High-thermal-conductivity graphene heat dissipation film and preparation method thereof

Abstract

The invention relates to the field of nano materials, and discloses a high-thermal-conductivity graphene heat dissipation film which comprises the following components in parts by mass: 40-60 parts of biomass derived carbon nanosheets; 20 to 40 parts of functionalized graphene; 5 to 10 parts of an iron / cobalt bimetallic catalyst; 0.1 to 0.5 part of a dispersant; 10 to 30 parts of a solvent; wherein the sum of the mass parts of the biomass derived carbon nanosheets and the functionalized graphene is less than or equal to 90; the molar ratio of iron to cobalt of the iron / cobalt bimetallic catalyst is (1: 0.8)-(1: 2), the biomass derived carbon nanosheets are prepared from lignin through hydrothermal carbonization, and the hydrothermal carbonization conditions are as follows: the addition amount of diammonium hydrogen phosphate is 5-10% of the mass of lignin; the reaction temperature is 180-220 DEG C, and the reaction time is 4-8 hours. According to the method, a hydrothermal-microwave synergistic stripping process and a phosphate template regulation and control technology are adopted, so that accurate regulation and control of a cross-scale structure of the biomass carbon nanosheet are realized, the technical contradiction that pore size distribution and layer thickness uniformity cannot be considered in a traditional method is solved, and the phonon scattering bottleneck caused by disordered stacking is broken through.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a high-thermal-conductivity graphene heat dissipation film and a preparation method thereof. Background Art

[0002] As the power density of electronic devices such as 5G communications and high-power chips continues to rise, heat dissipation materials face an urgent need to improve both thermal conductivity and lightweighting. Graphene, with its ultra-high thermal conductivity (approximately 5300 W / (m·K)) and intrinsic flexibility, is considered a core material for the next generation of high-performance heat dissipation films. However, the large-scale application of graphene heat dissipation films is still limited by bottlenecks such as the complexity of the preparation process, high costs, and insufficient structural controllability.

[0003] Currently, the industry mainly uses mechanical exfoliation, chemical vapor deposition (CVD), or high-temperature graphitization to prepare graphene materials. Among them, mechanical exfoliation obtains a few-layer graphene by exfoliating graphite through shear force, but its product layer thickness is highly discrete (10-100nm) and has a high defect density. Although chemical vapor deposition can produce high-quality graphene films, it is limited by the substrate size and transfer process, making large-scale continuous production difficult. High-temperature graphitization (>2500℃) produces graphitized carbon films by pyrolyzing polymer precursors, but it has problems such as high energy consumption and loss of flexibility.

[0004] Existing technologies for producing heat dissipation films using biomass-derived carbon often rely on a single hydrothermal carbonization or mechanical exfoliation process, resulting in uneven carbon nanosheet thickness (deviations >50%) and a discrete pore size distribution (50-500nm). This structural defect causes severe phonon boundary scattering, resulting in actual thermal conductivity less than 30% of the theoretical value. Achieving precise cross-scale structural control of biomass carbon nanosheets (balancing pore size uniformity and layer thickness controllability) has become a core challenge hindering the performance improvement of high-thermal conductivity heat dissipation films. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a high thermal conductivity graphene heat dissipation film and a preparation method thereof, which solves the core technical problems of the existing biomass-derived carbon heat dissipation film, such as severe phonon scattering caused by uneven thickness of carbon nanosheets and discrete pore size distribution, and the actual thermal conductivity coefficient being less than 30% of the theoretical value.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A high thermal conductivity graphene heat dissipation film, comprising the following components in parts by weight: Biomass-derived carbon nanosheets: 40-60 parts; Functionalized graphene: 20-40 parts; Iron / cobalt bimetallic catalyst: 5-10 parts; Dispersant: 0.1-0.5 parts; Solvent: 10-30 parts; The total weight of the biomass-derived carbon nanosheets and the functionalized graphene is ≤ 90 parts; The molar ratio of iron to cobalt in the iron / cobalt bimetallic catalyst is 1:0.8-1:2.

[0007] Preferably, the biomass-derived carbon nanosheets are prepared by hydrothermal carbonization of lignin, and the hydrothermal carbonization conditions include: The amount of diammonium phosphate added is 5-10% of the lignin mass; Reaction temperature 180-220°C, time 4-8 hours; The biomass-derived carbon nanosheets have a pore size of 50-300 nm and a thickness of 5-20 nm.

[0008] Preferably, the iron / cobalt bimetallic catalyst is loaded on the surface of the biomass-derived carbon nanosheets by a stepwise impregnation method, comprising: The iron salt is ferric nitrate solution with a concentration of 0.05-0.2M; The cobalt salt is a cobalt chloride solution with a concentration of 0.02-0.1M; Calcination conditions: air atmosphere, temperature 300-500℃, time 1-3 hours; Reduction conditions: H2 / Ar mixed gas, H2 accounting for 5-15%, temperature 400-600℃, time 0.5-2 hours.

[0009] Preferably, the solvent is deionized water with a conductivity of ≤1 μS / cm; the amount of the solvent used is such that the solid content of the dispersion is 5-15 wt%.

[0010] Preferably, the dispersant is polyvinyl pyrrolidone with a molecular weight of 40,000-60,000; The added amount of the dispersant is 0.1-0.5% of the total mass of the biomass-derived carbon nanosheets and the functionalized graphene.

[0011] The present invention also provides a method for preparing a high thermal conductivity graphene heat dissipation film, comprising the following steps: Step 1: subjecting the biomass raw material to hydrothermal carbonization and microwave exfoliation to obtain biomass-derived carbon nanosheets; Step 2: The biomass-derived carbon nanosheets are sequentially impregnated with iron salt and cobalt salt solutions, and subjected to calcination and reduction treatment to load the iron / cobalt bimetallic catalyst; Step 3: pre-reducing the graphene oxide and reacting it with an aminosilane coupling agent to obtain functionalized graphene; Step 4: mixing the biomass-derived carbon nanosheets, functionalized graphene and a dispersant and then electrostatically spraying the mixture into a film to form a three-dimensional porous skeleton; Step 5: Perform low-temperature catalytic graphitization treatment in a hydrogen atmosphere to obtain a graphene heat dissipation film.

[0012] Preferably, in step 1: The hydrothermal carbonization is carried out in a nitrogen atmosphere, and after the reaction, the reaction is centrifuged and washed until neutral; The microwave stripping adopts a pulse mode, and the total processing time is 20-40 minutes.

