Graphene oxide film and preparation method thereof
By coating graphene oxide liquid film onto an unsaturated hydrogel substrate and combining it with multi-step heat treatment, the compromise between thickness and strength/thermal conductivity in the preparation of graphene oxide films was solved, enabling rapid assembly and the preparation of high-performance graphene films suitable for large-scale production.
Patent Information
- Application Number
- CN202511065992.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-31
- Publication Date
- 2025-11-11
AI Technical Summary
Existing methods for preparing graphene oxide films involve compromises between thickness and strength/thermal conductivity, making it difficult to meet the needs of large-scale commercial production, and the assembly time is too long.
Using unsaturated hydrogel as a supporting substrate, a graphene oxide dispersion was coated and the drying process was accelerated by natural evaporation and interfacial penetration of water. Subsequently, multilayer stacking and multi-step heat treatment were carried out to prepare a high-quality graphene film.
Rapid assembly of graphene oxide films was achieved, reducing wrinkles, improving structural regularity and electrical and thermal conductivity, making them suitable for large-scale production and expanding the assembly strategies for two-dimensional materials.
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Figure CN120922860A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of two-dimensional material assembly technology, and in particular to a graphene oxide film and its preparation method. Background Technology
[0002] Graphene films, as an emerging material in the field of heat dissipation for electronic devices, are highly favored due to their numerous advantages, including high thermal conductivity, light weight, good flexibility, low coefficient of thermal expansion, and stable physicochemical properties. They are generally derived from the reduction of graphene oxide films. Currently, the preparation process of graphene oxide films is relatively mature, mainly obtained through various bottom-up macroscopic assembly methods, such as: blade coating, filtration, electrophoresis, wet spinning, and centrifugal casting. Among them, blade coating can be used for large-scale continuous preparation. A uniform and stable graphene oxide dispersion is blade-coated onto a hard substrate (e.g., PET release film, glass plate) and then naturally dried. This method is simple to operate, and the geometric dimensions of the film can be controlled, but the thickness is generally thin, only on the order of a few micrometers.
[0003] However, because the concentration of the graphene oxide dispersion is low, and the rest is water except for the graphene oxide, hydrogen bonds exist between the graphene oxide sheets and water molecules, causing cross-linking between the sheets. This results in a very thin skin layer forming on the surface of the spread graphene oxide liquid film during natural drying due to the "skin effect," while the interior remains in a solution state. This "liquid skin" significantly slows down the evaporation of water inside the liquid film. Therefore, the preparation of thick graphene oxide films by the blade coating method usually requires a long time, which is not conducive to mass production in factories. In addition, to obtain thicker films (>50 μm), it is necessary to increase the concentration of the graphene oxide dispersion or the thickness of the blade-coated liquid film. However, this not only requires a longer drying time, but also results in a thick film structure with a large number of pores and disordered sheet orientation, which significantly reduces thermal and electrical conductivity.
[0004] Ideally, macroscopically assembled thick graphene oxide films should possess the following key characteristics: (1) short assembly time to meet the requirements of large-scale commercialization; (2) adjustable thickness to achieve thicknesses from nanometers to hundreds of micrometers, or even millimeters, to adapt to various applications; and (3) certain mechanical strength to ensure long-term structural stability. Traditional blade coating methods are difficult to simultaneously achieve multiple expectations through optimized operation processes. Among them, the ultra-long assembly time is the main obstacle to expanding the application of graphene oxide films. In order to quickly assemble graphene oxide films, researchers have also conducted many explorations. For example, by using the method of quenching high-temperature metals in liquid carbon sources, graphene films with a thickness of nanometers can be prepared in just a few seconds; intercalating agents can also be introduced between graphene oxide sheets to expand water "channels" and accelerate the drying of the film; in addition, by using the liquid / liquid interface of hydrogels and silicone oils, graphene oxide nanosheets can also be rapidly spread into films under the action of strong shear flow. Although the above methods can shorten the assembly time, they often lead to compromises in thickness and physical properties (such as strength and thermal conductivity), and some are not suitable for industrialization. Summary of the Invention
[0005] This invention addresses the problem that current graphene film preparation methods lead to compromises in thickness and strength / thermal conductivity, and some are not suitable for large-scale economic production, by providing a method for preparing graphene oxide films.
