High-solid-content graphene oxide slurry, viscosity reducer, graphene film and preparation method

Abstract

The invention discloses high-solid-content graphene oxide slurry, a viscosity reducer, a graphene film and a preparation method, and belongs to the technical field of graphene oxide slurry. Wherein the high-solid-content graphene oxide slurry contains a quaternary ammonium salt viscosity reducer, and the quaternary ammonium salt viscosity reducer is prepared by performing quaternization reaction on a tertiary amine compound, a halogenated hydrocarbon derivative and a solvent at 80-150 DEG C to obtain the quaternary ammonium salt viscosity reducer. The graphene oxide slurry with high solid content and low viscosity can be obtained, the flow ductility and the coating effect of the slurry are remarkably improved, and then the thermal conductivity and the yield of a graphene film are remarkably improved.

Description

Technical Field

[0001] This invention relates to the technical field of graphene oxide slurry, and particularly to high solids content graphene oxide slurry, viscosity reducer, graphene film, and preparation method. Background Technology

[0002] With the increasing miniaturization, high integration, and intelligence of electronic devices, their heat dissipation is rising sharply, seriously affecting performance, reliability, and lifespan. Statistics show that approximately 55% of electronic device failures are caused by overheating, and the failure rate of electronic components increases exponentially with operating temperature; for every 10°C increase in temperature, system reliability decreases by 50%. Therefore, efficient and stable heat dissipation has become a critical issue that urgently needs to be addressed in the consumer electronics field.

[0003] Traditional metal heat dissipation materials such as copper and aluminum are limited in application in fields such as flexible electronics, 5G communications, high-power LEDs, and aerospace due to their high density, poor corrosion resistance, and poor processability. In contrast, non-metallic materials such as graphene have significant advantages such as ultra-high theoretical thermal conductivity (approximately 5300 W / m·K), lightweight, flexibility, and high stability, making them ideal heat dissipation materials and widely used in mid-to-high-end smartphones, tablets, and other consumer electronics products. With the surge in demand for heat dissipation in the consumer electronics market, the penetration rate of graphene heat dissipation films will continue to increase, and it is expected to become the mainstream heat dissipation technology in the 5G era.

[0004] Graphene heat dissipation films are typically fabricated using graphene oxide (GO) as a precursor through processes such as dispersion, degassing, coating, drying, thermal reduction, and calendering. GO nanosheets are rich in polar functional groups such as carboxyl, hydroxyl, and epoxy groups, giving them excellent dispersibility and self-assembly capabilities, enabling them to form highly ordered layered self-assembled structures. The thermal reduction process removes oxygen-containing functional groups and repairs lattice defects, forming a near-single-crystal graphene film with a highly oriented sp² hybrid carbon network structure. This network achieves efficient phonon transport through π-π interactions, resulting in superior thermal conductivity.

[0005] In the GO slurry coating process, the slurry's flowability directly affects film quality (such as smoothness and self-assembly behavior). The suitable viscosity range for continuous coating is typically 15,000-35,000 mPa·s, depending on the coating process, substrate, and coating thickness. The slurry's solid content directly affects viscosity: higher solid content results in higher viscosity. Generally, when the solid content exceeds 4.5 wt%, excessively high viscosity or gelation is likely to occur, affecting coating quality. Increasing the solid content helps reduce solvent usage, optimize the drying process, and lower costs. Therefore, developing low-viscosity, high-solids-content GO slurries is key to achieving low-cost, large-scale production of graphene films.

[0006] Existing technologies mostly regulate slurry properties by adding additives. For example, patent application 202311269279.9 uses a compound of two polymeric dispersants to reduce viscosity and increase solid content, which can prepare GO films with high thickness and high cohesion. However, the dispersant structure is complex and the cost is high. Patent application 202110369771.8 treats the oxygen-containing functional groups on the GO surface with group binders and modifiers, and uses steric hindrance and electrostatic repulsion to regulate the interaction between the layers, thereby reducing viscosity and preventing sedimentation, solving the problem of high viscosity and difficulty in homogenization of high solid content slurries.

