CN114873587A - Graphene heat-conducting film and preparation method thereof - Google Patents
Graphene heat-conducting film and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a preparation method of a graphene heat-conducting film, which comprises the following steps: dispersing graphene prepared by a physical stripping method in an organic solvent to prepare a graphene dispersion liquid; placing the graphene dispersion liquid in a magnetic field, carrying out orientation treatment in the horizontal direction, and removing the organic solvent to prepare a fluffy graphene film; and clamping the fluffy graphene film between templates with smooth mirror surfaces, and performing vacuum pressing to prepare the graphene heat-conducting film. According to the preparation method of the graphene heat-conducting film, provided by the invention, the graphene prepared by a physical stripping method is used as a raw material, and is matched with the action of an organic solvent and a magnetic field, so that the obtained graphene is in oriented arrangement, the problem that the graphene prepared by the physical stripping method is difficult to form a film is solved, and the prepared graphene heat-conducting film has a high heat conductivity coefficient. In addition, the preparation method of the graphene heat-conducting film does not need carbonization and graphitization treatment, and is few in preparation process, low in equipment requirement and lower in product cost.
Description
Technical Field
The invention relates to the technical field of functional thin film materials, in particular to a graphene heat-conducting film and a preparation method thereof.
Background
With the development of mobile phones towards high performance and miniaturization, the heat productivity of chips is larger and larger, and the chips are limited in narrow space, and heat is easy to gather to form hot spots, so that the chips cannot work normally, and therefore materials with high transverse heat conductivity need to be adopted for heat equalization. For 4G mobile phones, the material is usually an artificial graphite heat dissipation film, which is prepared from a polyimide film as a raw material through carbonization, graphitization and calendaring processes. The artificial graphite heat dissipation film is limited by polyimide film raw materials, has limited thickness (less than 100 micrometers), and cannot cope with higher heat productivity of a 5G mobile phone chip. The graphene heat dissipation film can break through the limitation of thickness and meet the requirement of even heating of a 5G mobile phone chip, so that the graphene heat dissipation film is widely applied.
The graphene heat-conducting film is prepared by adopting pulping, coating, carbonizing, graphitizing and rolling processes, and the preparation raw materials mainly comprise two types: graphene oxide and graphene prepared by a physical stripping method. Due to the rich oxygen-containing functional groups, the graphene oxide is very easy to disperse in water, stable high-solid-content slurry is obtained, and the graphene oxide has high viscosity suitable for a coating process. In the slurry coating process, the graphene oxide is self-assembled into oriented arrangement through the hydrogen bond between sheets and the van der waals force action. The method for preparing the graphene heat-conducting film by taking the graphene oxide as the raw material has mass production, but the prepared graphene heat-conducting film has limited heat conductivity which is generally less than 1500W/m.degree, and is difficult to meet the increasing heat dissipation requirement of the mobile phone. The graphene prepared by the physical stripping method has larger sheet diameter and relatively perfect crystal lattice, and the graphene heat-conducting film prepared by the physical stripping method theoretically has higher heat conductivity, but the graphene prepared by the physical stripping method has poor dispersibility, and slurry with high solid content cannot be obtained, so that the slurry has lower viscosity and is not suitable for the existing coating process. Therefore, a method for preparing a graphene thermal conductive film using a physical peeling method as a raw material, and a graphene thermal conductive film having a high thermal conductivity prepared by the method are needed.
Disclosure of Invention
Based on the above, one of the purposes of the present invention is to provide a preparation method of a graphene thermal conductive film with high thermal conductivity.
The preparation method of the graphene heat-conducting film comprises the following steps:
dispersing graphene prepared by a physical stripping method in an organic solvent to prepare a graphene dispersion liquid;
placing the graphene dispersion liquid in a magnetic field, carrying out orientation treatment in the horizontal direction, and removing the organic solvent to prepare a fluffy graphene film;
and clamping the fluffy graphene film between templates with smooth mirror surfaces, and performing vacuum pressing to prepare the graphene heat-conducting film.
In one embodiment, the graphene prepared by the physical stripping method is a lamellar structure graphene with 5-20 layers obtained by physically stripping natural graphite or expanded graphite.