[0006] One technical solution of this invention provides a method for preparing a graphene oxide film, comprising: preparing an unsaturated hydrogel and a graphene oxide dispersion respectively; using the unsaturated hydrogel as a supporting substrate; coating the graphene oxide dispersion onto the supporting substrate to obtain a graphene oxide liquid film; bonding the graphene oxide liquid film with the supporting substrate to form a graphene oxide gel; separating the graphene oxide gel from the supporting substrate to obtain a near-dry graphene oxide gel; stacking the near-dry graphene oxide gel in multiple layers to obtain a multilayer graphene oxide gel; and heat-treating the near-dry graphene oxide gel to obtain a graphene oxide film; alternatively, a thick graphene oxide film can be obtained by heat-treating the multilayer graphene oxide gel. The preparation processes for both the thick and thick graphene oxide films are the same, except that the thick film is thicker. In other words, a thick graphene oxide film is simply a relatively thick graphene oxide film, generally referring to a graphene oxide film with a thickness greater than 50 micrometers.
[0007] Specifically, this invention utilizes the natural evaporation and interfacial penetration of water to rapidly assemble graphene oxide sheets. The nearly dry graphene oxide film is then peeled off from the hydrogel surface, completely dried by heating, and finally thermally reduced to prepare a graphene film with electrical and thermal conductivity. An unsaturated hydrogel is used as the supporting substrate for coating. Compared to traditional hard substrates, the elastic modulus of the hydrogel is between that of a liquid and a solid. On the one hand, its elastic deformation can counteract capillary forces during drying, reducing wrinkle formation; on the other hand, its hydrophilicity and smoother surface facilitate the diffusion and spreading of the liquid film. During the drying process, a small portion of the water in the graphene oxide liquid film evaporates naturally through exposure to air on the upper surface; the remainder penetrates through the bottom interface with the unsaturated hydrogel. The nearly dry graphene oxide film is then peeled off, completely dried by heating, and finally thermally reduced to obtain a high-quality graphene film. This invention features a simple, efficient, and low-cost process, enabling large-scale continuous production. Compared to traditional coating, the prepared graphene oxide film has fewer wrinkles, a more regular structure, and superior thermal and electrical conductivity after thermal reduction.
[0008] Another embodiment of the present invention is as follows: The preparation of the unsaturated hydrogel includes slowly adding acrylamide, ammonium persulfate, N,N-methyleneacrylamide and sodium polyacrylate powder to deionized water in sequence according to a certain ratio, stirring, dissolving, mixing and degassing, pouring into a mold, and heating in an oven to form a hydrogel with regular shape, smooth surface, colorless and transparent, good elasticity and water absorption.
[0009] The ratio of acrylamide, ammonium persulfate, N,N-methyleneacrylamide, and sodium polyacrylate powder is 100:2:5:5. Dissolution requires 30 minutes of stirring, followed by 15 minutes of mixing and degassing. The heating and molding temperature is 60°C, and the molding time is 5 hours. The unsaturated hydrogel is hygroscopic; to achieve this characteristic, the amount of deionized water used can be reduced before heating and molding, or the saturated hydrogel can be heated to remove water after molding.
[0010] Another embodiment of the present invention is that the water content of the unsaturated hydrogel is 50% to 75% of that in a saturated state.
[0011] Another embodiment of the present invention is as follows: the preparation of the graphene oxide dispersion includes centrifuging and washing aqueous graphene oxide, lyophilizing and calibrating the concentration, and then diluting with deionized water to obtain the graphene oxide dispersion. This assembly method is also applicable to other two-dimensional sheets or two-dimensional / one-dimensional composite systems, such as boron nitride, MXene, graphene oxide / montmorillonite, graphene oxide / carbon nanotubes, etc.
