CN114835494A - Preparation method of high-performance graphene heat-conducting film - Google Patents
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Abstract
The invention relates to a preparation method of a high-performance graphene heat-conducting film, which comprises the steps of introducing a gaseous carbon source diluted by inert gas into high-temperature molten liquid metal, blowing bubbles into the liquid metal to grow to obtain graphene powder, fully mixing the prepared graphene powder with a resin binder solution in a spraying and stirring mixing mode, carrying out calendaring molding and graphitization treatment in sequence, controlling the residual carbon amount formed by the binder resin to account for 2-5% of the weight of a second graphene film after the graphitization treatment, and carrying out film densification treatment to obtain the complete high-performance graphene heat-conducting film. The preparation method is simple in preparation process and easy to expand production, and the prepared graphene heat-conducting film is excellent in heat-conducting property and heat-radiating performance; the method can realize no waste water and waste gas emission in the preparation process of the graphene heat conducting film, and cannot pollute the environment.
Description
Technical Field
The invention relates to the technical field of graphene, in particular to a preparation method of a high-performance graphene heat-conducting film.
Background
With the development of high power electronics, the heat dissipation efficiency of thermal management materials has become a critical issue, which determines the operational reliability and stability of the device. The graphene heat-conducting film with high heat-conducting property can effectively spread out local heat, and particularly has a remarkable heat dissipation effect in electronic equipment with a complex structure.
In the preparation of the graphene heat-conducting film in the prior art, firstly, graphene oxide is dispersed into slurry in water, then the slurry is coated into a film, the film is heated and dried, and then the graphene heat-conducting film is obtained through low-temperature carbonization reduction and high-temperature graphitization processes and finally calendering. In the prior art, graphene oxide is used as a raw material, and a large amount of strong acid and strong oxidant are needed in the process of obtaining the graphene oxide, so that a large amount of wastewater is inevitably generated to be discharged, and the environment is seriously polluted. In addition, a plurality of series of procedures are required in the preparation process of the graphene oxide, the process is complex, and the energy consumption is high. Finally, for highly integrated high-power electronic devices, the graphene heat-conducting film is required to have higher heat-conducting performance, but the current production process has a technical bottleneck for further improving the heat-conducting performance of the graphene heat-conducting film, and the requirement of terminal electronic manufacturers on the graphene heat-conducting film with higher heat-conducting performance is difficult to meet.
Disclosure of Invention
In order to solve the technical problem that the existing graphene heat-conducting film is poor in heat-conducting property, a preparation method of a high-performance graphene heat-conducting film is provided. The graphene heat-conducting film prepared by the method disclosed by the invention is excellent in heat-conducting property and faster in heat diffusion.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a preparation method of a high-performance graphene heat-conducting film comprises the following steps:
(1) preparing graphene powder in liquid metal by utilizing a CVD method for bubbling growth;
(2) spraying and simultaneously mixing the collected graphene powder by using a resin binder solution, and uniformly mixing to obtain viscous powder;
the resin binder solution is obtained by diluting aqueous bonding resin or oily bonding resin with a solvent; the adhesive resin is resin with high carbon residue at high temperature, and is selected from one of polyurethane, epoxy resin, phenolic resin, acrylic resin, amino resin, unsaturated polyester resin and saturated polyester resin;
(3) feeding the viscous powder into a calender for primary calendering to obtain a first graphene film;
(4) graphitizing the first graphene film under the protection of inert gas to obtain a second graphene film; controlling the carbon residue formed by the binding resin after graphitization treatment to account for 2-5% of the weight of the second graphene film, calculating the using amount of the binding resin according to the carbon residue, and diluting the binding resin to a solid content capable of being used for spraying by adopting a corresponding diluent;
(5) and placing the second graphene film in the calender for secondary calendering to obtain the high-performance graphene heat-conducting film.
Further, the specific process of step (1) is: introducing mixed gas of a gaseous carbon source and nitrogen below the liquid level of molten metal under normal pressure and nitrogen protection, generating bubbles below the liquid level of the molten metal, growing graphene on the surfaces of the bubbles by the gaseous carbon source under the catalytic action of the molten metal, separating and collecting graphene powder and the molten metal after the bubbles rise above the liquid level of the molten metal due to surface tension difference, wherein the proportion of the graphene powder to the molten metal is more than or equal to 85 percent, and the graphene powder prepared by the method has larger sheet diameter.
