Graphene oxide slurry and preparation method thereof, reduced graphene oxide film and graphene porous film

Abstract

According to the graphene oxide slurry and the preparation method thereof, the reduced graphene oxide film and the graphene porous film, the influence of the oxygen content, the C-O content, the C = O content and other parameters of the graphene oxide raw material on the heat conduction performance of the reduced graphene oxide film and the graphene porous film is explored; the basic parameter properties of the graphene oxide and the graphene oxide slurry required for preparing the high-thermal-conductivity finished product film are provided, the situation that a large amount of time is input for preparing and screening the graphene oxide precursor is avoided, and the industrial production efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of graphene preparation technology, specifically to a graphene oxide slurry and its preparation method, a reduced graphene oxide membrane, and a porous graphene membrane. Background Technology

[0002] With the advancement of electronic and communication technologies, intelligent devices are becoming increasingly portable and integrated, which places higher demands on the heat dissipation performance of these devices. Single-layer graphene has a thermal conductivity of 5300 W / mK, which is the highest among known materials. Reduced graphene oxide film and its derivatives are among the most industrialized graphene thermal management materials to date.

[0003] Graphene oxide is a commonly used raw material for preparing reduced graphene oxide films and their derivatives. However, the quality of the raw material is a crucial factor in preparing high-quality reduced graphene oxide films and their derivatives. The quality of the raw material is determined by a variety of intrinsic properties, such as specific surface area, particle size, C content, O content, functional group types, resistivity, ash content, moisture content, monolayer ratio, and tap density. Because there are too many factors affecting the quality of raw materials, characterizing all properties during the raw material selection process is impractical. Therefore, identifying key properties and selecting suitable raw materials is a problem that researchers should consider.

[0004] Based on this, this application is hereby submitted. Summary of the Invention

[0005] The primary objective of this application is to provide a method for preparing graphene oxide slurry, the preparation steps of which include screening of graphene oxide and compounding of graphene oxide with a solvent. Solvents include one or more of deionized water, ammonia, DMF, NMP, ethanol, and isopropanol; The screening factors for graphene oxide include oxygen content, C=O content, and CO content.

[0006] As part of the embodiments of the first aspect of this application, the oxygen content of graphene oxide is 30%~45%, and the CO content is greater than the C=O content.

[0007] As part of the embodiments of the first aspect of this application, (CO content) - (C=O content) ≥ 20%, preferably, (CO content) - (C=O content) ≥ 23%.

[0008] As part of the embodiments of the first aspect of this application, CO ≥ 35% and C=O content ≤ 20%.

[0009] As part of the embodiments of the first aspect of this application, the compounding of graphene oxide and solvent includes: taking graphene oxide and solvent, mixing them, adjusting the pH value, homogenizing, and defoaming to obtain graphene oxide slurry.

[0010] As part of the embodiments of the first aspect of this application, the pH value of the graphene oxide slurry is 5.5~7.

[0011] As part of the embodiments of the first aspect of this application, the solid content of the graphene oxide slurry is 3%-8% and the viscosity is 8000cp~15000cp.

[0012] A second objective of this application is to provide a graphene oxide slurry prepared by the method provided in the first aspect of this application.

[0013] The third objective of this application is to provide a reduced graphene oxide film, which is obtained by coating the graphene oxide slurry provided in the second objective of this application into a base film, drying, heat treatment, and calendering.

[0014] The fourth objective of this application is to provide a graphene porous membrane, which is obtained by coating the graphene oxide slurry provided in the second objective of this application into a base film, chemically foaming, drying, heat treatment, and calendering.

[0015] The beneficial effects of this application are as follows: This application investigates the effects of the degree of oxidation of graphene oxide and the types and contents of oxygen-containing functional groups on the thermal conductivity of reduced graphene oxide films and their derivatives; it provides a basic parameter property of graphene oxide required for preparing high thermal conductivity finished films, avoiding the need to invest a lot of time in the preparation and screening of graphene oxide precursors, and improving industrial production efficiency.

