CN111944497B

CN111944497B - Graphene oxide composite carbon source mixture and preparation method thereof, graphene heat-conducting film and preparation method thereof

Info

Publication number: CN111944497B
Application number: CN201910404255.7A
Authority: CN
Inventors: 吴艳红; 唐润理; 方钢; 耿飚; 张婧; 瞿研
Original assignee: SIXTH ELEMENT (CHANGZHOU) MATERIALS TECHNOLOGY CO LTD
Current assignee: SIXTH ELEMENT (CHANGZHOU) MATERIALS TECHNOLOGY CO LTD
Priority date: 2019-05-16
Filing date: 2019-05-16
Publication date: 2022-02-22
Anticipated expiration: 2039-05-16
Also published as: CN111944497A

Abstract

The invention provides a graphene oxide composite carbon source mixture and a preparation method thereof, and a graphene heat-conducting film and a preparation method thereof. The preparation method of the graphene oxide composite carbon source mixture comprises the following steps: and adding a carbon source dispersion liquid in the process of preparing the graphene oxide to obtain a graphene oxide composite carbon source mixture. The preparation method of the graphene heat-conducting film comprises the following steps: and dispersing the graphene oxide composite carbon source mixture in water, coating the mixture on a substrate, drying, and performing high-temperature treatment to obtain the graphene heat-conducting film. According to the invention, the carbon source dispersion liquid is introduced in the process of preparing the graphene oxide, so that the carbon source is uniformly and stably inserted into the layers of the graphene oxide, and the graphene oxide is fully stripped. The graphene oxide is subjected to dispersion, film coating, drying and reduction to prepare the graphene heat-conducting film, so that the time of high-temperature heat treatment is greatly reduced, the thermal reduction efficiency is improved, and the heat conductivity coefficient of the graphene heat-conducting film is improved.

Description

Graphene oxide composite carbon source mixture and preparation method thereof, graphene heat-conducting film and preparation method thereof

Technical Field

The invention relates to a preparation process of a graphene film material, and belongs to the field of heat conduction materials and devices.

Background

With the popularization of industrial automation and artificial intelligence, the requirements of correspondingly matched material devices and the like are higher and higher. Thermally conductive and heat dissipating materials are indispensable components, and are limited by low thermal conductivity, which limits the design of devices or systems. In the electronics industry, in particular, the miniaturization of integrated electronic circuits requires increasingly higher heat dissipation materials, and the demand is also increasing. The traditional heat-conducting and heat-dissipating material is mostly prepared by taking metal or graphite as a base material, and the heat-conducting and heat-dissipating performance of the traditional heat-conducting and heat-dissipating material cannot meet the development requirements of the electronic industry. Graphene is a star choice for heat conducting materials due to excellent properties of electric conduction, heat conduction and the like.

The existing graphene heat-conducting film materials are basically divided into three categories, one is that graphene powder and different additives are directly dispersed and uniformly blended in water, a composite film containing graphene is obtained after suction filtration or spraying, and the graphene heat-conducting film is obtained through drying or film pressing molding, wherein the graphene heat-conducting film obtained by the method has extremely high flexibility, but the heat-conducting and heat-dissipating rate of the graphene heat-conducting film prepared by the method is lower and is less than 1500W/m.k; the second method is to directly prepare a thin graphene film on a substrate by a CVD method, and the graphene heat-conducting film obtained by the CVD method has excellent heat-conducting property, but has obvious defects, cannot be prepared in a large area, has high cost, high transfer difficulty and the like, and basically stays in the scientific research aspect; the third method is to obtain the graphene heat-conducting film by taking the graphene oxide film as a precursor through thermal reduction, chemical reduction, electrochemical reduction and other modes, and the method has the main advantage of large-area manufacturing, but the carbon content of the main component of the graphene prepared by the graphene oxide film is generally difficult to regulate and control, and the main performance of the graphene heat-radiating film is generally determined by the graphene oxide which is used as the raw material, and is a relatively limited key point.

When the graphene heat-conducting film is prepared by the third method, graphene oxide is completely reduced into graphene, in the process, graphene oxide sheets obtain graphene through different reduction modes, a large number of oxygen-containing functional groups are lost, and the graphene exists in a full-carbon form, so that the residual carbon content of the finally obtained graphene is low. The residual carbon content is the proportion of the graphene film obtained after heat treatment in the original graphene oxide. The lower the amount of residual carbon, the lower the conversion rate or yield of the graphene oxide film into the graphene thermal conductive film in the industrial process. The yield is higher, the market share of the graphene heat-conducting film is improved, and the scale of the graphene heat-conducting film is promoted. The method for improving the yield can be divided into two methods: firstly, the oxidation degree of graphene oxide is reduced, so that oxygen-containing functional groups on the surface of the graphene oxide are reduced, the oxygen-containing functional groups are less lost in the reduction process, the gram number of graphene converted from each 100g of graphene oxide is increased, and the yield of a corresponding graphene oxide film converted into a graphene heat-conducting film is increased accordingly; secondly, a stable carbon source is introduced into the graphene oxide film, and after reduction heat treatment and other treatment, the carbon source does not generate mass loss in the subsequent reduction treatment process, so that the yield of the graphene heat-conducting film is improved. The stable carbon source is that the original stable state is maintained without physical and chemical changes, mass loss and the like under the existence of reducing agent, weak oxidant, light, heat and other conditions. The invention discusses the stable carbon source which is added and mainly comprises carbon spheres, carbon nano tubes and graphite micro-sheets. According to the invention, through controlling the size (nano-microstructure) and the addition amount of the stable carbon source, the graphene oxide can be assembled with a proper amount of nano-microstructure carbon source to obtain a film with good layer-by-layer stacking, and the graphene heat-conducting film obtained by reducing the orderly and compact graphene oxide film has stronger interlayer interaction and more excellent longitudinal heat-conducting property. Therefore, the performance of the graphene thermal conductive film is directly influenced by the assembling condition of the graphene oxide film.

The method has the disadvantages that the carbon source and the graphene oxide are difficult to be uniformly mixed, the orderliness of stacking and assembling graphene oxide layers is reduced, and the heat conductivity coefficient of the graphene heat-conducting film is finally reduced.

The statements in the background section are merely prior art as they are known to the inventors and do not, of course, represent prior art in the field.

Disclosure of Invention

Aiming at one or more problems in the prior art, the invention aims to meet the requirement of large-area manufacturing in industrial production, pursue a high-heat-conductivity graphene heat-conducting film material, improve the gram number of raw materials per 100g of graphene oxide reduced into graphene, and directly improve the yield of the process; meanwhile, the cost of the reduction preparation in the reduction preparation process of the graphene heat-conducting film is reduced, and the reduction degree and efficiency of the graphene heat-conducting film are improved.

