Graphene oxide film with surface roughness of 0.5-5.0 [mu] m, graphene heat-conducting film with surface roughness of 0.2-1.0 [mu] m and preparation methods of graphene oxide film and graphene heat-conducting film

Abstract

The invention discloses a preparation method of a graphene oxide film with the surface roughness of 0.5-5.0 microns. The preparation method comprises the following steps: (1) coating a base material with graphene oxide slurry; (2) drying the coated graphene oxide to obtain a graphene oxide film; wherein the drying temperature is 20-45 DEG C, the drying air speed is 1-10 m / s, and the drying time is 1.0-60 h. The invention also discloses a graphene oxide film, a graphene heat-conducting film with the surface roughness of 0.2-1.0 mu m and a preparation method of the graphene heat-conducting film. The thermal diffusion coefficient of the finally prepared graphene heat-conducting film is improved.

Description

Technical Field

[0001] The present invention relates to the field of new materials, and in particular to the field of graphene. Background Art

[0002] Graphene oxide is a nanomaterial with a two-dimensional structure, and there are many oxygen-containing functional groups such as hydroxyl (-OH-) and carboxyl (-COOH-) on its surface. Wrinkling is a common phenomenon in two-dimensional materials. Since graphene oxide is atomic-level in thickness and has low out-of-plane stiffness, it will show a wrinkled state when subjected to intermolecular or interfacial interactions. Since the rest of the graphene oxide slurry except graphene oxide is water, graphene oxide is easily affected during the water drying process, resulting in some changes.

[0003] In the prior art, the method for mass production of graphene oxide membranes is continuous coating and drying, the drying method is heating and drying, the heating method is hot air circulation heating, the heating temperature curve is divided into a preheating section and a constant temperature drying section, the preheating section temperature is (50-70)°C, the constant temperature section is (70-110)°C; the heating wind speed is (5-30) m / s, and the water evaporation rate is fast under high temperature and high wind speed. When the graphene oxide dispersion is dried quickly, the surface tension of the liquid increases rapidly, thereby generating a large capillary force on the graphene oxide nanosheets, causing the graphene oxide membrane layer to wrinkle. The distance between the layers will also increase. During the heat transfer process of the prepared graphene thermal conductive film, the phonon scattering effect is enhanced and the heat transfer performance decreases. The production process of graphene thermal conductive film in the prior art can be seen in Figure 1 .

[0004] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the prior art in the field. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a graphene oxide film with a surface roughness of 0.5-5.0 μm, comprising the following steps:

[0006] (1) coating graphene oxide slurry onto a substrate;

[0007] (2) slowly drying the coated graphene oxide at low temperature to obtain a graphene oxide film; wherein the drying temperature is 20-45° C. and the drying wind speed is 1-10 m / s.

[0008] When the temperature is too high and the wind speed is too high, the graphene oxide dispersion dries quickly, and the surface tension of the liquid increases rapidly, which generates a large capillary force on the graphene oxide nanosheets, causing the graphene oxide membrane layer to wrinkle. The distance between the sheets will also increase, which is not conducive to the assembly of the GO membrane. The phonon scattering effect of the prepared graphene thermal conductive film is enhanced during the heat transfer process, and the heat transfer performance decreases, and the thermal diffusion coefficient is low. If the temperature is too low, the coating drying cost is high. The drying time is related to the drying temperature, wind speed, and especially the thickness of the coating slurry. As the thickness increases, the drying time approaches an exponential increase.

[0009] Furthermore, in step (1), the solid content of the graphene oxide slurry is 4-8%, preferably 5-7%, and more preferably 6%. Too high a solid content will result in a high viscosity of the graphene oxide slurry after dispersion, poor fluidity, and difficulty in coating; too low a solid content will result in a high coating and drying cost.

[0010] Furthermore, the viscosity of the graphene oxide slurry in step (1) is 10000-50000 mPa·s, preferably 20000-30000 mPa·s. Too high a viscosity will result in failure to coat or poor appearance and uneven thickness of the coated wet film, while too low a viscosity and too good fluidity will result in failure to form.