[0016] Based on this, this application also investigated the effects of particle size, viscosity, and solid content of graphene oxide slurry on the thermal conductivity of reduced graphene oxide films and their derivatives, providing basic parameter properties of graphene oxide slurry, avoiding the need to spend a lot of time on experiments to find the optimal graphene oxide slurry, and improving industrial production efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1XPS image of the graphene oxide dry powder provided in Example 1 Figure 2 The horizontal thermal diffusivity test diagram of the reduced graphene oxide film provided in Example 1. Figure 3 XPS image of the graphene oxide dry powder provided in Example 2 Figure 4 The horizontal thermal diffusivity test diagram of the reduced graphene oxide film provided in Example 2. Figure 5 XPS image of the graphene oxide dry powder provided in Example 3 Figure 6 The horizontal thermal diffusivity test diagram of the reduced graphene oxide film provided in Example 3. Figure 7 The graph shows the horizontal thermal diffusivity test result of the graphene porous membrane provided in Example 4. Figure 8 XPS plot of graphene oxide dry powder provided for Comparative Example 1 Figure 9 The horizontal thermal diffusivity test diagram of the reduced graphene oxide film provided in Comparative Example 1 Figure 10 XPS plot of graphene oxide dry powder provided for Comparative Example 2 Figure 11 The horizontal thermal diffusivity test diagram of the reduced graphene oxide film provided for Comparative Example 2 Figure 12 XPS plot of graphene oxide dry powder provided for Comparative Example 3 Figure 13 The horizontal thermal diffusivity test diagram of the reduced graphene oxide film provided in Comparative Example 3. Figure 14 XPS plot of graphene oxide dry powder provided for Comparative Example 4 Figure 15 The horizontal thermal diffusivity test diagram of the reduced graphene oxide film provided in Comparative Example 4 Detailed Implementation

[0019] The following detailed description of exemplary embodiments of this application refers to the accompanying drawings, which form part of the description, illustrating exemplary embodiments in which this application may be implemented, wherein features of this application are identified by reference numerals. The more detailed description of embodiments of this application below is not intended to limit the scope of the claimed application, but is merely illustrative and does not limit the description of the features and characteristics of this application, in order to suggest the best mode for carrying out this application and sufficient to enable those skilled in the art to implement it. However, it should be understood that various modifications and variations can be made without departing from the scope of this application as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of this application described herein. Furthermore, the background art is intended to illustrate the current state of research and development and significance of the technology, and is not intended to limit this application or its application areas.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0022] To make the technical problems, technical solutions and advantages of this application clearer, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments.

[0023] The applicant discovered that the properties of the raw materials play a crucial role in preparing reduced graphene oxide films and their derivatives (such as porous graphene films) with high thermal conductivity. The raw material for reduced graphene oxide films and their derivatives is graphene oxide, and the quality of the raw material is determined by a variety of intrinsic properties, such as specific surface area, particle size, C content, O content, functional group types, resistivity, ash content, moisture content, monolayer ratio, and tap density. Because there are too many factors affecting the quality of raw materials, characterizing all properties during the raw material selection process is impractical. Therefore, identifying key properties and selecting suitable raw materials is a problem that researchers should consider.

[0024] The first aspect of this application provides a method for preparing graphene oxide slurry, the preparation steps of which include screening of graphene oxide and compounding of graphene oxide with solvent. Solvents include one or more of deionized water, ammonia, DMF, NMP, ethanol, and isopropanol; The screening factors for graphene oxide include oxygen content, C=O content, and CO content.

[0025] The degree of oxidation of graphene oxide affects the thermal conductivity of reduced graphene oxide films. Microscopically, the degree of oxidation of graphene oxide is reflected in the abundance of hydrophilic oxygen-containing functional groups on the graphene oxide sheets (such as carboxyl and carbonyl groups with C=O, and hydroxyl and epoxy groups with CO). The presence of these hydrophilic functional groups facilitates the dispersion of graphene oxide, which is beneficial for forming a stable graphene oxide slurry during preparation. Furthermore, the degree of oxidation and the presence of hydrophilic functional groups also determine the degree of exfoliation, monolayer ratio, and self-assembly ability of graphene oxide, which in turn determine the thermal conductivity of reduced graphene oxide films and their derivatives.

[0026] In some embodiments of the first aspect of this application, the oxygen content of graphene oxide is 30% to 45%, and the CO content is greater than the C=O content.