In one embodiment, the physical stripping process comprises at least one of ultrasound, microwave, and sanding; and/or
The graphene prepared by the physical stripping method does not contain heteroatoms; and/or
The sheet diameter of the graphene prepared by the physical stripping method is more than or equal to 10 microns.
In one embodiment, the organic solvent comprises one or more of ethanol, diethyl ether, isopropanol, and acetone.
In one embodiment, the solid content of the graphene dispersion liquid is 0.5 wt% to 2 wt%.
In one embodiment, the magnetic field has a strength of 5 tesla to 20 tesla.
In one embodiment, the vacuum pressing pressure is 20 tons to 1000 tons for 2 minutes to 30 minutes.
In one embodiment, the magnetic field is applied by a magnetic field orienting device, and the magnetic field orienting device comprises a power supply (1), two coils (2) and (3) which are connected with the power supply and distributed at intervals, an electric heating plate (4) positioned between the two coils (2) and (3), and a mold (5) placed on the electric heating plate (4); the two coils (2) and (3) have the same radius and are arranged oppositely; the central connecting line of the two coils (2) and (3) is superposed with the central axis of the mould (5);
and during pressing, placing the fluffy graphene film and the template into a forming groove of the mold (5).
The invention further provides a graphene heat-conducting film, which is prepared by adopting the preparation method of the graphene heat-conducting film.
In one embodiment, the thickness of the graphene thermal conductive film is 60-300 microns; and/or
The thermal conductivity of the graphene heat-conducting film is more than or equal to 1500W/m.degree.
Compared with the prior art, the invention has the following advantages and beneficial effects:
according to the preparation method of the graphene heat-conducting film, the graphene prepared by a physical stripping method is used as a raw material, the graphene is arranged in an oriented manner under the action of a magnetic field, and the problem of film formation of the graphene prepared by the physical stripping method is solved by the process of heating and evaporating a solvent, and the prepared graphene heat-conducting film has a high heat conductivity coefficient.
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FIG. 1 is a schematic view of a magnetic field orienting device.
Reference numerals:
1: a power source; 2 and 3: a coil; 4: an electric hot plate; 5: and (5) molding.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the following description. The following is a description of preferred embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Reference herein to numerical intervals is deemed to be continuous, unless otherwise stated, and includes both the minimum and maximum values of that range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range-describing features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein.
The temperature parameter herein is not particularly limited, and is allowed to be either constant temperature treatment or treatment within a certain temperature range. The constant temperature process allows the temperature to fluctuate within the accuracy of the instrument control.
An embodiment provides a method for preparing a graphene thermal conductive film, including the following steps:
s110: and dispersing the graphene prepared by a physical stripping method in an organic solvent to prepare a graphene dispersion solution.
In one embodiment, the graphene prepared by the physical exfoliation method is a lamellar graphene with 5-20 layers obtained by physically exfoliating natural graphite or expanded graphite. In some specific examples, the lamellar structure graphene may be obtained with 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 layers, preferably, the number of graphene layers is between 7 and 15, and more preferably, between 9 and 11.
In one example, the physical stripping method includes at least one of ultrasound, microwave, and sanding.
In one example, the graphene prepared by the physical stripping method does not contain a heteroatom.
The heteroatom is one or more of an oxygen atom, a nitrogen atom and a hydrogen atom.
In one example, the sheet size of the graphene prepared by the physical stripping method is greater than or equal to 10 microns, such as greater than or equal to 12 microns, greater than or equal to 15 microns, greater than or equal to 18 microns, or greater than or equal to 20 microns, and preferably, the sheet size of the graphene is not greater than 100 microns.
In one example, the organic solvent includes one or more of ethanol, diethyl ether, isopropanol, and acetone.
In one example, the graphene dispersion has a solid content of 0.5 wt% to 2 wt%, for example, the graphene dispersion may have a solid content of 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2 wt%, and preferably, the graphene dispersion has a solid content of 1 wt% to 1.5 wt%.
S120: placing the graphene dispersion liquid in a magnetic field, carrying out orientation treatment in the horizontal direction, and removing the organic solvent to prepare a fluffy graphene film;
in one example, the strength of the magnetic field is 5 tesla to 20 tesla, and specifically, the strength of the magnetic field may be 5 tesla, 6 tesla, 7 tesla, 8 tesla, 9 tesla, 10 tesla, 11 tesla, 12 tesla, 13 tesla, 14 tesla, 15 tesla, 16 tesla, 17 tesla, 18 tesla, 19 tesla, or 20 tesla, and preferably, the strength of the magnetic field is between 10 tesla to 15 tesla.