[0013] Preferably, in the step 2: After impregnation with iron salt, ultrasonic dispersion treatment is performed with a power of 200-400W for 20-40 minutes; The heating rate of calcination and reduction is 2-5°C / min.

[0014] Preferably, in step three: Pre-reduction treatment: Graphene oxide is heat treated in a H2 / N2 mixture at 150-250°C for 0.5-2 hours; Coupling treatment: react with KH-792 ethanol solution at 40-80°C for 2-6 hours.

[0015] Preferably, in step 4 and step 5: Before electrostatic spraying, the dispersion liquid is vacuum degassed for 30-60 minutes; During the catalytic graphitization treatment, inert gas is introduced to dilute the hydrogen, and the dilution ratio is H2:Ar=1:1-1:3.

[0016] The present invention provides a high thermal conductivity graphene heat dissipation film and a preparation method thereof. It has the following beneficial effects: 1. The present invention adopts a hydrothermal-microwave synergistic exfoliation process and phosphate template control technology to achieve precise cross-scale structural control of biomass carbon nanosheets. Compared with the mechanical exfoliation or single hydrothermal carbonization process in the existing technology, it solves the technical contradiction that the traditional method cannot take into account both pore size distribution and layer thickness uniformity, and breaks through the bottleneck of phonon scattering caused by disordered stacking.

[0017] 2. The present invention constructs an iron / cobalt bimetallic interface synergistic catalytic system through a step-by-step impregnation and gradient heat treatment strategy. Compared with the co-impregnation or single metal loading process in the existing technology, it solves the defects of metal particle coarsening and insufficient dispersion in the traditional process, and realizes nano-scale precise guidance of the carbon atom migration path.

[0018] 3. The present invention is based on the electric field-flow field coupling technology of electrostatic spraying to form a three-dimensional interpenetrating thermal conductive network structure. Compared with the existing scraping and spin coating film forming processes, it breaks through the bottleneck of disordered stacking of traditional coating methods, increases the in-plane orientation degree to more than 70%, and eliminates the anisotropic heat transfer barrier.

[0019] 4. The present invention combines low-temperature catalytic graphitization with gradient passivation technology to achieve a performance balance between high order and high stability. Compared with the high-temperature pyrolysis or single passivation treatment in the existing technology, it overcomes the problems of flexibility loss and performance degradation in humid and hot environments caused by traditional high-temperature processes, and extends the service life of the material by more than 3 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the method of the present invention. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] An embodiment of the present invention provides a high thermal conductivity graphene heat dissipation film, comprising the following components in parts by weight: Biomass-derived carbon nanosheets: 40-60 parts; Functionalized graphene: 20-40 parts; Iron / cobalt bimetallic catalyst: 5-10 parts; Dispersant: 0.1-0.5 parts; Solvent: 10-30 parts; The total weight of the biomass-derived carbon nanosheets and the functionalized graphene is ≤ 90 parts; The molar ratio of iron to cobalt in the iron / cobalt bimetallic catalyst is 1:0.8-1:2.

[0023] Biomass-derived carbon nanosheets are prepared by hydrothermal carbonization of lignin. The hydrothermal carbonization conditions include: The amount of diammonium phosphate added is 5-10% of the lignin mass; Reaction temperature 180-220°C, time 4-8 hours; The biomass-derived carbon nanosheets have a pore size of 50-300 nm and a thickness of 5-20 nm.

[0024] The iron / cobalt bimetallic catalyst was loaded onto the surface of biomass-derived carbon nanosheets via a step-by-step impregnation method, including: The iron salt is ferric nitrate solution with a concentration of 0.05-0.2M; The cobalt salt is a cobalt chloride solution with a concentration of 0.02-0.1M; Calcination conditions: air atmosphere, temperature 300-500℃, time 1-3 hours; Reduction conditions: H2 / Ar mixed gas, H2 accounting for 5-15%, temperature 400-600℃, time 0.5-2 hours.

[0025] The solvent is deionized water with a conductivity of ≤1 μS / cm; the amount of the solvent is such that the solid content of the dispersion is 5-15 wt %.

[0026] The dispersant is polyvinylpyrrolidone with a molecular weight of 40,000-60,000; The added amount of the dispersant is 0.1-0.5% of the total mass of the biomass-derived carbon nanosheets and the functionalized graphene.

[0027] The preparation method of a high thermal conductivity graphene heat dissipation film described below and the high thermal conductivity graphene heat dissipation film described above can correspond to each other.

[0028] Please see the attached Figure 1 A method for preparing a high thermal conductivity graphene heat dissipation film comprises the following steps: Step 1: subjecting the biomass raw material to hydrothermal carbonization and microwave exfoliation to obtain biomass-derived carbon nanosheets; Step 2: The biomass-derived carbon nanosheets are sequentially impregnated with iron salt and cobalt salt solutions, and subjected to calcination and reduction treatment to load the iron / cobalt bimetallic catalyst; Step 3: pre-reducing the graphene oxide and reacting it with an aminosilane coupling agent to obtain functionalized graphene; Step 4: mixing the biomass-derived carbon nanosheets, functionalized graphene and a dispersant and then electrostatically spraying the mixture into a film to form a three-dimensional porous skeleton; Step 5: Perform low-temperature catalytic graphitization treatment in a hydrogen atmosphere to obtain a graphene heat dissipation film.

[0029] In step one: The hydrothermal carbonization was carried out in a nitrogen atmosphere and the reaction was followed by centrifugal washing until neutrality; Microwave exfoliation was performed in pulse mode with a total treatment time of 20-40 minutes.

[0030] In step 2: After impregnation with iron salt, ultrasonic dispersion treatment is performed with a power of 200-400W for 20-40 minutes; The heating rate of calcination and reduction is 2-5°C / min.

[0031] In step three: Pre-reduction treatment: Graphene oxide is heat treated in a H2 / N2 mixture at 150-250°C for 0.5-2 hours; Coupling treatment: react with KH-792 ethanol solution at 40-80°C for 2-6 hours.

[0032] In steps 4 and 5: Before electrostatic spraying, the dispersion liquid is vacuum degassed for 30-60 minutes; During the catalytic graphitization treatment, inert gas is introduced to dilute the hydrogen, and the dilution ratio is H2:Ar=1:1-1:3.

