CN111154461B - Oriented assembly graphene, graphene-carbon nanotube composite heat-conducting film and preparation method thereof - Google Patents
Oriented assembly graphene, graphene-carbon nanotube composite heat-conducting film and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a preparation method of directionally assembled graphene, which comprises the following steps: and mixing the graphene oxide aqueous solution and water-soluble metal salt, slowly cooling until water molecules are crystallized to ice, performing freeze drying treatment to obtain directionally assembled graphene oxide, and reducing to obtain directionally assembled graphene loaded with metal nanoparticles. The directionally assembled graphene has a three-dimensional layered structure with layers arranged in parallel, interlayer gaps exist among the layers, and metal nanoparticles are riveted in the three-dimensional layered structure of the directionally assembled graphene. The present application also relates to an oriented assembled graphene prepared by the method as described above. The application also relates to a graphene-carbon nanotube composite heat-conducting film prepared by utilizing the directionally assembled graphene and a preparation method thereof. The composite heat-conducting film has the advantages of low cost, high phase extraction of graphene, ultrahigh heat-conducting coefficient, controllable thickness of ultrahigh-flexibility products and the like, and the vertical heat-conducting coefficient can reach about 100W/(m.K).
Description
Technical Field
The invention relates to the technical field of graphene and graphene composite materials. Specifically, the present application relates to an oriented graphene, a method for preparing the oriented graphene, a graphene-carbon nanotube composite thermal conductive film, and a method for preparing the composite thermal conductive film.
Background
In solid materials, phonons and electrons are key mediators of heat transfer. The higher thermal conductivity of metals depends mainly on the electron transport process at high concentration, while silver metal has the highest thermal conductivity (K429W/(m · K)) among all metals, but this thermal conductivity is still not ideal in practical applications. The thermal conductivity of the non-metal mainly depends on the propagation rate of phonons, the thermal conductivity of different elements is greatly different, and the different lattice arrangements of the same element also have greatly different thermal conductivities (such as diamond and graphite), so that how to obtain the non-metal thermal conductive material with more excellent performance still has great challenge.
Graphene is currently an extensively studied two-dimensional carbon material consisting of a unique monolayer of parallel conjugated atomic layers arranged into a honeycomb lattice. The graphene has the characteristics of low atomic mass, strong bond energy, single crystal structure and low non-simple harmonic vibration, and the theoretical thermal conductivity coefficient of the graphene is as high as 5300W/(m.K). Meanwhile, the unique single-layer structure of the graphene endows the graphene with ultrahigh flexibility. These unique properties make graphene more likely to be a thermally conductive material with ultra-high thermal conductivity and ultra-flexibility.
Carbon nanotubes are considered to be a promising heat conducting material due to their excellent mechanical strength, unique spatial dimension structure, and good heat and electrical conductivity. The carbon nano tube is used as the filler, so that the performances of the material in the aspects of heat, electricity and machinery can be obviously improved, and particularly, the composite material has more excellent performances including mechanical properties, physical and chemical properties and electrical properties due to the directional arrangement of the carbon nano tube in a magnetic field. The directional arrangement realizes the design of the composite material on the microstructure, so that the excellent performance of the carbon nano tube is fully reflected, and the carbon nano tube is suitable for the application of various sustainable energy and environmental engineering.
In the prior art, various studies have been made on graphene-based heat conductive materials. For example, chinese patent application No. 201811434574.4 discloses a method for preparing a graphene thermal conductive film, in which a graphene emulsion is coated on the surface of a polyimide film to obtain a graphene polyimide composite film, and then the graphene polyimide composite film is carbonized at 800 to 1000 ℃ and graphitized at 2000 to 2300 ℃ for several hours to obtain the thermal conductive film. The thermal conductivity coefficient of the thermal conductive film obtained by the method is in the range of 1600-1950W/(m.K), but the method is expensive because the main raw material is polyimide, and is difficult to be practically applied.
In addition, the chinese patent application with application number 201310380233.4 discloses a method for preparing a graphene thermal conductive film, which includes dispersing graphene oxide in a liquid phase environment, then obtaining a graphene oxide film by suction filtration drying or coating drying, and further obtaining the graphene thermal conductive film by high temperature (2000-. The thermal conductivity coefficient range of the thermal conductive film obtained by the method is 400-2000W/(m.K), but the thermal conductive film has smaller size, is difficult to be produced in an enlarged mode and has higher energy consumption.