[0012] Another embodiment of the present invention is as follows: the concentration of the graphene oxide dispersion is 8 mg / g, and the average size of the flakes is 10 μm.
[0013] Another embodiment of the present invention is that the thickness of the graphene oxide liquid film is 1 to 5 mm.
[0014] A nearly dry graphene oxide film was obtained by drying the liquid graphene film on an unsaturated hydrogel for a period of time. The film was then peeled off from the surface of the hydrogel and heated in an oven at 60°C for 3 hours to completely dehydrate it.
[0015] Another embodiment of the present invention is: heat treatment of the graphene oxide thick film or graphene oxide film is the drying and thermal reduction of the graphene oxide thick film or graphene oxide thick film, wherein the thermal reduction includes four processes: 1) firstly, the graphene oxide film is hot-pressed using a flat vulcanizing machine at a pressure of 10 MPa and a temperature of 280°C for 1 hour, thereby removing all the bound water and most of the oxygen-containing functional groups of the graphene oxide.
[0016] 2) Next, heat treatment at 1200℃ is carried out in a tube furnace, with the temperature increased at a rate of 2℃ / min and held for 1 hour. The membrane is placed in a custom fixture to restrict its deformation. The gas in the furnace is a hydrogen-argon mixture (5% hydrogen and 95% argon).
[0017] 3) Then, hot pressing is carried out in a graphitization furnace at 2800℃. The gas in the furnace is high-purity argon. The temperature is increased at a rate of 10℃ / min and held for 1 hour at a pressure of 10 MPa.
[0018] 4) Finally, the membrane is cold-pressed at approximately 50 MPa for 24 hours. This invention also provides a graphene oxide membrane prepared by the method described above.
[0019] Another embodiment of the present invention provides that the thermal conductivity of the graphene oxide film is 1450–1700 W / mK, and the electrical conductivity of the graphene oxide film is 3 × 10⁻⁶ W / mK. 5 ~8×10 5 S / m.
[0020] Another embodiment of the present invention is that the thickness of the graphene oxide film is 1 to 100 μm.
[0021] Compared with the prior art, the present invention has the following advantages: 1) The low-wrinkle graphene oxide film of this invention not only has the advantages of low wrinkle count and regular layer stacking, but also high overall uniformity and tensile strength, and excellent electrical and thermal conductivity after heat treatment. Specifically, the material is composed of an 8 mg / g aqueous solution of graphene oxide, which is formed by the orderly stacking of two-dimensional graphene oxide nanosheets.
[0022] 2) This invention relates to a low-wrinkle graphene oxide film and a method for its rapid assembly. This method is simple, efficient, and low-cost. Using an unsaturated hydrogel as the supporting substrate for coating, the water in the graphene oxide liquid film is reduced through natural evaporation on the upper surface and interfacial penetration on the lower surface, enabling rapid assembly of the graphene oxide sheets. Simultaneously, the low surface roughness and hydrophilic nature of the hydrogel facilitates the diffusion and spreading of the liquid film, and elastic deformation can counteract capillary forces during the drying process, improving the structural regularity and overall uniformity of the graphene oxide film. Notably, the hydrogel used possesses a certain mechanical strength, making it promising for large-scale production via roll-to-roll processes. This method is also versatile and can be used to assemble other two-dimensional materials such as boron nitride and Mxene. Furthermore, the heat-treated graphene film exhibits excellent electrical and thermal conductivity, showing significant application potential in the field of thermal management for electronic devices.
[0023] 3) An improved blade coating method was established, enabling rapid assembly of graphene oxide films on water-absorbing elastic substrates.
[0024] 4) In addition to natural evaporation in the air, the water absorption of the unsaturated hydrogel adds another driving force to the drying of the graphene oxide liquid film—interfacial penetration, which shortens the assembly time.