The invention mainly adopts the third mode of preparing the graphene heat-conducting film in the background technology, adopts the process method of preparing the graphene heat-conducting film by taking the graphene oxide film as a precursor, adopts the mode of directly introducing a stable carbon source to prepare the graphene heat-conducting film in the process of preparing the precursor graphene oxide, and obtains the high-yield graphene heat-conducting film after uniformly compounding the graphene oxide and the carbon source, dispersing, coating, drying and reducing the graphene oxide and the carbon source.

The invention provides a graphene oxide composite carbon source mixture, which comprises the following components: the carbon source composite material comprises graphene oxide and a carbon source, wherein in the graphene oxide carbon source composite mixture, the ratio of the mass of carbon in the graphene oxide to the carbon source is 100: (0.5-10), preferably 100: (4-8).

In one aspect of the present invention, the carbon source includes one or a mixture of two or more of graphite micro-flakes, carbon spheres, or carbon nanotubes.

Due to the existence of a proper amount of two-dimensional structures, the graphene nanoplatelets are favorable for barrier-free assembly and stacking with graphene oxide sheets, so that a graphene heat-conducting film which is well assembled by stacking layer by layer can be obtained during later reduction treatment, and the heat conductivity and the stability are favorably improved.

The carbon spheres are used as a nano zero-dimensional material, the assembly and stacking of the two-dimensional graphene oxide sheets are not influenced by the introduction of a proper amount, and the thermal conductivity of the prepared graphene thermal conductive film is not influenced.

The carbon nano tubes are used as one-dimensional nano materials and are compounded with graphene oxide, and finally the carbon nano tubes are formed in the obtained graphene heat-conducting film and penetrate among graphene layers to form a network structure, so that the gap defect between the graphene layers is repaired, the heat-conducting performance of the graphene heat-conducting film is enhanced, and the heat conductivity of the graphene heat-conducting film is improved.

In one aspect of the invention, the graphite micro-platelets have a platelet size of less than 50 μm, preferably 20. + -.5 μm.

Preferably, the graphite micro-platelets have a thickness of less than 5 μm, preferably 1 μm.

In one aspect of the present invention, the diameter of the carbon pellet is less than 100nm, preferably 10 to 80nm, and more preferably 20 to 30 nm.

As one aspect of the present invention, the carbon nanotube is a single-walled or multi-walled carbon nanotube.

Preferably, the tube diameter of the carbon nanotube is less than 100nm, preferably 20 ± 5 nm.

The invention also provides a preparation method of the graphene oxide composite carbon source mixture, which comprises the following steps: and adding a carbon source dispersion liquid in the process of preparing the graphene oxide to obtain a graphene oxide composite carbon source mixture.

In one aspect of the present invention, the dispersion solvent of the carbon source dispersion liquid is water, and the concentration of the carbon source dispersion liquid is 0.001 to 10%.

As one aspect of the present invention, the preparation method of the graphene oxide composite carbon source mixture comprises the following specific steps:

s1: mixing graphene, an oxidant and concentrated acid, and stirring for reaction;

s2: adding a carbon source dispersion liquid to the reaction liquid obtained in the step S1;

s3: adding an aqueous hydrogen peroxide solution to the solution prepared in step S2 until no bubbles are generated; and

s4: and separating to obtain the graphene oxide composite carbon source mixture.

The concentrated acid helps to prop open the graphite layers, so that the oxidant can be better inserted into the graphite layers for intercalation reaction. In the later stage of the oxidation intercalation of the oxidant and the graphite, blending a carbon source and water to obtain stable dispersion liquid, and directly and slowly adding the dispersion liquid into a reaction system in the later stage of the oxidation intercalation; meanwhile, the water adding process is an effect of fully stripping graphene oxide in a reaction system, in the full stripping process of the graphene oxide, a carbon source is directly contacted with the stripped graphite oxide, the carbon source is inserted between the graphite oxide layers, the compatibility between the carbon source and the graphene oxide is enhanced fundamentally, a composite system with the carbon source uniformly and stably dispersed in the graphene oxide is obtained, and the problem that in the prior art, the carbon source is unevenly dispersed in the graphene oxide due to the fact that the graphene oxide and the carbon source are directly and mechanically blended conventionally, and the stacking assembly orderliness of the graphene oxide layers is reduced is solved.

In the method, the graphene oxide and the carbon source are well assembled, and the good assembly is a key determining factor for the heat conductivity of the graphene heat-conducting film. Theoretically, other materials, such as zero-dimensional, one-dimensional and two-dimensional materials, are doped into the two-dimensional graphene oxide sheets, so that the ordering of the stacked assembled film of graphene oxide layers cannot be realized, and the defects of unevenness and the like occur, so that the interlayer compactness is obviously reduced, and the heat conductivity of the graphene heat-conducting film obtained after the reduction of the graphene oxide film is finally reduced. When the materials introduced into the graphene oxide are agglomerated or poorly dispersed, the order of the graphene oxide sheets assembled into a film is also affected, and the heat-conducting property of the graphene heat-conducting film is also reduced. The carbon source dispersion liquid is introduced in the graphene oxide reaction process, so that the graphene oxide can be fully stripped, and the carbon source can be inserted between the graphene oxide layers. By adopting the method of introducing the carbon source dispersion liquid, the problem that ordered assembly and film formation of graphene oxide sheets cannot be realized due to the fact that concave-convex defects occur between graphene oxide layers is solved, the combination between graphene oxide and a carbon source is more stable, the assembly and arrangement between graphene heat-conducting film layers are more ordered, the wafer structure tends to be complete, the heat conductivity coefficient is improved, and the yield is improved.

The aqueous solution of hydrogen peroxide is commonly called hydrogen peroxide, and the hydrogen peroxide has oxidation and reduction effects under different conditions. The method promotes the hydrogen peroxide to exert the reducibility, removes the residual oxidant in the solution and does not bring other impurities to the reaction solution.

According to an aspect of the present invention, in the step S1, the graphite, the oxidant and the concentrated acid are mixed in a manner that: firstly, mixing graphite with concentrated acid, uniformly stirring, and then adding an oxidant.

Preferably, the stirring is carried out for 10-30min, preferably 20min after the addition of the oxidizing agent.

Preferably, the temperature range for mixing the graphite, the oxidizing agent and the concentrated acid is 0-15 ℃.

The dissolution of the oxidizing agent in the concentrated acid is exothermic and can create a hazard if the temperature conditions are high.

Preferably, the mass ratio of the graphite to the oxidant to the concentrated acid is 1: (1.1-6): (15-40).

According to an aspect of the present invention, in the step S1, the mesh number of the graphite is 100-5000 mesh, preferably 200 mesh.

Preferably, the purity of the graphite is 90-99.99%.

According to an aspect of the invention, in the step S1, the oxidant includes one or a combination of two or more of potassium permanganate, sodium nitrate, potassium perchlorate, or potassium ferrate.

Preferably, the concentrated acid comprises one or a mixture of two or more of concentrated sulfuric acid, concentrated nitric acid, or concentrated phosphoric acid.

