed on top of the graphene oxide. The clamped polyester cloth was soaked in deionized water for 18 minutes, and the soaked graphite oxide was dried in a blast drying oven at 50°C. After drying, the graphene oxide film was removed (i.e., the polyester cloth was removed).

[0042] The dried graphene oxide film is re-immersed in deionized water for 10 minutes to allow the graphene oxide to fully swell in the water, then the graphene oxide film is taken out, the films are stacked in position, the edges of the films are overlapped and aligned, and the film is dried at 50°C in a blast drying oven, and a pressure of 5MPa is applied on the overlapped graphene oxide film until it is completely dry. Then the film is placed in a 1000°C carbonization furnace filled with nitrogen for carbonization for 2 hours. After the film is taken out, it is placed in a graphitization furnace filled with nitrogen at 3000°C for graphitization, and the graphitization time is 5 hours. After the film is taken out again, it is compressed using a 100MPa vacuum press to obtain a thickened graphene thermal conductive film. After testing, the shear fracture strength of the graphene thermal conductive film prepared in Example 1 is 1.2MPa, and the thermal conductivity is: 800W / mK.

[0043] Example 2

[0044] The other conditions are the same as those in Example 1, except that the mesh number of the polyester cloth is 300. According to the test, the shear fracture strength of the graphene thermal conductive film prepared in Example 2 is 1.4 MPa, and the thermal conductivity is 860 W / mK.

[0045] Example 3

[0046] The other conditions are the same as those in Example 1, except that the mesh number of the polyester cloth is 500. According to the test, the shear fracture strength of the graphene thermal conductive film prepared in Example 3 is 2 MPa, and the thermal conductivity is 860 W / mK.

[0047] Comparative Example 1

[0048] The other conditions are the same as those in Example 1, except that: polyester cloth is not provided, and PET film is used as the base material (to take over the role of graphene oxide film). After the graphene oxide film is overlapped and dried, the shear fracture strength is 0.6 MPa, and the thermal conductivity of the prepared graphene thermal conductive film is: 800 W / mK.

[0049] Comparative Example 2

[0050] The other conditions are the same as those in Example 1, except that the second drying process is carried out under normal pressure.

[0051] The shear fracture strength is 0.6MPa, and the thermal conductivity of the prepared graphene thermal conductive film is 1500W / mK.

[0052] It can be seen from Example 1 and Comparative Examples 1-2 that by providing polyester cloth in the first drying step and applying pressure in the second drying step, the shear fracture strength of the graphene thermal conductive film can be improved under conditions of higher thermal conductivity.

[0053] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0054] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A method for preparing a thickened graphene thermally conductive film, characterized in that: The following steps are involved: S1. providing a graphene oxide film; S2, placing the graphene oxide film between two pieces of polyester cloth to form a graphene oxide film composite structure; S3, placing the graphene oxide film composite structure into deionized water, soaking it, and then drying it; S4, removing the polyester cloth from the dried composite structure, and subjecting the dried graphene oxide film to a second immersion treatment; S5, stacking at least two graphene oxide films that have been soaked for the second time, overlapping and aligning the edges of the films, and performing a second drying process; S6, graphitizing the stacked graphene oxide films that have undergone the second drying process to obtain the thickened graphene thermal conductive film.

2. The preparation method according to claim 1, characterized in that: The step S2 specifically includes: placing the graphene oxide film on a tight polyester cloth, and placing another layer of tight polyester cloth on the graphene oxide film to form a graphene oxide film composite structure.

3. The preparation method according to claim 1, characterized in that: In the step S2, the mesh number of the polyester cloth is 100-500 mesh, preferably 300 mesh.

4. The preparation method according to claim 1, characterized in that: In step S3, the soaking time is 10 min-25 min, preferably 18 min.

5. The preparation method according to claim 1, characterized in that: In step S3, the drying temperature is 30-60°C, preferably 50°C.

6. The preparation method according to claim 1, characterized in that: In step S4, the second immersion treatment lasts for 8-12 minutes, preferably 10 minutes.

7. The preparation method according to claim 1, characterized in that: In step S5, the pressure of the second drying process is 4-6 MPa, preferably 5 MPa.

8. The preparation method according to claim 1, characterized in that: In step S5, the temperature of the second drying treatment is 20-60°C, preferably 50°C.

9. The preparation method according to claim 1, characterized in that: The graphene oxide films used for alignment and stacking in step S5 have the same size.

10. The preparation method according to claim 1, characterized in that: In step S6, the conditions for the graphitization treatment are: carbonizing the dried graphene oxide film under an inert atmosphere at 900-1200° C. for 1-3 hours; then graphitizing it under an inert atmosphere at 2800-3200° C. for 4-6 hours; and then compressing it at 90-110 MPa using a vacuum press to obtain the graphene thermal conductive film.

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