[0033] In this embodiment, the preparation of biomass-derived carbon nanosheets is achieved through a synergistic process of hydrothermal carbonization and microwave exfoliation. The core of this process is to construct a porous carbon skeleton with high specific surface area and uniform pore size distribution through molecular-level precursor design and energy field regulation.

[0034] Alternatively, the biomass feedstock includes, but is not limited to, softwood lignin, hardwood lignin, or lignin extracted from herbaceous plants, preferably high-purity lignin with an ash content of ≤0.5%. Specifically, the phenylpropane structural units in the lignin molecule form a three-dimensional network through cross-linking reactions, with the internal hydroxyl and carboxyl functional groups providing active sites for the subsequent directional growth of the carbon skeleton.

[0035] In one possible implementation, the hydrothermal carbonization process uses diammonium hydrogen phosphate as a catalyst and pore structure regulator. It should be noted that the NH4 generated by the decomposition of diammonium hydrogen phosphate in the hydrothermal environment + With PO4 3- Ions, adsorbed electrostatically between lignin molecular chains, inhibit excessive carbon stacking while inducing the conversion of micropores to mesopores. For example, the addition of diammonium hydrogen phosphate (DAP) accounts for 5%-10% of the lignin mass. Its amount is positively correlated with the pore size distribution of the final product: when the addition amount is less than 5%, pore connectivity decreases; when it is greater than 10%, the excess phosphorus may form an amorphous carbon coating, hindering subsequent catalytic graphitization.

[0036] It is understood that the temperature and time of the hydrothermal reaction have a decisive influence on the crystallinity of the carbon microsphere precursor. Preferably, the hydrothermal reaction temperature is controlled in the range of 180°C to 220°C and the reaction time is 4-8 hours. Under these conditions, the lignin molecules undergo dehydration, decarboxylation and aromatization reactions to form sp 2 The graphite-like microcrystalline structure is mainly composed of hybrid carbon, while retaining some oxygen-containing functional groups (such as carbonyl and ether bonds) as trigger sites for microwave exfoliation.

[0037] Regarding the microwave stripping process, specifically, a pulsed microwave mode is used to perform layered stripping of the carbon microspheres. Exemplarily, the microwave power is alternately switched between a high-power segment (e.g., 600-1000W) and a low-power segment (e.g., 100-300W), with a single high-power duration of no more than 15 seconds, and a low-power duration of 1.5-2 times that. It should be noted that the non-steady-state thermal field generated by the pulsed microwave can induce a local plasma effect at the oxygen-containing groups between the carbon layers, and achieve interlayer cleavage through the gasification pressure difference, while the intermittent low-power segment can avoid edge curling or structural collapse caused by continuous high heat. Compared with continuous microwave treatment, the pulsed mode can reduce the thickness deviation of the nanosheets by more than 60%.

[0038] In one embodiment, the microwave-treated product is washed and dried. Preferably, centrifugal washing is performed alternately with deionized water and ethanol until the wash solution has a conductivity of ≤5 μS / cm to remove residual phosphate and unreacted lignin fragments. Drying is performed under vacuum at a temperature of 50-80°C for 8-12 hours to prevent secondary agglomeration of the nanosheets.

[0039] In this embodiment, the loading of the iron / cobalt bimetallic catalyst is achieved through a step-by-step impregnation and heat treatment process. The core of this process is to construct a highly dispersed and strongly bonded metal-carbon interface structure through ion adsorption sequence control and thermodynamic phase change regulation.

[0040] As an option, the iron salt includes but is not limited to an aqueous solution of ferric nitrate, ferric sulfate or ferric chloride, preferably a solution of ferric nitrate. Specifically, nitrate ions (NO4 - ) can be hydrolyzed to generate H under weak acidic conditions + , by protonation to enhance the iron ion (Fe 3+ ) with the oxygen-containing functional groups on the surface of biomass-derived carbon nanosheets (BDCN). Exemplarily, the concentration of the iron salt solution is controlled within the range of 0.05-0.2 M. Preferably, when the concentration is below 0.05 M, the active site coverage is insufficient; when the concentration is above 0.2 M, the excess iron ions tend to form heterogeneous nucleation on the BDCN surface, resulting in particle coarsening.

[0041] In one possible implementation, the loading of cobalt salt adopts a post-impregnation strategy. It should be noted that the iron ions loaded first can preferentially occupy the high-energy adsorption sites on the BDCN surface (such as edge carboxyl groups and defect sites), and the cobalt ions (Co 2 + ) forms coordination bonds with the iron sites through a charge compensation effect, thereby inhibiting the migration and agglomeration of the bimetallic particles. Preferably, the cobalt salt solution concentration is controlled within the range of 0.02-0.1M, and the molar concentration ratio with the iron salt is 1:2 to 1:5, to ensure that the iron / cobalt atomic ratio falls within the range of 1:0.8-1:2.

[0042] Regarding the ultrasonic treatment after immersion, specifically, its mechanism of action includes the micro-jet impact caused by the cavitation effect and the local high temperature and high pressure environment. It can be understood that when the transient cavitation bubbles generated by ultrasound in the liquid phase collapse, local hot spots exceeding 1000K and 10 5 Pa-level shock waves break the van der Waals stacking of BDCN sheets and promote the diffusion of metal ions into the internal pores. Preferably, the ultrasonic power is controlled in the range of 200-400W and the treatment time is 20-40 minutes. Too low a power density may lead to uneven ion distribution, while too high a power density may destroy the carbon skeleton structure.

[0043] In a specific embodiment, the reduction treatment uses a H2 / Ar mixed gas as a reducing medium. Preferably, the volume proportion of hydrogen is 5%-15%, the reduction temperature is 400℃-600℃, and the time is 0.5-2 hours. It is understandable that too high a hydrogen partial pressure (such as pure H2) will lead to excessive reduction of the carbon skeleton, which manifests as jagged etching of the edges of the sheets and pore collapse; while too low a hydrogen partial pressure will make it difficult to completely reduce the metal oxide to a metallic state. During the reduction process, H2 molecules dissociate and adsorb on the surface of the metal oxide, and gradually reduce Fe2O3 to α-Fe and Co3O4 to β-Co through the electron transfer mechanism, eventually forming an Fe / Co alloy phase.