According to one aspect of the present invention, in the step S1, the stirring reaction time is 1 to 6 hours, preferably 3 hours.

Preferably, the temperature conditions for the stirred reaction are 20-50 ℃, preferably 35 ℃.

According to an aspect of the present invention, in the step S2, the method for adding the carbon source dispersion liquid includes: the carbon source dispersion liquid was slowly dropped into the reaction liquid obtained in step S1 while stirring.

Preferably, the mass ratio of the carbon source to the graphite is (0.5-10): 100, preferably (4-8): 100, more preferably 6: 100.

According to an aspect of the present invention, in the step S2, the temperature of the reaction solution is controlled to be 40 to 90 ℃.

The temperature of the reaction solution is controlled to be 40-90 ℃, so that the active free radicals generated by the oxidant and the water can take the effect of stripping graphene sheets, and finally, the carbon source can be more fully and uniformly mixed with the graphene oxide.

Preferably, after the carbon source dispersion liquid is dropwise added, stirring is continued for 20-180min, preferably for 1 h.

According to an aspect of the present invention, in the step S4, the separating method includes: and separating out the graphene oxide composite carbon source mixture in a suction filtration or centrifugation mode.

Preferably, the graphene oxide composite carbon source mixture is further washed and purified after the separation of the product.

Further preferably, the washing and purifying method is to wash the graphene oxide composite carbon source mixture with an acidic solution.

Preferably, the acidic solution is a hydrochloric acid solution.

Further preferably, the mass fraction of the HCL in the hydrochloric acid solution is 7-8%.

Preferably, the number of washes is 3-5, preferably 4.

The invention also provides a graphene heat-conducting film, wherein the heat conductivity of the graphene heat-conducting film is 600-2000W/m.k, and is preferably 1200 +/-200W/m.k.

Preferably, the carbon content of the graphene thermal conductive film is 100%.

The graphene in the graphene heat-conducting film does not contain impurities such as oxygen-containing functional groups and the like, and is graphene with carbon content of 100% after graphitization.

The invention also provides a preparation method of the graphene heat-conducting film, which comprises the following steps:

dispersing the graphene oxide composite carbon source mixture in water to obtain aqueous slurry of the graphene oxide composite carbon source;

coating the aqueous slurry of the graphene oxide composite carbon source on a substrate, and drying to obtain a carbon source-doped graphene oxide film; and

and carrying out high-temperature treatment on the graphene oxide film doped with the carbon source to obtain the graphene heat-conducting film.

Every 100g of graphene oxide film doped with a carbon source is subjected to the method to obtain 45-60 g of graphene heat-conducting film.

According to one aspect of the invention, the dispersing means includes stirring, ultrasonic or shaking.

According to an aspect of the present invention, the content of the graphene oxide composite carbon source mixture in the graphene oxide composite carbon source aqueous slurry is 0.1 to 10wt%, preferably 0.25 wt%.

According to one aspect of the invention, the manner of coating the aqueous slurry of the graphene oxide composite carbon source on the substrate is knife coating or spraying.

Preferably, the substrate comprises glass, copper foil or a polymeric material.

According to one aspect of the invention, the temperature of the drying is 60 to 120 ℃, preferably 100 ℃.

Preferably, the drying time is 0.5 to 2 hours, preferably 1 hour.

According to one aspect of the invention, the temperature rise rate of the high temperature treatment is 0.5-3 ℃/min, preferably 1 ℃/min;

preferably, the temperature of the high temperature treatment is 2000-.

Preferably, the high temperature treatment time is 1-3h, preferably 1.5-2.5 h.

The invention has the beneficial effects that:

according to the invention, the carbon source dispersion liquid is introduced in the process of preparing the graphene oxide, so that the carbon source is uniformly and stably inserted into the layers of the graphene oxide, and the graphene oxide is fully stripped. The graphene oxide is subjected to dispersion, film coating, drying and reduction to prepare the graphene heat-conducting film, so that the time of high-temperature heat treatment is greatly reduced, the thermal reduction efficiency is improved, and the heat conductivity coefficient of the graphene heat-conducting film is improved. The advantages of the invention are illustrated in particular by the following points:

(1) the introduction of a zero-dimensional, one-dimensional and two-dimensional nanoscale stable carbon source enables the carbon content of the graphene heat-conducting film to be purposefully increased by 10-20% in a controllable manner, the gram number of the graphene heat-conducting film prepared by dispersing, coating, drying and reducing every 100g of graphene oxide is increased, and the gram number is directly increased to 45-60 g from 30-50 g when the carbon source is not introduced; meanwhile, the high-temperature treatment time for preparing the graphene heat-conducting film is reduced by 30%, and the thermal reduction efficiency is improved.

(2) In the preparation process of the graphene oxide, deionized water is replaced by the carbon source dispersion liquid, so that the graphene oxide and the carbon source are well assembled, the carbon source is inserted between the graphene oxide layers, the graphene oxide is fully stripped, the graphene oxide and the carbon source are dispersed more uniformly and stably, and poor dispersion or agglomeration cannot occur. By adopting the method of introducing the carbon source dispersion liquid, the problem that ordered assembly and film formation of graphene oxide sheets cannot be realized due to the fact that concave-convex defects occur between graphene oxide layers is avoided, the combination between the graphene oxide and a carbon source is more stable, the assembly arrangement between graphene heat-conducting membrane layers is more ordered, the wafer structure tends to be complete, the heat conductivity coefficient is improved, and the heat conductivity is improved by 100 plus 500W/m.k due to the addition amount of the carbon source below 5%.

(3) The invention not only provides a method for preparing a heat-conducting film, but also provides a technology for compounding graphene oxide and other target substances; other target substances are introduced in the synthesis process of the graphene oxide, the graphene oxide is modified creatively, the problem that substances with poor compatibility of the graphene oxide and other target substances are mixed uniformly is solved fundamentally, the thermal conductivity of the graphene heat-conducting film obtained by the method is enhanced, and meanwhile, the uniformity of the target substances in the graphene oxide is good, so that the graphene oxide film is assembled to obtain the good graphene heat-conducting film.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic flow chart of a process for preparing a graphene heat-conducting film by compounding a carbon source with graphene.

Detailed Description

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize applications of other processes and/or uses of other materials.

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

As a first embodiment of the present invention, there is provided a graphene oxide composite carbon source mixture including: the carbon source composite material comprises graphene oxide and a carbon source, wherein in the graphene oxide carbon source composite mixture, the ratio of the mass of carbon in the graphene oxide to the carbon source is 100: (0.5-10), for example: 100:0.5, 100:0.6, 100:0.7, 100:0.8, 100:0.9, 100:1.0, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:9.5, 100:9.6, 100:9.7, 100:9.8, 100:9.9, 100:10, etc. The carbon source comprises one or a mixture of more than two of graphite micro-sheets, carbon spheres or carbon nanotubes.