[0025] 5) The obtained graphene oxide film has fewer wrinkles, a more regular structure, and a more uniform thickness. The hydrogel substrate is hydrophilic and has a smoother surface, which is conducive to the diffusion and spreading of the liquid film. It can also use elastic deformation to counteract capillary forces during the drying process and reduce wrinkle formation. In addition, water permeates rapidly inside the liquid film, weakening the influence of the "skin effect" on the film drying process, and the appearance of the drying front is almost unobserved.
[0026] 6) The near-dry graphene oxide gel obtained by this method can be used to prepare graphene oxide thick films with a thickness of hundreds of micrometers through multilayer fusion bonding.
[0027] 7) It expands the assembly strategy for two-dimensional sheets, and the method is universal. For example, aqueous systems of two-dimensional sheets such as boron nitride and Mxene can also be rapidly assembled into films.
[0028] 8) The obtained graphene film has excellent thermal and electrical conductivity and has good application prospects in the field of thermal management.
[0029] 9) The raw materials used are inexpensive, the preparation process is simple, and the subsequent assembly process adopts the mature scraping method. The hydrogel substrate has sufficient mechanical strength to be adapted to roll-to-roll process, and it is expected to be used for large-scale production. Attached Figure Description
[0030] Figure 1 The preparation process of hydrogels; Figure 2A schematic diagram of a film coating process on an unsaturated hydrogel substrate; Figure 3 Different substrate surface roughness and water contact angle; Figure 4 Mass loss rate curves of graphene oxide liquid film drying on different substrates; Figure 5 Assembly time for graphene oxide films prepared by blade coating on different substrates; Figure 6 Drying states of graphene oxide liquid films on different substrates; Figure 7 The uniformity of graphene oxide film thickness obtained by scraping on different substrates; Figure 8 Tensile strength curves of graphene oxide films obtained by scraping on different substrates; Figure 9 Cross-sectional SEM images of graphene oxide films obtained by scraping on different substrates. Detailed Implementation
[0031] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.
[0032] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.
[0033] The embodiments of the present invention will be further described below with reference to several examples.
[0034] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.
[0035] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.
[0036] This invention provides a low-wrinkle graphene oxide film, which not only has advantages such as fewer wrinkles and regular stacking of layers, but also high overall uniformity and tensile strength, and excellent electrical and thermal conductivity after heat treatment. Specifically, the material is composed of an 8 mg / g aqueous solution of graphene oxide, and is formed by the orderly stacking of two-dimensional graphene oxide nanosheets.
[0037] According to another aspect of the present invention, a rapid assembly method for a low-wrinkle graphene oxide film is also provided. The method comprises: first, preparing an unsaturated polyacrylamide-based hydrogel; then, coating a liquid graphene oxide film onto the hydrogel substrate; after roughly drying, stacking and fusing the nearly dry graphene oxide gel layer by layer to prepare a thick film; and finally, reducing it through multi-step heat treatment to produce a thermally and electrically conductive graphene film.
[0038] Specifically, the following steps are included: (1) Preparation of water-absorbing substrate-unsaturated hydrogel.
[0039] First, according to the experimental protocol, weigh the following reagents: acrylamide, ammonium persulfate, N,N-methyleneacrylamide and sodium polyacrylate, and slowly add them to a certain amount of deionized water in sequence. Stir at 40°C for more than 30 minutes until the powder is completely dissolved. Next, place it in a planetary mixer and mix for 10 minutes, then degas for 5 minutes; Then, slowly pour the above solution into the pre-designed mold and heat it in a 60°C oven for 5 hours. Finally, the molded hydrogel is demolded and removed. It has a regular shape, a smooth surface, is colorless and transparent, and has good elasticity. The unsaturated property can be obtained by reducing the amount of deionized water before heating and molding or by heating the saturated hydrogel to lose water after molding, and controlling its water content between 50% and 75%.
