Graphene film and method for preparing the same

Abstract

This invention relates to the field of graphene material preparation technology, specifically to a graphene film and its preparation method, comprising graphene oxide, thermally exfoliated graphene, and naphthalene, obtained by in-situ cleaning with carbon dioxide and hot pressing under an argon atmosphere. The mass ratio of graphene oxide to thermally exfoliated graphene is 0.5:1 to 2:1, and the mass fraction of naphthalene is 0.08% to 0.18% of the total mass of graphene oxide and thermally exfoliated graphene. This invention uses a composite of graphene oxide and thermally exfoliated graphene as a carbon source, which can effectively improve the sheet dispersion state, suppress agglomeration from the root, and make the internal structure of the film more uniform and regular, laying a structural foundation for the stable performance of various properties.

Description

Technical Field

[0001] This invention relates to the field of graphene material preparation technology, specifically to a graphene film and its preparation method. Background Technology

[0002] Graphene films, with their outstanding electrical, thermal, mechanical, and electromagnetic shielding properties, have become key functional materials in fields such as electronic information, energy devices, and thermal management systems, possessing extremely high industrial application value. Currently, the mainstream preparation route for graphene films is based on the reduction of graphene oxide. Although it has the advantages of mature technology and easy scalability, there are still many technical shortcomings that are difficult to overcome in actual production and application.

[0003] Existing preparation techniques mostly use a single carbon source to construct thin film systems. Graphene sheets are prone to spontaneous aggregation during the dispersion and film formation stages, resulting in a loose and uneven internal structure of the film, which directly affects the macroscopic performance stability of the material.

[0004] The reduction process of graphene oxide often relies on a single reducing agent, and the degree of reduction is difficult to control precisely. This can easily lead to incomplete reduction or damage to the sheet structure, making it impossible to simultaneously achieve both the conductivity and mechanical strength of the film.

[0005] Amorphous carbon impurities are easily generated throughout the thin film preparation process. Traditional post-processing methods lack selective cleaning capabilities, and these impurities continuously disrupt the integrity of the graphene lattice, significantly reducing material purity and conductivity. Modification schemes for high thermal conductivity requirements lack stable interfacial interaction mechanisms, making it difficult to form continuous and interconnected thermal conduction channels within the thin film, thus limiting the improvement in thermal performance.

[0006] Meanwhile, the existing processes have poor adaptability in terms of raw material ratios and process parameters, which cannot cover the preparation needs of different production scenarios and lack industrialization flexibility; the densification process after film formation is relatively crude, leaving a large number of pores inside the film, resulting in insufficient structural strength and stability, making it difficult to meet the stringent requirements of high-end application scenarios. Summary of the Invention

[0007] The primary objective of this invention is to provide a graphene film and a method for preparing the same.

[0008] A further objective of this invention is to provide a graphene film composed of graphene oxide, thermally exfoliated graphene, and naphthalene, prepared by in-situ cleaning with carbon dioxide and hot pressing under an argon atmosphere.

[0009] Preferably, the mass ratio of graphene oxide to thermally exfoliated graphene is 0.5:1 to 2:1, and the mass fraction of naphthalene is 0.08% to 0.18% of the total mass of graphene oxide and thermally exfoliated graphene.

[0010] Preferably, the graphene film has a stacked sheet structure.

[0011] A method for preparing a graphene film includes the following steps: raw material pretreatment, composite dispersion, chemical reduction, vacuum filtration film formation, and hot pressing post-treatment; the raw materials include graphene oxide and thermally exfoliated graphene, and the chemical reduction uses 57% hydroiodic acid or a composite reducing agent composed of sodium borohydride and hydroiodic acid.

[0012] Preferably, the mass ratio of graphene oxide to thermally exfoliated graphene is 0.5:1 to 2:1, and naphthalene is added in the composite dispersion step, with the mass fraction of naphthalene being 0.08% to 0.18% of the total mass of graphene oxide and thermally exfoliated graphene.

[0013] Preferably, the raw material pretreatment involves vacuum drying of graphene oxide and annealing of thermally exfoliated graphene in an argon atmosphere.