[0011] Furthermore, the graphene oxide coated in step (1) has a thickness of 500-5000 μm, preferably 1500-3000 μm; if the thickness is too thick, the water escape channel is blocked, the drying is slow and the appearance is poor. If the thickness is too thin, the equipment precision is insufficient and the film thickness is uneven.

[0012] And / or, the substrate is preferably a polypropylene textile. Polypropylene textile is a breathable material, which is conducive to improving the drying speed.

[0013] Furthermore, in the step (2), the drying temperature is 30-40°C, and the drying wind speed is 3-7m / s.

[0014] Furthermore, in step (2), the drying temperature is 30-35° C., and the drying wind speed is 5 m / s.

[0015] Furthermore, in step (2), the drying time is 1.0-60 h, preferably 1.5-6.0 h, and more preferably 2.0-4.0 h.

[0016] On the other hand, the present invention provides a graphene oxide film with a surface roughness of 0.5-5.0 μm, which is prepared by the graphene oxide film preparation method, and the gram weight of the graphene oxide film is 30-300 g / cm 2 , wherein the weight of the graphene oxide film is preferably 90-150 g / cm2 The surface roughness is preferably 2.0-3.0 μm. The lower the surface roughness of the graphene oxide film, the smaller the surface roughness of the prepared graphene thermal conductive film, and the less likely the graphene thermal conductive film will be delaminated during die cutting.

[0017] On the other hand, the present invention provides a method for preparing a graphene thermally conductive film with a surface roughness of 0.2-1.0 μm, wherein the graphene thermally conductive film is prepared by subjecting the graphene oxide film to heat treatment.

[0018] Furthermore, the heat treatment is performed in a vacuum or inert atmosphere.

[0019] The further heat treatment is carried out in a vacuum or inert atmosphere, including carbonization and graphitization stages;

[0020] The maximum temperature in the carbonization stage is 900-1200°C, preferably 1000-1100°C, and the time is 10-20h, preferably 15-17h; the maximum temperature in the graphitization stage is 2800-3100°C, preferably 2950-3000°C, and the time is 25-35h, preferably 28-32h.

[0021] Furthermore, multiple graphene oxide films are stacked and fired during heat treatment.

[0022] On the other hand, the present invention provides a graphene thermally conductive film with a surface roughness of 0.2-1.0 μm, which is prepared by the above-mentioned method for preparing the graphene thermally conductive film, wherein the graphene thermally conductive film has a thickness of 10-500 μm and a density of 1.8-2.2 g / cm 3 Preferably, the graphene thermal conductive film has a thickness of 30-50 μm and a density of 2.05-2.15 g / cm 3

[0023] and / or, thermal diffusivity 600-1200 mm 2 / s; thermal diffusion coefficient is 850-950mm 2 / s.

[0024] In the present invention:

[0025] 1. When the graphene oxide dispersion is dried quickly, the surface tension of the liquid increases rapidly, thereby generating a large capillary force on the graphene oxide nanosheets, so that the graphene oxide film layer wrinkles, and the distance between the sheets increases. During the heat transfer process of the prepared graphene thermal conductive film, the phonon scattering effect is enhanced but the heat transfer performance decreases. The present invention adopts a slow drying method to greatly reduce the capillary force during the assembly process of the graphene oxide nanosheets, so that the interlayer stacking and assembly between the sheets are more orderly, providing a good path for planar heat conduction, and the thermal diffusion coefficient of the prepared graphene thermal conductive film is increased by 10-30%.

[0026] 2. When drying slowly, the side of the graphene oxide film in contact with the substrate has a more uniform appearance due to the slower evaporation of water, and the surface roughness of the graphene oxide film and graphene thermal conductive film prepared thereby is lower.

