Reduced graphene oxide film, preparation method thereof and coating device of reduced graphene oxide film

Abstract

The invention provides a preparation method of a reduced graphene oxide film. The preparation method specifically comprises the following steps: (1) preparing graphene oxide slurry; (2) preparing a roller, arranging a coating base material in the roller, spraying the graphene oxide slurry on the coating base material in a rotating state of the roller, and shaping to obtain a graphene oxide film; and (3) the graphene oxide film is subjected to carbonization, graphitization and calendaring treatment, the reduced graphene oxide film is obtained, and a cold wall shaping process is adopted when the graphene oxide film is shaped. The graphene oxide slurry is spread by centrifugal force to improve the self-assembly orderliness and compactness of the reduced graphene oxide film, and through rapid cooling shaping and freeze drying, part of oxygen-containing functional groups can be prevented from falling off in the heat drying process, and self-assembly of the reduced graphene oxide film is facilitated.

Description

Technical Field

[0001] The present application relates to the field of graphene preparation, and specifically, to a reduced graphene oxide film and a preparation method thereof, as well as a coating device for the reduced graphene oxide film. Background Art

[0002] With the rapid development of 5G technology and artificial intelligence, the power consumption of electronic devices has increased, and higher requirements have been placed on the performance and thermal conductivity of thermal conductive materials. Graphene has an ultra-high theoretical thermal conductivity, so reduced graphene oxide films have received widespread attention in the field of thermal management. One of the decisive factors for the improvement of the thermal conductivity of reduced graphene oxide films is the degree of order in their self-assembly. Reduced graphene oxide films are often coated by a doctor blade method during the preparation process. This method does not control the arrangement orientation of the graphene oxide raw material. From this aspect, the improvement of the thermal conductivity of reduced graphene oxide films is limited. Summary of the invention

[0003] Based on the above, the present application provides a reduced graphene oxide film and a preparation method thereof.

[0004] The first object of the present application is to provide a method for preparing a reduced graphene oxide film, comprising the following steps: (1) Preparation of graphene oxide slurry; (2) preparing a drum, placing a coating substrate in the drum, spraying the graphene oxide slurry on the coating substrate while the drum is rotating, and obtaining a graphene oxide film after shaping; (3) The dried graphene oxide film is subjected to carbonization, graphitization and calendering treatment to obtain a reduced graphene oxide film.

[0005] Different from the conventional blade coating method, the present application adopts a high-speed rotating drum and utilizes centrifugal force to spread the graphene oxide slurry in the drum to form a film. The graphene oxide slurry has a tendency to move in the same direction on the inner wall of the drum. Compared with flat coating, graphene oxide has a more orderly arrangement orientation, which can improve the self-assembly order and density of the GO film.

[0006] In some embodiments of the present application, the coating substrate is any one of PET, PP, and non-woven fabric.

[0007] Furthermore, the rotation speed of the drum is 300~5000rpm / min. Under the action of high-speed centrifugal force, most of the water in the graphene oxide slurry is thrown out, and the graphene oxide sheets obtain a high relative speed with the substrate under the condition of high-speed centrifugal spin coating, so that the graphene oxide sheets have a better paving effect.

[0008] Furthermore, in step (2), the spraying position and / or spraying angle of the graphene oxide slurry can be controlled so that the spraying of the graphene oxide slurry has a higher relative speed relative to the rotation of the drum, thereby achieving a better paving effect of the graphene oxide sheets.

[0009] Furthermore, in step (2), the graphene oxide slurry is sprayed by atomization spraying, and the atomization method can make the spraying effect more uniform.

[0010] Further, the solid content of the graphene oxide slurry is 1% to 5%. Compared with the conventional flat blade coating scheme, the scheme provided in the present application can complete the coating of the graphene oxide film using a graphene oxide slurry with a lower solid content. In the conventional flat coating process, it is usually necessary to make the solid content of the graphene oxide slurry 3% to 8%, so as to prevent the slurry with too low solid content from flowing and diffusing during the coating process, resulting in uneven coating, spots, stripes and other problems, and if the solid content is low, the slurry contains more solvent, and more time is required for evaporation and drying; and the use of high-speed rotary coating of the drum, under the action of high-speed centrifugal force, the low-solid content of the graphene oxide sheet can also be evenly coated on the coating substrate of the inner wall of the drum, and the lower the solid content of the slurry, the better the fluidity, but it is easier to spread on the inner wall of the drum through centrifugation, and the use of low-solid slurry can further save raw materials and improve the utilization rate of raw materials.