[0014] Preferably, after vacuum filtration to form a membrane, in-situ cleaning is performed, and carbon dioxide gas is introduced and high-temperature insulation treatment is carried out during in-situ cleaning.

[0015] Preferably, the mass ratio of sodium borohydride to hydroiodic acid in the composite reducing agent is 1:3, and the mass ratio of the composite reducing agent to graphene oxide is 0.9:1 to 1.4:1.

[0016] Preferably, the composite dispersion is carried out in deionized water and ultrasonic dispersion treatment is used.

[0017] Preferably, the hot pressing post-treatment is carried out under high temperature and high pressure in an argon protective atmosphere.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses a combination of graphene oxide and thermally exfoliated graphene as a carbon source, which can effectively improve the dispersion state of the sheets, suppress agglomeration from the source, and make the internal structure of the film more uniform and regular, laying a structural foundation for the stable performance of various properties.

[0019] 2. This invention introduces specific carbon-rich molecules for modification, which can construct a continuous and stable thermal conductivity path inside the film, significantly improving the thermal conductivity efficiency without negatively affecting the film's electrical conductivity and light transmittance. The composite reduction system is used to act on the graphene oxide in steps, which can accurately complete the reduction of oxygen-containing functional groups. While ensuring sufficient reduction, it avoids structural damage to the graphene sheets and simultaneously optimizes the electrical and mechanical properties of the film.

[0020] 3. This invention selectively removes amorphous carbon impurities through an in-situ cleaning process, preserving the integrity of the graphene lattice to the greatest extent possible, effectively improving the purity and conductivity of the film. The process parameters of this invention can be adapted to different raw material ratios, possessing a wide range of preparation adaptability capabilities, and can meet diverse industrial production scenarios. The hot-pressing post-processing further eliminates internal porosity in the film, improving material density and structural stability, and enhancing the film's mechanical strength and durability.

[0021] 4. The various technical aspects of this invention work together synergistically to achieve a balanced improvement in key properties of graphene films, such as electrical conductivity, thermal conductivity, light transmittance, and electromagnetic shielding. The overall preparation process is highly controllable and stable, and the resulting films possess both excellent comprehensive performance and good industrial adaptability. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: Raw material preparation: Graphene oxide was prepared by chemical oxidation, with a particle size of 8 μm and 2 layers; thermally exfoliated graphene was prepared by graphite intercalation thermal exfoliation, with a particle size of 5 μm and 1-3 layers; the hydroiodic acid concentration was 57%; the resistivity of deionized water was 18.2 MΩ·cm; and the pore size of the polytetrafluoroethylene filter membrane was 0.22 μm.

[0024] The mass ratio of graphene oxide to thermally exfoliated graphene is 0.5:1, the mass ratio of hydroiodic acid to graphene oxide is 1:1, and the amount of deionized water used is 80 times the total mass of graphene oxide and thermally exfoliated graphene.

[0025] Preparation steps: Raw material pretreatment: Place the graphene oxide in a DZF-6050 vacuum drying oven and dry at 80℃ for 2 hours to remove surface adsorbed moisture; place the thermally exfoliated graphene in a tube furnace and anneal it in an argon atmosphere with an argon purity of 99.99%, a flow rate of 50 sccm, an annealing temperature of 300℃, and a time of 30 minutes to remove residual amorphous carbon impurities on the surface.

[0026] Composite dispersion: Pretreated graphene oxide and thermally exfoliated graphene were added to deionized water and dispersed for 40 minutes at 200W using a KQ-500DE ultrasonic disperser. The dispersion temperature was controlled at 25℃ to avoid agglomeration of the sheets, and finally a uniform and stable composite dispersion was obtained.

[0027] Chemical reduction: The composite dispersion was placed in an HH-S6 constant temperature water bath and the temperature was controlled at 60℃. Hydroiodic acid was slowly added dropwise at a rate of 5 mL / min. After the addition was completed, the reaction was carried out at a constant temperature for 2 hours to achieve the conversion of graphene oxide to reduced graphene oxide, thereby restoring the conjugated structure of graphene and improving its conductivity.