[0007] In addition, the existing technology still has the following problems: structural defects introduced in the preparation and self-assembly process of graphene macromaterials become phonon scattering centers, which hinder heat conduction; the viscosity of high solid content GO slurry is difficult to control, which restricts the reduction of production costs; low solid content slurry is prone to wrinkles, cracks and other defects due to uneven drying when forming films, which affects the film quality and thermal conductivity.

[0008] Therefore, optimizing the dispersion process, developing new additives or surface modification strategies to prepare high-solids-content, low-viscosity GO slurries to obtain graphene oxide films with orderly stacking, high interlayer bonding, few defects, and good uniformity, thereby improving the thermal conductivity and production economy of graphene heat dissipation films, remains a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a novel viscosity reducer for high-solids-content graphene oxide slurry, the resulting high-solids-content graphene oxide slurry, a high-thermal-conductivity graphene film, and a preparation method thereof. The viscosity reducer is a small-molecule quaternary ammonium salt, which can yield a graphene oxide slurry with high solids content and low viscosity, significantly improving the slurry's flowability and coating effect, thereby significantly improving the thermal conductivity and yield of the graphene film.

[0010] The technical solution of the present invention is as follows: A method for preparing a quaternary ammonium salt viscosity reducer for high solids content graphene oxide slurry, comprising: subjecting a tertiary amine compound, a haloalkane derivative, and a solvent to a quaternization reaction at 80-150°C to obtain the quaternary ammonium salt viscosity reducer, wherein the molar ratio of the tertiary amine compound to the haloalkane derivative is 1:2.2-2.4; the tertiary amine compound is selected from tetramethylethylenediamine, tetramethylpropylenediamine, triethylenediamine, and... N , N -Dimethylpiperazine, N , N One or more of dimethylbenzylamine; the halocarbon derivative is selected from one or more of 3-chloro-2-hydroxypropyltrimethylammonium chloride, 3-chloro-1,2-propanediol, chlorooctane, and (3-chloropropyl)-trimethylammonium chloride; the solvent is selected from water, acetonitrile,N , N One or more of dimethylformamide.

[0011] The quaternary ammonium salt viscosity reducer synthesized by the above preparation method of the present invention contains multiple quaternary ammonium structures in its end group region. It exhibits excellent solubility in both weak acid and weak alkaline aqueous solvents and can exert excellent viscosity-reducing effect at extremely low addition amounts. It can significantly increase the solid content of graphene oxide slurry and improve the viscosity and flowability of high solid content graphene oxide slurry.

[0012] Meanwhile, the quaternary ammonium salt viscosity reducer synthesized by the above preparation method of the present invention can form multiple non-covalent interactions with the abundant negatively charged oxygen-containing functional groups (such as carboxyl, hydroxyl, carbonyl, and epoxy groups) on the surface of graphene oxide in the positively charged quaternary ammonium salt cation in the graphene oxide slurry, inducing the formation of a highly ordered interlayer stacked self-assembled structure of graphene oxide nanosheets; at the same time, it can combine with the negative charge on the surface of graphene oxide through electrostatic interaction, increasing the interlayer spacing of graphene oxide, effectively weakening the non-covalent bond (hydrogen bond and van der Waals force) interactions between graphene oxide sheets, making it easier for solvent molecules (such as water) to insert into the graphene oxide sheets. During this process, swelling pressure is generated, which improves the exfoliation effect and dispersibility of graphene oxide and reduces the working pressure of homogenization equipment. The influence of the above quaternary ammonium salt molecules on the intercalation and self-assembly behavior of graphene oxide sheets can be further used to finely control the yield, sheet size and surface properties of monolayer graphene oxide in the slurry. In this process, the inventors unexpectedly discovered that factors such as the charge density, ionic radius, concentration of the obtained quaternary ammonium salt cations and the pH value of the solution affect the intercalation effect. Generally, the higher the charge number of the cations, the stronger the electrostatic interaction with the surface of graphene oxide, the easier it is to intercalate, and the better the corresponding intercalation effect.