In one example, the vacuum pressing is performed at a pressure of 20 tons to 1000 tons for 2 minutes to 30 minutes. Specifically, the pressure of the above vacuum pressing may be 20 tons, 50 tons, 100 tons, 150 tons, 200 tons, 300 tons, 400 tons, 500 tons, 600 tons, 700 tons, 800 tons, 900 tons, or 1000 tons, and the time may be 30 minutes, 25 minutes, 20 minutes, 15 minutes, 10 minutes, 5 minutes, or 2 minutes.
In one example, the magnetic field is applied by a magnetic field orienting device, which comprises a power supply 1, two coils 2 and 3 connected with the power supply and distributed at intervals, an electric heating plate 4 positioned between the two coils 2 and 3, and a mold 5 placed on the electric heating plate 4; the two coils 2 and 3 have the same radius and are arranged oppositely; the central connecting line of the two coils 2 and 3 is superposed with the central axis of the mould 5.
In one example, the two sides of the electric heating plate 4 are provided with fixing brackets, and the fixing brackets are provided with fixing grooves which are electrically connected with a power supply.
In one example, when the two coils 2 and 3 are energized, a magnetic field is formed along the direction of the central connection line of the two coils, and the magnetic field passes through a mold 5 which is arranged on an electric hot plate 4 and is provided with graphene dispersion liquid.
In one example, under the action of a magnetic field, the graphene is arranged along the direction of the magnetic field, i.e., in the horizontal direction.
In one example, when the electric heating plate is electrified and heated, and the solvent is volatilized, the fluffy graphene film in the horizontal orientation arrangement is obtained. The fluffy appearance is caused by the existence of voids left after more solvent is volatilized.
In one example, the mold 5 is made of stainless steel and has a molding groove, and the surface of the molding groove is plated with fluorine.
In one example, the depth of the molding groove is set according to a target thickness of the prepared graphene thermal conductive film.
In one example, the forming groove has a depth of 1.5 cm to 10 cm.
S130: and clamping the fluffy graphene film between templates with smooth mirror surfaces, and performing vacuum pressing to prepare the graphene heat-conducting film.
In one example, the fluffy graphene film and the template are placed in a forming groove of the mold 5 during pressing.
In one example, the fluffy graphene film has a density of 1.9 g/cm after vacuum pressing 3 2.2 g/cm 3 . Due to the fact that the graphene is high in horizontal orientation degree and high in density, the prepared graphene heat conduction film has high heat conductivity in the horizontal direction.
In one example, the preparation method of the graphene thermal conductive film comprises the following steps:
1. dispersing the laminated graphene with 5-20 layers of layers prepared by a physical stripping method into one or more organic solvents of ethanol, ether, isopropanol and acetone, and ultrasonically treating to obtain a graphene dispersion liquid with a solid content of 0.5-2 wt%;
the graphene prepared by the physical stripping method is obtained by subjecting natural graphite or expanded graphite to ultrasonic treatment, microwave treatment or sanding.
The graphene prepared by the physical stripping method does not contain heteroatoms, and the sheet diameter is more than or equal to 10 microns.
2. And transferring the graphene dispersion liquid into a magnetic field orientation device, carrying out orientation treatment in the horizontal direction, carrying out orientation arrangement on the graphene along the horizontal direction under the action of a magnetic field with the strength of 5-20 Tesla, and heating to completely volatilize the solvent to obtain the fluffy graphene film.
The magnetic field is applied by a magnetic field orientation device shown in fig. 1, which comprises a power supply 1, two coils 2 and 3 connected with the power supply and distributed at intervals, an electric heating plate 4 positioned between the two coils 2 and 3, and a mold 5 placed on the electric heating plate 4; the two coils 2 and 3 have the same radius and are arranged oppositely; the central connecting line of the two coils 2 and 3 is superposed with the central axis of the mould 5. After the two coils 2 and 3 are electrified, a magnetic field is formed along the central connection line direction of the two coils, and the magnetic field passes through a die 5 which is positioned on the electric hot plate 4 and is provided with graphene dispersion liquid. The two sides of the electric heating plate 4 are provided with fixing supports, fixing grooves are arranged on the fixing supports, and the fixing grooves are electrically connected with a power supply. The die 5 is made of stainless steel and is provided with a forming groove, and the surface of the forming groove is plated with fluorine. The depth of the molding groove is set according to the target thickness of the prepared graphene heat-conducting film, and is specifically 1.5-10 cm.