[0044] Regarding the size control of metal particles, specifically, it is limited by the heating rate and gas diffusion dynamics during the calcination and reduction stages. Preferably, when the heating rate is ≤5°C / min, the surface diffusion rate of metal atoms and the bulk diffusion rate reach a balance, which can inhibit the Ostwald ripening process and stabilize the particle size in the range of 15-30nm. Compared with the co-impregnation method, the step-by-step impregnation strategy can increase the metal dispersion by more than 40%, because the directional anchoring of cobalt ions on iron sites reduces the stress concentration caused by lattice mismatch.

[0045] In this embodiment, the preparation of functionalized graphene is achieved through a synergistic process of pre-reduction and interfacial coupling reaction. The core of this process is to construct a functionalized graphene (F-Gr) material with high interfacial bonding strength and stable dispersibility through gradient reduction and directional bonding strategy.

[0046] As an option, graphene oxide (GO) includes but is not limited to single-layer graphene oxide prepared by Hummers method, improved Hummers method or electrochemical exfoliation method, preferably a pre-oxidized product with a C / O atomic ratio of ≥2.0. Specifically, the carboxyl group (-COOH) at the edge of the GO sheet and the epoxy group (-O-) on the basal surface provide active sites for the subsequent coupling reaction, and the pre-reduction treatment partially restores sp 2 The conjugated structure balances conductivity and reactivity.

[0047] In one possible implementation, the pre-reduction treatment is carried out in a reducing atmosphere. It should be noted that the volume ratio of the H2 / N2 mixed gas is controlled in the range of 1:3 to 1:5. Preferably, when the hydrogen ratio is less than 15%, the reduction driving force is insufficient and the oxygen-containing group removal rate is <50%; when it is higher than 25%, it may cause excessive curling or breakage of the GO sheets. Exemplarily, the heat treatment temperature is controlled in the range of 150-250°C and the time is 0.5-2 hours. Under this condition, the C / O ratio of GO is increased from the initial 1.5-2.0 to 4.0-6.0, while retaining about 10-20% of the oxygen-containing functional groups for subsequent coupling reactions.

[0048] Regarding the application of KH-792 coupling agent, specifically, its epoxy group (-CH(O)CH-) forms a covalent bond with the carboxyl group of pre-reduced GO through a nucleophilic ring-opening reaction. It is understood that the pH value of the reaction system needs to be maintained in the range of 8.5-9.5. Preferably, the pH value of the ethanol solution is adjusted with ammonia water. Under this alkaline condition, the carboxyl group of GO is ionized to -COO - , reacting with the epoxy group of KH-792 via an SN2 mechanism to generate a stable β-hydroxylamine bond. Compared to aminosilanes such as KH-550, the diepoxy structure of KH-792 can provide a higher crosslinking density, increasing the interfacial bonding energy to 0.8-1.2 J / m 2 .

[0049] In a specific embodiment, the coupling reaction is carried out in a liquid phase environment. Exemplarily, the pre-reduced GO is dispersed in a 5-10wt% KH-792 ethanol solution, the solid-liquid ratio is controlled in the range of 1:50 to 1:100, the reaction temperature is 40-80°C, and the time is 2-6 hours. It should be noted that when the temperature is below 40°C, the reaction kinetics are slow and the bonding rate is <30%; when the temperature is above 80°C, the evaporation of the ethanol solvent is aggravated, which may cause local excessive concentration to induce GO sheet agglomeration. Preferably, magnetic stirring is combined with inert gas protection (such as nitrogen) to ensure reaction uniformity and prevent oxidation side reactions.

[0050] In this embodiment, the construction of a three-dimensional porous skeleton is achieved through an electrostatic spraying process. The core of the process is to use the electric field to drive the directional arrangement of nanosheets and the pore self-organization effect induced by solvent volatilization to form a highly connected and low-tortuosity thermal conductive network.

[0051] As an option, the dispersion is prepared by synergistically mixing biomass-derived carbon nanosheets (BDCN), functionalized graphene (F-Gr), a dispersant (PVP), and a solvent. Specifically, the large pore structure (50-300 nm) of BDCN provides the main channel for phonon transmission, the chemical bonding interface of F-Gr reduces lattice scattering, and PVP inhibits nanosheet aggregation through steric hindrance. Exemplarily, the mixing mass ratio is controlled in the range of BDCN:F-Gr:PVP = 3:2:0.3 to 5:3:0.5 to ensure that the dispersion has both rheological stability and high solid content properties.

[0052] In one possible implementation, the vacuum degassing process uses a stepped pressure control strategy. It should be noted that in the initial stage, the vacuum level is rapidly reduced to -0.08 to -0.10 MPa to remove large bubbles, and then slowly reduced to -0.095 to -0.098 MPa and maintained for 10-30 minutes to gradually remove submicron bubbles. It is understandable that bubbles in the undegassed dispersion burst during spraying, resulting in pinhole defects in the film layer, whose density and diameter directly affect the uniformity of the final pore distribution.

[0053] Regarding the electric field regulation mechanism of electrostatic spraying, specifically, it includes the dual effects of electrophoretic migration and dielectrophoretic focusing. Preferably, the spray gun voltage is controlled in the range of 10-20kV, and the distance between the nozzle and the substrate is 10-30cm. Under this condition, the charged droplets are accelerated in the electric field and unfolded into a thin liquid film. The solvent evaporates rapidly, causing the nanosheets to be driven by the dielectrophoretic force to align along the direction of the electric field. Exemplarily, when the voltage is 15kV and the flow rate is 0.2mL / min, the in-plane orientation of BDCN and F-Gr can reach 70%-85%, forming a penetrating heat conduction path.

[0054] In one embodiment, the spray path utilizes a multi-angle cross-scanning pattern. For example, the spray gun is positioned at a 75° angle to the substrate during the first layer, and the second layer is adjusted to a 15° angle, thereby creating an interlocking structure of nanosheets. It should be noted that this angle change can break down the anisotropy caused by a single-direction arrangement, reducing the isotropic variation of the in-plane thermal conductivity from over 50% to less than 15%.

[0055] In this embodiment, low-temperature catalytic graphitization treatment is achieved through the synergistic effect of hydrogen reduction and metal catalysis. The core of the treatment is to construct a highly ordered graphitized thermal conductive network through the kinetic regulation of gas-solid interface reaction and the lattice directional rearrangement mechanism.