[0027] 3. Due to the low surface roughness of the graphene oxide film, the effective contact area between the surfaces is larger when multiple sheets are stacked during heat treatment, the bonding force is greater during thermal reduction foaming, and stratification is not easy to occur during die cutting. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 It is the production flow chart of graphene thermal conductive film;

[0030] Figure 2 is a cross-sectional SEM image of the graphene oxide film at a magnification of 5000x in Example 1;

[0031] Figure 3 is a cross-sectional SEM image of the graphene thermal conductive film at a magnification of 2000x in Example 1;

[0032] Figure 4 is a cross-sectional SEM image of the graphene oxide film at a magnification of 5000x in Example 2;

[0033] Figure 5 is a cross-sectional SEM image of the graphene thermal conductive film at a magnification of 2000x in Example 2;

[0034] Figure 6 is a cross-sectional SEM image of the graphene oxide film at a magnification of 5000x in Example 3;

[0035] Figure 7 is a cross-sectional SEM image of the graphene thermal conductive film at a magnification of 2000x in Example 3;

[0036] Figure 8 This is a cross-sectional SEM image of the graphene oxide film at a magnification of 5000x in Comparative Example 1;

[0037] Fig. 9 This is a cross-sectional SEM image of the graphene thermal conductive film at a magnification of 2000x in Comparative Example 1;

[0038] Fig.10 This is a cross-sectional SEM image of the graphene oxide film at a magnification of 5000x in Comparative Example 2;

[0039] Fig.11 This is a cross-sectional SEM image of the graphene thermal conductive film at a magnification of 2000x in Comparative Example 2;

[0040] Fig.12 This is a cross-sectional SEM image of the graphene oxide film at a magnification of 5000x in Comparative Example 3;

[0041] Fig.13 This is a cross-sectional SEM image of the graphene thermal conductive film in Comparative Example 3 at a magnification of 2000x. DETAILED DESCRIPTION

[0042] In the following description, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0043] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention will have the meanings commonly understood by those of ordinary skill in the art. In addition, unless the context otherwise requires, terms in the singular shall include plural forms, and terms in the plural shall include singular forms. More specifically, as used in this specification and the appended claims, unless the context otherwise clearly indicates, the singular forms "one", "an" and "the" include plural indicators. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "comprising" and other forms (such as "including" and "containing") is not restrictive. In addition, the ranges provided in the specification and the appended claims include all values ​​between the endpoints and the endpoints. The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, and it should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0044] The present invention provides a method for preparing a graphene oxide film, comprising the following steps:

[0045] (1) coating graphene oxide slurry onto a substrate;

[0046] (2) Drying the coated graphene oxide to obtain a graphene oxide film.

[0047] The coating substrate used is a breathable or non-breathable substrate. The breathable material is conducive to improving the drying speed, and a breathable polypropylene textile is preferred;

[0048] The drying temperature is 20-45°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, preferably 30-40°C, more preferably 30-35°C. The drying wind speed is 1-10m / s, such as 1m / s, 2m / s, 3m / s, 4m / s, 5m / s, 6m / s, 7m / s, 8m / s, 9m / s, 10m / s, preferably 3-7m / s, more preferably 5m / s. If the temperature is too high and the wind speed is too high, the graphene oxide dispersion is drying rapidly, and the surface tension of the liquid increases rapidly, thereby generating a large capillary force on the graphene oxide nanosheets, so that the graphene oxide film layer wrinkles, and the distance between the sheets will also increase, which is not conducive to the assembly of the GO membrane. The phonon scattering effect of the prepared graphene thermal conductive film is enhanced during the heat transfer process, the heat transfer performance decreases, and the thermal diffusion coefficient is low. If the temperature is too low, the coating and drying cost is high.

[0049] The coating thickness is 500-5000 μm, for example, 500 μm, 1000 μm, 2000 μm, 3000 μm, 4000 μm, 5000 μm, preferably 1500-3000 μm. If the thickness is too thick, the water escape channel is blocked, the drying is slow and the appearance is likely to be poor. If the thickness is too low, the equipment precision is insufficient, which is likely to cause uneven film thickness.

[0050] The drying time is 1.0-60h, such as 1.0h, 10h, 20h, 30h, 40h, 50h, 60h, preferably 1.5-6.0h, and more preferably 2.0-4.0h. The dryness and humidity of the graphene oxide film are moderate under this time. The drying time is related to the drying temperature, wind speed, and especially the thickness of the coating slurry. As the thickness increases, the drying time increases exponentially.