[0027] Generally speaking, the higher the degree of oxidation, the more oxygen-containing functional groups are present, resulting in more complete exfoliation of graphene oxide sheets and a higher monolayer ratio. The prepared slurry achieves better high-directional self-assembly during coating and drying. Therefore, if the oxygen content is <30%, the graphene oxide sheets only carry a small number of oxygen-containing functional groups, making it difficult to achieve chemical bonding between adjacent graphene oxide sheets during the self-assembly process. This means that the self-assembly performance of graphene oxide is poor, and a large number of hanging (or pore) defects are introduced between the graphene oxide sheets, leading to a decrease in thermal conductivity. However, if the oxygen content is >45%, the graphene oxide sheets carry a large number of oxygen-containing functional groups for self-assembly, which leads to an increase in the viscosity of the slurry. This is not conducive to the uniform dispersion of the slurry and the smoothness of the subsequent coating into the original film, and will also lead to a decrease in the thermal conductivity of the product.

[0028] The applicant found that, for CO, the increase of CO functional groups helps to improve the thermal conductivity of reduced graphene oxide films and their derivatives. This is mainly because CO functional groups (hydroxyl and epoxy groups) are located on the surface of graphene oxide sheets and are removed after subsequent heat treatment, restoring the original conjugated structure. This not only preserves the complete structure of graphite but also increases the exfoliation rate. However, for C=O (carboxyl and carbonyl groups), the applicant found that a high C=O content is not conducive to thermal conductivity. C=O is generally considered to be located at the defect pores or edges in the GO plane. During the preparation of graphene oxide, C=O is formed by the cleavage of C-C bonds through strong oxidation, which is usually accompanied by the formation of permanent structural defects. During heat treatment, it is removed in the form of CO2, forming carbon etching, which is not conducive to defect repair.

[0029] Therefore, when the oxygen content of graphene oxide is 30%~45% and the CO content is greater than the C=O content, it is beneficial to improve the thermal conductivity of reduced graphene oxide films and their derivatives.

[0030] In some embodiments of the first aspect of this application, the (CO content) - (C=O content) is ≥20%, preferably, the (CO content) - (C=O content) is ≥23%. The applicant has found that within this parameter range, the thermal conductivity of reduced graphene oxide films and their derivatives is significantly improved.

[0031] As part of an embodiment of the first aspect of this application, CO ≥ 35% and C=O content ≤ 20%. The applicant has found that within this parameter range, the thermal conductivity of reduced graphene oxide films and their derivatives is significantly improved.

[0032] As part of the embodiments of the first aspect of this application, the compounding of graphene oxide and solvent includes: taking graphene oxide and solvent, mixing them, adjusting the pH value, homogenizing, and defoaming to obtain graphene oxide slurry; Preferably, the graphene oxide slurry has a pH value of 5.5-7, a solid content of 3%-8%, and a viscosity of 8000cp-15000cp.

[0033] The pH value should be 5.5-7 to avoid the graphene oxide slurry being too acidic and causing corrosion to the equipment during the preparation process.

[0034] The uniform dispersion of graphene oxide in graphene oxide slurry requires homogenization and other processes to maintain the solid content of the graphene oxide slurry at 3%-8%, which ensures that it is uniformly dispersed in the slurry and also ensures that the effective components in the graphene oxide slurry are sufficient.

[0035] Viscosity is inextricably linked to the degree of oxidation. If the oxygen content in the graphene oxide slurry is too high, the graphene oxide sheets will carry a large number of oxygen-containing functional groups for self-assembly, leading to an increase in slurry viscosity, which is detrimental to the uniform dispersion of the slurry and the smoothness of the coating film. The applicant found that when the oxygen content is between 30% and 45%, the slurry viscosity is optimally between 8000 cp and 15000 cp.

[0036] A second objective of this application is to provide a graphene oxide slurry prepared by the method provided in the first aspect of this application.

[0037] The graphene oxide slurry provided in the second objective of this application includes a solvent and a solute, wherein the solvent is one or more of deionized water, ammonia, DMF, NMP, ethanol and isopropanol, and the solute is graphene oxide, and the parameters of the solute are consistent with the parameters of graphene oxide mentioned in the first aspect of this application.

[0038] The third objective of this application is to provide a reduced graphene oxide film, which is obtained by coating the graphene oxide slurry provided in the second objective of this application into a base film, drying, heat treatment, and calendering. The heat treatment includes a pretreatment process at 150-380℃, a carbonization process at 900-1400℃, and a graphitization process at 2000-3300℃.