[0011] Furthermore, the shaping method of the graphene oxide film in the drum is cold wall freezing shaping, the temperature of the cold wall freezing shaping is -50°C to 0°C, and / or the time of the cold wall freezing shaping is 5 to 60 minutes, and the lower the temperature, the shorter the freezing shaping time. Compared with thermal evaporation shaping, cold wall freezing shaping can ensure that the graphene oxide sheet retains all oxygen-containing groups during the drying process, which is conducive to the subsequent self-assembly reaction. This is mainly attributed to the deposition of the atomized graphene oxide sheet in a single layer or a few layers. The single layer or a few layers of graphene oxide sheets are very sensitive to temperature, which easily leads to the loss of oxygen-containing groups carried by the graphene oxide sheet, which is not conducive to the subsequent heat treatment and self-assembly process by overlapping functional groups.

[0012] Furthermore, the graphene oxide film further includes a drying step after shaping. The drying method of the graphene oxide film is freeze drying. Also based on the consideration of oxygen-containing group protection, the freeze drying temperature is less than 0° C., and / or the freeze drying time is 8-48 hours.

[0013] Furthermore, the carbonization temperature of the graphene oxide film is 900-1600°C, and the graphitization temperature is 2800-3200°C. In the carbonization stage, most of the oxygen-containing functional groups are removed, and in the graphitization stage, the graphene sheet further optimizes its structure, the carbon atom structure is rearranged, and various defects are repaired, and the intrinsic thermal conductivity of graphene is improved.

[0014] Furthermore, the graphene oxide film also includes a pretreatment before the carbonization treatment, and the pretreatment temperature is 200-360° C. Through the pretreatment, the moisture and CO-type oxygen-containing functional groups in the graphene oxide sheet can be removed first, the severity of the reaction can be alleviated, and the direct carbonization treatment can be prevented, and a large number of oxygen-containing functional groups can be simultaneously shed and rapidly produce gas, resulting in bubbling, delamination, fracture or burning of the film material.

[0015] The second object of the present application is to provide a coating device for reducing graphene oxide film, the coating device comprising: The drum comprises an outer shell and an inner liner sleeved in the outer shell, and an air gap exists between the inner liner and the outer shell; An air inlet is arranged on the shell; The inner tank comprises an inner tank wall and a bottom plate. The bottom plate is connected to a motor, and the motor drives the inner tank to rotate. A drainage outlet is also arranged on the bottom plate.

[0016] The third object of the present application is to provide a reduced graphene oxide film, which is prepared by any one of the preparation methods described in the first object of the present application or prepared by coating using the coating device provided by the second object of the present application.

[0017] The beneficial effects of this application are: 1. The present application uses centrifugal force to spread the graphene oxide slurry through high-speed rotation of the drum to improve the orderliness and density of the self-assembly of the reduced graphene oxide film, and through rapid cooling and shaping and freeze drying, it can avoid the shedding of some oxygen-containing functional groups during the heat drying process, which is beneficial to the self-assembly of the reduced graphene oxide film.

[0018] 2. This application uses low-solid graphene oxide slurry with low viscosity and good fluidity, which not only saves raw materials but also helps the rapid film formation of graphene oxide, greatly improving the utilization rate of raw materials.