[0056] As an option, the treatment process is carried out in a tubular atmosphere furnace using a H2 / Ar mixed gas as the reaction medium. Specifically, hydrogen acts as a reducing agent to selectively etch the amorphous phase and defective carbon in the carbon skeleton, while the iron / cobalt bimetallic catalyst guides the sp2 Directed growth of hybrid structures. Exemplarily, the hydrogen volume fraction is controlled within the range of 10%-30%. Preferably, when the hydrogen ratio is less than 10%, insufficient reduction driving force results in a graphitization degree less than 70%. When the hydrogen ratio is greater than 30%, excessive reduction activity may cause the carbon skeleton to break.

[0057] In one possible implementation, the temperature rise program adopts a staged gradient control strategy. It should be noted that in the initial stage, the temperature is raised to 200-300°C at a rate of 2-5°C / min to fully decompose the PVP dispersant and residual solvent; in the second stage, the temperature is raised to the target temperature (300-500°C) at a rate of 1-3°C / min to extend the migration time of carbon atoms on the metal catalyst surface. It is understandable that too fast a heating rate (>5°C / min) will lead to thermal stress concentration, which manifests as warping of the film edge or crack expansion.

[0058] Regarding the microscopic mechanism of catalytic graphitization, specifically, it involves the dissolution-precipitation process at the metal-carbon interface. Preferably, the iron / cobalt alloy particles are activated in a hydrogen atmosphere to form a liquid metal film, and carbon atoms diffuse to the catalyst surface through a solid solution mechanism and grow epitaxially along low-energy crystal planes (such as graphite (002) planes). For example, when the calcination temperature is 450°C, the migration rate of carbon atoms on the Fe / Co alloy surface reaches 10 -8 m 2 / s level, which causes the graphite crystallite size (La value) to grow to 50-70nm.

[0059] In this embodiment, the surface passivation treatment is achieved through controlled oxidation and interface modification processes. The core of the process is to improve the environmental stability and long-term service performance of the graphene heat dissipation film by constructing an atomic-level protective layer and defect repair mechanism.

[0060] As an option, the passivation treatment is carried out in situ after the catalytic graphitization is completed. Specifically, while maintaining an inert atmosphere (Ar or N2) in a tube furnace, a trace amount of oxygen (O2 volume share ≤0.1%) is introduced into the reaction system, and selective oxidation is achieved by precisely controlling the oxygen partial pressure. It should be noted that the amount of oxygen introduced must be strictly limited to prevent excessive oxidation of the bulk carbon structure (C / O ratio decrease rate ≤5%). Preferably, the oxygen flow rate is controlled within the range of 1-5sccm by a mass flow meter.

[0061] In one possible implementation, the oxidation reaction follows a three-stage mechanism of surface adsorption-dissociation-bonding. For example, oxygen molecules are first physically adsorbed on the dangling bond sites at the edge of graphene, and then dissociated into active oxygen atoms (O*) under the action of residual metal catalysts (Fe / Co), and finally form stable COC ether bonds or C=O carbonyl groups with carbon atoms. It is understandable that the residual amount of metal catalyst (0.1-0.5wt%) plays a key role in this process: too low a metal content leads to insufficient oxygen dissociation efficiency (coverage <30%), and too high a metal content may trigger deep oxidation of the bulk carbon.

[0062] Regarding the structural characteristics of the passivation layer, specifically, its thickness is controlled by the oxidation time and temperature. Preferably, the treatment temperature is controlled in the range of 250-350 ° C, and the time is 10-30 minutes. Under this condition, a graphene oxide (GO-like) coating layer with a thickness of 1-2 nm is formed on the surface. It should be noted that the coating is tightly combined with the base graphene through π-π conjugation, and its oxygen-containing functional groups (such as epoxy and hydroxyl groups) can effectively passivate the edge active sites, reducing the surface charge density from 10 15 cm -2 Down to 10 13 cm -2 Magnitude.

[0063] In a specific embodiment, the performance stabilization treatment includes mechanical strengthening and interface coupling optimization. Preferably, a 2-5 nm thick Al2O3 dielectric layer is grown on the surface of the film layer by plasma enhanced atomic layer deposition (PE-ALD) technology. It should be noted that the Al2O3 layer is chemically bonded to the carbon substrate through an Al-OC bond, and its Young's modulus (≈300GPa) can improve the bending resistance of the film layer (no cracks when the bending radius is ≤1mm), while blocking the bulk diffusion of oxygen ions at high temperatures (the diffusion coefficient is reduced by 3 orders of magnitude).

[0064] Regarding the correlation between process parameters, specifically, the passivation layer thickness and thermal conductivity decay rate have a nonlinear relationship. Preferably, when the passivation layer thickness is ≤2nm, the phonon scattering effect caused by it is negligible (thermal conductivity decay rate ≤3%), while when the thickness is >5nm, due to the increased interface scattering, the in-plane thermal conductivity coefficient decreases by up to 15-20%. This relationship is verified by molecular dynamics simulation (MD), which shows that the phonon state density matching at the interface needs to be ≥80% to maintain efficient heat transport.

[0065] Example 1: Recipe ingredients: Biomass-derived carbon nanosheets (BDCN): 50 parts; Functionalized graphene (F-Gr): 30 parts; Iron / cobalt bimetallic catalyst: 8 parts; Polyvinylpyrrolidone (PVP): 0.3 parts; Deionized water: 11.7 parts.

[0066] Preparation process parameters BDCN preparation: Hydrothermal carbonization: 8 wt% diammonium hydrogen phosphate, 200°C / 6 hours, nitrogen atmosphere; Microwave stripping: pulse mode (800W / 200W alternating, 5 seconds per cycle, total time 30 minutes).

[0067] Catalyst loading: The concentration of ferric nitrate was 0.1 M, and ultrasonic dispersion was performed at 300 W for 30 minutes. Calcination at 400°C / 2 hours, reduction with H210% / 500°C / 1 hour.

[0068] F-Gr preparation: Pre-reduction H25% / 200℃ / 1 hour; KH-792 coupling (3 wt% ethanol solution, 60°C / 4 hours).

[0069] Film formation and graphitization: Electrostatic spraying: +15kV / -8kV, 15cm; Graphitization: H2:Ar=1:2, 750°C / 2 hours.

[0070] Example 2: Formula components (parts by mass): BDCN: 60 parts; F-Gr: 30 parts; Iron / cobalt catalyst: 10 parts, Fe:Co=1:0.8; PVP: 0.1 parts; Deionized water: 10 parts, solid content 12 wt%).

[0071] Preparation process parameters BDCN preparation: Diammonium hydrogen phosphate 10wt%, 220℃ / 5h; Microwave stripping: pulse mode (1000W / 300W alternating, cycle 3 seconds, total time 20 minutes).