[0028] Vacuum filtration to form a membrane: The reduced dispersion is poured into an SHB-III type vacuum filtration device and filtered using a polytetrafluoroethylene filter membrane. The pressure is controlled at 0.06 MPa and the filtration time is 30 min, so that the graphene sheets are stacked on the surface of the filter membrane to form a self-supporting wet membrane.

[0029] Post-hot pressing treatment: The wet film is peeled off from the filter membrane and placed in a flatbed hot press. It is then hot-pressed under an argon protective atmosphere with an argon purity of 99.99% and a flow rate of 50 sccm. The hot pressing temperature is 150℃, the pressure is 0.3MPa, and the time is 60min. This process removes residual moisture and pores, improves the film's density and mechanical properties, and finally yields a basic graphene film.

[0030] Example 2: Raw material preparation: The specifications of graphene oxide are the same as those in Example 1; the specifications of thermally exfoliated graphene are the same as those in Example 1; the concentration of hydroiodic acid is 57%; naphthalene with a purity of 99% is selected as the carbon-rich molecule, which has strong π-π interaction with the graphene sheets and stable modification effect; the resistivity of deionized water is 18.2 MΩ·cm; the pore size of polytetrafluoroethylene filter membrane is 0.22 μm.

[0031] The mass ratio of graphene oxide to thermally exfoliated graphene is 1:1, the mass ratio of hydroiodic acid to graphene oxide is 1.2:1, the carbon-rich molecular weight fraction is 0.15% of the total mass of graphene oxide and thermally exfoliated graphene, and the amount of deionized water used is 85 times the total mass of the two.

[0032] Preparation steps: Raw material pretreatment: The pretreatment steps are completely consistent with those in Example 1.

[0033] Composite dispersion: Pretreated graphene oxide, thermally exfoliated graphene, and carbon-rich molecules were added to deionized water and dispersed for 40 minutes at 200W power using a KQ-500DE ultrasonic disperser, with the temperature controlled at 25℃, to obtain a uniform and stable composite dispersion. The carbon-rich molecules can effectively inhibit the aggregation of the sheets and lay the foundation for the formation of subsequent heat conduction channels.

[0034] Chemical reduction: The reduction reaction of graphene oxide was completed using the exact same reduction conditions as in Example 1.

[0035] Vacuum filtration membrane formation: Using the same filtration conditions as in Example 1, a graphene wet membrane was formed.

[0036] Post-hot pressing treatment: The wet film is placed in a flatbed hot press and hot-pressed under an argon protective atmosphere. The argon flow rate is 50 sccm, the hot pressing temperature is 180℃, the pressure is 0.4 MPa, and the time is 50 min. This allows the carbon-rich molecules to form continuous thermally conductive channels, ultimately yielding a high thermal conductivity graphene film.

[0037] Example 3: Raw material preparation: The specifications of the graphene oxide are the same as those in Example 1; the specifications of the thermally exfoliated graphene are the same as those in Example 1; the concentration of hydroiodic acid is 57%; the carbon-rich molecule is naphthalene with a purity of 99%; the purity of carbon dioxide is 99.99%; the resistivity of deionized water is 18.2 MΩ·cm; and the pore size of the polytetrafluoroethylene filter membrane is 0.22 μm.

[0038] The mass ratio of graphene oxide to thermally exfoliated graphene is 1.5:1, the mass ratio of hydroiodic acid to graphene oxide is 1.1:1, the carbon-rich molecular weight fraction is 0.12% of the total mass of the two, the amount of deionized water is 80 times the total mass of the two, and the carbon dioxide flow rate is 50 sccm.

[0039] Preparation steps: Raw material pretreatment to vacuum filtration and film formation: The steps are completely consistent with those in Example 2, ensuring uniform dispersion of graphene sheets and sufficient reduction of graphene oxide.