3. And (3) clamping a fluffy graphene film between stainless steel sheets with smooth mirror surfaces, stacking the fluffy graphene film in a mould, and performing vacuum pressing for 2-30 minutes under the pressure of 20-1000 tons through a vacuum flat press to obtain the graphene heat-conducting film.
An embodiment also provides a graphene heat-conducting film prepared by the preparation method of the graphene heat-conducting film.
In one example, the thickness of the graphene thermal conductive film is 60 to 300 micrometers.
In one example, the thermal conductivity of the graphene thermal conductive film is more than or equal to 1500W/m.degree.
In one example, the graphene thermal conductive film has a density of 1.9-2.2 g/cm 3 。
According to the preparation method of the graphene heat-conducting film, the graphene prepared by a physical stripping method is used as a raw material, the graphene is arranged in an oriented manner under the action of a magnetic field, the problem of film formation of the graphene prepared by the physical stripping method is solved by the process of heating and evaporating a solvent, and the prepared graphene heat-conducting film has a high heat conductivity coefficient.
In addition, the preparation method of the graphene heat-conducting film does not need carbonization and graphitization treatment, and is few in preparation process, low in equipment requirement and lower in product cost.
The following are specific examples.
Example 1: preparation of graphene heat-conducting film
The preparation method of the graphene heat conduction film comprises the following steps:
1. dispersing 5-20 layers of graphene with a lamellar structure prepared by a physical stripping method into ethanol, and performing ultrasonic treatment to obtain a graphene dispersion liquid with a solid content of 2 wt%;
the graphene prepared by the physical stripping method is obtained by sanding expanded graphite.
The graphene prepared by the physical stripping method does not contain heteroatoms, and the sheet diameter is 10 microns.
2. And transferring the graphene dispersion liquid into a magnetic field orientation device, carrying out orientation treatment in the horizontal direction, enabling the graphene to be arranged in an oriented manner along the horizontal direction under the action of a magnetic field with the strength of 5 Tesla, and heating to completely volatilize ethanol to obtain the fluffy graphene film.
The magnetic field is applied by a magnetic field orienting device shown in fig. 1, which comprises a power supply 1, two coils 2 and 3 connected with the power supply and distributed at intervals, an electric heating plate 4 positioned between the two coils 2 and 3, and a mold 5 placed on the electric heating plate 4; the two coils 2 and 3 have the same radius and are arranged oppositely; the central connecting line of the two coils 2 and 3 is superposed with the central axis of the mould 5. After the two coils 2 and 3 are electrified, a magnetic field is formed along the central connection line direction of the two coils, and the magnetic field passes through a die 5 which is positioned on the electric hot plate 4 and is provided with graphene dispersion liquid. The two sides of the electric heating plate 4 are provided with fixing supports, fixing grooves are arranged on the fixing supports, and the fixing grooves are electrically connected with a power supply. The die 5 is made of stainless steel and is provided with a forming groove, and the surface of the forming groove is plated with fluorine. The depth of the forming groove is 1.5 cm.
3. Placing a smooth-mirror-surface stainless steel sheet between every two fluffy graphene films, stacking the stainless steel sheets in a grinding tool, and performing vacuum pressing for 10 minutes under the pressure of 50 tons through a vacuum flat press to obtain the graphene heat-conducting film.
Example 2: preparation of graphene heat-conducting film
The preparation method of the graphene heat conduction film comprises the following steps:
1. dispersing the laminated graphene with 5-20 layers prepared by a physical stripping method into acetone, and performing ultrasonic treatment to obtain a graphene dispersion liquid with solid content of 0.5 wt%;
the graphene prepared by the physical stripping method is obtained by carrying out ultrasonic treatment on natural graphite.
The graphene prepared by the physical stripping method does not contain heteroatoms, and the sheet diameter is 100 microns.