[0051] The solid content of the graphene oxide slurry is 4-8%, such as 4%, 5%, 6%, 7%, 8%, preferably 5-7%, and more preferably 6%. Too high a solid content will result in a high viscosity of the graphene oxide slurry after dispersion, poor fluidity, and difficulty in coating; too low a solid content will result in a high coating and drying cost.

[0052] Solid content refers to the mass percentage of the remaining part of the slurry after drying under specified conditions.

[0053] The viscosity of the graphene oxide slurry is 10000-50000 mPa·s, such as 10000 mPa·s, 20000 mPa·s, 30000 mPa·s, 40000 mPa·s, 50000 mPa·s, preferably 20000-30000 mPa·s. Too high viscosity will result in failure to coat or poor appearance and uneven thickness of the coated wet film, while too low viscosity and too good fluidity will result in failure to form.

[0054] In some embodiments of the present invention, a graphene oxide film is provided.

[0055] The weight of graphene oxide film is 30-300g / cm 2 , for example 30g / cm 2 , 100g / cm 2 , 150g / cm 2 , 200g / cm 2 , 250g / cm 2 , 300g / cm 2 , preferably 90-150g / cm 2 ;

[0056] In this application, gram weight is also known as surface density, which is the weight per unit area, and the unit is g / cm 2 .

[0057] The surface roughness Ra of the graphene oxide film is 0.5-5.0 μm; for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm; preferably 2.0-3.0 μm. The lower the surface roughness of the graphene oxide film, the smaller the surface roughness of the prepared graphene thermal conductive film, and the less likely the graphene thermal conductive film will be delaminated during die cutting.

[0058] In some embodiments of the present invention, a graphene thermal conductive film is provided, which is obtained by heat treating the above-mentioned graphene oxide film. The heat treatment process is to reduce the graphene oxide film to a graphene film at a high temperature. The heat treatment methods in the prior art for reducing the graphene oxide film to a graphene film are all applicable to the present invention.

[0059] A specific heat treatment method is listed below:

[0060] The heat treatment method of the present invention needs to be carried out in a vacuum or inert atmosphere in order to prevent the oxidizing gas in the air, such as oxygen, from reoxidizing the already reduced graphene, thereby hindering the reduction reaction. The inert atmosphere is achieved by introducing an inert gas; the inert gas is a gas that does not react with graphene oxide and graphene, preferably one or a combination of at least two of nitrogen, helium, neon, argon, krypton, xenon, and radon, such as a combination of nitrogen and argon, a combination of helium and argon, a combination of neon / argon / helium, etc., further preferably nitrogen and / or argon, and most preferably nitrogen with a purity of 99.999% and / or argon with a purity of 99.99%.

[0061] Preferably, the flow rate of the inert gas is 50-150 cm 3 / min, preferably 100cm 3 / min. The realization of the inert atmosphere is a technique well known to those skilled in the art. For example, the reaction container may be evacuated to a high vacuum degree at one time, and then the inert gas may be introduced; or the reaction container may be evacuated first, and then the inert gas may be introduced, and the steps may be repeated until the oxidizing gas in the reaction container is completely exhausted.

[0062] The heat treatment includes carbonization and graphitization stages;

[0063] Among them, the maximum temperature of the carbonization stage is 900-1200°C, preferably 1000-1100°C, and the time is 10-20h, preferably 15-17h; the maximum temperature of the graphitization stage is 2800-3100°C, preferably 2950-3000°C, and the time is 25-35h, preferably 28-32h.

[0064] The thickness of the graphene thermal conductive film is 10-500μm, for example, 10μm, 100μm, 200μm, 300μm, 400μm, 500μm; preferably 30-50μm; if the thickness of the graphene thermal conductive film is too low, it is easy to be damaged during the production process. To produce a high-thickness graphene thermal conductive film, multiple sheets of graphene oxide films need to be stacked during the heat treatment process. If the graphene thermal conductive film prepared by this method is too thick, the interlayer bonding force is weak, and stratification is easy to occur in the subsequent die-cutting process.