[0039] The fourth objective of this application is to provide a graphene porous membrane, which is obtained by coating the graphene oxide slurry provided in the second objective of this application into a base film, chemically foaming, drying, heat treatment, and calendering. The heat treatment includes a pretreatment process at 150-380℃, a carbonization process at 900-1400℃, and a graphitization process at 2000-3300℃; the chemical foaming involves immersing the base film in a chemical reagent with a mass concentration of 0.5-30%, the chemical reagent being at least one selected from hydrazine hydrate, sodium borate, dimethylhydrazine, and thiourea.

[0040] In this embodiment of the application, the detection methods for each parameter are as follows: O content, CO content, and C=O content: XPS testing was conducted using an ESCA lab 250 XPS analyzer, with the sample subjected to a base pressure of 3 × 10⁻⁶. -8 In the Pa energy analysis mode, X-rays of Al Ka ​​1486.8 eV were used as the excitation source to test the chemical composition of the sample.

[0041] Thermal diffusivity test method: The method described in standard Q / GDMR 04-2023 "Laser flash method for testing thermal conductivity".

[0042] pH value test method for graphene oxide slurry: The test is performed using a PHS-2F Leici pH meter. The temperature of the graphene oxide slurry is measured with a thermometer. The pH meter temperature is adjusted to match the temperature of the graphene oxide slurry. The electrode ball of the pH meter is immersed in the graphene oxide slurry. The slurry is stirred with a glass rod to make it uniform. After the pH value on the display screen stabilizes, the data is recorded.

[0043] Viscosity test method for graphene oxide slurry: Use a viscometer of model NDJ-9S for testing. Select rotor No. 4 and rotate at 12 r / min. Immerse the graphene oxide slurry through the scale line of the rotor and perform the test. Record the data after the viscometer reading stabilizes.

[0044] In this invention application, graphene oxide cake is used as the raw material, but this does not mean that the morphology of the raw material graphene oxide is limited in this respect. Example 1

[0045] A graphene oxide slurry is prepared by the following steps: S1. Screening of graphene oxide: 50g of graphene oxide cake was flattened in a glass petri dish and dried in a 78℃ forced-air oven until its mass no longer changed. The solid content of the graphene oxide cake was calculated to be 44.45%. Another 50g of graphene oxide cake was dried in a 78℃ forced-air oven, then ground through a 150-mesh sieve to obtain dry graphene oxide powder. The obtained dry graphene oxide powder was subjected to XPS characterization tests, and the XPS spectra were processed by peak fitting to obtain... Figure 1 The XPS spectrum shown has an oxygen content of 36.77%, a CO content of 49.91%, and a C=O content of 11.58%.

[0046] S2. Blending of Graphene Oxide with Solvent: Weigh a certain mass of the above-mentioned graphene oxide cake, use water as a solvent, add ammonia water, adjust the pH of the solution to 6, and prepare a graphene oxide slurry with a solid content of 4% and a viscosity of 15000 cp. Disperse the slurry using a planetary mixer, setting the stirring speed to 100 r / min, the dispersion speed to 3000 r / min, and the working time to 3 hours. Homogenize the slurry and perform vacuum defoaming to obtain the target graphene oxide slurry.

[0047] A reduced graphene oxide film is prepared by the following steps: The above-mentioned graphene oxide slurry was coated with a thickness of 5 mm and dried in a low humidity atmosphere to obtain a graphene oxide film. The film was then pretreated at 260°C for 1 hour, carbonized at 1200°C for 1 hour in a nitrogen atmosphere, and graphitized at 2900°C for 1 hour in an argon atmosphere. All of the above pretreatment, carbonization and graphitization were carried out under a pressure of 343 N. Finally, the target reduced graphene oxide film was obtained by flat pressing.

[0048] The horizontal thermal diffusivity of the reduced graphene oxide film was measured to be 1047.505 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 2 As shown. Example 2

[0049] A graphene oxide slurry is prepared by the following steps: S1. Screening of graphene oxide: 50g of graphene oxide cake was flattened in a glass petri dish and dried in a 78℃ forced-air oven until its mass no longer changed. The solid content of the graphene oxide cake was calculated to be 43.88%. Another 50g of graphene oxide cake was dried in a 78℃ forced-air oven, then ground through a 150-mesh sieve to obtain dry graphene oxide powder. The obtained dry graphene oxide powder was subjected to XPS characterization tests, and the XPS spectrum was processed by peak fitting to obtain... Figure 3The XPS spectrum shown has an oxygen content of 33.58%, a CO content of 43.89%, and a C=O content of 13.81%.