[0013] Meanwhile, due to the strong electrostatic interaction between the quaternary ammonium salt viscosity reducer and the surface of the graphene oxide nanosheets, the graphene oxide sheets are easier to peel off, and the layer-by-layer ordered self-assembly behavior of the graphene oxide nanosheets is also significantly improved, thus obtaining a tightly stacked and ordered graphene oxide dry film. At the same time, during the high-temperature (2000℃) heat treatment, the nitrogen element in the quaternary ammonium salt viscosity reducer can dope the graphene with nitrogen, retaining more structural defects such as vacancies, dislocations and grain boundaries in the graphene. These structural defects promote the ordering and grain growth of the graphene film during the graphitization process, thereby preparing a graphene film with a tightly ordered microstructure and excellent thermal conductivity.

[0014] The preparation method of the present invention can efficiently prepare a variety of quaternary ammonium salt viscosity reducers through a simple one-step reaction, and the yield of the obtained quaternary ammonium salt viscosity reducers can reach more than 95%.

[0015] According to some preferred embodiments of the present invention, the molar ratio of the tertiary amine compound to the haloalkane derivative is 1:2.2, and the temperature of the quaternization reaction is 110-130°C.

[0016] According to some preferred embodiments of the present invention, the tertiary amine compound is selected from tetramethylethylenediamine and / or tetramethylpropylenediamine.

[0017] According to some preferred embodiments of the present invention, the halohydrocarbon derivative is selected from 3-chloro-2-hydroxypropyltrimethylammonium chloride and / or 3-chloro-1,2-propanediol.

[0018] According to some preferred embodiments of the present invention, the solvent is water.

[0019] The inventors unexpectedly discovered that, among the tertiary amine compounds, tetramethylethylenediamine and / or tetramethylpropanediamine are the optimal choices; among the halocarbon derivatives, 3-chloro-2-hydroxypropyltrimethylammonium chloride and / or 3-chloro-1,2-propanediol are the optimal choices; and among the solvents, water is the optimal choice.

[0020] The present invention further provides a quaternary ammonium salt viscosity reducer for high solids content graphene oxide slurry prepared according to the above preparation method.

[0021] The present invention further provides a high solids content graphene oxide slurry containing the above-mentioned high solids content graphene oxide slurry quaternary ammonium salt viscosity reducer.

[0022] This high-solids-content graphene oxide slurry combines high solids content with low viscosity. Its solids content can reach over 9.5wt%, and its viscosity is only 12000-36000 mPa.s. It is suitable for coating and the resulting graphene oxide wet film has a smooth and flat surface.

[0023] According to some preferred embodiments of the present invention, the method for preparing the high solids content graphene oxide slurry includes: (1) A graphene oxide filter cake with a solid content of 45-55 wt%, water, the high solid content graphene oxide slurry, a quaternary ammonium salt viscosity reducer, and a pH adjuster are mixed and stirred to obtain a mixed slurry; the solid content of the mixed slurry is 5-12 wt%, and the pH value is 6-7; the net weight of the quaternary ammonium salt viscosity reducer added to the high solid content graphene oxide slurry is 0.5-3 wt% of the mixed slurry; (2) The mixed slurry is subjected to high-pressure homogenization at a pressure of 800-1200 bar to obtain a homogenized slurry; (3) The homogenized slurry is degassed to obtain the high solids content graphene oxide slurry.

[0024] The inventors unexpectedly discovered that it is better to control the content of the quaternary ammonium salt viscosity reducer between 0.5-3wt%, which can give full play to the excellent viscosity reduction effect, overcome the problem of viscosity runaway in high solid content graphene oxide slurry during high pressure homogenization, and avoid the problem of graphene oxide wet film curling or even breaking during drying due to excessive addition content.

[0025] In the above preparation method of the present invention, the solid content of the mixed slurry is 5-12 wt%, for example, it can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, etc.; the mass of the quaternary ammonium salt viscosity reducer added to the high solid content graphene oxide slurry is 0.5-3 wt% of the mixed slurry, for example, it can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc.