[0019] 3. The reduced graphene oxide film prepared by the preparation method provided in this application has high thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0021] Figure 1 This is a structural diagram of a coating device for reducing graphene oxide film as shown in Example 1 of the present application; Figure 2 A structural diagram of the coating device for reducing graphene oxide film shown in Example 1 of the present application from another angle; Figure 3 This is a schematic diagram of coating the reduced graphene oxide film shown in Example 2 of the present application; Figure 4 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Example 2 of the present application; Figure 5 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Example 3 of the present application; Figure 6 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Example 4 of the present application; Figure 7 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Example 5 of the present application; Figure 8 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Example 6 of the present application; Fig. 9 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Example 7 of the present application; Fig.10 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Example 8 of the present application; Fig.11 This is a test graph of the thermal diffusion coefficient of the reduced graphene oxide film prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0022] The following detailed description of the exemplary embodiments of the present application refers to the accompanying drawings, which form a part of the description, and in which the exemplary embodiments that can be implemented by the present application are shown as examples, wherein the features of the present application are identified by the figure numerals. The following more detailed description of the embodiments of the present application is not intended to limit the scope of the present application as required, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present application, so as to propose the best way to perform the present application, and is sufficient to enable those skilled in the art to implement the present application. However, it should be understood that various modifications and variations can be made without departing from the scope of the present application as defined by the appended claims. The detailed description and the accompanying drawings should be considered only as illustrative, not restrictive, and if there are any such modifications and variations, they will all fall within the scope of the present application described herein. In addition, the background technology is intended to illustrate the current status and significance of the research and development of the present technology, and is not intended to limit the present application or the application field of the present application and the present application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0024] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0025] In order to make the technical problems, technical solutions and advantages to be solved by the present application clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0026] In the present application, the thermal diffusion coefficient test method is the method described in the standard Q / GDMR 04-2023 "Laser flash method for testing thermal conductivity". Example 1

[0027] This embodiment provides a coating device for reducing graphene oxide film, and its specific structure is as follows Figure 1 , Figure 2 .

[0028] The coating device includes: The drum comprises an outer shell 1 and an inner liner 2 which is sleeved in the outer shell 1, and there is an air gap 3 between the inner liner and the outer shell An air inlet 11 is provided on the housing 1; The inner tank 2 includes an inner tank wall 21 and a bottom plate 22 . The bottom plate 22 is connected to a motor 4 . The motor 4 drives the inner tank 2 to rotate. Furthermore, a drain port 221 is provided on the bottom plate 22 .

[0029] During the coating process, a coating substrate is arranged on the inner wall of the drum inner tank, the motor 4 drives the inner tank 2 to rotate, and an external nozzle (not shown) fixes the spraying angle to spray the graphene oxide slurry on the coating substrate; at the same time, a refrigerator (not shown) introduces a cold flow into the drum air gap 3 through the air inlet 11 so that the inner wall of the drum has a low temperature environment, and the graphene oxide slurry is deposited by centrifugal spin coating under the high-speed rotation of the inner tank. Under the action of high-speed centrifugal force, most of the water is thrown out in the drain port, thereby completing the coating and shaping of the graphene oxide film. Example 2

[0030] This embodiment provides a method for preparing a reduced graphene oxide film: S1. Weigh a certain mass of graphene oxide cake (purchased from Yuntian Mo Rui Technology), use water as solvent, add ammonia water, adjust the pH of the solution to 7, prepare graphene oxide slurry with a solid content of 3%, and disperse it through a planetary stirring equipment. Set the stirring rate at 1500r / min, the dispersion rate at 2000r / min, and the stirring and dispersion time for 2h. Then, the composite slurry is homogenized at a pressure of 1000bar for 3h, and then defoaming is performed for 3h to obtain graphene oxide slurry.

[0031] S2, such as Figure 3As shown, a peristaltic pump is used to pump the slurry in step S1 to the sprayer, an atomizing nozzle 5 is used, the drum rotates clockwise, the atomizing nozzle 5 is parallel to the center of the drum, and the atomizing nozzle 5 is located at the 1 / 2 radius position on the left side of the center of the drum and sprays in the direction of A to obtain a greater relative spraying speed, and a vortex tube refrigerator is used to introduce the cold flow into the drum air gap 3 through the air inlet (the vortex tube is purchased from Taobao, the vortex tube specification is 10-100cfm, and the maximum air flow rate is 10-100 cubic feet per minute), the air inlet end of the vortex tube is connected to the air compressor of the refrigerator, and high-pressure air is introduced to obtain a low temperature of -50°C~0°C at the cold air outlet end, which is used for freezing and shaping the graphene oxide spin-coated film), so that the temperature of the inner wall of the drum is controlled to -35°C, and the atomized graphene oxide slurry is subjected to deposition-type centrifugal spin coating at a speed of 2000rpm / min. Under the action of high-speed centrifugal force, most of the water is discharged in the drainage. The graphene oxide sheets are thrown out from the port 221, and the graphene oxide sheets obtain a high relative sliding speed with the substrate under the condition of high-speed centrifugal spin coating, so that the graphene oxide sheets have a better paving effect; and due to the centrifugal throwing out of water, the graphene oxide sheets are arranged more densely; cold wall freezing shaping is relatively thermal evaporation shaping, which can ensure that the graphene oxide sheets retain all the oxygen-containing groups in the drying process, which is conducive to the subsequent self-assembly reaction. This is mainly attributed to the fact that the atomized graphene oxide sheets are deposited in a single layer or a few layers. The single layer or a few layers of graphene oxide sheets are very sensitive to temperature, which can easily lead to the loss of oxygen-containing groups carried by the graphene oxide sheets; finally, a frozen-shaped graphene oxide film is obtained by cold wall freezing shaping for 10 minutes, and the obtained frozen-shaped graphene oxide film is quickly transferred into a freeze dryer, the freeze drying temperature is set to -5°C, and the freeze drying time is set to 48h, and finally a dry graphene oxide film is obtained.