[0050] S2. Blending of Graphene Oxide with Solvent: Weigh a certain mass of the above-mentioned graphene oxide cake, use water as a solvent, add ammonia water, adjust the pH of the solution to 6.5, and prepare a graphene oxide slurry with a solid content of 8% and a viscosity of 12000 cp. Disperse the slurry using a planetary mixer with a stirring rate of 100 r / min, a dispersion speed of 3000 r / min, and a working time of 4 hours. Homogenize the slurry and perform vacuum defoaming to obtain the target graphene oxide slurry.

[0051] A reduced graphene oxide film is prepared by the following method: The horizontal thermal diffusivity of the reduced graphene oxide film was measured to be 967.055 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 4 As shown. Example 3

[0052] A graphene oxide slurry is prepared by the following steps: S1. Screening of graphene oxide: 50g of graphene oxide cake was flattened in a glass petri dish and dried in a 78℃ forced-air oven until its mass no longer changed. The solid content of the graphene oxide cake was calculated to be 44.54%. Another 50g of graphene oxide cake was dried in a 78℃ forced-air oven, then ground through a 150-mesh sieve to obtain dry graphene oxide powder. The obtained dry graphene oxide powder was subjected to XPS characterization tests, and the XPS spectrum was processed by peak fitting to obtain... Figure 5 The XPS spectrum shown has an oxygen content of 43.05%, a CO content of 44.33%, and a C=O content of 19.84%.

[0053] S2. Blending of Graphene Oxide with Solvent: Weigh a certain mass of the above-mentioned graphene oxide cake, use water as a solvent, add ammonia water, adjust the pH of the solution to 7, and prepare a graphene oxide slurry with a solid content of 3% and a viscosity of 8000 cp. Disperse the slurry using a planetary mixer, setting the stirring speed to 100 r / min, the dispersion speed to 3000 r / min, and the working time to 3 hours. Homogenize the slurry and perform vacuum defoaming to obtain the target graphene oxide slurry.

[0054] A reduced graphene oxide film was prepared by the same method as in Example 1.

[0055] The horizontal thermal diffusivity of the reduced graphene oxide film was measured to be 991.751 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 6 As shown. Example 4

[0056] The difference between this embodiment and Embodiment 1 is that the graphene oxide slurry prepared in Embodiment 1 is used as the raw material, and a porous graphene membrane is prepared through the following steps: The above-mentioned graphene oxide slurry was coated with a thickness of 5 mm and dried in a low humidity atmosphere to obtain a graphene oxide film. The graphene oxide film was immersed in a 1% concentration of hydrazine hydrate solution for 30 seconds, then taken out and dried. After pretreatment at 260℃ for 1 hour, carbonization at 1200℃ for 1 hour in a nitrogen atmosphere, and graphitization at 2900℃ for 1 hour in an argon atmosphere, the target graphene porous film was finally obtained by flat pressing.

[0057] The horizontal thermal diffusivity of the graphene porous membrane was measured to be 1028.305 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 7 As shown. Comparative Example 1

[0058] A graphene oxide slurry is prepared by the following steps: S1. Screening of graphene oxide: 50g of graphene oxide cake was flattened in a glass petri dish and dried in a 78℃ forced-air oven until its mass no longer changed. The solid content of the graphene oxide cake was calculated to be 44.54%. Another 50g of graphene oxide cake was dried in a 78℃ forced-air oven, then ground through a 150-mesh sieve to obtain dry graphene oxide powder. The obtained dry graphene oxide powder was subjected to XPS characterization tests, and the XPS spectrum was processed by peak fitting to obtain... Figure 8 The XPS spectrum shown has an oxygen content of 29.14%, a CO content of 43.03%, and a C=O content of 3.82%.