[0072] Catalyst loading: 0.2M ferric nitrate, ultrasound 400W / 20min; Calcination at 450°C for 1.5 hours, reduction with H2 15% at 600°C for 0.5 hours.

[0073] F-Gr preparation: Pre-reduction H210% / 250℃ / 0.5h; KH-792 coupling (5 wt% ethanol solution, 80°C / 2 hours).

[0074] Film formation and graphitization: Electrostatic spraying: +20kV / -10kV, 10cm; Graphitization: H2:Ar=1:1, 900°C / 0.5 hour.

[0075] Example 3: Formula components (parts by mass): BDCN: 40 parts; F-Gr: 40 parts; Iron / cobalt catalyst: 5 parts, Fe:Co=1:2; PVP: 0.5 parts; Deionized water: 30 parts, solid content 8 wt%).

[0076] Preparation process parameters BDCN preparation: Diammonium hydrogen phosphate 5wt%, 180℃ / 8h; Microwave stripping: pulse mode (500W / 100W alternating, cycle 10 seconds, total time 40 minutes).

[0077] Catalyst loading: Ferric nitrate 0.05M, ultrasound 200W / 40min; Calcination at 300°C / 3 hours, reduction at H25% / 400°C / 2 hours.

[0078] F-Gr preparation: Pre-reduction H23% / 150℃ / 2 hours; KH-792 coupling (1 wt% ethanol solution, 40°C / 6 hours).

[0079] Film formation and graphitization: Electrostatic spraying: +10kV / -5kV, 20cm; Graphitization: H2:Ar=1:3, 700℃ / 3 hours.

[0080] Comparative Example 1: Compared with Example 1, the difference is that the iron / cobalt bimetallic catalyst is replaced by an equal amount of iron monometallic (Fe:Co=1:0), and the cobalt salt impregnation step is eliminated. The other components and process parameters are the same.

[0081] Comparative Example 2: Compared with Example 1, the difference is that the microwave stripping treatment adopts a continuous 800 W mode (non-pulse mode), the total time is still 30 minutes, and the other components and process parameters are the same.

[0082] Comparative Example 3: Compared with Example 2, the difference is that the KH-792 coupling agent is replaced by an equal amount of KH-550, and the other components and process parameters are the same.

[0083] Comparative Example 4: Compared with Example 2, the difference is that hydrogen is not diluted during the catalytic graphitization treatment (H2:Ar=1:0, not 1:1), and the other components and process parameters are the same.

[0084] Comparative Example 5: Compared with Example 3, the difference is that no polyvinyl pyrrolidone (PVP) dispersant is added to the formula, and the other components and process parameters are the same.

[0085] Comparative Example 6: Compared with Example 3, the difference is that the calcination temperature is adjusted to 600° C., and the other components and process parameters are the same.

[0086] Experiment 1: Verification of the synergistic effect of biomass carbon nanosheet preparation process Experimental Description Test Subject: Example 1 (bimetallic catalyst + pulse microwave); Comparative Example 1 (single metal Fe catalyst + pulse microwave); Comparative Example 2 (bimetallic catalyst + continuous microwave).

[0087] Purpose of the experiment: Verify the synergistic effect of bimetallic catalyst (Fe / Co) and pulsed microwave process on the structure and thermal conductivity of biomass carbon nanosheets.

[0088] Experimental procedures Materials preparation: lignin (Sigma-Aldrich, purity ≥95%); Ferric nitrate; Cobalt chloride (CoCl26H2O, analytical grade); Deionized water (conductivity ≤ 1 μS / cm).

[0089] Instruments and equipment: Hydrothermal reactor (200 mL, with polytetrafluoroethylene lining); Microwave reactor (pulse / continuous mode adjustable, power range 100-1000W); Laser thermal conductivity instrument (LFA467, Netzsch); atomic force microscope (AFM, Bruker Dimension Icon); Raman spectrometer (RenishawinVia).

[0090] Specific steps: Step 1: Preparation of BDCN (Example 1 and Comparative Example 2): Lignin was mixed with diammonium hydrogen phosphate (8 wt%) and subjected to hydrothermal reaction (200 °C, 6 h); The mixture was washed by centrifugation until neutral, and then treated with microwave (Example 1: pulse 800W / 200W, 30 minutes; Comparative Example 2: continuous 800W, 30 minutes).

[0091] Step 2: Catalyst loading (Example 1 and Comparative Example 1): Example 1: impregnation with 0.1M ferric nitrate and 0.05M cobalt chloride solutions in steps; Comparative Example 1: Immersed in 0.1M ferric nitrate solution only; Calcination (400°C, 2 hours) and reduction (500°C, 1 hour).

[0092] Step 3: Performance Testing: Raman spectroscopy analysis of ID / IG values; AFM measurement of BDCN thickness distribution; The in-plane thermal conductivity was measured by the laser flash method.

[0093] Table Name: Test Example 1: Effect of Biomass Carbon Nanosheet Preparation Process - Experimental Data Summary sample ID / IG value In-plane thermal conductivity (W / (m·K)) BDCN thickness deviation (nm) Example 1 0.25 1052.3 ±2.1 Comparative Example 1 0.78 598.7 ±3.5 Comparative Example 2 0.34 703.5 ±24.8 According to Table 1 above, we can see that: The introduction of bimetallic catalysts (Fe / Co) significantly reduces the activation energy of carbon skeleton graphitization through the electronic coupling effect between metals. Iron atoms provide high catalytic activity sites, while cobalt enhances the interaction between iron and carbon matrix through d-orbital electron transfer, promoting the orderly rearrangement of carbon atoms at low temperatures. Experimental data show that the monometallic iron catalyst (Comparative Example 1) lacks the electronic synergy of cobalt, resulting in a graphitization degree (ID / IG=0.78) of only 32% of that of Example 1 (ID / IG=0.25), and a decrease in thermal conductivity of 43%. This verifies the necessity of the Fe:Co molar ratio (1:0.8-1:2)-the synergistic catalysis of bimetallic is the core mechanism for achieving low-temperature and efficient graphitization.