Furthermore, the temperature of the molten metal is 1050-; the gaseous carbon source is one of methane, ethane, propane, propylene, propyne, ethylene, acetylene, natural gas, liquefied petroleum gas, butane and butylene; the flow rate of the gaseous carbon source is 1-15L/min, the flow rate of the nitrogen gas is 50-300L/min, and the flow rate of the nitrogen gas is preferably 120-250L/min.
Further, the solvent used for dilution in step (2) is water and/or an organic solvent, and a corresponding dilution solvent is selected according to the type of the resin, for example, the aqueous binding resin can be directly diluted with water, while the oily binding agent can be diluted and dissolved with an organic solvent and then sprayed, the organic solvent can be, for example, an alcohol solvent, acetone, benzene, toluene, xylene, an ester organic solvent, an amide organic solvent, and the like, and a good solvent capable of dissolving the corresponding resin is generally selected as the diluted organic solvent; spraying and mixing in the step (2) are carried out in a spraying mixer, the spraying pressure is 0.5-2.5MPa, the flow rate of the sprayed solution is 3-15mL/min, the mixing speed is 800-2200rpm, and the mixing time is 1-3 h; preferably the solids content of the resinous binder solution is from 10 to 20 wt%; the amount of carbon residue formed by the binder resin after the graphitization treatment is preferably controlled to be 2-3.5% of the weight of the second graphene film.
Further, the pressure of the first rolling in the step (3) is 10-20 MPa; the pressure of the second rolling in the step (5) is 8-25MPa, preferably 10-16MPa, and the second rolling is carried out until the density of the obtained film is more than or equal to 2g/cm 3 The thickness is more than or equal to 100 mu m.
Further, the graphitization treatment in the step (4) is performed by raising the temperature to 500 ℃ at a speed of 2-5 ℃/min, then raising the temperature from 500 ℃ to 2800 ℃ and 3200 ℃ at a speed of 5-10 ℃/min, and then preserving the heat for 1-3h at 2800 ℃ and 3200 ℃.
The beneficial technical effects are as follows:
the technical scheme for preparing the graphene heat-conducting film can be briefly summarized as graphene powder preparation → addition of resin binder solution/spray mixing → rolling film preparation → graphitization → film densification, the method is simple in preparation process and easy to expand production, and the prepared graphene heat-conducting film is excellent in heat-conducting property and heat-radiating performance; the method can realize no waste water and waste gas emission in the preparation process of the graphene heat conducting film, and cannot pollute the environment.
According to the method, the graphene powder and a small amount of binder are fully and uniformly mixed by adopting a spraying and stirring mixing mode, so that the problems that the heat-conducting performance of the final graphene heat-conducting film is influenced due to excessive binder consumption during conventional stirring and mixing, and the graphene film cannot be formed due to too little binder consumption are solved.
The binder provided by the invention is a resin binder (or called as binding resin) with high-temperature carbon residue, which not only has the function of binding graphene powder to facilitate calendaring and forming during forming, but also fuses the binding interface of the graphene microchip and the microchip together through graphitized carbon at a high-temperature graphitization stage; in addition, the graphene powder prepared by the CVD bubbling growth in the molten liquid metal has larger sheet diameter, and after the film is formed and graphitized, the graphene micro-sheet and the micro-sheet have few combined interfaces and low thermal resistance, so that the graphene heat-conducting film with higher heat-conducting performance is obtained.
According to the invention, the graphene powder prepared by the CVD bubbling growth method in the liquid metal is used as a raw material for preparing the graphene heat-conducting film, and the CVD bubbling growth method is used for preparing the graphene powder, so that no wastewater discharge of strong acid and strong oxidant is caused, and no greenhouse gas CO is generated 2 The discharge can not cause pollution to the environment;
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Unless specifically stated otherwise, the numerical values set forth in these examples do not limit the scope of the invention. Techniques, methods known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
In addition, it should be noted that the terms "first", "second", and the like are used to define the graphene film in the preparation process, and are only used for convenience of distinguishing the products obtained in each step, and unless otherwise stated, the terms do not have any special meaning, and therefore, the scope of the present invention is not to be construed as being limited.
The experimental methods of the following examples, which are not specified under specific conditions, are generally determined according to national standards; if no corresponding national standard exists, the method is carried out according to the universal international standard or the standard requirement proposed by related enterprises. Unless otherwise indicated, all parts are parts by weight and all percentages are percentages by weight.