[0026] According to some preferred embodiments of the present invention, the mixing and stirring time is 30-60 minutes.

[0027] According to some preferred embodiments of the present invention, in order to ensure that the graphene oxide slurry after adding quaternary ammonium salt viscosity reducer has a uniform color and no agglomeration, the stirring speed of the mixing is 200-500 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, etc.

[0028] According to some preferred embodiments of the present invention, in order to ensure that graphene oxide is uniformly and stably dispersed in deionized water, the pressure of the high-pressure homogenization treatment is 800-1200 bar, for example, 800 bar, 900 bar, 950 bar, 1000 bar, 1100 bar, 1200 bar, etc.

[0029] According to some preferred embodiments of the present invention, the pH adjuster is selected from industrial ammonia.

[0030] The present invention further provides a graphene oxide dry film, which is obtained by coating and drying the high solids content graphene oxide slurry.

[0031] According to some preferred embodiments of the present invention, the method for preparing the graphene oxide dry film includes: (1) The graphene oxide slurry is uniformly coated on the substrate at a coating speed of 1-5 m / min to obtain a graphene oxide wet film with a thickness of 2000-3000 μm. (2) The graphene oxide wet film is subjected to forced air drying treatment. The treatment process is as follows: the wind speed is controlled at 0.5-1.5m / s, and then dried at 30-40℃ for 1-2h, and then the temperature is raised to 50-60℃ for 2-3h to obtain graphene oxide dry film.

[0032] The above preparation method of the present invention can achieve excellent coating effect while significantly reducing the cost of blower drying, laying the foundation for low-cost preparation of graphene heat dissipation film.

[0033] The inventors unexpectedly discovered that in the above preparation methods, excessively high drying temperatures cause the solvent on the surface of the graphene oxide wet film to evaporate rapidly, forming a thin film similar to milk skin. This hinders the evaporation pathway of the internal solvent, leading to a drying gradient within the film. Ultimately, under the action of internal stress, this causes cracks, bulges, and even severe damage to the ordered stacking structure of the graphene oxide sheets in the dry film. This invention, after comprehensively considering the wet film thickness, forced-air drying temperature, and wind speed, adopts a gradient temperature drying method, solving the above problems and simultaneously addressing the issues of increased dry film brittleness and difficulty in demolding caused by excessively long high-temperature drying times.

[0034] In the above preparation method of the present invention, the thickness of the graphene oxide wet film is 2000-3000 μm, for example, it can be 2000 μm, 2200 μm, 2400 μm, 2600 μm, 2800 μm, 3000 μm, etc.

[0035] The coating speed is 1-5 m / min, for example, 1 m / min, 2.5 m / min, 4 m / min, 5 m / min, etc.

[0036] The present invention further provides a graphene heat dissipation film, which is prepared by carbonization and graphitization of the graphene oxide dry film.

[0037] According to some preferred embodiments of the present invention, the method for preparing the graphene heat dissipation film includes: (1) Under an inert atmosphere, the graphene oxide dry film is subjected to low-temperature carbonization treatment at a temperature of 1000-1200℃ and a holding time of 8-12h to obtain a carbonized film. (2) Under an inert atmosphere, the carbonized film is subjected to high-temperature graphitization treatment at a temperature of 2850-3000℃ and a holding time of 2-3h to obtain an expanded graphene film. (3) The expanded graphene film is calendered at a pressure of 200-600 tons in a step-by-step manner to obtain a dense graphene heat dissipation film.

[0038] According to some preferred embodiments of the present invention, during the low-temperature carbonization process, appropriate pressure can be applied to the graphene oxide dry film during the process of heating to 1000-1200°C to avoid the film material wrinkling or excessive volume expansion causing the film material to break.

[0039] According to some preferred embodiments of the present invention, the calendering process is performed using a flatbed press and / or a roll press.

