Graphene composite film with high radiation and high thermal conductivity and preparation method thereof

Abstract

The invention belongs to the field of vacuum environment thermal management materials, and particularly relates to a graphene composite film with high radiation and high thermal conductivity and a preparation method of the graphene composite film. From the perspective of graphene structure design, reduced graphene oxide is adopted as a morphology regulating agent to modify the surface structure of the graphene heat-conducting film, directional construction of a micro-nano structure is achieved, the internal heat conductivity of the graphene film is not affected, and the graphene composite film with high radiation and high heat conductivity is successfully prepared; the problem that a traditional graphene film is high in heat conductivity but low in emissivity is solved. The method is simple, the heat conduction performance and the heat radiation performance are both high, and a new thought can be provided for batch preparation of the graphene heat conduction film in a novel application scene.

Description

Technical Field

[0001] The present invention belongs to the field of thermal management materials in a vacuum environment, and particularly relates to a graphene composite film with both high radiation and high thermal conductivity and a preparation method thereof. Background Art

[0002] With the rapid development of commercial aerospace, as the main detection tool, the power consumption of the internal signal processing and data transmission electronic modules of advanced spacecraft has increased significantly. The power of a single local chip exceeds 30W, resulting in many "hot spots" inside. To prevent the heat generated by internal electronic devices from accumulating, a layer of heat spreader material needs to be encapsulated at the position of the electronic device board to make the local heat uniform and then transfer it to the environment. Since heat convection cannot occur in the vacuum environment of outer space, the interior of the spacecraft can only exchange heat with the environment through thermal radiation. Therefore, there is an urgent need to develop a flexible heat spreader material with both high thermal radiation performance and high thermal conductivity to solve the problems of heat spreading and radiation of internal electronic devices in the spacecraft. However, traditional heat dissipation materials cannot meet these requirements simultaneously. Graphene films are considered ideal materials for heat dissipation of spacecraft electronic devices due to their light weight, high flexibility, stable chemical structure, high thermal conductivity, etc. The thermal conductivity of graphene films can reach more than 1300 W / (m·K). The high-thermal-conductivity graphene film has a long-range ordered structure inside, which is beneficial to the ordered transmission of phonons. However, it also indicates that the disordered transmission of phonons is less and the radiation relaxation time is shorter, resulting in a lower infrared emissivity and poor thermal radiation performance. Patent CN 109618428 B reports a high-emissivity infrared emission film based on graphene and a preparation method thereof. This patent focuses on solving the problem of preparing a high-emissivity infrared radiation film by in-situ growing graphene. A liquid adhesive is used to grow a rough layer on a catalytic substrate to make the emissivity reach 0.95. However, this patent does not solve the problem of high thermal conductivity, and the transfer process after chemical vapor deposition is complex, the transfer efficiency is low, the thickness of the prepared product is small, and it is difficult to achieve batch preparation. Therefore, developing a graphene composite film with excellent thermal radiation performance and thermal conductivity is an urgent need for spacecraft thermal management. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a graphene composite film with both high radiation and high thermal conductivity and a preparation method thereof. The present invention uses reduced graphene oxide as a morphology regulator to modify the surface structure of the graphene thermal conductivity film, realizes the directional construction of micro-nano structures, does not affect the internal thermal conductivity of the graphene film, and can simultaneously achieve the functions of high thermal conductivity (1200 W / (m·K)) and high thermal radiation (0.96). The preparation process of this method is simple, efficient, and suitable for batch preparation requirements. In addition, the morphology regulator and the matrix material of the present invention belong to the same material system, and have high structural compatibility and stability.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] On the one hand, the present invention provides a method for preparing a graphene composite film with both high radiation and high thermal conductivity, comprising the following steps:

[0006] Step 1: Prepare a highly thermally conductive graphene film by sequentially processing graphene oxide through ordered assembly, drying, high-temperature carbonization, ultra-high-temperature graphitization, and densification processes, and use this as a thermal conductive matrix;

[0007] Step 2: Prepare a mixed slurry by adjusting the ratio of reduced graphene oxide, polymer binder, and organic solvent, and use this as a radiation layer morphology control agent;

[0008] Step 3: Coat the mixed slurry on the surface of the graphene film, and obtain the graphene composite film after drying and curing treatments.

[0009] Further, the method adopted for ordered assembly in Step 1 is vacuum filtration, blade coating, centrifugal casting, or spin coating (for the detailed assembly method, refer to Reference 10.3390 / nano11102539).

[0010] Further, the drying temperature in Step 1 is 25 - 150 °C, and the time is 1 - 15 h.

[0011] Further, the high-temperature carbonization temperature in Step 1 is 200 - 1500 °C, and the time is 1 - 5 h.

[0012] Further, the ultra-high-temperature graphitization temperature in Step 1 is 2200 - 2500 °C, and the time is 1 - 3 h.

[0013] Further, the conditions for the densification process in Step 1 are: flat pressing method, 50 - 200 MPa, and the pressure holding time is 1 - 5 h.