[0040] In-situ cleaning: The graphene wet film is placed in a tube furnace, carbon dioxide gas is introduced, the temperature is controlled at 500℃, and the temperature is maintained for 20 minutes. Carbon dioxide has high etching selectivity for amorphous carbon, and can react with amorphous carbon to generate carbon monoxide without destroying the graphene lattice structure, thereby completely removing amorphous carbon contaminants from the surface and interior of the film.

[0041] Post-hot pressing treatment: Using the hot pressing parameters of Example 2, hot pressing was performed for 50 minutes under an argon protective atmosphere to ensure the integrity of the heat conduction channels, and finally an ultra-clean, highly conductive graphene film was obtained.

[0042] Example 4: Raw material preparation: The specifications of the graphene oxide are the same as those in Example 1; the specifications of the thermally exfoliated graphene are the same as those in Example 1; the reducing agent is a sodium borohydride-hydroiodic acid composite reducing agent, wherein the sodium borohydride has a purity of 98% and the hydroiodic acid has a concentration of 57%, and the synergistic effect of the two can balance the reduction efficiency and the protection of the sheet; the carbon-rich molecule is naphthalene with a purity of 99%; the carbon dioxide has a purity of 99.99%; the resistivity of the deionized water is 18.2 MΩ·cm; the pore size of the polytetrafluoroethylene filter membrane is 0.22 μm.

[0043] The mass ratio of graphene oxide to thermally exfoliated graphene is 2:1, the mass ratio of composite reducing agent to graphene oxide is 1.4:1, the mass ratio of sodium borohydride to hydroiodic acid in the composite reducing agent is 1:3, the mass fraction of carbon-rich molecules is 0.18% of the total mass of the two, the amount of deionized water is 70 times the total mass of the two, and the carbon dioxide flow rate is 60 sccm.

[0044] Preparation steps: Raw material pretreatment: The pretreatment steps are completely consistent with those in Example 1.

[0045] Composite dispersion: Pretreated graphene oxide, thermally exfoliated graphene, and carbon-rich molecules are added to deionized water and dispersed for 50 minutes at 220W using a KQ-500DE ultrasonic disperser, with the temperature controlled at 25℃, to meet the dispersion requirements of high proportion graphene oxide and avoid sheet aggregation.

[0046] Chemical reduction: The composite reducing agent is slowly added dropwise to the dispersion at a rate of 5 mL / min. The mixture is placed in an HH-S6 constant temperature water bath and the temperature is controlled at 70℃ for 2.5 h. Sodium borohydride preferentially reduces the strong oxidizing functional groups on the surface of graphene oxide, while hydroiodic acid supplements the reduction of the remaining weak oxidizing functional groups, effectively avoiding sheet damage.

[0047] Vacuum filtration for film formation: The SHB-III type vacuum filtration device is used, and polytetrafluoroethylene filter membrane is selected for filtration. The pressure is controlled at 0.07MPa and the time is 25min, which is suitable for the film formation requirements of high concentration dispersions.

[0048] In-situ cleaning: Place the wet film into a tube furnace, introduce carbon dioxide gas, control the temperature at 500℃, and keep it at that temperature for 25 minutes to completely remove amorphous carbon from the film.

[0049] Post-hot pressing treatment: The wet film is placed in a flatbed hot press and hot-pressed under an argon protective atmosphere. The hot pressing temperature is 190℃, the pressure is 0.45MPa, and the time is 40min to improve the film density and finally obtain a wide-fit graphene film.

[0050] Example 5: Raw material preparation: The specifications of graphene oxide are the same as those in Example 1; the specifications of thermally exfoliated graphene are the same as those in Example 1; the specifications of the composite reducing agent are the same as those in Example 4; naphthalene with a purity of 99% is selected as the carbon-rich molecule; the purity of carbon dioxide is 99.99%; the resistivity of deionized water is 18.2 MΩ·cm; and the pore size of the polytetrafluoroethylene filter membrane is 0.22 μm.

[0051] The mass ratio of graphene oxide to thermally exfoliated graphene is 0.5:1, the mass ratio of composite reducing agent to graphene oxide is 0.9:1, the mass ratio of sodium borohydride to hydroiodic acid in the composite reducing agent is 1:3, the mass fraction of carbon-rich molecules is 0.08% of the total mass of the two, the amount of deionized water is 90 times the total mass of the two, and the carbon dioxide flow rate is 40 sccm.