[0040] The present invention has the following beneficial effects: The quaternary ammonium salt type small molecule viscosity reducer prepared by this invention has a simple synthesis process, uses environmentally friendly and inexpensive reaction medium (pure water), and has a high conversion rate in the reaction type (quaternization reaction). At the same time, it has excellent viscosity reduction effect, and can produce significant viscosity reduction effect at a low addition amount (0.5-3wt%), thereby significantly reducing the overall cost of graphene heat dissipation film, while greatly improving the thermal conductivity of graphene oxide. This helps to rapidly increase the market penetration rate of graphene heat dissipation film in the field of thermal management of consumer electronics products, and at the same time provide end users with a better product experience.

[0041] The quaternary ammonium salt viscosity reducer prepared by this invention exhibits good dispersibility in water. It can be obtained by directly mixing and dispersing graphene oxide, water and quaternary ammonium salt viscosity reducer in sequence to obtain graphene oxide slurry with high solid content and low viscosity without additional processing operations, and has wide process applicability. The graphene oxide slurry prepared by this invention has high solids content and low viscosity. Graphene oxide dry films have a tightly ordered interlayer stacked structure. Graphene oxide dry films prepared by this high-solids-content, low-viscosity graphene oxide slurry can significantly reduce drying costs and structural defects such as wrinkles and cracks caused by the significant drying rate gradient formed inside the film during the thick film drying process.

[0042] The graphene heat dissipation film prepared by this invention exhibits ultra-high thermal conductivity (horizontal thermal conductivity 1600-2000 W / m∙K). Attached Figure Description

[0043] Figure 1 This is a TEM image of the cross-section of the graphene oxide dry film obtained in Example 7; Figure 2 This is a TEM image of the cross-section of the graphene heat dissipation film obtained in Example 9. Detailed Implementation

[0044] The technical solutions of the present invention will be further described below with reference to the embodiments and accompanying drawings. The embodiments described below 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 should fall within the scope of protection of the present invention.

[0045] Example 1 The high solids content graphene oxide slurry quaternary ammonium salt viscosity reducer G-2OH was prepared by the following steps: (1) Add 0.4 mol tetramethylethylenediamine and 0.88 mol 3-chloro-1,2-propanediol (the molar ratio of tetramethylethylenediamine to 3-chloro-1,2-propanediol is 1:2.2) to 50 mL of deionized water to obtain a mixture; (2) The mixture was stirred at 120°C for 24 hours. After the reaction was completed, it was cooled to room temperature, and the aqueous solvent was removed by vacuum. The pale yellow viscous substance was collected to obtain the target product, quaternary ammonium salt viscosity reducer G-2OH.

[0046] The yield of the obtained quaternary ammonium salt viscosity reducer G-2OH was 96%. Before use, an appropriate amount of deionized water was added to prepare a 20wt% aqueous solution.

[0047] The reaction process is shown in the following reaction equation:

[0048] Example 2 The high solids content graphene oxide slurry quaternary ammonium salt viscosity reducer G-2OH was prepared by the following steps: (1) Add 0.4 mol tetramethylethylenediamine and 0.88 mol 3-chloro-1,2-propanediol (the molar ratio of tetramethylethylenediamine to 3-chloro-1,2-propanediol is 1:2.2) to 50 mL acetonitrile to obtain a mixture; (2) The mixture was stirred at 100°C for 24 hours. After the reaction was completed, it was cooled to room temperature, and the acetonitrile solvent was removed by vacuum rotation. The pale yellow viscous substance was collected to obtain the target product, quaternary ammonium salt viscosity reducer G-2OH.

[0049] The yield of the obtained quaternary ammonium salt viscosity reducer G-2OH was 98%. Before use, an appropriate amount of deionized water was added to prepare a 20wt% aqueous solution.

[0050] The reaction process is shown in the following reaction equation:

[0051] Example 3 The following steps were used to prepare a quaternary ammonium salt viscosity reducer G-OH for high solids content graphene oxide slurry: (1) Add 0.4 mol tetramethylethylenediamine and 0.88 mol 3-chloro-2-hydroxypropyltrimethylammonium chloride (the molar ratio of tetramethylethylenediamine to 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1:2.2) to 50 mL of deionized water to obtain a mixture; (2) The mixture was stirred at 120°C for 24 hours. After the reaction was completed, it was cooled to room temperature, and the aqueous solvent was removed under reduced pressure. The pale yellow viscous substance was collected to obtain the target product, quaternary ammonium salt viscosity reducer G-OH.