[0040] (2) Prepare a graphene oxide dispersion of a certain concentration.
[0041] The purchased aqueous graphene oxide was centrifuged and washed to remove impurities such as metal ions and acid radicals introduced during the preparation process, and then prepared to a concentration of 8 mg / g for later use.
[0042] (3) Obtain graphene oxide liquid film by scraping method.
[0043] Using the aforementioned unsaturated hydrogel as a substrate, a 1–3 mm thick graphene oxide liquid film is uniformly coated onto the substrate using a coating machine. The drying process is accelerated by the natural evaporation and interfacial penetration of water, allowing for rapid assembly of the graphene oxide sheets. After 6–18 hours, a near-dry graphene oxide gel assembly is obtained. Due to its low water content, the graphene oxide sheets form a cross-linked structure based on π-π interactions and hydrogen bonds, exhibiting a certain mechanical strength, allowing them to be directly peeled from the hydrogel surface.
[0044] This method is also applicable to other two-dimensional sheets or two-dimensional / one-dimensional composite aqueous systems, such as boron nitride, Mxene, graphene oxide / montmorillonite, graphene oxide / carbon nanotubes, etc.
[0045] (4) Graphene oxide thick film is obtained by multilayer stacking.
[0046] Due to hydrogen bonding, wet graphene oxide macroscopic assemblies exhibit a self-fusion effect. Therefore, near-dry graphene oxide gels can be stacked in multiple layers and completely dried by hot pressing at 60°C to prepare graphene oxide thick films ranging from a few micrometers to hundreds of micrometers in size.
[0047] (5) Graphene oxide film was obtained through multi-step heat treatment.
[0048] First, the above-mentioned graphene oxide thick film is placed in a flat vulcanizing machine for hot pressing to remove all bound water and most oxygen-containing functional groups. Further, the hot pressing temperature is 280°C, the pressure is 10 MPa, and the holding time is 1 hour.
[0049] Next, the graphene oxide thick film was placed in a tube furnace for heat treatment. The heat treatment temperature was 1200°C, the heating rate was 2°C / min, the holding time was 1 hour, and the furnace gas was a hydrogen-argon mixture (5% hydrogen, 95% argon), followed by natural cooling. Furthermore, the graphene oxide thick film was placed in a custom-made fixture to limit its deformation during heat treatment.
[0050] Then, the above-mentioned graphene oxide thick film is placed in a graphitization furnace for hot pressing repair. Further, the temperature is 2800℃, the heating rate is 10℃ / minute, the holding time is 1 hour, the gas in the furnace is high-purity argon, and the pressure is 10 MPa.
[0051] Finally, the above-mentioned graphene oxide thick film is cold-pressed to obtain a graphene oxide film with electrical and thermal conductivity. Furthermore, the pressure is 50 MPa and the holding time is 24 hours.
[0052] Example 1 A rapid assembly method for a less wrinkled graphene oxide film specifically includes the following steps: (1) According to the experimental scheme (Table 1), unsaturated polyacrylamide-based hydrogels were prepared by heat molding. Figure 1 The shape of the hydrogel is determined by the mold, allowing for high design flexibility. The dimensions used in this invention are 8 cm × 8 cm × 0.5 cm. This hydrogel has a regular shape, a smooth surface, is colorless and transparent, and has good elasticity, with a water content of 50% of its saturated state.
[0053] (2) Prepare an 8 mg / g graphene oxide aqueous solution. On the above unsaturated hydrogel, use a coating machine to uniformly coat a 1 mm thick graphene oxide liquid film with a blade. The graphene oxide sheets are rapidly assembled by the natural evaporation of water and interfacial penetration. Figure 2After 6 hours, a near-dry graphene oxide gel can be obtained, which is then directly peeled off from the hydrogel surface and completely dried in an oven at 60°C.