[0065] The density of graphene thermal conductive film is 1.8-2.2g / cm 3 , for example 1.8 g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , preferably 2.05-2.15g / cm 3 ; The density is too low and the thermal conductivity is low;

[0066] The thermal diffusion coefficient of graphene thermal conductive film is 800-1200mm 2 / s, for example 800mm 2 / s、900mm 2 / s、1000mm 2 / s、1100mm 2 / s、1200mm 2 / s, preferably 850-950mm 2 / s; the higher the thermal diffusion, the better the thermal conductivity;

[0067] The surface roughness of the graphene thermal conductive film is 0.2-1.0 μm, for example, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, preferably 0.5 μm; the lower the roughness, the better; if the roughness is too high, the appearance is poor and it is not conducive to subsequent die-cutting processing.

[0068] The present invention is further illustrated by the following examples and comparative examples.

[0069] A single graphene oxide film is stacked, that is, a graphene oxide film is stacked with a graphite paper, and then heat-treated. After the heat treatment, a graphene film made of a graphene oxide film is obtained.

[0070] Multiple graphene oxide films are stacked and fired, that is, multiple graphene oxide films are stacked and then a piece of graphite paper is added. After heat treatment, the stacked multiple graphene oxide films are made into a thick graphene film.

[0071] The thermal diffusion coefficient of the graphene film decreases as the number of graphene oxide films increases when multiple graphene oxide films are stacked and fired.

[0072] The roughness test method refers to the standard ISO 4287-1997.

[0073] Thermal diffusivity test reference standard ASTM E 1461.

[0074] Embodiment 1:

[0075] This embodiment shows a graphene oxide film and a graphene thermal conductive film, and the preparation parameters thereof are as follows:

[0076] 1) coating a graphene oxide slurry with a solid content of 4% and a viscosity of 10000 mPa·s on a substrate; the coating substrate is an airtight PET film; the thickness of the graphene oxide slurry is 1.0 mm;

[0077] 2) Drying the coated graphene oxide to obtain a graphene oxide film. The drying temperature is 20°C, the wind speed is 1m / s, and the drying time is 4h;

[0078] 3) The heat treatment method is stacking and firing of a single graphene oxide film;

[0079] 4) The weight of graphene oxide film is 30g / cm 2 , surface roughness is 0.5μm;

[0080] 5) Calendering the graphene oxide film after heat treatment to obtain a graphene thermal conductive film with a thickness of 10 μm and a density of 1.8 g / cm 3 , thermal diffusivity is 1200mm 2 / s, surface roughness is 0.2μm.

[0081] The cross-sectional SEM images of the graphene oxide film and the graphene film prepared in this embodiment are shown in Figure 2 , Figure 3 It can be seen that the graphene oxide film and the graphene thermal conductive film are assembled in an orderly manner, the layers are very tightly combined, and the wrinkles are small.

[0082] Embodiment 2:

[0083] This embodiment shows a graphene oxide film and a graphene thermal conductive film, and the preparation parameters thereof are as follows:

[0084] 1) coating a graphene oxide slurry with a solid content of 6% and a viscosity of 25000 mPa·s on a substrate; the coated substrate is a polypropylene textile breathable material; the graphene oxide slurry has a thickness of 2.5 mm;

[0085] 2) Drying the coated graphene oxide to obtain a graphene oxide film. The drying temperature is 45°C, the wind speed is 5m / s, and the drying time is 4h;

[0086] 3) The heat treatment method is to stack and burn 6 graphene oxide films;

[0087] 4) The weight of graphene oxide film is 150g / cm 2 , surface roughness is 2.5μm;

[0088] 5) Calendering the graphene oxide film after heat treatment to obtain a graphene thermal conductive film with a thickness of 250 μm and a density of 2.2 g / cm 3 , thermal diffusivity is 850mm 2 / s, surface roughness is 0.5μm.

[0089] The cross-sectional SEM images of the graphene oxide film and the graphene film prepared in this embodiment are shown in Figure 4 , Figure 5 It can be seen that the graphene oxide film and the graphene thermal conductive film are assembled in an orderly manner, the layers are very tightly combined, and the wrinkles are small.