In summary, the prior art for preparing graphene has the defects of high cost or difficulty in scale-up production. Therefore, there is a continuing need in the art to develop a graphene-based thermally conductive film and a method of making the same.
Disclosure of Invention
In addition to the technical defects of the graphene-based heat conducting film, as the graphene heat conducting film is used more and more as a heat dissipation material in a 5G flexible electronic device, higher requirements are also placed on the vertical heat conducting performance of the graphene heat conducting film. However, the vertical thermal conductivity of the graphene thermal conductive film in the prior art is only about 5W/(m · K), which is far from meeting the practical application requirements.
The invention aims to provide a novel heat-conducting film preparation technology aiming at the defects and shortcomings of high production cost, low heat-conducting coefficient, poor flexibility, non-adjustable product thickness and the like of the conventional heat-conducting film. The heat-conducting film has the advantages of low cost, high phase extraction of graphene, ultrahigh heat conductivity coefficient, controllable thickness of ultrahigh-flexibility products and the like.
The present application aims to provide a method for preparing directionally assembled graphene, which is low in cost and easy to scale up, so as to solve the technical problems in the prior art.
It is also an object of the present application to provide an aligned assembled graphene prepared by the method as described above.
The present application further provides a method for preparing a graphene-carbon nanotube composite thermal conductive film.
The present application also aims to provide a graphene-carbon nanotube composite thermal conductive film prepared by the method as described above.
Specifically, the method comprises the steps of slowly cooling graphene oxide to the freezing rate of water molecules in water molecule crystallization ice formation, further utilizing freeze drying to induce the graphene oxide to form a three-dimensional layered graphene oxide structure with layers arranged in parallel, and obtaining the directionally assembled graphene which has a three-dimensional layered structure and is loaded with metal nanoparticles after reduction.
In addition, the carbon nano tube grows in situ on the directionally assembled graphene loaded with the metal nano particles by controlling the magnetic field intensity, and the graphene-carbon nano tube composite heat-conducting film is prepared. The carbon nano tubes are overlapped in the interlayer gaps of the directionally assembled graphene and are vertical to the plane where the graphene is located, so that the horizontal heat conductivity coefficient and the vertical heat conductivity coefficient of the graphene-carbon nano tube composite heat-conducting film are obviously improved.
In order to solve the above technical problem, the present application provides the following technical solutions.
In a first aspect, the present application provides a method for preparing directionally assembled graphene, wherein the method comprises the following steps:
s1: mixing graphene oxide and an aqueous solvent to obtain a graphene oxide aqueous solution;
s2: mixing the graphene oxide aqueous solution and a water-soluble metal salt to obtain a graphene oxide aqueous solution containing metal ions;
s3: slowly freezing and freeze-drying the graphene oxide aqueous solution containing the metal ions to obtain directionally assembled graphene oxide; and
s4: treating the directionally assembled graphene oxide in a reducing atmosphere at the temperature of 200-600 ℃ for 1-10 hours to obtain the directionally assembled graphene loaded with metal nanoparticles;
the directionally assembled graphene loaded with the metal nanoparticles has a three-dimensional layered structure with layers arranged in parallel, and interlayer gaps exist among the layers;
wherein, in the directionally assembled graphene loaded with the metal nanoparticles, the metal nanoparticles are riveted in a three-dimensional layered structure of the directionally assembled graphene.
In one embodiment of the first aspect, the slowly reducing the temperature until the water molecules are crystallized into ice includes placing the aqueous graphene oxide solution containing the metal ions in a refrigerator at-1 ℃ to-3 ℃ for 10 hours to 15 hours, and slowly reducing the temperature until the water molecules are crystallized into ice.
In one embodiment of the first aspect, the mass ratio of the graphene oxide to the aqueous solvent is 1:10 to 1: 100.
in one embodiment of the first aspect, the mass ratio of the water-soluble metal salt to the aqueous graphene oxide solution is 1:100 to 1: 1000.
in one embodiment of the first aspect, the water-soluble metal salt is selected from one or more of the following: copper, iron, cobalt or nickel salts.