[0052] The yield of the obtained quaternary ammonium salt viscosity reducer was 97%. Before use, an appropriate amount of deionized water was added to prepare a 20wt% aqueous solution.

[0053] The reaction process is shown in the following reaction equation:

[0054] Example 4 The following steps were used to prepare a quaternary ammonium salt viscosity reducer G-OH for high solids content graphene oxide slurry: (1) Add 0.4 mol tetramethylethylenediamine and 0.88 mol 3-chloro-2-hydroxypropyltrimethylammonium chloride (the molar ratio of tetramethylethylenediamine to 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1:2.2) to 50 mL acetonitrile to obtain a mixture; (2) The mixture was stirred at 100°C for 24 hours. After the reaction was completed, it was cooled to room temperature, and the acetonitrile solvent was removed by vacuum. The pale yellow viscous substance was collected to obtain the target product, quaternary ammonium salt viscosity reducer G-OH.

[0055] The yield of the obtained quaternary ammonium salt viscosity reducer was 97%. Before use, an appropriate amount of deionized water was added to prepare a 20wt% aqueous solution.

[0056] The reaction process is shown in the following reaction equation:

[0057] Example 5 A high-solids-content, low-viscosity graphene oxide slurry was prepared using the following steps: (1) Graphene oxide filter cake with a solid content of 45wt%, deionized water, a 20wt% aqueous solution of the quaternary ammonium salt viscosity reducer G-2OH obtained in Example 1, and industrial ammonia water as a pH adjuster were added sequentially to a double planetary mixer and stirred for 30 min to obtain a pre-dispersed mixed slurry. In order to ensure that the graphene oxide slurry after adding the quaternary ammonium salt viscosity reducer has a uniform color and no agglomeration, the stirring speed was controlled at 400 rpm. The added mass of graphene oxide filter cake was 211 g, and the net weight of added G-2OH was 0.5wt% of the weight of graphene oxide filter cake. The added mass of industrial ammonia water was 2.1% of the total weight of the pre-dispersed mixed slurry, and the pH of the pre-dispersed mixed slurry was about 6-7. (2) The obtained pre-dispersed slurry is transferred to a high-pressure homogenizer for high-pressure homogenization. In order to ensure that the graphene oxide can be uniformly and stably dispersed in deionized water, the high-pressure homogenization pressure is controlled at 800 bar. Then, the graphene oxide slurry obtained after homogenization is degassed to obtain a high solid content and low viscosity graphene oxide slurry.

[0058] The obtained graphene oxide slurry was tested and found to have a solid content of 9.5 wt% and a viscosity of 21000 mPa·s.

[0059] Example 6 A high-solids-content, low-viscosity graphene oxide slurry was prepared using the following steps: (1) Graphene oxide filter cake with a solid content of 45wt%, deionized water, and a 20wt% aqueous solution of the quaternary ammonium salt viscosity reducer G-OH obtained in Example 4, and industrial ammonia water as a pH adjuster were added sequentially to a double planetary mixer and stirred for 30 min to obtain a pre-dispersed mixed slurry. In order to ensure that the graphene oxide slurry after adding the quaternary ammonium salt viscosity reducer has a uniform color and no agglomeration, the stirring speed was controlled at 400 rpm. The added mass of graphene oxide filter cake was 211 g, and the net added mass of G-OH was 0.5 wt% of the weight of graphene oxide filter cake. The added mass of industrial ammonia water was 2.1% of the total weight of the pre-dispersed mixed slurry, and the pH of the pre-dispersed mixed slurry was about 6-7. (2) The obtained pre-dispersed slurry is transferred to a high-pressure homogenizer for high-pressure homogenization. In order to ensure that the graphene oxide is uniformly and stably dispersed in deionized water, the high-pressure homogenization pressure is controlled at 800 bar. Then, the graphene oxide slurry obtained after homogenization is degassed to obtain a high solid content and low viscosity graphene oxide slurry.