[0054] (3) The above-mentioned graphene oxide film is subjected to multi-step heat treatment at 280℃~1200℃~2800℃ to prepare a graphene film. The whole process is under pressure, which limits the interlayer foaming caused by gas generation during thermal reduction, which is beneficial to improving the density and crystallinity of the graphene film.
[0055] Comparative Example 1-1 A conventional method for assembling a graphene oxide film specifically includes the following steps: (1) Apply an 8 mg / g aqueous solution of graphene oxide to a PET release film and coat it evenly with a blade to form a 1 mm thick graphene oxide liquid film. Dry the film by natural evaporation of water on the surface. After 36 hours, a dry graphene oxide film can be obtained.
[0056] (2) The heat treatment process is the same as in Example 1.
[0057] Compared to Example 1, the supporting substrates of the two are different. The hydrogel has a lower surface roughness and a smaller water contact angle than the PET release film. The smooth and hydrophilic hydrogel is more conducive to the uniform spreading of the graphene oxide liquid film. Figure 3 ).
[0058] Comparative Examples 1-2 The difference from Example 1 is that the water content of the unsaturated hydrogel prepared is 75% of that in the saturated state, and a near-dry graphene oxide gel assembly can be obtained after 9 hours.
[0059] Comparative Examples 1, 1-1, and 1-2, the water loss of their wet graphene oxide assemblies was recorded in real time over 8 hours. After 6 hours, 80%, 20%, and 60% of the water were lost, respectively. This indicates that the water absorption of the unsaturated hydrogel does indeed accelerate the drying of the graphene oxide liquid film. Moreover, the higher the degree of unsaturation of the hydrogel and the lower the water content, the faster the assembly speed of the graphene oxide film. Figure 4 The assembly times of Example 1 and Comparative Example 1-1 were statistically analyzed. The results showed that the assembly time of unsaturated hydrogel film coating was approximately 1 / 7 that of PET release film. Figure 5 Furthermore, the thickness and density of the completely dried graphene oxide film are shown in Table 2.
[0060] Example 2 The difference from Example 1 is that the thickness of the graphene oxide liquid film is 2 mm, and a near-dry graphene oxide gel assembly can be obtained after 12 hours.
[0061] Comparative Example 2 The difference from Comparative Example 1-1 is that the thickness of the graphene oxide liquid film is 2 mm, and a dry graphene oxide film can be obtained after 78 hours.
[0062] Compared with Example 2, the graphene oxide liquid film on the unsaturated hydrogel is not affected by the preferential drying at the film edge during the dehydration process, and the film thickness is more uniform. Figures 6-7 ).
[0063] Example 3 The difference from Example 1 is that the thickness of the graphene oxide liquid film is 3 mm, and a near-dry graphene oxide gel assembly can be obtained after 18 hours.
[0064] Comparative Example 3 The difference from Comparative Example 1-1 is that the thickness of the graphene oxide liquid film is 3 mm, and a dry graphene oxide film can be obtained after 120 hours.
[0065] Comparing Example 3 and Comparative Example 3, cross-sectional SEM images show that the graphene oxide film prepared by scraping onto the unsaturated hydrogel has fewer wrinkles and pores, and the tightly and orderly stacked sheets give it higher tensile strength. Figure 8-9 ).
[0066] Example 4 Using the near-dry graphene oxide gel peeled off in Example 2, based on the self-fusion effect of the macroscopic graphene oxide assembly in the wet state, it was stacked layer by layer (10 layers), and then completely dried by hot pressing at 60°C to prepare a graphene oxide film of approximately 100 μm. Furthermore, the heat treatment process was the same as in Example 1.
[0067] Comparative Example 4 Using the dry graphene oxide film from Comparative Example 2, based on the self-fusion effect, it was swollen in water for 10 minutes and then stacked layer by layer (10 layers). The subsequent operation process was the same as in Example 4.