[0014] Further, the polymer binder in Step 2 is at least one of epoxy resin, acrylic resin, phenolic resin, polyimide, polydimethylsiloxane, and polymethyl methacrylate, and the organic solvent is at least one of DMF, DMAc, NMP, acetone, and ethanol.

[0015] Further, the mass ratio of reduced graphene oxide to polymer binder in Step 2 is 1:1 - 1:8.

[0016] Further, the coating thickness in Step 3 is 0.1 - 1 mm.

[0017] Further, the drying temperature in Step 3 is 20 - 80 °C, and the time is 1 - 5 h; the curing temperature is 80 - 200 °C, and the time is 2 - 10 h.

[0018] On the other hand, the present invention provides a graphene composite film prepared by the preparation method as described above. It is a graphene composite film modified by a reduced graphene oxide morphology control agent, having a long-range ordered graphene heat-conducting layered structure and a flower-like graphene radiation structure; within the wide wavelength range of 2.5 - 18 μm, the infrared emissivity of the graphene composite film is 0.9 - 0.99, and at the same time, the in-plane thermal conductivity can be maintained at 1000 - 1200 W / (m·K).

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) The graphene composite film prepared by the present invention is a graphene integrated material with an asymmetric structure, having high structural stability. Among them, the asymmetric structure is a long-range ordered graphene heat-conducting layered structure and a flower-like graphene radiation structure.

[0021] (2) In the present invention, the graphene film used as the heat-conducting layer is subjected to high-temperature graphitization treatment, ensuring a high degree of graphitization, which is beneficial to the orderly transfer of phonons and ensures a high thermal conductivity. As the heat-radiation layer, the reduced graphene oxide flower-like structure has a lower degree of graphitization, which can effectively capture incident infrared rays and make them reflect multiple times until they are completely absorbed.

[0022] (3) The graphene composite film prepared by the present invention has excellent thermal conductivity (1196 W / (m·K)), and also has a high infrared emissivity. Within the wide wavelength range of 2.5 - 18 μm, the infrared emissivity is increased to more than 0.96, solving the problem that the existing graphene film has only high thermal conductivity but low emissivity. Description of the Drawings

[0023] Figure 1 SEM images of a pure graphene film (a) and the graphene composite film prepared in Example 1 (b).

[0024] Figure 2 Microscopic morphology pictures of a pure graphene film (a) and the graphene composite film prepared in Example 3 (b).

[0025] Figure 3 In-plane thermal conductivity and thermal diffusivity of a pure graphene film (a) and the graphene composite film prepared in Example 4 (b).

[0026] Figure 4 Infrared emissivity of a pure graphene film and the graphene composite film prepared in Example 7 in the wavelength range of 2 - 18 μm. Detailed Embodiments

[0027] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0028] Example 1

[0029] (1) Using graphene oxide (GO) as a raw material, a highly thermally conductive graphene film (GF) was prepared through continuous processing of ordered assembly, rapid drying, high-temperature carbonization, ultra-high-temperature graphitization, and densification processes, and this was used as a thermally conductive matrix. Specifically: The graphene film was prepared by the vacuum filtration method. 20 ml of a 2 g / ml GO slurry was poured into a device with a vacuum degree of 0.06 Pa, and an ordered assembly of a graphene oxide wet film was formed at room temperature. Then, it was dried in a forced-air drying oven at 150 °C for 1 h to obtain a graphene oxide dry film. Then, continuous high-temperature carbonization at 200 °C for 5 h and ultra-high-temperature graphitization at 2500 °C for 1 h were carried out. Finally, the highly thermally conductive graphene film was prepared by the flat pressing method, with rolling at 200 MPa for 5 h.

[0030] (2) Using reduced graphene oxide powder as a raw material, a mixed slurry was prepared by adjusting the ratios of reduced graphene oxide, polymer binder, and organic solvent, and this was used as a radiation layer morphology control agent. Specifically: 1 g of reduced graphene oxide (RGO) and 4 g of polyimide were mixed and added to 50 mL of acetone, and mechanical stirring and dispersion were carried out using a stirring disperser at a rotation speed of 1000 rpm for 10 h.

[0031] (3) A conventional coater was used to quickly scrape the mixed slurry onto the surface of the graphene film GF at a blade height of 1 mm. Then, it was placed in a vacuum oven and dried at 80 °C for 3 h, and then the temperature was raised to 200 °C and maintained for 5 h, and then cooled to obtain a graphene composite film modified with a reduced graphene oxide morphology control agent.

[0032] Example 2

[0033] The preparation steps were basically the same as those in Example 1, except that: in step (1), continuous high-temperature carbonization at 1500 °C for 5 h and ultra-high-temperature graphitization at 2200 °C for 3 h were carried out; in step (2), 1 g of RGO and 2 g of epoxy resin were mixed and added to 50 mL of DMAc solvent.