[0052] Preparation steps: Raw material pretreatment: The pretreatment steps are completely consistent with those in Example 1.

[0053] Composite dispersion: Pretreated graphene oxide, thermally exfoliated graphene, and carbon-rich molecules were added to deionized water and dispersed for 30 minutes at 180W using a KQ-500DE ultrasonic disperser, with the temperature controlled at 25℃, to meet the dispersion requirements of low proportion graphene oxide.

[0054] Chemical reduction: The composite reducing agent is slowly added dropwise to the dispersion at a rate of 5 mL / min. The mixture is placed in an HH-S6 constant temperature water bath and the temperature is controlled at 50℃. The reaction time is 1.5 h to ensure that the graphene oxide is fully reduced without damaging the graphene sheets.

[0055] Vacuum filtration for film formation: The SHB-III type vacuum filtration device is used, and polytetrafluoroethylene filter membrane is selected for filtration. The pressure is controlled at 0.05MPa and the time is 35min, which is suitable for the film formation requirements of low concentration dispersions.

[0056] In-situ cleaning: The wet film is placed in a tube furnace, carbon dioxide gas is introduced, the temperature is controlled at 490℃, and the temperature is maintained for 15 minutes, which saves energy while ensuring the cleaning effect.

[0057] Post-hot pressing treatment: The wet film is placed in a flatbed hot press and hot-pressed under an argon protective atmosphere. The hot pressing temperature is 150℃, the pressure is 0.3MPa, and the time is 70min to ensure the film density and finally obtain a wide-fit graphene film.

[0058] Comparative Example 1: Raw material preparation: The specifications of graphene oxide are the same as in Example 1; the concentration of hydroiodic acid is 57%; the resistivity of deionized water is 18.2 MΩ·cm; the pore size of polytetrafluoroethylene filter membrane is 0.22 μm; the proportions of other raw materials are completely the same as in Example 1.

[0059] Preparation steps: exactly the same as in Example 1, except that thermally exfoliated graphene is not added.

[0060] Due to the lack of a composite carbon source, the graphene sheets in this scheme exhibit severe agglomeration, resulting in poor overall film performance.

[0061] Comparative Example 2: Raw material preparation: No carbon-rich molecules are added, and the specifications and proportions of the other raw materials are completely consistent with those in Example 2.

[0062] Preparation steps: completely consistent with Example 2.

[0063] Because this scheme does not involve carbon-rich molecule modification, it cannot form a continuous heat conduction channel, resulting in a significant decrease in the thermal conductivity of the thin film, which cannot meet the requirements of high thermal conductivity applications.

[0064] Comparative Example 3: The raw material preparation is exactly the same as in Example 3. The preparation steps are as follows: the in-situ cleaning step is omitted, and the remaining steps and process parameters are exactly the same as in Example 3.

[0065] The lack of an in-situ cleaning step in this method resulted in residual amorphous carbon contaminants on and inside the film surface, leading to a significant decrease in the film's conductivity and purity.

[0066] Comparative Example 4: Raw material preparation: Sodium borohydride was used as the reducing agent, with a purity of 98%. The mass ratio of reducing agent to graphene oxide was 1.4:1. The specifications and proportions of the other raw materials were completely consistent with those in Example 4.

[0067] Preparation steps: exactly the same as in Example 4.

[0068] This scheme uses a single reducing agent system, resulting in insufficient reduction of graphene oxide and thus poor mechanical and electrical properties of the film.

[0069] Comparative Example 5: Raw material preparation: The mass ratio of graphene oxide to thermally exfoliated graphene is 2.5:1, the carbon-rich molecular weight fraction is 0.25%, and the specifications and proportions of the remaining raw materials are completely consistent with those in Example 4.

[0070] Preparation steps: exactly the same as in Example 4.

[0071] Because the raw material ratio deviates from the scope of protection of this invention, the graphene sheets in this solution are severely agglomerated, resulting in a significant decrease in the overall performance of the film.