Yield of graphene powder ═ m 2 /m 1 ×100％；
Wherein: m is 1 Is the mass of carbon atoms in the carbon source gas at the beginning of the reaction;
m 2 is the mass of the collected graphene powder.
Example 1
A preparation method of a high-performance graphene heat-conducting film comprises the following steps:
(1) preparing graphene powder by CVD bubbling growth in liquid metal: under normal pressure and nitrogen protection, introducing a methane/nitrogen mixed gas into molten liquid copper at 1285 ℃, wherein the flow rate of methane is 10L/min, the flow rate of nitrogen is 150L/min, the mixed gas generates bubbles below the liquid level of the molten copper, meanwhile, the methane grows graphene on the surfaces of the bubbles under the catalytic action of the molten copper, after the bubbles rise above the liquid level of the molten copper, the bubbles are broken due to surface tension difference, the graphene powder is separated from the molten copper, and then the graphene powder enters a collecting device along with air flow for later use;
by calculation, the yield of the graphene powder is 55 wt%, and the proportion of the graphene powder with the sheet diameter of more than 100 μm is 85 wt% by SEM observation and data statistics;
(2) placing the graphene powder prepared in the step (1) in a spraying mixer, stirring at a rotating speed of 1500 rpm, spraying the graphene powder in the mixer by using an aqueous polyurethane emulsion with a solid content of 10 wt% diluted with water through a spray gun, wherein the spraying pressure is 1.5MPa, the flow rate of the aqueous polyurethane emulsion is 5mL/min, and stirring and mixing are carried out for 2 hours, so that the graphene powder and the polyurethane emulsion are fully mixed to obtain viscous graphene powder, wherein the adhesive resin is the aqueous polyurethane emulsion, and the using amount of the adhesive resin is calculated according to the proportion that the carbon residue of the adhesive resin after graphitization treatment in the following step (4) accounts for 2% of the weight of the second graphene film;
(3) primary forming of the graphene film: performing primary rolling on the viscous graphene powder obtained in the step (2) by using a rolling machine, wherein the primary rolling is performed by performing two-time rolling and rolling, and the two-time rolling pressure is 15MPa, so as to obtain a first graphene film;
(4) graphitization treatment: placing the first graphene film in a graphitization furnace, heating the first graphene film to 500 ℃ from room temperature at a speed of 2 ℃/min under the protection of argon, then heating the first graphene film to 3000 ℃ from 500 ℃ at a speed of 7 ℃/min, and carrying out heat preservation at 3000 ℃ for graphitization treatment for 1h to obtain a second graphene film;
(5) graphene film densification treatment: and (3) placing the second graphene film in a calender again, and rolling under the pressure of 10MPa to finally obtain the compact high-performance graphene heat-conducting film.
The thickness of the graphene thermal conductive film prepared in the embodiment is 100 μm, and the density is 2.1g/cm 3 The thermal conductivity data are shown in Table 1.
Example 2
A preparation method of a high-performance graphene heat-conducting film comprises the following steps:
(1) preparing graphene powder by CVD bubbling growth in liquid metal: under normal pressure and nitrogen protection, introducing mixed gas of ethane and nitrogen into a molten liquid copper-nickel alloy at 1330 ℃, wherein the flow rate of ethane is 7L/min, the flow rate of nitrogen is 140L/min, the mixed gas generates bubbles below the liquid level of the molten copper-nickel alloy, meanwhile, the ethane gas grows graphene on the surfaces of the bubbles under the catalytic action of the molten copper-nickel alloy, after the bubbles rise to the liquid level of the molten copper-nickel alloy, the bubbles are broken due to surface tension difference, graphene powder is separated from the molten copper-nickel alloy, and then the graphene powder enters a collecting device along with airflow for later use;
by calculation, the yield of the graphene powder is 52 wt%, and the proportion of the graphene powder with the sheet diameter of more than 100 μm is 85.4 wt% by SEM observation and data statistics;
(2) placing the graphene powder prepared in the step (1) in a spraying mixer, stirring at a rotation speed of 1200 rpm, spraying a water-based epoxy resin solution with a solid content of 17 wt% diluted by water into the graphene powder in the mixer through a spray gun, wherein the spraying pressure is 2MPa, the flow rate of the water-based epoxy resin solution is 8mL/min, and stirring and mixing are carried out for 2.5h, so that the graphene powder and the water-based epoxy resin solution are fully mixed to obtain viscous graphene powder, wherein the adhesive resin is water-based epoxy resin, and the using amount of the adhesive resin is calculated according to the proportion that the carbon residue of the adhesive resin after graphitization treatment in the following step (4) accounts for 2.8% of the weight of the second graphene film;
(3) primary forming of the graphene film: performing primary rolling on the viscous graphene powder obtained in the step (2) by using a rolling machine, wherein the primary rolling is performed by performing two-time rolling under the condition that the two-time rolling pressure is 12MPa, so as to obtain a first graphene film;
(4) graphitization treatment: placing the first graphene film in a graphitization furnace, heating the first graphene film to 500 ℃ from room temperature at a speed of 3 ℃/min under the protection of argon, then heating the first graphene film to 2900 ℃ from 500 ℃ at a speed of 6 ℃/min, and carrying out heat preservation at 2900 ℃ for graphitization treatment for 2h to obtain a second graphene film;
(5) graphene film densification treatment: and (3) placing the second graphene film in a calender again, and rolling under the pressure of 13MPa to finally obtain the compact high-performance graphene heat-conducting film.