[0090] Embodiment 3:

[0091] This embodiment shows a graphene oxide film and a graphene thermal conductive film, and the preparation parameters thereof are as follows:

[0092] 1) coating a graphene oxide slurry with a solid content of 8% and a viscosity of 50000 mPa·s on a substrate; the coated substrate is a polyester textile breathable material; the thickness of the graphene oxide slurry is 5.0 mm;

[0093] 2) Drying the coated graphene oxide to obtain a graphene oxide film. The drying temperature is 35°C, the wind speed is 10m / s, and the drying time is 25h;

[0094] 3) The heat treatment method is to stack and sinter 6 graphene oxide films;

[0095] 4) The weight of graphene oxide film is 300g / cm 3 , surface roughness is 5.0μm;

[0096] 5) Calendering the graphene oxide film after heat treatment to obtain a graphene thermal conductive film with a thickness of 500 μm and a density of 2.1 g / cm 3 , thermal diffusivity is 600mm 2 / s, surface roughness is 1.0μm.

[0097] The cross-sectional SEM images of the graphene oxide film and the graphene film prepared in this embodiment are shown in Figure 6 , Figure 7 It can be seen that the graphene oxide film and the graphene thermal conductive film are assembled in an orderly manner, the layers are very tightly combined, and the wrinkles are small.

[0098] Comparative Example 1:

[0099] This comparative example shows a graphene oxide film and a graphene thermal conductive film, and the preparation parameters thereof are as follows:

[0100] 1) coating a graphene oxide slurry with a solid content of 8% and a viscosity of 20000 mPa·s on a substrate; the coating substrate is a polypropylene breathable material; the thickness of the graphene oxide slurry is 1.5 mm;

[0101] 2) Drying the coated graphene oxide to obtain a graphene oxide film. The drying temperature is 100°C, the wind speed is 20m / s, and the drying time is 30min;

[0102] 3) The heat treatment method is stacking and firing of a single graphene oxide film;

[0103] 4) The weight of graphene oxide film is 300g / cm 3 , surface roughness is 10.0μm;

[0104] 5) Calendering the graphene oxide film after heat treatment to obtain a graphene thermal conductive film with a thickness of 40 μm and a density of 2.0 g / cm 3 , thermal diffusivity is 500mm 2 / s, surface roughness is 3.0μm.

[0105] The cross-sectional SEM images of the graphene oxide film and the graphene film prepared in this comparative example are shown in Figure 8 , Fig. 9 It can be seen that the wrinkles of the graphene oxide film and the graphene thermal conductive film are obvious.

[0106] Comparative Example 2:

[0107] This embodiment shows a graphene oxide film and a graphene thermal conductive film, and the preparation parameters thereof are as follows:

[0108] 1) coating a graphene oxide slurry with a solid content of 4% and a viscosity of 10000 mPa·s on a substrate; the coating substrate is an airtight PET film; the thickness of the graphene oxide slurry is 1.0 mm;

[0109] 2) Drying the coated graphene oxide to obtain a graphene oxide film. The drying temperature is 20°C, the wind speed is 30m / s, and the drying time is 1.5h;

[0110] 3) The heat treatment method is stacking and firing of a single graphene oxide film;

[0111] 4) The weight of graphene oxide film is 30g / cm 2 , surface roughness is 2.5μm;

[0112] 5) Calendering the graphene oxide film after heat treatment to obtain a graphene thermal conductive film with a thickness of 10 μm and a density of 1.8 g / cm 3 , thermal diffusivity is 900mm 2 / s, surface roughness is 1.0μm.

[0113] The cross-sectional SEM images of the graphene oxide film and the graphene film prepared in this embodiment are shown in Fig.10 , Fig.11 It can be seen that the wrinkles of the graphene oxide film and the graphene thermal conductive film are obvious.