[0072] Comparative Example 6: Raw material preparation: The specifications of graphene oxide are the same as in Example 1; the specifications of thermally exfoliated graphene are the same as in Example 1; the concentration of hydroiodic acid is 57%; the resistivity of deionized water is 18.2 MΩ·cm; the pore size of polytetrafluoroethylene filter membrane is 0.22 μm.

[0073] The mass ratio of graphene oxide to thermally exfoliated graphene is 1:1, the mass ratio of hydroiodic acid to graphene oxide is 1.2:1, and the amount of deionized water used is 85 times the total mass of the two.

[0074] Preparation steps: including raw material pretreatment, composite dispersion, chemical reduction, vacuum filtration to form a film, and hot pressing post-treatment. No carbon-rich molecule modification and in-situ cleaning steps were set. The remaining steps and process parameters were completely consistent with those in Example 2.

[0075] This solution lacks the core technical features of the present invention, and the overall performance of the thin film is lower than that of Example 2.

[0076] Comparative Example 7: Raw material preparation: The graphene oxide specifications are the same as in Example 1; the hydroiodic acid concentration is 57%; the carbon-rich molecule is naphthalene with a purity of 99%; the resistivity of deionized water is 18.2 MΩ·cm; and the pore size of the polytetrafluoroethylene filter membrane is 0.22 μm.

[0077] The mass ratio of hydroiodic acid to graphene oxide is 1.2:1, the mass fraction of carbon-rich molecules is 0.15% of the mass of graphene oxide, and the amount of deionized water used is 85 times the mass of graphene oxide.

[0078] Preparation steps: including raw material pretreatment, dispersion, chemical reduction, vacuum filtration to form film, hot pressing post-treatment, no thermally exfoliated graphene added and no in-situ cleaning step, the remaining steps and process parameters are completely consistent with Example 2.

[0079] This solution lacks the core technical features of the present invention, and the problems of graphene sheet agglomeration and film contamination are not solved, resulting in overall performance far lower than that of Example 2.

[0080] Performance testing and results analysis: The graphene films prepared in Examples 1 to 5 and Comparative Examples 1 to 7 were subjected to comprehensive performance tests. The test items included thickness, specific surface area, bulk density, electrical conductivity, thermal conductivity, light transmittance, electromagnetic shielding effectiveness, and surface purity. The test methods all conformed to industry standards and practical test principles. The test data were true and reliable, and standard symbols were used to ensure that the test results were objective and comparable.

[0081] Test Method Description (1) Thickness test: Using an atomic force microscope, five test points were selected at different locations on the film, and the average value was taken as the final thickness data; (2) Specific surface area test: The BET specific surface area analyzer was used to complete the test by nitrogen adsorption-desorption method; (3) Bulk density test: The bulk density is calculated by combining the weighing method with the thickness test results; (4) Conductivity test: The four-probe method was used, the test temperature was controlled at 25℃, 5 test points were selected, and the average value was taken as the final conductivity data; (5) Thermal conductivity test: The laser flash method was used, and the test temperature was controlled at 25℃; (6) Transmittance test: A UV-Vis spectrophotometer was used, and the test wavelength was 550 nm; (7) Electromagnetic shielding effectiveness test: A vector network analyzer was used, and the test frequency range was 4 GHz to 18 GHz; (8) Surface purity test: Raman spectrometer was used to characterize the amorphous carbon content by the intensity ratio of D peak to G peak (ID / IG). The smaller the ID / IG value, the lower the amorphous carbon content and the higher the surface purity of the film.

[0082] The test results are shown in Table 1 below: Table 1: Results analysis: The test results show that the graphene films prepared in Examples 1 to 5 have excellent comprehensive performance and exhibit a stepwise improvement trend.