The graphite micro-sheets have a sheet diameter of less than 50 μm, for example: 0.001 μm, 0.002 μm, 0.005 μm, 0.008 μm, 0.01 μm, 0.02 μm, 0.05 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 49.9 μm, and the like. In a preferred embodiment, the graphite micro-platelets have a platelet diameter of 15 to 25 μm, for example: 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, and the like.

The graphite micro-platelets have a thickness of less than 5 μm, for example: 0.001. mu.m, 0.002. mu.m, 0.003. mu.m, 0.005. mu.m, 0.008. mu.m, 0.009. mu.m, 0.01. mu.m, 0.02. mu.m, 0.03. mu.m, 0.05. mu.m, 0.08. mu.m, 0.1. mu.m, 0.2. mu.m, 0.3. mu.m, 0.5. mu.m, 0.8. mu.m, 1. mu.m, 1.5. mu.m, 2. mu.m, 2.5. mu.m, 3. mu.m, 3.5. mu.m, 4. mu.m, 4.5. mu.m, 4.9. mu.m, 4.95. mu.m, 4.98. mu.m, 4.99. mu.m, etc. In a preferred embodiment, the graphite micro-platelets have a thickness of 1 μm.

The diameter of the carbon spheres is less than 100nm, for example: 0.001nm, 0.002nm, 0.005nm, 0.008nm, 0.01nm, 0.02nm, 0.05nm, 0.08nm, 0.09nm, 0.1nm, 0.5nm, 0.8nm, 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 15nm, 18nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 49.9nm, 50nm, 52nm, 53nm, 55nm, 58nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 96nm, 97nm, 98nm, 99nm, 99.5nm, 99.8nm, 99.9nm, etc. In a preferred embodiment, the carbon beads have a diameter of 10 to 80nm, for example, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 18nm, 20nm, 22nm, 25nm, 28nm, 30nm, 32nm, 35nm, 38nm, 40nm, 42nm, 45nm, 48nm, 50nm, 52nm, 55nm, 58nm, 60nm, 62nm, 65nm, 68nm, 70nm, 72nm, 75nm, 78nm, 79nm, 80nm, and the like. As a most preferred embodiment, the carbon globules have a diameter of 20-30nm, for example: 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, etc.

Carbon nanotubes are single-walled or multi-walled carbon nanotubes with a tube diameter of less than 100nm, for example: 0.01nm, 0.02nm, 0.03nm, 0.05nm, 0.08nm, 0.1nm, 0.11nm, 0.05nm, 0.18nm, 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.8nm, 0.9nm, 1nm, 2nm, 3nm, 5nm, 8nm, 10nm, 12nm, 15nm, 20nm, 22nm, 25nm, 28nm, 30nm, 32nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 96nm, 97nm, 98nm, 99nm, 99.9nm, 99.99nm, etc. As a preferred embodiment, the tube diameter of the carbon nanotubes is 15 to 25nm, for example: 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, etc.

As a second embodiment of the present invention, a method for preparing a graphene oxide composite carbon source mixture is presented, which includes: and adding a carbon source dispersion liquid in the process of preparing the graphene oxide to obtain a graphene oxide composite carbon source mixture. The dispersion solvent of the carbon source dispersion is water, and the concentration of the carbon source dispersion is 0.001 to 10%, for example: 0.001%, 0.002%, 0.003%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.3%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 9.9.9%, 9.99%, 10%, etc.

The preparation method of the graphene oxide composite carbon source mixture comprises the following specific steps:

The concentrated acid helps to prop open the graphite layers, so that the oxidant can be better inserted into the graphite layers for intercalation reaction. In the later stage of the oxidation intercalation of the oxidant and the graphite, blending a carbon source and water to obtain stable dispersion liquid, and directly and slowly adding the dispersion liquid into a reaction system in the later stage of the oxidation intercalation; meanwhile, the water adding process is an effect of fully stripping graphene oxide in a reaction system, in the full stripping process of the graphene oxide, a carbon source is directly contacted with the stripped graphite oxide, the carbon source is inserted between layers of the graphite oxide, the compatibility between the carbon source and the graphene oxide is enhanced fundamentally, a composite system with the carbon source uniformly and stably dispersed in the graphene oxide is obtained, and the problem that in the prior art, the carbon source is unevenly dispersed in the graphene oxide due to the fact that the conventional method directly mechanically blends the graphene oxide and the carbon source, and the stacking assembly orderliness of the graphene oxide layers is reduced is solved.

The graphene oxide and the carbon source are well assembled, and the good assembly is a key factor for the good heat-conducting property of the graphene heat-conducting film. Theoretically, other materials, such as zero-dimensional, one-dimensional and two-dimensional materials, are doped into the two-dimensional graphene oxide sheets, so that the order of the stacked assembled graphene oxide layers to form the film can be directly influenced, and the interlayer compactness is obviously reduced due to the defects of unevenness and the like, so that the heat conductivity of the graphene heat-conducting film obtained after the reduction of the graphene oxide film is directly reduced. When the materials introduced into the graphene oxide are agglomerated or poorly dispersed, the order of the graphene oxide sheets assembled into a film is also affected, and the heat-conducting property of the graphene heat-conducting film is also reduced. The carbon source dispersion liquid is introduced in the graphene oxide reaction process, so that the graphene oxide can be fully stripped, and the carbon source can be inserted between the graphene oxide layers. By adopting the method of introducing the carbon source dispersion liquid, the problem that ordered assembly and film formation of graphene oxide sheets cannot be realized due to the fact that concave-convex defects occur between graphene oxide layers is solved, the combination between graphene oxide and a carbon source is more stable, the assembly and arrangement between graphene heat-conducting film layers are more ordered, the wafer structure tends to be complete, the heat conductivity coefficient is improved, and the yield is improved.

The aqueous solution of hydrogen peroxide is commonly called hydrogen peroxide, and the hydrogen peroxide has oxidation and reduction effects under different conditions. The invention utilizes the reducibility of hydrogen peroxide to remove residual oxidant in the solution, and does not bring other impurities to the reaction solution.