[0034] Example 3

[0035] The preparation steps are basically the same as those in Example 1, except that: in step (1), high-temperature carbonization is carried out at 500 °C continuously for 2 h and ultra-high-temperature graphitization is carried out at 2500 °C for 3 h, and finally, a high thermal conductivity graphene film is prepared by flat rolling at 200 MPa for 5 h; in step (2), 1 g of RGO and 4 g of polydimethylsiloxane are mixed and added to 50 mL of NMP solvent, and the stirring speed is 1200 rpm for 8 h.

[0036] Example 4

[0037] The preparation steps are basically the same as those in Example 1, except that: in step (1), a graphene oxide film is prepared by a doctor blade coating method, with a GO slurry concentration of 20 g / L, a doctor blade height of 6 mm, and orderly assembly by single doctor blade coating. The graphene oxide film is dried in a blast drying oven at 150 °C for 15 h. In step (2), 1 g of RGO and 6 g of phenolic resin are mixed and added to 50 mL of NMP; in step (3), the doctor blade height is set to 0.8 mm.

[0038] Example 5

[0039] The preparation steps are basically the same as those in Example 1, except that: in step (2), 1 g of RGO and 5 g of acrylic resin are mixed and added to 50 mL of ethanol solvent; in step (3), it is placed in a vacuum oven and dried at 80 °C for 5 h.

[0040] Example 6

[0041] The preparation steps are basically the same as those in Example 1, except that: in step (1), a graphene oxide film is prepared by a doctor blade coating method, with a GO slurry concentration of 20 g / L, a doctor blade height of 3 mm, and orderly assembly by single doctor blade coating. The graphene oxide film is dried in a blast drying oven at 150 °C for 8 h. In step (2), 1 g of RGO and 8 g of PI are mixed and added to 30 mL of NMP solvent; in step (3), it is placed in a vacuum oven and dried at 80 °C for 5 h.

[0042] It can be seen from Figure 1 that there are a large number of wrinkled structures on the surface of the graphene composite film prepared by the present invention, while the pure graphene film only has a small number of wrinkled structures.

[0043] It can be seen from Figure 2 that the surface of the graphene composite film prepared by the present invention has a high surface roughness, with a maximum undulation height of 18.77 μm and an amplitude parameter of 1.82 μm. While the surface of the pure graphene film is smooth, with a maximum undulation height of 2.96 μm and an amplitude parameter of 0.41 μm.

[0044] It can be seen from Figure 3It can be seen that the in-plane thermal conductivities of the graphene composite film and the pure graphene film prepared by the present invention are 1196 W / (m K) and 1387 W / (m K), respectively, both above 1000 W / (m·K), and the thermal diffusivities are 701 mm 2 ·s -1 and 788 mm 2 ·s -1 .

[0045] It can be seen from Figure 4 that the average emissivity of the graphene composite film prepared by the present invention in the 2-18 μm band is 0.96, while the average emissivity of the pure graphene film is only 0.47.

[0046] The above are only examples for better explaining the present invention and are not intended to limit it. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention falls within the scope covered by the present invention.

Claims

1. A method for preparing a graphene composite film having both high radiation and high thermal conductivity, characterized in that: The following steps are involved: Step 1: preparing a high thermal conductivity graphene film by sequentially treating graphene oxide through orderly assembly, drying, high temperature carbonization, ultra-high temperature graphitization and densification processes, and using this as a thermal conductive matrix; Step 2: preparing a mixed slurry by adjusting the ratio of reduced graphene oxide, polymer binder and organic solvent to use it as a radiation layer morphology control agent; Step 3: Scrape the mixed slurry onto the surface of the graphene film, and obtain the graphene composite film after drying and curing.

2. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: The drying temperature in step 1 is 25-150° C. and the drying time is 1-15 hours.

3. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: The temperature of high temperature carbonization in step 1 is 200-1500° C. and the time is 1-5 hours.

4. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: The temperature of ultrahigh temperature graphitization in step 1 is 2200-2500° C. and the time is 1-3 hours.

5. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: The conditions of the densification process in step 1 are: flat pressing method, 50-200 MPa, and holding time of 1-5 hours.

6. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: In step 2, the polymer binder is at least one of epoxy resin, acrylic resin, phenolic resin, polyimide, polydimethylsiloxane, and polymethyl methacrylate, and the organic solvent is at least one of DMF, DMAc, NMP, acetone, and ethanol.

7. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: In step 2, the mass ratio of reduced graphene oxide to polymer binder is 1:1-1:

8.

8. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: The thickness of the scraping in step 3 is 0.1-1 mm.

9. The method for preparing a graphene composite film having both high radiation and high thermal conductivity according to claim 1, characterized in that: In step 3, the drying temperature is 20-80° C. and the time is 1-5 hours; the curing temperature is 80-200° C. and the time is 2-10 hours.

10. The graphene composite film obtained by the preparation method according to any one of claims 1 to 9, characterized in that: It is a graphene composite film modified by a reduced graphene oxide morphology control agent, having a long-range ordered graphene thermal conductive layered structure and a flower-shaped graphene radiation structure; within a wide band of 2.5-18μm, the infrared emissivity of the graphene composite film is 0.9-0.99, while the in-plane thermal conductivity can be maintained at 1000-1200W / (mK).

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