2. And transferring the graphene dispersion liquid into a magnetic field orientation device, carrying out orientation treatment in the horizontal direction, enabling the graphene to be arranged in an oriented manner along the horizontal direction under the action of a magnetic field with the strength of 20 Tesla, and heating to completely volatilize ethanol to obtain the fluffy graphene film.
The magnetic field is applied by a magnetic field orienting device shown in fig. 1, which comprises a power supply 1, two coils 2 and 3 connected with the power supply and distributed at intervals, an electric heating plate 4 positioned between the two coils 2 and 3, and a mold 5 placed on the electric heating plate 4; the two coils 2 and 3 have the same radius and are arranged oppositely; the central connecting line of the two coils 2 and 3 is superposed with the central axis of the mould 5. After the two coils 2 and 3 are electrified, a magnetic field is formed along the central connection line direction of the two coils, and the magnetic field passes through a die 5 which is positioned on the electric hot plate 4 and is provided with graphene dispersion liquid. The two sides of the electric heating plate 4 are provided with fixing supports, fixing grooves are arranged on the fixing supports, and the fixing grooves are electrically connected with a power supply. The die 5 is made of stainless steel and is provided with a forming groove, and the surface of the forming groove is plated with fluorine. The depth of the forming groove is 10 cm.
3. Placing a smooth-mirror-surface stainless steel sheet between every two fluffy graphene films, stacking the stainless steel sheets in a grinding tool, and performing vacuum pressing for 30 minutes under the pressure of 1000 tons through a vacuum flat press to obtain the graphene heat-conducting film.
Comparative example 1: preparation of graphene heat-conducting film
Comparative example 1 differs from example 1 in that: graphene prepared by the physical stripping method in example 1 is replaced by graphene oxide, and the graphene thermal conductive film is prepared by adopting the processes of pulping, coating, carbonizing, graphitizing and rolling.
The preparation method comprises the following steps:
(1) dispersing graphene oxide in deionized water, adding ammonia water to adjust the pH value to 7.5, and stirring in vacuum to obtain graphene oxide slurry with the mass percentage of 6%;
(2) treating the graphene oxide slurry for 30 minutes by a high-pressure homogenizer under the pressure of 500MPa, so as to improve the dispersion stability of the graphene oxide slurry;
(3) coating the graphene oxide slurry on a substrate through a coating machine, controlling the thickness to be 1.5 cm, then baking for 1 hour at 90 ℃ through a tunnel furnace, and then rolling to obtain a graphene oxide film;
(4) cutting the graphene oxide film into sheets, and then placing the sheets in a vacuum drying oven to be processed for 5 hours at the temperature of 150 ℃ to obtain a partially reduced graphene oxide film;
(5) placing the partially reduced edge graphene oxide film in a carbonization furnace to be treated for 6 hours at 1500 ℃, and then treating the film in a graphitization furnace for 10 hours at 3000 ℃ to obtain a graphene film;
(6) placing a stainless steel sheet with a smooth mirror surface between every two graphene films, stacking the stainless steel sheets in a mold, and performing vacuum pressing for 2 minutes under the pressure of 1000 tons through a vacuum flat press to obtain the graphene heat-conducting film.
Comparative example 2: preparation of graphene heat-conducting film
Comparative example 2 differs from example 1 in that: the graphene oxide at the edge of the embodiment 1 is replaced by graphene oxide, and the graphene thermal conductive film is prepared by adopting the processes of pulping, coating, carbonizing, graphitizing and calendaring.
The preparation method comprises the following steps:
(1) dispersing graphene oxide in deionized water, adding ammonia water to adjust the pH value to 7.5, and stirring in vacuum to obtain graphene oxide slurry with the mass percentage of 6%;
(2) treating the graphene oxide slurry for 30 minutes by a high-pressure homogenizer under the pressure of 500MPa, so as to improve the dispersion stability of the graphene oxide slurry;
(3) coating the graphene oxide slurry on a substrate through a coating machine, controlling the thickness to be 1.5 cm, then baking for 1 hour at 70 ℃ through a tunnel furnace, and then rolling to obtain a graphene oxide film;
(4) cutting the graphene oxide film into sheets, stacking every 5 sheets together, placing the sheets in a clamp, giving a certain fastening force to the graphene oxide film through a fastening screw by the clamp, and placing the graphene oxide film in a vacuum drying oven to be treated for 5 hours at the temperature of 150 ℃ to obtain a partially reduced graphene oxide film;
(5) placing the partially reduced graphene oxide film in a carbonization furnace to be treated for 6 hours at 1500 ℃, and then treating the partially reduced graphene oxide film in a graphitization furnace for 10 hours at 3000 ℃ to obtain a graphene film;
(6) placing a stainless steel sheet with a smooth mirror surface between every two graphene films, stacking the stainless steel sheets in a mold, and performing vacuum pressing for 30 minutes under the pressure of 1000 tons through a vacuum flat press to obtain the graphene heat-conducting film.