[0060] The obtained graphene oxide slurry was tested and found to have a solid content of 9.5 wt% and a viscosity of 23,000 mPa·s.

[0061] Example 7 Graphene oxide dry film was prepared by the following steps: (1) The graphene oxide slurry obtained in Example 5 was uniformly coated onto the PP substrate using a slit coating device at a coating speed of 1 m / min to obtain a graphene oxide wet film with a thickness of 2000 μm. (2) The graphene oxide wet film was dried in a forced-air drying oven. The drying process was as follows: drying at 30℃ for 2 hours, then heating to 50℃ for 3 hours. The wind speed was controlled at 0.5 m / s during the drying process to obtain the graphene oxide dry film.

[0062] A cross-sectional TEM image of the obtained graphene oxide dry film is attached. Figure 1 As shown, through Figure 1 It can be seen that the obtained graphene oxide dry film has a highly regular and tightly ordered layered stacked structure.

[0063] Example 8 Graphene oxide dry film was prepared by the following steps: (1) The graphene oxide slurry obtained in Example 6 was uniformly coated onto the substrate using a slit coating device at a coating speed of 5 m / min to obtain a graphene oxide wet film with a thickness of 3000 μm. (2) The graphene oxide wet film was dried in a forced-air drying oven. The drying process was as follows: drying at 40℃ for 1 hour, then heating to 60℃ for 2 hours. The wind speed was controlled at 1.5 m / s during the drying process to obtain the graphene oxide dry film.

[0064] The resulting graphene oxide dry film has a highly regular and tightly ordered layered stacked structure.

[0065] Example 9 The graphene heat dissipation film is prepared by the following steps: (1) The graphene oxide dry film obtained in Example 7 was subjected to low-temperature carbonization treatment in an argon atmosphere. The carbonization treatment temperature was 1000℃ and the treatment time was 8h to obtain a carbonized film. (2) In an argon atmosphere, the obtained carbonized film was subjected to high-temperature graphitization treatment at a temperature of 2850℃ for 2 hours to obtain an expanded graphene film. (3) The expanded graphene film is densified by calendering using a flat press. The calendering is carried out by a gradient pressure of 200-600 tons for a total time of 2 hours to obtain a graphene heat dissipation film.

[0066] A TEM image of the cross-section of the obtained graphene heat dissipation film is attached. Figure 2 As shown in the figure, the obtained heat dissipation film has a layered structure with a tight and orderly arrangement.

[0067] Further Raman spectroscopy was used to test its degree of graphitization, and the results showed that its I D / I GA value of 0.03 indicates a graphitization degree greater than 95%, meaning that the nitrogen element in the quaternary ammonium salt was used for nitrogen doping of the graphene during the high-temperature treatment. Nitrogen-doped graphene retains more defect structures such as vacancies, dislocations, and grain boundaries. As the graphitization temperature increases, these lattice defects can significantly promote the structural ordering and grain growth of the graphene film during the graphitization process, thereby obtaining a graphene film with excellent electrical and thermal conductivity.

[0068] Further thermal conductivity tests using the laser scintillation method revealed that the graphene heat dissipation film exhibits ultra-high horizontal thermal conductivity, reaching 1600-2000 W / m·K.

[0069] Example 10 The graphene heat dissipation film is prepared by the following steps: (1) The graphene oxide dry film obtained in Example 8 was subjected to low-temperature carbonization treatment in an argon atmosphere. The carbonization treatment temperature was 1000℃ and the treatment time was 12h to obtain a carbonized film. (2) In an argon atmosphere, the obtained carbonized film was subjected to high-temperature graphitization treatment at a temperature of 2850℃ for 3 hours to obtain an expanded graphene film. (3) The expanded graphene film is densified by calendering using a flat press. The calendering is carried out by a gradient pressure of 200-600 tons for a total time of 2 hours to obtain a graphene heat dissipation film.