[0114] Comparative Example 3:

[0115] This embodiment shows a graphene oxide film and a graphene thermal conductive film, and the preparation parameters thereof are as follows:

[0116] 1) coating a graphene oxide slurry with a solid content of 4% and a viscosity of 10000 mPa·s on a substrate; the coating substrate is an airtight PET film; the thickness of the graphene oxide slurry is 1.0 mm;

[0117] 2) Drying the coated graphene oxide to obtain a graphene oxide film. The drying temperature is 55°C, the wind speed is 5m / s, and the drying time is 1h;

[0118] 3) The heat treatment method is stacking and firing of a single graphene oxide film;

[0119] 4) The weight of graphene oxide film is 30g / cm 2 , surface roughness is 3.0μm;

[0120] 5) Calendering the graphene oxide film after heat treatment to obtain a graphene thermal conductive film with a thickness of 10 μm and a density of 1.8 g / cm3 , thermal diffusivity is 850mm 2 / s, surface roughness is 0.8μm.

[0121] The cross-sectional SEM images of the graphene oxide film and the graphene film prepared in this embodiment are shown in Fig.12 , Fig.13 It can be seen that the wrinkles of the graphene oxide film and the graphene thermal conductive film are obvious.

[0122] It can be seen from the examples and comparative examples that the surface roughness of the graphene oxide film dried at low temperature in the examples is reduced, the interlayer bonding is tight, the graphene oxide layer has fewer wrinkles, and the interlayer spacing is lower. The graphene film made from the graphene oxide film in the examples of the present application has a higher thermal diffusion coefficient and reduced surface roughness.

[0123] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a graphene oxide film with a surface roughness of 0.5-5.0 μm, characterized in that: The following steps are involved: (1) coating graphene oxide slurry onto a substrate; (2) slowly drying the coated graphene oxide at low temperature to obtain a graphene oxide film; wherein the drying temperature is 20-45° C. and the drying wind speed is 1-10 m / s.

2. The method for preparing a graphene oxide film according to claim 1, wherein: In step (1), the solid content of the graphene oxide slurry is 4-8%, preferably 5-7%, and more preferably 6%. And / or, the viscosity of the graphene oxide slurry in step (1) is 10000-50000 mPa·s, preferably 20000-30000 mPa·s; And / or, the graphene oxide slurry coated in step (1) has a thickness of 500-5000 μm, preferably 1500-3000 μm; And / or, the substrate is preferably a polypropylene textile.

3. The method for preparing a graphene oxide film according to claim 1, characterized in that: In the step (2), the drying temperature is 30-40°C, and the drying wind speed is 3-7 m / s.

4. The method for preparing a graphene oxide film according to claim 3, characterized in that: In the step (2), the drying temperature is 30-35°C and the drying wind speed is 5m / s.

5. The method for preparing a graphene oxide film according to claim 4, characterized in that: In the step (2), the drying time is 1.0-60 h, preferably 1.5-6.0 h, and more preferably 2.0-4.0 h.

6. A graphene oxide film having a surface roughness of 0.5-5.0 μm, characterized in that: The graphene oxide film is prepared by the method for preparing the graphene oxide film according to any one of claims 1 to 5, wherein the gram weight of the graphene oxide film is 30-300 g / cm 2 ; Wherein, the gram weight of the graphene oxide film is preferably 90-150g / cm 2 ; And / or, the surface roughness of the graphene oxide film is preferably 2.0-3.0 μm.

7. A method for preparing a graphene thermally conductive film with a surface roughness of 0.2-1.0 μm, characterized in that: The graphene thermal conductive film is obtained by subjecting the graphene oxide film described in claim 6 to heat treatment.

8. The method for preparing the graphene thermally conductive film according to claim 7, characterized in that: The thermal diffusion coefficient of the graphene thermal conductive film is 600-1200 mm 2 / s.

9. The method for preparing the graphene thermally conductive film according to claim 8, characterized in that: During the heat treatment, multiple graphene oxide films are stacked and fired.

10. A graphene thermal conductive film with a surface roughness of 0.2-1.0 μm, characterized in that: The method according to any one of claims 7 to 9 is used to prepare the graphene thermal conductive film, wherein the graphene thermal conductive film has a thickness of 10-500 μm and a density of 1.8-2.2 g / cm 3 ; Among them, the preferred thickness of the graphene thermal conductive film is 30-50 μm and the density is 2.05-2.15 g / cm 3 ; and / or, thermal diffusivity 600-1200 mm 2 / s; the thermal diffusion coefficient is preferably 850-950mm 2 / s.

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