In step S1, the graphite, the oxidizing agent, and the concentrated acid are mixed in the following manner: firstly, mixing graphite with concentrated acid, uniformly stirring, and then adding an oxidant. Adding oxidant and stirring for 10-30min, for example: 10min, 11min, 12min, 13min, 15min, 18min, 20min, 22min, 24min, 25min, 28min, 29min, 30min, etc. In a preferred embodiment, the mixture is stirred for 20min after the addition of the oxidizing agent. The temperature range at which the graphite, oxidant and concentrated acid are mixed is 0-15 ℃, for example: 0 ℃, 1 ℃, 2 ℃, 3 ℃, 4 ℃, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃, 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃, 15 ℃, etc. The oxidant is exothermic during dissolution in solution, and can create a hazard if the temperature conditions are high. The mass ratio of the graphite to the oxidant to the concentrated acid is 1: (1.1-6): (15-40), for example: 1:1.1:15, 1:1.2:16, 1:1.5:20, 1:2:25, 1:3:30, 1:4:35, 1:5:38, 1:6:40, etc. The mesh number of the graphite is 100-5000 meshes, for example: 100 mesh, 110 mesh, 120 mesh, 150 mesh, 180 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh, 800 mesh, 900 mesh, 1000 mesh, 1500 mesh, 2000 mesh, 2500 mesh, 3000 mesh, 3500 mesh, 4000 mesh, 4500 mesh, 4600 mesh, 4700 mesh, 4800 mesh, 4900 mesh, 4950 mesh, 4960 mesh, 4970 mesh, 4980 mesh, 4990 mesh, 5000 mesh, etc. In a preferred embodiment, the mesh number of the graphite is 200 mesh. The purity of the graphite is 90-99.99%, for example: 90%, 90.01%, 90.02%, 90.05%, 90.08%, 90.1%, 90.2%, 90.5%, 90.8%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.5%, 99.8%, 99.9%, 99.91%, 99.95%, 99.98%, 99.99%, etc. The oxidant comprises one or the combination of more than two of potassium permanganate, sodium nitrate, potassium perchlorate or potassium ferrate. The concentrated acid comprises one or a mixture of more than two of concentrated sulfuric acid, concentrated nitric acid or concentrated phosphoric acid. The reaction time is stirred for 1 to 6 hours, for example: 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, and the like. In a preferred embodiment, the reaction time is 3 hours with stirring. The temperature conditions for the stirring reaction are 20 to 50 ℃, for example: 20 deg.C, 21 deg.C, 22 deg.C, 25 deg.C, 28 deg.C, 30 deg.C, 32 deg.C, 35 deg.C, 38 deg.C, 40 deg.C, 42 deg.C, 45 deg.C, 48 deg.C, 49 deg.C, 50 deg.C, etc. In a preferred embodiment, the temperature condition for the stirring reaction is 35 ℃.

In step S2, the method of adding the carbon source dispersion liquid includes: the carbon source dispersion liquid was slowly dropped into the reaction liquid obtained in step S1 while stirring. The mass ratio of the carbon source to the graphite is (0.5-10): 100, for example: 0.5: 100. 0.6: 100. 0.7: 100. 0.8: 100. 0.9: 100. 1.0: 100. 1.2: 100. 1.5: 100. 1.8: 100. 2: 100. 2.5: 100. 3: 100. 3.5: 100. 4: 100. 4.5: 100. 5: 100. 5.5: 100. 6: 100. 6.5: 100. 7: 100. 7.5: 100. 8: 100. 8.5: 100. 9: 100. 9.5: 100. 9.6: 100. 9.7: 100. 9.8: 100. 9.9: 100. 10: 100, etc. In a preferred embodiment, the mass ratio of the carbon source to the graphite is (4-8): 100, for example: 4: 100. 4.1: 100. 4.2: 100. 4.3: 100. 4.4: 100. 4.5: 100. 4.8: 100. 5: 100. 5.2: 100. 5.5: 100. 5.8: 100. 6: 100. 6.2: 100. 6.5: 100. 6.8: 100. 7: 100. 7.2: 100. 7.5: 100. 7.6: 100. 7.7: 100. 7.8: 100. 7.9: 100. 8: 100, etc. In a most preferred embodiment, the mass ratio of the carbon source to the graphite is 6: 100. The temperature of the reaction solution is controlled to be 40-90 ℃, for example: 40 ℃, 41 ℃, 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃, 88 ℃, 89 ℃, 90 ℃ and the like. The temperature of the reaction solution is controlled to be 40-90 ℃, so that the active free radicals generated by the oxidant and the water can take the effect of stripping graphene sheets, and finally, the carbon source can be more fully and uniformly mixed with the graphene oxide. After the carbon source dispersion liquid is added dropwise, stirring is continued for 20-180min, for example: 20min, 21min, 22min, 23min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, 65min, 70min, 75min, 80min, 85min, 90min, 95min, 100min, 105min, 110min, 115min, 120min, 125min, 130min, 135min, 140min, 145min, 150min, 155min, 160min, 168min, 170min, 175min, 176min, 177min, 178min, 179min, 180min, and the like. In a preferred embodiment, the carbon source dispersion is stirred for 1 hour after the addition.

In step S4, the separation method includes: and separating out the graphene oxide composite carbon source mixture in a suction filtration or centrifugation mode. And washing and purifying the graphene oxide composite carbon source mixture after separating the product. The washing and purifying method is to wash the graphene oxide composite carbon source mixture by using an acidic solution. The acidic solution is a hydrochloric acid solution. The mass fraction of HCL in the hydrochloric acid solution is 7-8%, for example: 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8%, etc. The number of washes is 3-5, for example: 3 times, 4 times, 5 times, etc. In a preferred embodiment, the number of washing is 4.

As a third embodiment of the invention, a graphene thermal conductive film is presented, the thermal conductivity of the graphene thermal conductive film is 600-2000W/m.k, for example: 600W/m.k, 610W/m.k, 620W/m.k, 650W/m.k, 670W/m.k, 700W/m.k, 800W/m.k, 900W/m.k, 1000W/m.k, 1100W/m.k, 1200W/m.k, 1300W/m.k, 1400W/m.k, 1500W/m.k, 1600W/m.k, 1700W/m.k, 1800W/m.k, 1900W/m.k, 1950W/m.k, 2000W/m.k, and the like. In a preferred embodiment, the thermal conductivity of the graphene thermal conductive film is 1000-1400W/m.k, for example: 1000W/m.k, 1050W/m.k, 1100W/m.k, 1150W/m.k, 1200W/m.k, 1250W/m.k, 1300W/m.k, 1350W/m.k, 1400W/m.k, etc. The carbon content of the graphene heat conduction film is 100%. The graphene in the graphene heat-conducting film does not contain impurities such as oxygen-containing functional groups and the like, and is graphene with carbon content of 100% after graphitization.