In a second aspect, the present application provides an aligned assembled graphene prepared by the method for preparing an aligned assembled graphene according to the first aspect.
In one embodiment of the second aspect, the gap between graphene layers of the metal nanoparticle-loaded aligned assembled graphene is 0.05 to 0.5 μm.
In a third aspect, the present application provides a method for preparing a graphene-carbon nanotube composite thermal conductive film, wherein the method comprises the following steps:
step (1): growing carbon nanotubes in situ on the metal nanoparticle-loaded directionally assembled graphene in the presence of a magnetic field and a carbon source gas to obtain a metal nanoparticle-loaded directionally assembled graphene-carbon nanotube composite material;
step (2): graphitizing the directionally assembled graphene-carbon nanotube composite material loaded with the metal nanoparticles at the temperature of 1000-1500 ℃, and rolling to obtain a graphene-carbon nanotube composite heat-conducting film;
wherein the carbon nanotubes form lap joints between layers of the directionally assembled graphene and are vertically arranged with a plane where the layered structure of the directionally assembled graphene is located.
In one embodiment of the third aspect, in step (1), the magnetic field strength is from 0.1 to 10A/m;
in the step (1), the carbon source gas is a mixed gas of methane and argon;
in the step (1), the conditions for growing the carbon nanotubes in situ are as follows: the flow rate of the carbon source gas is controlled to be 1-100ml/min, the reaction temperature is 900-.
In one embodiment of the third aspect, as in step (1), in the metal nanoparticle-loaded aligned assembled graphene-carbon nanotube composite material, the mass ratio of the metal nanoparticle-loaded aligned assembled graphene to the carbon nanotubes is 5: 1 to 50: 1.
in a fourth aspect, the present application provides a graphene-carbon nanotube composite thermal conductive film prepared by the method for preparing a graphene-carbon nanotube composite thermal conductive film according to the third aspect.
In an embodiment of the fourth aspect, the thickness of the graphene-carbon nanotube composite thermal conductive film is 30-100 μm, the horizontal thermal conductivity is 1500-.
Compared with the prior art, the heat conduction film has the advantages that the cost is low, the phase extraction performance of graphene is high, the ultrahigh heat conductivity coefficient is high, the thickness of the ultrahigh-flexibility product is controllable, and the like. The vertical thermal conductivity coefficient of the graphene-carbon nanotube composite thermal conductive film prepared by the method can reach 100W/(m.K) at most, and is far higher than that of the existing graphene thermal conductive film.
Drawings
The present application may be better understood by describing embodiments thereof in conjunction with the following drawings, in which:
fig. 1 shows a scanning electron microscope picture of directionally assembled graphene loaded with metal nanoparticles according to example 1;
fig. 2 shows a high resolution scanning electron microscope picture of the graphene-carbon nanotube composite thermally conductive film according to example 1;
fig. 3 shows a low-resolution scanning electron microscope picture of the graphene-carbon nanotube composite thermally conductive film according to example 1;
fig. 4 shows a low-resolution scanning electron microscope picture of the graphene-carbon nanotube composite thermally conductive film according to example 2;
fig. 5 shows a low-resolution scanning electron microscope picture of the graphene-carbon nanotube composite thermally conductive film according to example 3;
fig. 6 shows a low-resolution scanning electron microscope picture of the graphene-carbon nanotube composite thermal conductive film according to example 4.
Detailed Description
Unless otherwise defined, technical or scientific terms used herein in the specification and claims should have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All numerical values recited herein as between the lowest value and the highest value are intended to mean all values between the lowest value and the highest value in increments of one unit when there is more than two units difference between the lowest value and the highest value.
In the following detailed description of the embodiments of the present invention, reference is made to the accompanying drawings, which are included to provide a further understanding of the invention, and in which is shown by way of illustration specific embodiments in which the invention may be practiced.