[0083] Example 1, as the basic scheme, effectively suppressed graphene sheet aggregation through the reasonable combination of composite carbon sources, ensuring that the basic performance of the film met the standards. Example 2 modified the basic scheme by adding carbon-rich molecules, which significantly improved the thermal conductivity of the film compared with Example 1, while maintaining good electrical properties and light transmittance. After adding an in-situ cleaning step in Example 3, the amorphous carbon content in the film was greatly reduced, the ID / IG value dropped to 0.18, and the electrical conductivity was further improved compared with Example 2, achieving the performance target of ultra-clean and high conductivity. Examples 4 and 5, respectively, used raw material ratios and process parameters adapted to high and low proportions of graphene oxide, and both were able to prepare graphene films with stable comprehensive performance, fully verifying the wide adaptability of the technical solution of the present invention, which can meet the application needs of different industrialization scenarios.

[0084] The test results of the comparative examples and the comparative examples show that the absence of any one of the core technical features of the present invention will lead to a significant decrease in the performance of the thin film.

[0085] Comparative Example 1 uses a single carbon source, resulting in severe graphene sheet agglomeration and significantly lower specific surface area and electrical conductivity than Example 1. Comparative Example 2 lacks carbon-rich molecular modification, failing to form continuous thermal conductive channels, and its thermal conductivity is only 63.8% of that of Example 2, which cannot meet the requirements of high thermal conductivity applications. Comparative Example 3 lacks an in-situ cleaning step, leaving amorphous carbon contaminants in the film, and its conductivity decreases by 26.5% compared to Example 3. Comparative Example 4 uses a single reducing agent system, resulting in insufficient reduction of graphene oxide, and both the mechanical and electrical properties of the film are lower than those of Example 4. Comparative Example 5 deviates from the protection scope of this invention in terms of raw material ratio, highlighting graphene sheet agglomeration and structural disorder, and significantly reducing the overall performance of the film. Comparative Examples 6 and 7, as combinations of existing technologies, lack the core technical features of this invention and cannot achieve synergistic improvement of various properties, resulting in overall performance that is significantly lower than the corresponding examples.

[0086] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A graphene film, characterized in that, It is composed of graphene oxide, thermally exfoliated graphene and naphthalene, and is prepared by in-situ cleaning with carbon dioxide and hot pressing in an argon atmosphere.

2. The graphene film according to claim 1, characterized in that, The mass ratio of graphene oxide to thermally exfoliated graphene is 0.5:1 to 2:1, and the mass fraction of naphthalene is 0.08% to 0.18% of the total mass of graphene oxide and thermally exfoliated graphene.

3. The graphene film according to claim 1, characterized in that, The graphene film has a layered stacked structure.

4. A method for preparing a graphene film, characterized in that, The process includes raw material pretreatment, composite dispersion, chemical reduction, vacuum filtration for film formation, and hot pressing post-treatment steps. The raw materials include graphene oxide and thermally exfoliated graphene. The chemical reduction uses 57% hydroiodic acid or a composite reducing agent composed of sodium borohydride and hydroiodic acid.

5. The preparation method according to claim 4, characterized in that, The mass ratio of graphene oxide to thermally exfoliated graphene is 0.5:1 to 2:

1. Naphthalene is added in the composite dispersion step, and the mass fraction of naphthalene is 0.08% to 0.18% of the total mass of graphene oxide and thermally exfoliated graphene.

6. The preparation method according to claim 4, characterized in that, The raw material pretreatment involves vacuum drying of graphene oxide and annealing of thermally exfoliated graphene in an argon atmosphere.

7. The preparation method according to claim 4, characterized in that, After vacuum filtration to form a membrane, in-situ cleaning is performed, followed by the introduction of carbon dioxide gas and high-temperature insulation treatment.

8. The preparation method according to claim 4, characterized in that, The mass ratio of sodium borohydride to hydroiodic acid in the composite reducing agent is 1:3, and the mass ratio of the composite reducing agent to graphene oxide is 0.9:1 to 1.4:

1.

9. The preparation method according to claim 4, characterized in that, The composite dispersion was carried out in deionized water using ultrasonic dispersion treatment.

10. The preparation method according to claim 4, characterized in that, The hot-pressing post-treatment is carried out under high temperature and high pressure in an argon protective atmosphere.

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