[0059] S2. Blending of Graphene Oxide with Solvent: Weigh a certain mass of the above-mentioned graphene oxide cake, use water as a solvent, add ammonia water, adjust the pH of the solution to 6, and prepare a graphene oxide slurry with a solid content of 4% and a viscosity of 15000 cp. Disperse the slurry using a planetary mixer, setting the stirring speed to 100 r / min, the dispersion speed to 3000 r / min, and the working time to 3 hours. Homogenize the slurry and perform vacuum defoaming to obtain the target graphene oxide slurry.

[0060] A reduced graphene oxide film was prepared by the same method as in Example 1.

[0061] The horizontal thermal diffusivity of the reduced graphene oxide film was measured to be 772.429 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 9 As shown.

[0062] The applicant speculates that due to the low oxygen content in the graphene oxide sheets, which contain only a small number of oxygen-containing functional groups, it is difficult to achieve chemical bonding between adjacent graphene oxide sheets during the self-assembly process. Consequently, the thermal conductivity of the product decreases compared to Example 1. From the data in Comparative Example 1, we can also infer that the thermal conductivity of the reduced graphene oxide film is determined by several key factors, including oxygen content, CO content, and C=O content. Failure to meet the requirements of any one of these factors will lead to a decrease in thermal conductivity. Comparative Example 2

[0063] A graphene oxide slurry is prepared by the following steps: S1. Screening of graphene oxide: 50g of graphene oxide cake was flattened in a glass petri dish and dried in a 78℃ oven until its mass no longer changed. The solid content of the graphene oxide cake was calculated to be 44.37%. Another 50g of graphene oxide cake was dried in a 78℃ oven and then ground through a 150-mesh sieve to obtain dry graphene oxide powder. The obtained dry graphene oxide powder was subjected to XPS characterization tests, and the XPS spectrum was processed by peak fitting to obtain... Figure 10 The XPS spectrum shown has an oxygen content of 30.56%, a CO content of 33.55%, and a C=O content of 13.92%.

[0064] S2. Combination of graphene oxide and solvent: Same as in Example 1.

[0065] A reduced graphene oxide film was prepared by the same method as in Example 1.

[0066] The horizontal thermal diffusivity of the reduced graphene oxide film was measured to be 869.567 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 11 As shown.

[0067] The applicant speculates that the thermal conductivity of the reduced graphene oxide decreased relative to the example due to the CO content not meeting the requirements. Comparative Example 3

[0068] A graphene oxide slurry is prepared by the following steps: S1. Screening of graphene oxide: 50g of graphene oxide cake was flattened in a glass petri dish and dried in a 78℃ forced-air oven until its mass no longer changed. The solid content of the graphene oxide cake was calculated to be 42.56%. Another 50g of graphene oxide cake was dried in a 78℃ forced-air oven, then ground through a 150-mesh sieve to obtain dry graphene oxide powder. The obtained dry graphene oxide powder was subjected to XPS characterization tests, and the XPS spectrum was processed by peak fitting to obtain... Figure 12The XPS spectrum shown has an oxygen content of 50.84%, a CO content of 47.55%, and a C=O content of 24.98%.

[0069] S2. Blending of Graphene Oxide with Solvent: A certain mass of the above-mentioned graphene oxide cake was weighed, and ammonia was added using water as a solvent to adjust the pH of the solution to 6. A graphene oxide slurry with a solid content of 4% and a viscosity of 25000 cp was prepared. This slurry was dispersed using a planetary mixer with a stirring speed of 100 r / min, a dispersion speed of 3000 r / min, and a working time of 4 hours. The slurry was homogenized and subjected to vacuum defoaming to obtain the target graphene oxide slurry.

[0070] A reduced graphene oxide film was prepared by the same method as in Example 1.

[0071] The horizontal thermal diffusivity of the reduced graphene oxide film was measured to be 734.593 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 13 As shown.

[0072] The applicant speculates that due to the excessive oxygen content of graphene oxide, the graphene oxide sheets carry a large number of oxygen-containing functional groups for self-assembly, which leads to an increase in the viscosity of the slurry. This is not conducive to the uniform dispersion of the slurry and the smoothness of the subsequent coating into the original film. At the same time, the excessive C=O content is accompanied by the formation of too many permanent structural defects during the heat treatment process, thus the thermal conductivity of the product decreases compared with the example. Comparative Example 4

[0073] A graphene oxide slurry is prepared by the following steps: S1. Screening of graphene oxide: 50g of graphene oxide cake was flattened in a glass petri dish and dried in a 78℃ oven until its mass no longer changed. The solid content of the graphene oxide cake was calculated to be 44.09%. Another 50g of graphene oxide cake was dried in a 78℃ oven and then ground through a 150-mesh sieve to obtain dry graphene oxide powder. The obtained dry graphene oxide powder was subjected to XPS characterization tests, and the XPS spectrum was processed by peak fitting to obtain... Figure 14 The XPS spectrum shown has an oxygen content of 23.34%, a CO content of 30.24%, and a C=O content of 13.64%.