In one embodiment, the present application provides a three-dimensional lapping technique for porous graphene, resulting in directionally assembled graphene. In one embodiment, the technique includes the steps of: and (3) preparing graphene oxide: water in a ratio of 1:10 to 1:100, adding a water-soluble metal salt, wherein the mass ratio of the metal salt to the graphene oxide solution is 1:100 to 1: 1000. and slowly cooling the mixed solution until water molecules are crystallized into ice, placing the ice in a freeze dryer, inducing graphene oxide to form three-dimensional layered graphene oxide with layers arranged in parallel, reducing the three-dimensional layered graphene oxide in a hydrogen atmosphere at the reduction temperature of 200-600 ℃ for 1-10h to obtain the three-dimensional layered directionally assembled graphene loaded with metal nanoparticles, wherein the metal nanoparticles are riveted in the layered graphene, and the distance between graphene layers is 0.05-0.5 mu m.
In one embodiment, the step of slowly cooling the mixed solution until the water molecules are crystallized into ice includes placing the mixed solution in a refrigerator at a temperature of between-1 ℃ and-3 ℃ for 10 to 15 hours, and slowly cooling until the water molecules are crystallized into ice.
In a preferred embodiment, the mass ratio of graphene oxide to water may be 1:10, 1:20, 1:25, 1:30, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, or a range or sub-range between any two of these values.
In a preferred embodiment, the water-soluble metal salt may comprise copper acetate or ferric chloride. In a preferred embodiment, the mass ratio of the metal salt to the graphene oxide solution may be 1: 100. 1: 200. 1: 500. 1: 600. 1: 700. 1: 900. 1: 1000 or a range or subrange between any two of them.
In a preferred embodiment, the reduction temperature may be 200 ℃, 220 ℃, 250 ℃, 270 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃ or a range or sub-range between any two of them.
In a preferred embodiment, the reduction time may be 1 hour, 1.5 hours, 2 hours, 4 hours, 5 hours, 5.5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or a range or subrange between any two of them.
In one embodiment, the present application provides a technique for in situ growth of carbon nanotubes. In one embodiment, the technique includes the steps of: placing the three-dimensional layered graphene loaded with the metal nanoparticles in a tubular furnace, placing the tubular furnace in an external magnetic field, wherein the magnetic field intensity is 0.1-10A/m, introducing methane/argon mixed gas into the tubular furnace, controlling the flow rate of the mixed gas to be 1-100ml/min, reacting at the temperature of 900-1400 ℃, and reacting for 1-6h to obtain the graphene-carbon nanotube composite loaded with the metal nanoparticles, wherein the carbon nanotubes are lapped between graphene layers and vertically arranged with the graphene, and the mass ratio of the graphene to the carbon nanotubes is 5: 1 to 50: 1. further graphitizing the obtained graphene-carbon nanotube composite loaded with the metal nanoparticles at the temperature of 1000-1500 ℃ and rolling to obtain the metal-graphene-carbon nanotube heat-conducting film. The thickness of the graphene heat-conducting film is 30-100 mu m, the horizontal heat-conducting coefficient is 1500-2300W/(m.K), and the vertical heat-conducting coefficient is 30-100W/(m.K).
The graphene-carbon nanotube heat-conducting film with different carbon nanotube arrangement directions can be obtained by changing different magnetic field directions. The graphene-carbon nanotube heat-conducting films with different thicknesses can also be obtained by changing the magnetic field intensity.
Examples
The present application is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
In the following examples, the scanning electron microscope pictures were obtained by means of a scanning electron microscope of the type Phenom Pro.
Example 1
The three-dimensional space lapping technology of the porous graphene comprises the following steps: and (3) preparing graphene oxide: the water mass ratio is 1:10, adding copper acetate, wherein the mass ratio of the copper acetate to the graphene oxide solution is 1:100, and uniformly mixing. And slowly cooling the mixed solution until water molecules are crystallized into ice, and then moving the mixed solution to a freeze dryer for freeze drying, wherein the drying temperature is-50 ℃, the drying time is 24 hours, and three-dimensional layered graphene oxide arranged in parallel layer by layer can be obtained by controlling the freezing rate, wherein copper elements are uniformly distributed among graphene layers. And reducing the three-dimensional layered graphene in a hydrogen atmosphere at the reduction temperature of 300 ℃ for 2h to obtain the copper nanoparticles @ three-dimensional layered graphene. As can be seen from fig. 1, the copper nanoparticles are riveted into the layered graphene, and the graphene layer spacing is about 0.05 μm.