[0070] Tests showed that the obtained graphene heat dissipation film has a layered structure with a tight and orderly arrangement, a graphitization degree of 96%, and a horizontal thermal conductivity of up to 1800 W / m·K.

[0071] It should be noted that the above descriptions are merely preferred embodiments of the present invention and should not limit the scope of protection of the technical solutions of the present invention. Any modifications made to the technical solutions described in the foregoing embodiments, or equivalent substitutions of technical features, by those skilled in the art within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a quaternary ammonium salt viscosity reducer for high solids content graphene oxide slurry, characterized in that, It includes: quaternizing a tertiary amine compound, a haloalkanes derivative, and a solvent at 80-150 °C to obtain the quaternary ammonium salt viscosity reducer, wherein the molar ratio of the tertiary amine compound to the haloalkanes derivative is 1:2-2.5; the tertiary amine compound is selected from tetramethylethylenediamine, tetramethylpropylenediamine, triethylenediamine, etc. N , N One or more of dimethylpiperazine; the halocarbon derivative is selected from one or more of 3-chloro-2-hydroxypropyltrimethylammonium chloride, 3-chloro-1,2-propanediol, chlorooctane, and (3-chloropropyl)-trimethylammonium chloride; the solvent is selected from water, acetonitrile, etc. N , N One or more of dimethylformamide.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the tertiary amine compound to the haloalkane derivative is 1:2.2, and the temperature of the quaternization reaction is 110-130℃.

3. A quaternary ammonium salt viscosity reducer for high solids content graphene oxide slurry prepared by the preparation method according to claim 1 or 2.

4. A high-solids-content graphene oxide slurry containing the quaternary ammonium salt viscosity reducer for high-solids-content graphene oxide slurry as described in claim 3.

5. The method for preparing the high solids content graphene oxide slurry according to claim 4, characterized in that, It includes: (1) A graphene oxide filter cake with a solid content of 45-55 wt%, water, the high solid content graphene oxide slurry, a quaternary ammonium salt viscosity reducer, and a pH adjuster are mixed and stirred to obtain a mixed slurry; the solid content of the mixed slurry is 5-12 wt%, and the pH value is 6-7; the mass of the quaternary ammonium salt viscosity reducer added to the high solid content graphene oxide slurry is 0.5-3 wt% of the mixed slurry; (2) The mixed slurry is subjected to high-pressure homogenization at a pressure of 800-1200 bar to obtain a homogenized slurry; (3) The homogenized slurry is degassed to obtain the high solids content graphene oxide slurry.

6. The preparation method according to claim 5, characterized in that, The pH adjuster is selected from industrial ammonia.

7. A graphene oxide dry film, obtained by coating and drying the high solids content graphene oxide slurry as described in claim 4.

8. The method for preparing the graphene oxide dry film according to claim 7, characterized in that, It includes: (1) The graphene oxide slurry is uniformly coated on the substrate at a coating speed of 1-5 m / min to obtain a graphene oxide wet film with a thickness of 2000-3000 μm. (2) The graphene oxide wet film is subjected to forced air drying treatment. The treatment process is as follows: the wind speed is controlled at 0.5-1.5m / s, and then dried at 30-40℃ for 1-2h, and then the temperature is raised to 50-60℃ for 2-3h to obtain graphene oxide dry film.

9. A graphene heat dissipation film, which is prepared by carbonization and graphitization of the graphene oxide dry film as described in claim 7.

10. The preparation method according to claim 9, characterized in that, It includes: (1) Under an inert atmosphere, the graphene oxide dry film is subjected to low-temperature carbonization treatment at a temperature of 1000-1200℃ and a holding time of 8-12h to obtain a carbonized film. (2) Under an inert atmosphere, the carbonized film is subjected to high-temperature graphitization treatment at a temperature of 2850-3000℃ and a holding time of 2-3h to obtain an expanded graphene film. (3) The expanded graphene film is calendered at a pressure of 200-600 tons using a stepped pressure increase method to obtain a graphene heat dissipation film.

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