The thickness of the graphene thermal conductive film prepared in the embodiment is 120 μm, and the density is 2.13g/cm 3 The thermal conductivity data are shown in Table 1.
Example 3
A preparation method of a high-performance graphene heat-conducting film comprises the following steps:
(1) preparing graphene powder by CVD bubbling growth in liquid metal: introducing natural gas/nitrogen mixed gas into a molten liquid copper-iron alloy at 1350 ℃ under normal pressure and nitrogen protection, wherein the flow of the natural gas is 5L/min, the flow of the nitrogen is 80L/min, the mixed gas generates bubbles below the liquid level of the molten copper-iron alloy, meanwhile, the natural gas grows graphene on the surfaces of the bubbles under the catalytic action of the molten copper-iron alloy, after the bubbles rise to the liquid level of the molten copper-iron alloy, due to the difference of surface tension, the bubbles break, the graphene powder is separated from the molten copper-iron alloy, and then the graphene powder enters a collecting device along with the gas flow for later use;
by calculation, the yield of the graphene powder is 53 wt%, and the proportion of the graphene powder with the sheet diameter of more than 100 μm is 86 wt% by SEM observation and data statistics;
(2) placing the graphene powder prepared in the step (1) in a spraying mixer, stirring at the rotating speed of 1800 rpm, spraying a water-based acrylic resin solution with the solid content of 15 wt% diluted by water into the graphene powder in the mixer through a spray gun at the spraying pressure of 2.1MPa and the flow rate of the water-based acrylic resin solution of 5.5mL/min, and stirring and mixing for 1.8h to fully mix the graphene powder with the water-based epoxy resin solution to obtain viscous graphene powder, wherein the adhesive resin is water-based acrylic resin, and the using amount of the adhesive resin is calculated according to the proportion that the residual carbon amount of the adhesive resin after graphitization treatment in the following step (4) accounts for 5% of the weight of the second graphene film;
(3) primary forming of the graphene film: performing primary rolling on the viscous powder obtained in the step (2) by using a rolling machine, wherein the primary rolling is performed by performing two-time rolling and rolling, and the two-time rolling pressure is 10MPa, so as to obtain a first graphene film;
(4) graphitization treatment: placing the first graphene film in a graphitization furnace, heating the first graphene film to 500 ℃ from room temperature at a speed of 5 ℃/min under the protection of argon, then heating the first graphene film to 3050 ℃ from 500 ℃ at a speed of 8 ℃/min, and carrying out heat preservation at 3050 ℃ for graphitization treatment for 2.5 hours to obtain a second graphene film;
(5) graphene film densification treatment: and (3) placing the second graphene film in a calender again, and rolling under the pressure of 15MPa to finally obtain the compact high-performance graphene heat-conducting film.
The thickness of the graphene thermal conductive film prepared in the embodiment is 150 μm, and the density is 2.18g/cm 3 The thermal conductivity data are shown in Table 1.