In this embodiment, the "slowly reducing the temperature of the mixed solution until the water molecules are crystallized into ice" includes placing the mixed solution in a refrigerator at-1 ℃ for 10 hours, and slowly reducing the temperature until the water molecules are crystallized into ice.
In-situ growth technology of carbon nanotubes: the copper nanoparticles @ three-dimensional layered graphene is placed in a tube furnace, the tube furnace is placed in an external magnetic field, the direction of the magnetic field is perpendicular to the horizontal plane, and the magnetic field intensity is 0.5A/m. Introducing methane/argon mixed gas into the tubular furnace, wherein the flow rate of the mixed gas is 20ml/min, the reaction temperature is 900 ℃, and the reaction time is 1h, so as to obtain the copper nanoparticle @ graphene-carbon nanotube compound, wherein the mass ratio of graphene to carbon nanotubes is 5: 1. the obtained copper nanoparticle @ graphene-carbon nanotube composite is graphitized at 1000 ℃ and rolled to obtain the copper-graphene-carbon nanotube heat-conducting film. The graphene heat-conducting film is 30 mu m in thickness, the horizontal heat-conducting coefficient is 1500W/(m.K), and the vertical heat-conducting coefficient is 35W/(m.K).
As can be seen from fig. 2 and 3, the carbon nanotubes are aligned between graphene layers in a perpendicular manner to the graphene.
Example 2
The three-dimensional space lapping technology of the porous graphene comprises the following steps: and (3) preparing graphene oxide: the water mass ratio is 1:20, adding copper acetate, wherein the mass ratio of the copper acetate to the graphene oxide solution is 1: and 200, uniformly mixing. And slowly cooling the mixed solution until water molecules are crystallized into ice, and then moving the mixed solution to a freeze dryer for freeze drying, wherein the drying temperature is-50 ℃, the drying time is 24 hours, and three-dimensional layered graphene oxide arranged in parallel layer by layer can be obtained by controlling the freezing rate, wherein copper elements are uniformly distributed among graphene layers. And reducing the three-dimensional layered graphene in a hydrogen atmosphere at the reduction temperature of 400 ℃ for 2h to obtain copper nanoparticles @ the three-dimensional layered graphene, wherein the copper nanoparticles are riveted in the layered graphene, and the distance between graphene layers is about 0.1 mu m.
In this embodiment, the "slowly reducing the temperature of the mixed solution until the water molecules are crystallized into ice" includes placing the mixed solution in a refrigerator at-3 ℃ for 15 hours, and slowly reducing the temperature until the water molecules are crystallized into ice.
In-situ growth technology of carbon nanotubes: the copper nanoparticles @ three-dimensional layered graphene is placed in a tube furnace, the tube furnace is placed in an external magnetic field, the direction of the magnetic field is perpendicular to the horizontal plane, and the magnetic field intensity is 2A/m. Introducing methane/argon mixed gas into the tubular furnace, wherein the flow rate of the mixed gas is 20ml/min, the reaction temperature is 1000 ℃, and the reaction time is 1h, so as to obtain the copper nanoparticle @ graphene-carbon nanotube compound, wherein the mass ratio of graphene to carbon nanotubes is 20: 1. the obtained copper nanoparticle @ graphene-carbon nanotube composite is graphitized at 1000 ℃ and rolled to obtain the copper-graphene-carbon nanotube heat-conducting film. The thickness of the graphene heat-conducting film is 40 micrometers, the horizontal heat-conducting coefficient is 1800W/mK, and the vertical heat-conducting coefficient is 55W/mK.
As can be seen from fig. 4, the copper nanoparticles are riveted into the layered graphene, and the carbon nanotubes are connected between the graphene layers and vertically aligned with the graphene.
Example 3
The three-dimensional space lapping technology of the porous graphene comprises the following steps: and (3) preparing graphene oxide: the water mass ratio is 1:10, adding ferric chloride, wherein the mass ratio of the ferric chloride to the graphene oxide solution is 1:100, and uniformly mixing. And slowly cooling the mixed solution until water molecules are crystallized into ice, and then transferring the water molecules to a freeze dryer for freeze drying, wherein the drying temperature is-50 ℃, the drying time is 24 hours, and three-dimensional layered graphene oxide arranged in parallel layer by layer can be obtained by controlling the freezing rate, and iron elements are uniformly distributed among the graphene layers. And reducing the three-dimensional layered graphene in a hydrogen atmosphere at the reduction temperature of 400 ℃ for 2h to obtain iron nanoparticles @ the three-dimensional layered graphene, wherein the iron nanoparticles are riveted in the layered graphene, and the distance between graphene layers is about 0.2 mu m.