As a fourth embodiment of the present invention, a method for preparing a graphene thermal conductive film is presented, which includes the following steps:

The dispersion mode comprises a stirring mode, an ultrasonic mode or a shaking mode and other dispersion modes. The content of the graphene oxide composite carbon source mixture in the graphene oxide composite carbon source aqueous slurry is 0.1-10wt%, for example: 0.1 wt%, 0.2 wt%, 0.25wt%, 0.3 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.3 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5wt%, 6 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 9.6 wt%, 9.7 wt%, 9.8 wt%, 9.9 wt%, 10wt%, etc. In a preferred embodiment, the content of the graphene oxide composite carbon source mixture in the graphene oxide composite carbon source aqueous slurry is 0.25 wt%. The mode of coating the aqueous slurry of the graphene oxide composite carbon source on the substrate is blade coating or spraying. The substrate comprises glass, copper foil or a polymer material. The temperature of drying is 60-120 ℃, for example: 60 ℃, 61 ℃, 62 ℃, 63 ℃, 65 ℃, 67 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 116 ℃, 118 ℃, 119 ℃, 120 ℃, etc. In a preferred embodiment, the drying temperature is 100 ℃. The drying time is 0.5-2h, for example: 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h, and the like. In a preferred embodiment, the drying time is 1 hour. The temperature rise rate of the high-temperature treatment is 0.5-3 ℃/min, for example: 0.5 deg.C/min, 0.6 deg.C/min, 0.8 deg.C/min, 1 deg.C/min, 1.2 deg.C/min, 1.5 deg.C/min, 1.8 deg.C/min, 2.2 deg.C/min, 2.5 deg.C/min, 2.8 deg.C/min, 2.9 deg.C/min, 3 deg.C/min, etc. In a preferred embodiment, the temperature increase rate of the high-temperature treatment is 1 ℃/min. The temperature of the high-temperature treatment is 2000-3000 ℃, for example: 2000 ℃, 2010 ℃, 2020 ℃, 2030 ℃, 2040 ℃, 2050 ℃, 2080 ℃, 2100 ℃, 2200 ℃, 2300 ℃, 2400 ℃, 2500 ℃, 2600 ℃, 2700 ℃, 2800 ℃, 2900 ℃, 2950 ℃, 2960 ℃, 2970 ℃, 2980 ℃, 2990 ℃, 3000 ℃ and the like. In a preferred embodiment, the temperature of the high-temperature treatment is 2900 ℃. The high-temperature treatment time is 1-3h, for example: 1h, 1.5h, 2h, 2.5h, 3h, etc. In a preferred embodiment, the high temperature treatment is carried out for a period of 1.5 to 2.5 hours, for example: 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h and the like.

As shown in fig. 1, in the invention, at the later stage of graphite oxide synthesis and before water is added, a carbon source dispersion liquid is added, graphite oxide and a carbon source are compounded, then, the graphite oxide and the carbon source are dispersed and assembled to obtain a graphene oxide film stacked layer by layer, and the graphene oxide film is subjected to high-temperature thermal reduction to obtain a graphene heat-conducting film. The graphene heat-conducting film is prepared by the preparation method of the graphene heat-conducting film, and the high-temperature treatment time is short and is 1-3 h; every 100g of graphene oxide film doped with a carbon source is subjected to high-temperature treatment to obtain 45-60 g of graphene heat-conducting film; the thermal conductivity is improved, and the thermal conductivity is 600-. Under the condition that other conditions are not changed, replacing the carbon source dispersion liquid with deionized water, and treating the graphene oxide film at the high temperature of 2000-3000 ℃ for 2-6h to obtain the graphene heat-conducting film, wherein the high-temperature treatment time is 2-6 h; every 100g of graphene oxide film is subjected to high-temperature treatment to obtain 30-50 g of graphene heat-conducting film; the thermal conductivity is low, and the thermal conductivity is 600-1500W/m.k.

The advantages of the invention are further illustrated by the following examples and comparative examples:

example 1A:

this example shows a process for preparing a graphene oxide composite carbon source mixture.

Step S1:

weighing 25g of graphite powder, adding 200mL of concentrated sulfuric acid, stirring uniformly, slowly adding 25g of sodium nitrate under the ice bath condition, then adding 100g of potassium permanganate, stirring for 20min under the ice bath condition, removing ice, and heating to 35 ℃ for reaction for 3 h.

Step S2:

slowly dropwise adding the graphite microchip dispersion liquid into the reaction liquid after the reaction for 3 hours in the step S1, controlling the temperature to be not higher than 90 ℃, and stirring for 1 hour at 50 ℃ after the dropwise adding is finished.

The preparation method of the graphite microchip dispersion liquid comprises the following steps: adding 1 drop of dispersing agent into 2g of graphite micro-sheets with the sheet diameter and the thickness of 1 mu m, stirring, ultrasonically oscillating, and dispersing in 1000mL of deionized water to obtain graphite micro-sheet dispersion liquid.

Step S3:

hydrogen peroxide solution is added dropwise to the solution prepared in step S2 until no bubbles are generated.

Step S4:

and (4) standing the solution prepared in the step S3, removing the supernatant, performing suction filtration, washing the solid obtained after suction filtration with a hydrochloric acid solution with the mass fraction of 7.5%, and washing for 4 times to obtain the graphene oxide composite carbon source mixture.

Example 1B:

this example illustrates a method for preparing a graphene thermal conductive film using the graphene oxide composite carbon source mixture prepared by the method of example 1A.

Step 1):

and (3) dispersing the graphene oxide composite carbon source mixture prepared in the embodiment 1A in 1000mL of deionized water, and uniformly dispersing to obtain the aqueous slurry of the graphene oxide composite carbon source.

Step 2):

and (3) coating the aqueous slurry of the graphene oxide composite carbon source, and drying at 100 ℃ for 1h to obtain the graphene oxide film doped with the carbon source.

Step 3):

and carrying out high-temperature treatment at 2000-3000 ℃ for 2.5h on the graphene oxide film doped with the carbon source to obtain the graphene heat-conducting film doped with the graphite micro-sheets.

Every 100g of graphene oxide film doped with a carbon source is subjected to high-temperature treatment, and the obtained graphene heat-conducting film doped with graphite micro-sheets is 55 g, and the heat-conducting coefficient is 1245W/m.k.

Example 2A:

Step S1:

Step S2:

slowly dropwise adding the carbon bead dispersion liquid into the reaction liquid after the reaction for 3 hours in the step S1, controlling the temperature to be not higher than 90 ℃, and stirring for 1 hour at 50 ℃ after the dropwise adding is finished.

The preparation method of the carbon bead dispersion liquid comprises the following steps: 1g of carbon beads is added with 1 drop of dispersant, stirred and ultrasonically vibrated, and then dispersed in 1000mL of deionized water to obtain carbon bead dispersion liquid.

Step S3:

Step S4:

Example 2B:

this example illustrates a method for preparing a graphene thermal conductive film using the graphene oxide composite carbon source mixture prepared by the method of example 2A.

Step 1):

and (3) dispersing the graphene oxide composite carbon source mixture prepared in the embodiment 2A in 1000mL of deionized water, and uniformly dispersing to obtain the aqueous slurry of the graphene oxide composite carbon source.

Step 2):

Step 3):

and carrying out high-temperature treatment at 2000-3000 ℃ for 2h on the graphene oxide film doped with the carbon source to obtain the graphene heat-conducting film doped with the carbon globules.

Every 100g of graphene oxide film doped with a carbon source is subjected to high-temperature treatment, and the obtained graphene heat-conducting film doped with carbon pellets is 48 g, and the heat-conducting coefficient is 1180W/m.k.

Example 3A:

Step S1:

Step S2:

slowly dripping the carbon nano tube dispersion liquid into the reaction liquid after the reaction for 3 hours in the step S1, controlling the temperature to be not higher than 90 ℃, and stirring for 1 hour at 50 ℃ after finishing dripping.