Example 4
A preparation method of a high-performance graphene heat-conducting film comprises the following steps:
(1) preparing graphene powder by CVD bubbling growth in liquid metal: under the protection of normal pressure and nitrogen, introducing liquefied petroleum gas/nitrogen mixed gas into molten liquid copper-cobalt alloy at 1250 ℃, wherein the flow of the liquefied petroleum gas is 15L/min, the flow of the nitrogen is 220L/min, and the mixed gas is in the molten liquid copper-cobalt alloyOf molten copper-cobalt alloysGenerating bubbles below the liquid level, simultaneously growing graphene on the surfaces of the bubbles by the liquefied petroleum gas under the catalytic action of the molten copper-cobalt alloy, separating graphene powder from the molten copper-cobalt alloy due to the fact that the bubbles are broken due to the difference of surface tension after the bubbles rise above the liquid level of the molten copper-cobalt alloy, and then enabling the graphene powder to enter a collecting device along with airflow for later use;
by calculation, the yield of the graphene powder is 53.5 wt%, and the proportion of the graphene powder with the plate diameter of more than 100 μm is 85.7 wt% by SEM observation and data statistics;
(2) placing the graphene powder prepared in the step (1) in a spraying mixer, stirring at a rotating speed of 1700 rpm, spraying the graphene powder in the mixer by using a water-based phenolic resin solution with a solid content of 16 wt% diluted by water through a spray gun, wherein the spraying pressure is 1.65MPa, the flow rate of the water-based phenolic resin solution is 6mL/min, and stirring and mixing are carried out for 2.3h, so that the graphene powder and the water-based phenolic resin solution are fully mixed to obtain viscous graphene powder, wherein the adhesive resin is water-based phenolic resin, and the dosage of the adhesive resin is calculated according to the proportion that the carbon residue of the adhesive resin accounts for 3.5% of the weight of the second graphene film after graphitization treatment in the following step (4);
(3) primary forming of the graphene film: performing primary rolling on the viscous powder obtained in the step (2) by using a rolling machine, wherein the primary rolling is performed by performing two-time rolling and rolling, and the two-time rolling pressure is 13MPa, so as to obtain a first graphene film;
(4) graphitization treatment: placing the first graphene film in a graphitization furnace, heating the first graphene film to 500 ℃ from room temperature at a speed of 4 ℃/min under the protection of argon, then heating the first graphene film to 3100 ℃ from 500 ℃ at a speed of 10 ℃/min, and carrying out heat preservation at 3100 ℃ for graphitization treatment for 2.5 hours to obtain a second graphene film;
(5) graphene film densification treatment: and (3) placing the second graphene film in a calender again, and rolling under the pressure of 16MPa to finally obtain the compact high-performance graphene heat-conducting film.
The thickness of the graphene thermal conductive film prepared in the embodiment is 130 μm, and the density is 2.2g/cm 3 The thermal conductivity data are shown in Table 1.
Example 5
The graphene film of this example was prepared in the same manner as in example 1, except that the resin-based binder solution was an aqueous melamine formaldehyde resin (one of aqueous amino resins), and the binder solution was diluted with water to a solid content of 20 wt%, wherein the binder resin was an aqueous melamine formaldehyde resin and the amount of the binder resin was calculated from the ratio of the amount of carbon residue of the binder resin after graphitization to 3% by weight of the second graphene film.
The thickness of the graphene thermal conductive film prepared in the example was 130 μm, and the density was measured to be 2.21g/cm 3 The thermal conductivity data are shown in Table 1.
Example 6
The graphene film of this example was prepared in the same manner as in example 1, except that the resin binder solution was an aqueous saturated polyester resin, and the binder solution was diluted with water to a solid content of 20 wt%, wherein the binder resin was an aqueous saturated polyester resin, and the amount of the binder resin was calculated based on the ratio of the carbon residue of the binder resin after graphitization to 4% by weight of the second graphene film.
The thickness of the graphene thermal conductive film prepared in the embodiment is 150 μm, and the density is 2.16g/cm 3 The thermal conductivity data are shown in Table 1.
Example 7
The graphene film of the present embodiment is prepared in the same manner as in embodiment 3, except that the resin binder solution is an oily binder resin, and the polyurethane, the epoxy resin, the phenolic resin, the acrylic resin, the amino resin, the unsaturated polyester resin, and the saturated polyester resin are dissolved and diluted in an organic solvent until the solid content is 15 wt%, and the organic solvent is selected to be a good solvent capable of dissolving the corresponding resin; wherein the amount of each oleoresin binder is calculated according to the proportion of the carbon residue of the binder resin after graphitization treatment to 4.5% of the weight of the second graphene film.
The thickness of the graphene thermal conductive film prepared in the embodiment is 120 μm, and the density is 2.22g/cm 3 The thermal conductivity data are shown in Table 1.