In this embodiment, the "slowly reducing the temperature of the mixed solution until the water molecules are crystallized into ice" includes placing the mixed solution in a refrigerator at-2 ℃ for 12 hours, and slowly reducing the temperature until the water molecules are crystallized into ice.
In-situ growth technology of carbon nanotubes: the iron nanoparticle @ three-dimensional layered graphene is placed in a tubular furnace, the tubular furnace is placed in an external magnetic field, the direction of the magnetic field is perpendicular to the horizontal plane, and the magnetic field intensity is 5A/m. Introducing methane/argon mixed gas into the tubular furnace, wherein the flow rate of the mixed gas is 20ml/min, the reaction temperature is 1000 ℃, and the reaction time is 1h, so as to obtain the iron nanoparticle @ graphene-carbon nanotube compound, wherein the mass ratio of graphene to carbon nanotubes is 10: 1. the obtained iron nanoparticle @ graphene-carbon nanotube composite is graphitized at 1000 ℃ and rolled to obtain the iron-graphene-carbon nanotube heat-conducting film. The thickness of the graphene heat-conducting film is 80 micrometers, the horizontal heat-conducting coefficient is 2000W/mK, and the vertical heat-conducting coefficient is 75W/mK.
As can be seen from fig. 5, the iron nanoparticles are riveted into the graphene layer, and the carbon nanotubes are connected between the graphene layers in a lap joint manner and are vertically aligned with the graphene.
Example 4
The three-dimensional space lapping technology of the porous graphene comprises the following steps: and (3) graphene oxide: the water mass ratio is 1:30, adding ferric chloride, wherein the mass ratio of the ferric chloride to the graphene oxide solution is 1: 300, uniformly mixing. And slowly cooling the mixed solution until water molecules are crystallized into ice, and then transferring the water molecules to a freeze dryer for freeze drying, wherein the drying temperature is-50 ℃, the drying time is 24 hours, and three-dimensional layered graphene oxide arranged in parallel layer by layer can be obtained by controlling the freezing rate, and iron elements are uniformly distributed among the graphene layers. And reducing the three-dimensional layered graphene in a hydrogen atmosphere at the reduction temperature of 400 ℃ for 3h to obtain iron nanoparticles @ the three-dimensional layered graphene, wherein the iron nanoparticles are riveted in the layered graphene, and the distance between graphene layers is about 0.5 mu m.
In this embodiment, the "slowly reducing the temperature of the mixed liquid until the water molecules are crystallized into ice" includes placing the mixed liquid in a refrigerator at-3 ℃ for 11 hours, and slowly reducing the temperature until the water molecules are crystallized into ice.
In-situ growth technology of carbon nanotubes: the iron nanoparticle @ three-dimensional layered graphene is placed in a tubular furnace, the tubular furnace is placed in an external magnetic field, the direction of the magnetic field is perpendicular to the horizontal plane, and the magnetic field intensity is 10A/m. Introducing methane/argon mixed gas into the tubular furnace, wherein the flow rate of the mixed gas is 20ml/min, the reaction temperature is 1200 ℃, and the reaction time is 2 hours, so as to obtain the iron nanoparticle @ graphene-carbon nanotube compound, wherein the mass ratio of graphene to carbon nanotubes is 10: 1. the obtained iron nanoparticle @ graphene-carbon nanotube composite is graphitized at 1200 ℃ and rolled to obtain the iron-graphene-carbon nanotube heat-conducting film. The thickness of the graphene heat-conducting film is 100 micrometers, the horizontal heat-conducting coefficient is 2300W/mK, and the vertical heat-conducting coefficient is 100W/mK.
As can be seen from fig. 6, the iron nanoparticles are riveted into the graphene layer, and the carbon nanotubes are connected between the graphene layers in a lap joint manner and are vertically aligned with the graphene.