[0068] Comparative Example 4 and Comparative Example 4, such as Figure 9 As shown in Table 3, the internal structure of the graphene oxide thick film obtained in Example 4 is more regular, and its reduced graphene oxide film has higher in-plane thermal conductivity (1577 W / (mK)) and electrical conductivity (6.43 × 10⁻⁶). 5 S / m).
[0069] Table 1. Raw material ratios for hydrogels Table 2. Thickness and density of graphene oxide films Table 3. Thickness, density, thermal conductivity, and electrical conductivity of graphene films. Material Thickness (μm) <![CDATA[Density (g / cm 3 ).]]> In-plane thermal conductivity (W / mK) <![CDATA[In-plane conductivity (×10 5 S / m)]]> Example 1 3 2.05 1688±165 7.85±0.50 Comparative Example 1-1 3.2 1.96 1586±151 5.77±0.39 Comparative Examples 1-2 3 2.04 1676±142 7.78±0.48 Example 2 6 2.05 1661±146 7.39±0.71 Comparative Example 2 6.3 1.97 1540±123 5.55±0.48 Example 3 9 2.04 1644±146 7.08±0.59 Comparative Example 3 9.4 1.98 1508±146 5.18±0.38 Example 4 53 2.01 1577±148 6.43±0.46 Comparative Example 4 54 1.97 1381±128 4.12±0.33 The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.
[0070] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.
Claims
1. A method for preparing a graphene oxide film, characterized in that, Includes the following steps: Unsaturated hydrogels and graphene oxide dispersions were prepared separately. The unsaturated hydrogels were used as a supporting substrate, and the graphene oxide dispersions were coated onto the supporting substrate to obtain a graphene oxide liquid film. The graphene oxide liquid film and the supporting substrate were combined to form a graphene oxide gel. The graphene oxide gel was separated from the supporting substrate to obtain a near-dry graphene oxide gel. The near-dry graphene oxide gel was then heat-treated to obtain a graphene oxide film.
2. The preparation method according to claim 1, characterized in that, It also includes stacking the near-dry graphene oxide gel into multiple layers to obtain a multilayer graphene oxide gel, and then heat-treating the multilayer graphene oxide gel to obtain a thick graphene oxide film.
3. The preparation method according to claim 2, characterized in that, The preparation of the unsaturated hydrogel involves slowly adding acrylamide, ammonium persulfate, N,N-methyleneacrylamide and sodium polyacrylate powder to deionized water in sequence according to a certain ratio, stirring, dissolving, mixing and degassing, pouring into a mold and heating to form an unsaturated hydrogel.
4. The preparation method according to claim 3, characterized in that, The preparation of the graphene oxide dispersion includes centrifuging and washing the aqueous graphene oxide, lyophilizing it to determine its concentration, and then diluting it with deionized water to obtain the graphene oxide dispersion.
5. The preparation method according to claim 4, characterized in that, The unsaturated hydrogel has a water content of 50% to 75% of that in a saturated state; the graphene oxide dispersion has a concentration of 8 mg / g and an average sheet size of 10 μm.
6. The preparation method according to claim 5, characterized in that, The thickness of the graphene oxide liquid film is 1–5 mm.
7. The preparation method according to any one of claims 1 to 6, characterized in that, The heat treatment of the near-dry graphene oxide gel or the multilayer graphene oxide gel includes first drying the near-dry graphene oxide gel or the multilayer graphene oxide gel and then hot pressing it, then gradually increasing the temperature for heat treatment and then hot pressing at high temperature, and finally cold pressing to obtain a graphene oxide film with electrical and thermal conductivity.
8. A graphene oxide film or a thick graphene oxide film prepared by the method according to any one of claims 1 to 7.
9. The graphene oxide film according to claim 6, characterized in that, The thermal conductivity of the graphene oxide film is 1450–1700 W / mK, and the electrical conductivity of the graphene oxide film is 3 × 10⁻⁶ W / mK. 5 ~8×10 5 S / m.
10. The graphene oxide film according to claim 6, characterized in that, The thickness of the graphene oxide film is 1–100 μm.