Comparative example 1
The difference between the preparation method of the graphene thermal conductive film of the comparative example and the embodiment 3 is that the aqueous acrylic resin solution with the solid content of 15 wt% diluted by water is added into the graphene powder prepared in the step (1) to be mixed and stirred, and then the graphene powder is coated on a substrate to be molded and dried; the dosage of the binding resin water-based acrylic resin is calculated according to the proportion of the carbon residue of the binding resin after graphitization treatment to 5% of the weight of the graphene film.
Because the surface of the graphene powder prepared by bubbling growth in the liquid metal almost has no oxygen-containing group, and the content of the bonding resin is low, the dried graphene film cannot be completely separated from the substrate, so that the subsequent process cannot be carried out. On the other hand, if the amount of the binder resin is increased, the amount of carbon residue formed after graphitization increases, and only a part of the carbon residue can be converted into sp having anisotropy 3 The graphite structure is hybridized, so that the heat conductivity of the whole graphene film is reduced after the carbon residue is increased.
The thickness of the graphene heat-conducting film prepared by the comparative example is 150 mu m, and the density is 1.8g/cm 3 The thermal conductivity data are shown in Table 1.
Table 1 thermal conductivity data for graphene films of examples and comparative examples
As can be seen from Table 1, the complete graphene heat-conducting film can be prepared by the method, the heat-conducting property and the heat dissipation performance of the graphene heat-conducting film are excellent, the heat conductivity can reach more than 1700W/m.K, and the heat diffusion can reach 950mm 2 More than s.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (6)
1. A preparation method of a high-performance graphene heat-conducting film is characterized by comprising the following steps:
(1) preparing graphene powder in liquid metal by utilizing a CVD method for bubbling growth;
(2) spraying and simultaneously mixing the collected graphene powder by using a resin binder solution, and uniformly mixing to obtain viscous powder;
the resin binder solution is obtained by diluting aqueous binder resin or oily binder resin with a solvent, wherein the binder resin is selected from one of polyurethane, epoxy resin, phenolic resin, acrylic resin, amino resin, unsaturated polyester resin and saturated polyester resin;
(3) feeding the viscous powder into a calender for primary calendering to obtain a first graphene film;
(4) graphitizing the first graphene film under the protection of inert gas to obtain a second graphene film; controlling the amount of carbon residue formed by the bonding resin after graphitization treatment to be 2-5% of the weight of the second graphene film;
(5) and placing the second graphene film in the calender for secondary calendering to obtain the high-performance graphene heat-conducting film.
2. The preparation method of the high-performance graphene thermal conductive film according to claim 1, wherein the specific process of the step (1) is as follows: introducing mixed gas of a gaseous carbon source and nitrogen below the liquid level of the molten metal under normal pressure and nitrogen protection, generating bubbles below the liquid level of the molten metal, growing graphene on the surfaces of the bubbles by the gaseous carbon source under the catalytic action of the molten metal, and separating and collecting graphene powder from the molten metal due to the fact that the bubbles are broken after the bubbles rise above the liquid level of the molten metal due to surface tension difference.
3. The method as claimed in claim 2, wherein the temperature of the molten metal is 1050-;
the gaseous carbon source is one of methane, ethane, propane, propylene, propyne, ethylene, acetylene, natural gas, liquefied petroleum gas, butane and butylene;
the flow rate of the gaseous carbon source is 1-15L/min, and the flow rate of the nitrogen is 50-300L/min.
4. The method according to claim 1, wherein the solvent used for dilution in step (2) is water and/or an organic solvent, and the corresponding dilution solvent is selected according to the type of the resin;
the spraying and the mixing in the step (2) are carried out in a spraying mixer, the spraying pressure is 0.5-2.5MPa, the flow rate of the sprayed solution is 3-15mL/min, the mixing speed is 800-2200rpm, and the mixing time is 1-3 h.
5. The method for preparing a high-performance graphene thermal conductive film according to claim 1, wherein the pressure of the first calendering in the step (3) is 10-20 MPa;
the pressure of the second rolling in the step (5) is 8-25MPa, and the second rolling is carried out until the density of the obtained film is more than or equal to 2g/cm 3 The thickness is more than or equal to 100 mu m.
6. The method as claimed in claim 1, wherein the graphitization step (4) is performed by raising the temperature at a rate of 2-5 ℃/min to 500 ℃, then raising the temperature at a rate of 5-10 ℃/min from 500 ℃ to 2800-.
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