[0094] Pulsed microwave treatment, through alternating high and low power, generates a periodic thermal stress difference that precisely acts on defect sites between carbon layers (such as oxygen-containing groups or impurity interfaces), thereby directionally exfoliating the carbon layer along the weak areas, forming ultrathin nanosheets with uniform thickness (thickness deviation ±2.1nm in Example 1). In contrast, continuous microwave treatment (Comparative Example 2) results in localized overburning or insufficient exfoliation due to the continuous high heat load, resulting in a discrete thickness distribution (±24.8nm), disordered pore size expansion, and a final 33% reduction in in-plane thermal conductivity. The specific power alternation period is key to regulating the thermal stress distribution and achieving structural uniformity.

[0095] The synergistic effect of bimetallic catalysis and pulsed microwaves ultimately creates a highly ordered, low-defect thermal conductive network. The iron / cobalt catalytic sites drive the directional migration of carbon atoms, while the ultrathin porous structure formed by pulsed microwave exfoliation provides a low-resistance path for electron and phonon transmission. Together, these two factors guarantee the thermal conductivity of Example 1 (1050 W / (m·K)). The absence of any single condition (such as a single metal or continuous microwave) would disrupt this synergistic effect, leading to a break in the thermal conductive network or increased grain boundary scattering.

[0096] Experiment 2: Verification of the irreplaceability of functionalized graphene interface treatment Experimental Description Test Subject: Example 2 (KH-792 coupling agent + PVP dispersant); Comparative Example 3 (KH-550 coupling agent + PVP dispersant); Example 3 (KH-792 coupling agent + PVP dispersant); Comparative Example 5 (KH-792 coupling agent + no PVP).

[0097] Purpose of the experiment: Verify the irreplaceable role of KH-792 coupling agent and PVP dispersant in the interface bonding and film formation uniformity of functionalized graphene.

[0098] Experimental Description Test Subject: Example 2 (KH-792 coupling agent + PVP dispersant); Comparative Example 3 (KH-550 coupling agent + PVP dispersant); Example 3 (KH-792 coupling agent + PVP dispersant); Comparative Example 5 (KH-792 coupling agent + no PVP).

[0099] Purpose of the experiment: Verify the irreplaceable role of KH-792 coupling agent and PVP dispersant in the interface bonding and film formation uniformity of functionalized graphene.

[0100] Table Name: Test Example 2: Effect of Interface Treatment and Dispersant - Experimental Data Summary sample Dispersion sedimentation time (h) Tensile strength (MPa) Porosity distribution deviation (%) Example 2 >24 88.5 8.3 Comparative Example 3 4.2 62.7 34.6 Example 3 >24 89.1 7.9 Comparative Example 5 1.5 45.2 51.8 According to Table 2 above, we can see that: The epoxy groups of the KH-792 coupling agent form covalent bonds with the carboxyl groups on the surface of the functionalized graphene (F-Gr) through a nucleophilic ring-opening reaction, building a strong chemical bonding network at the interface. Experimental data show that in Comparative Example 3 (using KH-550), the interfacial bonding strength decreased by 29% because the amino and carboxyl groups relied only on weak hydrogen bonding, and the dispersion stability (4.2 hours of precipitation) was less than 20% of that of Example 2 (>24 hours of no precipitation). This verifies the necessity of KH-792 - the directional bonding ability of its epoxy groups is the core mechanism for ensuring the mechanical properties of the composite membrane.

[0101] The PVP dispersant inhibits the van der Waals aggregation of functionalized graphene sheets through the steric hindrance and electrostatic repulsion of long-chain molecules. Comparative Example 5 (without PVP) exhibits a pore distribution deviation of up to 51.8% due to nanosheet stacking, while Example 3 (with PVP) exhibits a pore uniformity deviation of only 7.9%. The polar ends of the pyrrolidone groups in the PVP molecules adsorb onto the graphene surface, while the non-polar segments extend into the aqueous phase to form a three-dimensional barrier. This dual-action mechanism is key to ensuring film uniformity and flexible life (2000 bends without cracks).

[0102] The synergistic effect of KH-792 and PVP enables cross-scale regulation from nanoscale interfacial bonding to macroscopic performance. The chemically bonded network provides a high-strength framework, while the dispersing effect of PVP ensures uniform arrangement of nanosheets during film formation; both are essential. The failures of Comparative Examples 3 and 5 demonstrate that the absence or substitution of any single component (such as KH-550 or the absence of PVP) will lead to interfacial debonding or structural collapse.

[0103] Experiment 3: Verification of precise control of graphitization process conditions Experimental Description Test Subject: Example 2 (H2:Ar=1:1, calcined at 450°C); Comparative Example 4 (H2:Ar=1:0, calcined at 450°C); Example 3 (H2:Ar=1:3, calcined at 300°C); Comparative Example 6 (H2:Ar=1:3, calcined at 600°C).

[0104] Purpose of the experiment: Experimental procedures Materials preparation: pretreated biomass carbon nanosheets (BDCN, pore size 80-250 nm); Ferric nitrate; High-purity hydrogen (99.999%) and argon (99.999%); Cobalt chloride (CoCl26H2O, analytical grade).

[0105] Instruments and equipment: Tubular atmosphere furnace (maximum 1200°C, gas ratio adjustable); Scanning electron microscopy (SEM, Hitachi SU8220); Transmission electron microscopy (TEM, JEOL JEM-2100F); X-ray diffractometer (XRD, Bruker D8 Advance).

[0106] Specific steps: Step 1: Catalytic graphitization treatment: Example 2: BDCN loaded with Fe / Co was treated at 750°C for 2 hours in a H2:Ar=1:1 atmosphere; Comparative Example 4: Same as Example 2, but H2:Ar=1:0 (pure H2); Example 3: BDCN loaded with Fe / Co was treated at 700°C for 3 hours in a H2:Ar=1:3 atmosphere; Comparative Example 6: Same as Example 3, but the calcination temperature was increased to 600°C.

[0107] Step 2: Structural Characterization: SEM observation of graphene sheet fracture; TEM analysis of metal particle dispersion; The porosity was determined by mercury intrusion porosimetry.

[0108] Step 3: Performance Testing: Lattice order (La value calculated by XRD); In-plane thermal conductivity (laser flash method) Verify the effects of hydrogen dilution ratio and calcination temperature range on graphitization structure integrity and catalytic activity.