The preparation method of the carbon nano tube dispersion liquid comprises the following steps: after 1 drop of dispersing agent is added into 1g of carbon nano tube, the mixture is stirred and ultrasonically vibrated, and then the mixture is dispersed in 1000mL of deionized water to obtain carbon nano tube dispersion liquid.

Step S3:

Step S4:

Example 3B:

this example illustrates a method for preparing a graphene thermal conductive film using the graphene oxide composite carbon source mixture prepared by the method of example 3A.

Step 1):

and (3) dispersing the graphene oxide composite carbon source mixture prepared in the embodiment 3A in 1000mL of deionized water, and uniformly dispersing to obtain the aqueous slurry of the graphene oxide composite carbon source.

Step 2):

Step 3):

and carrying out high-temperature treatment at 2000-3000 ℃ for 1.5h on the graphene oxide film doped with the carbon source to obtain the graphene heat-conducting film doped with the carbon nano tube.

Every 100g of graphene oxide film doped with a carbon source is subjected to high-temperature treatment, and the obtained graphene heat-conducting film doped with the carbon nanotube is 57 g, and the heat conductivity coefficient is 1300W/m.k.

Comparative example 4A:

the comparative example shows a preparation process of a graphene oxide composite carbon source mixture, and the carbon source content in the graphene oxide composite carbon source mixture is low.

Step S1:

Step S2:

The preparation method of the carbon nano tube dispersion liquid comprises the following steps: after 0.01g of carbon nanotube is added with 50 mul of dispersant, the mixture is dispersed in 1000mL of deionized water after stirring and ultrasonic oscillation, and then carbon nanotube dispersion liquid is obtained.

Step S3:

Step S4:

Comparative example 4B:

this comparative example shows a method of preparing a graphene thermal conductive film using the graphene oxide composite carbon source mixture prepared by the method of comparative example 4A.

Step 1):

and dispersing the graphene oxide composite carbon source mixture prepared in the comparative example 4A in 1000mL of deionized water, and uniformly dispersing to obtain the aqueous slurry of the graphene oxide composite carbon source.

Step 2):

Step 3):

and carrying out high-temperature treatment at 2000-3000 ℃ for 2h on the graphene oxide film doped with the carbon source to obtain the graphene heat-conducting film doped with the carbon nano tube.

Every 100g of graphene oxide film doped with a carbon source is subjected to high-temperature treatment, and the obtained carbon nanotube-doped graphene heat-conducting film is 49 g and has a heat-conducting coefficient of 1023W/m.k.

Comparative example 5A:

the comparative example shows a preparation process of a graphene oxide composite carbon source mixture, and the carbon source content in the graphene oxide composite carbon source mixture is high.

Step S1:

Step S2:

The preparation method of the carbon nano tube dispersion liquid comprises the following steps: after 3.75g of carbon nanotubes are added into 50 mul of dispersant, the mixture is stirred and ultrasonically vibrated, and then the mixture is dispersed into 1000mL of deionized water, so that carbon nanotube dispersion liquid is obtained.

Step S3:

Step S4:

Comparative example 5B:

this comparative example shows a method of preparing a graphene thermal conductive film using the graphene oxide composite carbon source mixture prepared by the method of comparative example 5A.

Step 1):

and dispersing the graphene oxide composite carbon source mixture prepared in the comparative example 5A in 1000mL of deionized water, and uniformly dispersing to obtain the aqueous slurry of the graphene oxide composite carbon source.

Step 2):

Step 3):

Every 100g of graphene oxide film doped with a carbon source is subjected to high-temperature treatment, and the obtained graphene heat-conducting film doped with the carbon nanotube is 63 g, and the heat conductivity coefficient is 908W/m.k.

Comparative example 6A:

this comparative example shows a process for preparing graphene oxide.

Step S1:

Step S2:

and (3) slowly dropwise adding 1000mL of deionized water into the reaction liquid after the reaction for 3 hours in the step S1, controlling the temperature to be not higher than 90 ℃, and stirring for 1 hour at 50 ℃ after the dropwise adding is finished.

Step S3:

Step S4:

and (4) standing the solution prepared in the step S3, removing the supernatant, performing suction filtration, washing the solid obtained after suction filtration with a hydrochloric acid solution with the mass fraction of 7.5%, and washing for 4 times to obtain the graphene oxide.

Comparative example 6B:

this comparative example shows a method of preparing a graphene thermal conductive film using the graphene oxide prepared by the method of comparative example 6A.

Step 1):

and dispersing the graphene oxide prepared in the comparative example 6A in 1000mL of deionized water, and uniformly dispersing to obtain the graphene oxide aqueous slurry.

Step 2):

and coating the graphene oxide aqueous slurry, and drying at 100 ℃ for 1h to obtain the graphene oxide film.

Step 3):

and carrying out high-temperature treatment at 3000 ℃ of 2000 ℃ for 3.5h on the graphene oxide film to obtain the graphene heat-conducting film.

Every 100g of graphene oxide film is subjected to high-temperature treatment to finally obtain 40 g of graphene heat-conducting film, and the heat conductivity coefficient is 1004W/m.k.

The test results for examples 1B-3B and comparative examples 4B-6B were compared by the following table:

in the embodiments 1B to 3B, the graphite nanoplatelets, the carbon spheres and the carbon nanotubes are respectively introduced in the graphene oxide preparation process, and as can be seen by comparing with the comparative example 6B, the graphene thermal conductive film obtained by performing high-temperature treatment on each 100g of graphene oxide film in the invention has the advantages of high gram number, short high-temperature treatment time, improved thermal conductivity, saving of a large amount of cost, and suitability for large-scale industrial production.

Compared with the comparative examples 4B and 4B, the carbon source is less than 0.5% of the graphite content, the gram number of the graphene heat-conducting film obtained by processing each 100g of graphene oxide film at high temperature is not high, and the heat conductivity coefficient is not obviously improved; the carbon source exceeds 10% of the graphite content, the gram number of the graphene heat-conducting film finally obtained by processing each 100g of graphene oxide film at high temperature is not high, the heat conductivity coefficient is reduced, the amount of the added carbon source is large, and the cost is increased.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a graphene oxide composite carbon source mixture is characterized by comprising the following steps: the method comprises the following steps:

step S1: mixing graphite, an oxidant and concentrated acid, and stirring for reaction, wherein the mass ratio of the graphite to the oxidant to the concentrated acid is 1: (1.1-6): (15-40);

step S2: adding a carbon source dispersion liquid into the reaction liquid obtained in the step S1, wherein the carbon source comprises graphite micro-sheets, and the mass ratio of the carbon source to the graphite is (0.5-10): 100, respectively;

step S3: adding an aqueous hydrogen peroxide solution to the solution prepared in step S2 until no bubbles are generated; and

step S4: separating to obtain a graphene oxide composite carbon source mixture;

the dispersion solvent of the carbon source dispersion liquid is water; the concentration of the carbon source dispersion liquid is 0.001-10%;

in the step S1, mixing graphite and concentrated acid, adding an oxidant after uniformly stirring, adding the oxidant, and stirring for 10-30 min; in the step S2, the method for adding the carbon source dispersion liquid includes: slowly dropwise adding the carbon source dispersion liquid to the reaction liquid obtained in the step S1 while stirring; and after the carbon source dispersion liquid is dripped, continuously stirring for 20-180 min.

2. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S1, the oxidant is added and stirred for 20 min.

3. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S1, the temperature range for mixing the graphite, the oxidant and the concentrated acid is 0 to 15 ℃.

4. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S1, the mesh number of the graphite is 100-5000 meshes.

5. The method for preparing a graphene oxide composite carbon source mixture according to claim 4, wherein: in step S1, the mesh number of the graphite is 200 mesh.

6. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S1, the purity of the graphite is 90 to 99.99%.

7. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in step S1, the oxidizing agent includes one or a combination of two or more of potassium permanganate, sodium nitrate, potassium perchlorate, and potassium ferrate.

8. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S1, the concentrated acid includes one or a mixture of two or more of concentrated sulfuric acid, concentrated nitric acid, and concentrated phosphoric acid.

9. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S1, the stirring reaction time is 1-6 h.

10. The method for preparing a graphene oxide composite carbon source mixture according to claim 9, wherein: in the step S1, the stirring reaction time is 3 h.

11. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S1, the temperature condition of the stirring reaction is 20 to 50 ℃.

12. The method for preparing a graphene oxide composite carbon source mixture according to claim 11, wherein: in the step S1, the temperature condition of the stirring reaction is 35 ℃.

13. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S2, the mass ratio of the carbon source to the graphite is (4-8): 100.

14. the method for preparing a graphene oxide composite carbon source mixture according to claim 13, wherein: in the step S2, the mass ratio of the carbon source to the graphite is 6: 100.

15. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in the step S2, the temperature of the reaction solution is controlled to be 40-90 ℃.

16. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: and in the step S2, after the carbon source dispersion liquid is dripped, continuously stirring for 20-180 min.

17. The method for preparing a graphene oxide composite carbon source mixture according to claim 16, wherein: in the step S2, after the carbon source dispersion liquid is added dropwise, stirring is continued for 1 hour.

18. The method for preparing a graphene oxide composite carbon source mixture according to claim 1, wherein: in step S4, the separation method includes: and separating out the graphene oxide composite carbon source mixture in a suction filtration or centrifugation mode.

19. The method for preparing a graphene oxide composite carbon source mixture according to claim 18, wherein: in the step S4, the graphene oxide composite carbon source mixture is further washed and purified after the product is separated.

20. The method for preparing a graphene oxide composite carbon source mixture according to claim 19, wherein: in the step S4, the washing and purifying method is to wash the graphene oxide composite carbon source mixture with an acidic solution and then separate the mixture.

21. The method for preparing a graphene oxide composite carbon source mixture according to claim 20, wherein: in step S4, the acidic solution is a hydrochloric acid solution.

22. The method for preparing a graphene oxide composite carbon source mixture according to claim 21, wherein: in the step S4, the HCL in the hydrochloric acid solution has a mass fraction of 7-8%.

23. The method for preparing a graphene oxide composite carbon source mixture according to claim 22, wherein: in the step S4, the number of washing is 3 to 5.

24. The method for preparing a graphene oxide composite carbon source mixture according to claim 23, wherein: in step S4, the number of washing is 4.

25. A graphene oxide composite carbon source mixture obtained by the preparation method of claim 1, wherein: the carbon source composite material comprises graphene oxide and a carbon source, wherein the ratio of the mass of carbon in the graphene oxide composite carbon source mixture to the carbon source is 100: (0.5-10).

26. The graphene oxide composite carbon source mixture of claim 25, wherein the ratio of the mass of graphene oxide carbon to the carbon source in the graphene oxide composite carbon source mixture is 100: (4-8).

27. The graphene oxide composite carbon source mixture of claim 26, wherein the graphite micro-sheets have a sheet diameter of less than 50 μm.

28. The graphene oxide composite carbon source mixture according to claim 27, wherein the graphite micro-sheets have a sheet diameter of 20 ± 5 μm.

29. The graphene oxide composite carbon source mixture of claim 26, wherein the graphite micro-sheets have a thickness of less than 5 μ ι η.

30. The graphene oxide composite carbon source mixture of claim 29, wherein the graphite nanoplatelets have a thickness of 1 μ ι η.

31. A preparation method of a graphene heat conduction film is characterized by comprising the following steps: dispersing the graphene oxide composite carbon source mixture prepared by the preparation method of claim 1 in water to obtain an aqueous slurry of the graphene oxide composite carbon source;

32. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the dispersion mode comprises stirring, ultrasonic or shaking.

33. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the content of the graphene oxide composite carbon source mixture in the graphene oxide composite carbon source aqueous slurry is 0.1-10 wt%.

34. The method for preparing a graphene thermal conductive film according to claim 33, wherein: the content of the graphene oxide composite carbon source mixture in the graphene oxide composite carbon source aqueous slurry is 0.25 wt%.

35. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the mode of coating the aqueous slurry of the graphene oxide composite carbon source on the substrate is blade coating or spraying.

36. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the substrate comprises glass, copper foil or a polymer material.

37. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the drying temperature is 60-120 ℃.

38. The method for preparing a graphene thermal conductive film according to claim 37, wherein: the temperature of the drying was 100 ℃.

39. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the drying time is 0.5-2 h.

40. The method for preparing a graphene thermal conductive film according to claim 39, wherein: the drying time is 1 h.

41. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the temperature rise rate of the high-temperature treatment is 0.5-3 ℃/min.

42. The method for preparing a graphene thermal conductive film according to claim 41, wherein: the temperature rise rate of the high-temperature treatment is 1 ℃/min.

43. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the temperature of the high-temperature treatment is 2000-3000 ℃.

44. The method for preparing a graphene thermal conductive film according to claim 43, wherein: the temperature of the high-temperature treatment is 2900 ℃.

45. The method for preparing a graphene thermal conductive film according to claim 31, wherein: the time of the high-temperature treatment is 1-3 h.

46. The method for preparing a graphene thermal conductive film according to claim 45, wherein: the time of the high-temperature treatment is 1.5-2.5 h.

47. A graphene thermal conductive film obtained by the preparation method of claim 31, wherein: the thermal conductivity of the graphene thermal conductive film is 600-2000W/m.

48. The graphene thermal conductive film of claim 47, wherein: the thermal conductivity of the graphene thermal conductive film is 1200 +/-200W/m.

49. The graphene thermal conductive film of claim 48, wherein: the carbon content of the graphene heat conduction film is 100%.