The graphene thermal conductive films prepared in examples 1 to 2 and comparative examples 1 to 2 were subjected to density, thickness and thermal conductivity tests, and the test results are shown in table 1 below. The test standard of the thermal conductivity test is ASTM E1461.
TABLE 2 thickness and thermal conductivity test results
As can be seen from Table 1, the thermal conductivity of examples 1-2 is significantly higher than that of comparative examples 1-2. Specifically, it can be seen from the data of example 1 and comparative example 1, and the data of example 2 and comparative example 2 that graphene prepared by a physical exfoliation method is used as a raw material, and an organic solvent and a magnetic field are matched, so that the obtained graphene dispersion liquid is arranged in an oriented manner, the problem that the graphene prepared by the physical exfoliation method is difficult to form a film is solved, and the prepared graphene thermal conductive film has a high thermal conductivity coefficient. In addition, the preparation method of the graphene heat-conducting film does not need carbonization and graphitization treatment, and is few in preparation process, low in equipment requirement and lower in product cost.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A preparation method of a graphene heat conduction film is characterized by comprising the following steps:
dispersing graphene prepared by a physical stripping method in an organic solvent to prepare a graphene dispersion liquid;
placing the graphene dispersion liquid in a magnetic field, carrying out orientation treatment in the horizontal direction, and removing the organic solvent to prepare a fluffy graphene film;
and clamping the fluffy graphene film between templates with smooth mirror surfaces, and performing vacuum pressing to prepare the graphene heat-conducting film.
2. The method for preparing the graphene thermal conductive film according to claim 1, wherein the graphene prepared by the physical exfoliation method is a lamellar structure graphene having 5 to 20 layers obtained by physically exfoliating natural graphite or expanded graphite.
3. The method of claim 2, wherein the physical exfoliation method comprises at least one of ultrasound, microwave, and sanding; and/or
The graphene prepared by the physical stripping method does not contain heteroatoms; and/or
The sheet diameter of the graphene prepared by the physical stripping method is more than or equal to 10 microns.
4. The method according to claim 1, wherein the organic solvent comprises one or more of ethanol, diethyl ether, isopropanol, and acetone.
5. The method for preparing the graphene thermal conductive film according to claim 1, wherein the solid content of the graphene dispersion liquid is 0.5 wt% to 2 wt%.
6. The method according to claim 1, wherein the magnetic field has a strength of 5 tesla to 20 tesla.
7. The method according to claim 1, wherein the vacuum pressing is performed under a pressure of 20 tons to 1000 tons for 2 minutes to 30 minutes.
8. The method for preparing the graphene thermal conductive film according to any one of claims 1 to 7, wherein the magnetic field is applied by a magnetic field orienting device, the magnetic field orienting device comprises a power supply (1), two coils (2) and (3) which are connected with the power supply and are distributed at intervals, an electric heating plate (4) which is arranged between the two coils (2) and (3), and a mold (5) which is arranged on the electric heating plate (4); the two coils (2) and (3) have the same radius and are arranged oppositely; the central connecting line of the two coils (2) and (3) is superposed with the central axis of the mould (5);
and during pressing, placing the fluffy graphene film and the template into a forming groove of the mold (5).
9. A graphene thermal conductive film, characterized by being prepared by the method for preparing a graphene thermal conductive film according to any one of claims 1 to 8.
10. The graphene thermal conductive film of claim 9, wherein the graphene thermal conductive film has a thickness of 60 to 300 microns; and/or
The thermal conductivity of the graphene heat-conducting film is more than or equal to 1500W/m.degree.
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