The embodiments described above are intended to facilitate the understanding and appreciation of the application by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not limited to the embodiments herein, and those skilled in the art who have the benefit of this disclosure will appreciate that many modifications and variations are possible within the scope of the present application without departing from the scope and spirit of the present application.
Claims (9)
1. A preparation method of directionally assembled graphene is characterized by comprising the following steps:
s1: mixing graphene oxide and an aqueous solvent to obtain a graphene oxide aqueous solution;
s2: mixing the graphene oxide aqueous solution and a water-soluble metal salt to obtain a graphene oxide aqueous solution containing metal ions;
s3: slowly cooling the graphene oxide aqueous solution containing the metal ions until water molecules are crystallized to form ice, and then carrying out freeze drying treatment to obtain directionally assembled graphene oxide; and
s4: treating the directionally assembled graphene oxide in a reducing atmosphere at the temperature of 200-600 ℃ for 1-10 hours to obtain the directionally assembled graphene loaded with metal nanoparticles;
the directionally assembled graphene loaded with the metal nanoparticles has a three-dimensional layered structure with layers arranged in parallel, and interlayer gaps exist among the layers;
wherein, in the directionally assembled graphene loaded with the metal nanoparticles, the metal nanoparticles are riveted in a three-dimensional layered structure of the directionally assembled graphene;
the step of slowly cooling until water molecules are crystallized into ice comprises the steps of placing the graphene oxide aqueous solution containing the metal ions in a refrigerator at the temperature of-1 ℃ to-3 ℃, placing for 10 hours to 15 hours, and slowly cooling until the water molecules are crystallized into ice.
2. The method for preparing directionally assembled graphene according to claim 1, wherein the mass ratio of the graphene oxide to the aqueous solvent is 1:10 to 1:100, respectively;
the mass ratio of the water-soluble metal salt to the graphene oxide aqueous solution is 1:100 to 1: 1000, parts by weight;
the water-soluble metal salt is selected from one or more of the following: copper salt, iron salt, cobalt salt and nickel salt.
3. A directionally assembled graphene loaded with metal nanoparticles prepared by the method for preparing a directionally assembled graphene as claimed in claim 1 or 2.
4. The metal nanoparticle-loaded directionally assembled graphene of claim 3, wherein the metal nanoparticle-loaded directionally assembled graphene has an inter-graphene layer gap of 0.05-0.5 μm.
5. The preparation method of the graphene-carbon nanotube composite heat-conducting film is characterized by comprising the following steps of:
step (1): growing carbon nanotubes in situ on the metal nanoparticle-loaded aligned assembled graphene of claim 3 or 4 in the presence of a magnetic field and a carbon source gas to obtain a metal nanoparticle-loaded aligned assembled graphene-carbon nanotube composite;
step (2): graphitizing the directionally assembled graphene-carbon nanotube composite material loaded with the metal nanoparticles at the temperature of 1000-1500 ℃, and rolling to obtain a graphene-carbon nanotube composite heat-conducting film;
wherein the carbon nanotubes form lap joints between layers of the directionally assembled graphene and are vertically arranged with a plane where the layered structure of the directionally assembled graphene is located.
6. The method for preparing a graphene-carbon nanotube composite thermal conductive film according to claim 5, wherein in the step (1), the magnetic field strength is 0.1 to 10A/m;
in the step (1), the carbon source gas is a mixed gas of methane and argon;
in the step (1), the conditions for growing the carbon nanotubes in situ are as follows: the flow rate of the carbon source gas is controlled to be 1-100ml/min, the reaction temperature is 900-.
7. The method for preparing a graphene-carbon nanotube composite heat conductive film according to claim 5 or 6, wherein in the metal nanoparticle-loaded aligned assembled graphene-carbon nanotube composite material, the mass ratio of the metal nanoparticle-loaded aligned assembled graphene to the carbon nanotubes is 5: 1 to 50: 1.
8. a graphene-carbon nanotube composite thermal conductive film prepared by the method for preparing a graphene-carbon nanotube composite thermal conductive film according to any one of claims 5 to 7.
9. The graphene-carbon nanotube composite thermal conductive film according to claim 8, wherein the graphene-carbon nanotube composite thermal conductive film has a thickness of 30-100 μm, a horizontal thermal conductivity of 1500-.
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