[0032] S3, pre-treating the graphene oxide dry film in step S2, placing it in a blast oven, heating it from room temperature to 250°C, with a heating rate of 1°C / min; then carbonizing it, with a carbonization temperature of 1200°C, a heating rate of 5°C / min, and keeping it warm for 1h; finally, graphitizing it, with a graphitization temperature of 3100°C, a heating rate of 30°C / min, and keeping it warm for 1h.

[0033] S4, the film in step S3 is subjected to calendering treatment, the calendering pressure is 170 MPa, and finally a reduced graphene oxide film is obtained. The reduced graphene oxide film is subjected to a thermal diffusion test. The test results are as follows: Figure 4 As shown, the thermal diffusion coefficient is 924.507 mm 2 / s. Example 3

[0034] The difference between this embodiment and embodiment 2 is that the solid content of the graphene oxide slurry in step S1 is adjusted to 1.5%, and the other steps are the same as those in embodiment 2. The test results are as follows: Figure 5As shown, the thermal diffusion coefficient of the film is 932.810 mm 2 / s, compared with Example 2, due to the small solid content and low slurry viscosity, it is easier to spread by centrifugation, the self-assembly order is better, and the thermal diffusion coefficient is higher. Example 4

[0035] The difference between this embodiment and embodiment 2 is that the solid content of the graphene oxide slurry in step S1 is adjusted to 5%, and the other steps are the same as those in embodiment 2. The test results are as follows: Figure 6 As shown, the thermal diffusion coefficient of the film is 914.638 mm 2 / s, compared with Example 2, due to the higher solid content and viscosity of the slurry, the fluidity is relatively weaker and the thermal diffusion coefficient is slightly reduced.

[0036] In Example 2-4, the solid content of the graphene oxide slurry is controlled at 1% to 5%, and the reduced graphene oxide films prepared therefrom have a thickness of 900 mm. 2 / s or above thermal diffusivity. Example 5

[0037] The difference between this embodiment and embodiment 2 is that the rotation speed in step S2 is adjusted to 500 rpm / min, and the other steps are the same as those in embodiment 2. The test results are as follows: Figure 7 As shown, the thermal diffusion coefficient of the film is 906.305 mm 2 / s, compared with Example 2, the drum speed is reduced, the corresponding centrifugal force is reduced, the density of the reduced graphene oxide film is lower than that of Example 2, and the thermal diffusion coefficient is also slightly reduced. Example 6

[0038] The difference between this embodiment and embodiment 2 is that the rotation speed in step S2 is adjusted to 5000 rpm / min, and the other steps are the same as those in embodiment 2. The test results are as follows: Figure 8 As shown, the thermal diffusion coefficient of the film is 936.938 mm 2 / s, compared with Example 2, the drum speed is increased, the centrifugal force is increased, the GO membrane layer is denser, the arrangement is more orderly, and the thermal diffusion is higher.