[0074] S2. Blending of Graphene Oxide with Solvent: A certain mass of the above-mentioned graphene oxide cake was weighed, and ammonia was added using water as a solvent to adjust the pH of the solution to 6. A graphene oxide slurry with a solid content of 4% and a viscosity of 5000 cp was prepared. This slurry was dispersed using a planetary mixer with a stirring speed of 100 r / min, a dispersion speed of 3000 r / min, and a working time of 4 hours. The slurry was homogenized and then subjected to vacuum defoaming to obtain the target graphene oxide slurry.

[0075] The above-mentioned graphene oxide slurry was coated with a thickness of 3 mm and dried in a low humidity atmosphere to obtain a graphene oxide film. The film was then pretreated at 260°C for 1 hour, carbonized at 1200°C for 1 hour in a nitrogen atmosphere, and graphitized at 2900°C for 1 hour in an argon atmosphere. All of the above pretreatment, carbonization and graphitization were carried out under a pressure of 343 N. Finally, the target reduced graphene oxide film was obtained by flat pressing.

[0076] The horizontal thermal diffusivity of the reduced graphene oxide film was measured to be 715.323 mm. 2 / s, its horizontal thermal diffusivity test graph is as follows Figure 15 As shown.

[0077] The applicant speculates that in this comparative example, the oxygen content of graphene oxide is too low, and the sheets only carry a small number of oxygen-containing functional groups. It is difficult to achieve chemical bonding between adjacent graphene oxide sheets during the self-assembly process. Furthermore, a large number of hanging (or pore) defects are introduced between the graphene oxide sheets. Due to the low oxygen content, the viscosity of the slurry cannot meet the target requirements, and the coating cannot be too thick. At the same time, the low viscosity of the slurry will also result in less overlap between the graphene sheets, leading to a decrease in thermal conductivity compared to Example 1.

[0078] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0079] The above description describes specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a graphene oxide slurry, characterized in that, This includes the screening of graphene oxide and the compounding of graphene oxide with solvents; The solvent includes one or more of deionized water, ammonia, DMF, NMP, ethanol, and isopropanol; The screening factors for the graphene oxide include oxygen content, C=O content, and CO content.

2. The method for preparing graphene oxide slurry according to claim 1, characterized in that, The oxygen content of the graphene oxide is 30% to 45%, and the CO content is greater than the C and O content.

3. The method for preparing graphene oxide slurry according to claim 2, characterized in that, The (CO content) - (C=O content) is ≥20%, preferably, the (CO content) - (C=O content) is ≥23%.

4. The method for preparing graphene oxide slurry according to claim 2, characterized in that, The CO content is ≥ 35%, and the C=O content is ≤ 20%.

5. The method for preparing graphene oxide slurry according to claim 1, characterized in that, The compounding of graphene oxide and solvent includes: mixing graphene oxide and solvent, adjusting the pH value, homogenizing, and defoaming to obtain graphene oxide slurry.

6. The method for preparing graphene oxide slurry according to claim 5, characterized in that, The pH value of the graphene oxide slurry is 5.5~7.

7. The method for preparing graphene oxide slurry according to claim 5, characterized in that, The solid content of the graphene oxide slurry is 3%-8%, and the viscosity is 8000cp~15000cp.

8. A graphene oxide slurry, characterized in that, The graphene oxide slurry is prepared according to any one of claims 1-7.

9. A reduced graphene oxide film, characterized in that, The graphene oxide slurry of claim 8 is used as raw material, and the film is obtained by coating the graphene oxide slurry into a base film, drying, heat treatment, and calendering.

10. A graphene porous membrane, characterized in that, The graphene oxide slurry of claim 8 is used as raw material, and the process involves coating the graphene oxide slurry into a base film, chemical foaming, drying, heat treatment, and calendering.

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