[0109] Table Name: Test Example 3: Effect of Graphitization Process Conditions - Experimental Data Summary According to Table 3 above, we can see that: The dilution ratio of hydrogen regulates the reduction kinetic balance to form a moderate carbon-metal interaction during the graphitization process. The excessive reduction activity of high-purity hydrogen (Comparative Example 4) leads to local over-etching of the carbon skeleton, and the lamella fracture rate increases to 22.7% (only 4.8% in Example 2). At the same time, the metal particles migrate and aggregate (30-45nm) under the severe reducing environment, weakening the guiding role of the catalytic sites on the orderly arrangement of carbon atoms. This destructive reduction of diluted hydrogen (H2:Ar=1:1-1:3) is in sharp contrast - the diluted hydrogen not only provides sufficient reduction driving force, but also suppresses the cleavage of the carbon layer through the buffering effect of argon, maintaining the continuity of the porous structure (porosity 65.3% in Example 2 vs. 50.1% in Comparative Example 4).

[0110] Precise control of the calcination temperature directly affects the surface energy state and dispersion of the metal catalyst. When the temperature rises to 600°C (Comparative Example 6), the Ostwald ripening process of the iron / cobalt particles is accelerated, and the particle size increases sharply from 12-25nm in Example 3 to 50-110nm. Excessively large metal particles lose the ability to regulate the carbon migration path at the nanoscale, resulting in an increase in the lattice defect density (La value drops from 58.7nm to 12.3nm). Low-temperature calcination (300°C in Example 3) maintains a high-density distribution of catalytic active sites by limiting the migration rate of metal atoms. This thermodynamic control mechanism is the core of ensuring graphitization efficiency.

[0111] The synergistic effect of hydrogen dilution and temperature control is reflected in the spatiotemporal matching of carbon skeleton evolution. Diluted hydrogen slows down the intensity of the reduction reaction, while the appropriate calcination temperature extends the metal catalytic activity window. Together, they guide the directional rearrangement of carbon atoms along low-energy interfaces. The failure of Comparative Examples 4 and 6 shows that an imbalance in any one condition will break this synergy—excessive hydrogen concentration triggers structural collapse, and excessively high temperatures lead to catalytic deactivation, ultimately causing the material to lose its balance between high thermal conductivity and porous properties. This cross-scale control logic reveals the scientific rigor of the process parameter design of the present invention.

[0112] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high thermal conductivity graphene heat dissipation film, characterized in that: The composition comprises the following components in parts by weight: Biomass-derived carbon nanosheets: 40-60 parts; Functionalized graphene: 20-40 parts; Iron / cobalt bimetallic catalyst: 5-10 parts; Dispersant: 0.1-0.5 parts; Solvent: 10-30 parts; The total weight of the biomass-derived carbon nanosheets and the functionalized graphene is ≤ 90 parts; The molar ratio of iron to cobalt in the iron / cobalt bimetallic catalyst is 1:0.8-1:

2.

2. The high thermal conductivity graphene heat dissipation film according to claim 1, characterized in that: The biomass-derived carbon nanosheets are prepared by hydrothermal carbonization of lignin, and the hydrothermal carbonization conditions include: The amount of diammonium phosphate added is 5-10% of the lignin mass; Reaction temperature 180-220°C, time 4-8 hours; The biomass-derived carbon nanosheets have a pore size of 50-300 nm and a thickness of 5-20 nm.

3. The high thermal conductivity graphene heat dissipation film according to claim 1, characterized in that: The iron / cobalt bimetallic catalyst is loaded on the surface of biomass-derived carbon nanosheets by a step-by-step impregnation method, comprising: The iron salt is ferric nitrate solution with a concentration of 0.05-0.2M; The cobalt salt is a cobalt chloride solution with a concentration of 0.02-0.1M; Calcination conditions: air atmosphere, temperature 300-500℃, time 1-3 hours; Reduction conditions: H2 / Ar mixed gas, H2 accounting for 5-15%, temperature 400-600℃, time 0.5-2 hours.

4. The high thermal conductivity graphene heat dissipation film according to claim 1, characterized in that: The solvent is deionized water with a conductivity of ≤1 μS / cm; the amount of the solvent used is such that the solid content of the dispersion is 5-15 wt %.

5. The high thermal conductivity graphene heat dissipation film according to claim 1, characterized in that: The dispersant is polyvinyl pyrrolidone with a molecular weight of 40,000-60,000; The added amount of the dispersant is 0.1-0.5% of the total mass of the biomass-derived carbon nanosheets and the functionalized graphene.

6. A method for preparing a high thermal conductivity graphene heat dissipation film, according to the high thermal conductivity graphene heat dissipation film according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: subjecting the biomass raw material to hydrothermal carbonization and microwave exfoliation to obtain biomass-derived carbon nanosheets; Step 2: The biomass-derived carbon nanosheets are sequentially impregnated with iron salt and cobalt salt solutions, and subjected to calcination and reduction treatment to load the iron / cobalt bimetallic catalyst; Step 3: pre-reducing the graphene oxide and reacting it with an aminosilane coupling agent to obtain functionalized graphene; Step 4: mixing the biomass-derived carbon nanosheets, functionalized graphene and a dispersant and then electrostatically spraying the mixture into a film to form a three-dimensional porous skeleton; Step 5: Perform low-temperature catalytic graphitization treatment in a hydrogen atmosphere to obtain a graphene heat dissipation film.

7. The method for preparing a high thermal conductivity graphene heat dissipation film according to claim 6, characterized in that: In the step 1: The hydrothermal carbonization is carried out in a nitrogen atmosphere, and after the reaction, the reaction is centrifuged and washed until neutral; The microwave stripping adopts a pulse mode, and the total processing time is 20-40 minutes.

8. The method for preparing a high thermal conductivity graphene heat dissipation film according to claim 6, characterized in that: In the step 2: After impregnation with iron salt, ultrasonic dispersion treatment is performed with a power of 200-400W for 20-40 minutes; The heating rate of calcination and reduction is 2-5°C / min.

9. The method for preparing a high thermal conductivity graphene heat dissipation film according to claim 6, characterized in that: In the step three: Pre-reduction treatment: Graphene oxide is heat treated in a H2 / N2 mixture at 150-250°C for 0.5-2 hours; Coupling treatment: react with KH-792 ethanol solution at 40-80°C for 2-6 hours.

10. The method for preparing a high thermal conductivity graphene heat dissipation film according to claim 6, characterized in that: In the steps 4 and 5: Before electrostatic spraying, the dispersion liquid is vacuum degassed for 30-60 minutes; During the catalytic graphitization treatment, inert gas is introduced to dilute hydrogen, and the dilution ratio is H2:Ar=1:1-1:3.

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