[0039] By controlling the rotation speed of the drum at 300-5000 rpm / min through Examples 2, 5-6, the graphene oxide sheet can obtain a high relative speed with the substrate under high-speed centrifugal spin coating conditions, so that the graphene oxide sheet has a better paving effect, so that the prepared reduced graphene oxide film has a thickness of 900 mm. 2 / s or above thermal diffusivity. Example 7

[0040] The difference between this embodiment and embodiment 2 is that in step S2, the inner wall temperature of the drum is controlled to -5°C, and finally a frozen-set graphene oxide film is obtained by cold wall freezing and setting for 50 minutes. The obtained frozen-set graphene oxide film is quickly transferred into a freeze dryer, the freeze drying temperature is set to -20°C, the freeze drying time is set to 12 hours, and finally a dry graphene oxide film is obtained. The other steps are the same as those in embodiment 2. The test results are as follows: Fig. 9 As shown, the thermal diffusion coefficient of the prepared reduced graphene oxide film is 929.458 mm 2 / s. Example 8

[0041] The difference between this embodiment and embodiment 2 is that step S3 is specifically as follows: The graphene oxide dry film in step S2 was pretreated by placing it in a blast oven and heating it from room temperature to 340°C at a heating rate of 1°C / min; then carbonization was performed at a carbonization temperature of 1500°C, a heating rate of 5°C / min, and the temperature was kept for 1h; finally, graphitization was performed at a graphitization temperature of 2850°C, a heating rate of 30°C / min, and the temperature was kept for 1h. The remaining steps were consistent with Example 2, and the test results were as follows: Fig.10 As shown in Figure 2, the thermal diffusion coefficient of the prepared reduced graphene oxide film is 893.645 mm 2 / s. Comparative Example 1

[0042] Unlike Example 2, in step S2 of Comparative Example 1, the graphene oxide film is thermally evaporated and dried. The specific steps of Comparative Example 1 are as follows: Unlike Example 1, the hot air end of the vortex tube is introduced into the outer interlayer of the drum, so that the inner wall temperature of the drum reaches 80°C, and the thermal evaporation is performed for 10 minutes to obtain the GO film. The remaining steps are consistent with Example 2. The test results are as follows: Fig.11 As shown, the thermal diffusion coefficient of the prepared reduced graphene oxide film is 756.581 mm 2 / s. This is mainly attributed to the deposition of atomized graphene oxide sheets in a single layer or a few layers. The single layer or a few layers of graphene oxide sheets are very sensitive to temperature. Thermal evaporation causes the loss of oxygen-containing groups carried by the graphene oxide sheets. The self-assembly ability of the reduced graphene oxide film is weakened during the subsequent heat treatment, thereby reducing the thermal conductivity of the reduced graphene oxide film.

[0043] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0044] The above is a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a reduced graphene oxide film, characterized in that: The preparation method comprises the following steps: (1) Preparation of graphene oxide slurry; (2) preparing a drum, placing a coating substrate in the drum, spraying the graphene oxide slurry on the coating substrate while the drum is rotating, and obtaining a graphene oxide film after shaping; (3) The graphene oxide film is subjected to carbonization, graphitization and calendering treatment to obtain a reduced graphene oxide film.

2. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The rotating speed of the drum is 300-5000 rpm / min.

3. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: In step (2), the graphene oxide slurry is sprayed by atomization spraying.

4. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The solid content of the graphene oxide slurry is 1% to 5%.

5. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The shaping method of the graphene oxide film is cold wall freezing shaping, the temperature of the cold wall freezing shaping is -50°C to 0°C, and / or the cold wall freezing shaping time is 5 to 60 minutes.

6. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: After the graphene oxide film is shaped, a step of drying the graphene oxide film is also included. The drying method of the graphene oxide film is freeze drying. The freeze drying temperature is less than 0° C., and / or the freeze drying time is 8-48 hours.

7. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: The carbonization treatment temperature of the graphene oxide film is 900-1600°C, and the graphitization treatment temperature of the graphene oxide film is 2800-3200°C.

8. The method for preparing a reduced graphene oxide film according to claim 1, characterized in that: Before the carbonization treatment, a pretreatment is also included, and the pretreatment temperature is 200-360°C.

9. A coating device for reducing graphene oxide film, characterized in that: The coating device comprises: A drum, comprising an outer shell and an inner liner sleeved in the outer shell, with an air gap between the inner liner and the outer shell; The housing is provided with an air inlet; The inner tank comprises an inner tank wall and a bottom plate. The bottom plate is connected to a motor, and the motor drives the inner tank to rotate. A drainage port is arranged on the bottom plate.

10. A reduced graphene oxide film, characterized in that: The method according to any one of claims 1 to 8 is prepared or the coating device according to claim 9 is used to coat the coating.

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