CN111137878A - Graphene heat dissipation film and preparation method thereof - Google Patents

Graphene heat dissipation film and preparation method thereof Download PDF

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Publication number
CN111137878A
CN111137878A CN202010014065.7A CN202010014065A CN111137878A CN 111137878 A CN111137878 A CN 111137878A CN 202010014065 A CN202010014065 A CN 202010014065A CN 111137878 A CN111137878 A CN 111137878A
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graphene oxide
heat dissipation
graphene
film
dissipation film
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丁古巧
张明杰
周久顺
冯天英
颜柱
梁猛
李彦宏
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Shanghai Ewang Material Technology Co ltd
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Shanghai Ewang Material Technology Co ltd
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/15Nano-sized carbon materials
    • C01B32/182Graphene
    • C01B32/184Preparation
    • C01B32/19Preparation by exfoliation
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/15Nano-sized carbon materials
    • C01B32/182Graphene
    • C01B32/194After-treatment
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K7/00Constructional details common to different types of electric apparatus
    • H05K7/20Modifications to facilitate cooling, ventilating, or heating
    • H05K7/2039Modifications to facilitate cooling, ventilating, or heating characterised by the heat transfer by conduction from the heat generating element to a dissipating body

Abstract

The invention relates to a graphene heat dissipation film and a preparation method thereof. The preparation method comprises the following steps: s1, chemically oxidizing crystalline flake graphite by using bismuthate under a strong acid condition, washing until the pH value is 5-7, performing ultrasonic treatment to obtain graphene oxide aqueous dispersion liquid, and performing spray drying to obtain graphene oxide powder; s2, preparing the graphene oxide powder into slurry, and coating the graphene oxide slurry on a substrate material; s3, drying the substrate material coated with the graphene oxide slurry, and separating the substrate material from the dried graphene oxide film; and S4, reducing the dried graphene oxide film at high temperature to obtain the graphene heat dissipation film. The graphene heat dissipation film has the characteristics of low cost and good heat dissipation performance, and is suitable for 5G mobile phones.

Description

Graphene heat dissipation film and preparation method thereof
Technical Field
The invention relates to a graphene material, in particular to a graphene heat dissipation film and a preparation method thereof.
Background
The graphene serving as a newly developed two-dimensional material has a plurality of excellent performances, and the heat conductivity coefficient of the single-layer defect-free graphene can reach 5300W/mK and is far higher than that of metal heat conduction materials such as copper (398W/mK). Meanwhile, the graphene material has high strength and good flexibility, can be used for preparing a high-strength flexible film, and has a good development prospect in the field of heat conduction and heat dissipation.
The mobile phone has been gradually developed into a necessary working, living and entertainment tool for human as a communication tool for human from the beginning of birth. The heat dissipation of the mobile phone is one of the key problems affecting the service life of the mobile phone, how to effectively solve the heat dissipation problem of the mobile phone is also one of the keys of making a 5G mobile phone (a smart phone of a fifth generation communication system) have better usability and longer service life. The graphene film is used as a heat dissipation film of a mobile phone, which has become a trend in the mobile phone industry, but the graphene has poor film forming property, and the derivative graphene oxide with good film forming property is generally used as a raw material of the graphene heat dissipation film. Meanwhile, the mass production technology of the graphene oxide is complete, the single-layer rate is high, and a foundation is provided for the mass preparation of the high-performance graphene heat dissipation film. The prior art has more processes for preparing the graphene heat dissipation film of the mobile phone, but still has the defects. The Chinese patent with publication number CN106113731B, "graphene heat-conducting and heat-dissipating film", and the Chinese patent with publication number CN110381180A, "a mobile phone heat-dissipating film based on graphene material", utilize graphene film as a mobile phone heat-dissipating film, but the graphene heat-dissipating film has more carriers, complex preparation process and difficult batch preparation; chinese patent CN110255538A, "a method for preparing graphene heat dissipation sheet", directly uses graphene oxide film as a raw material for preparing graphene heat dissipation film for mobile phone, but additives difficult to remove are added during the preparation process, which affects heat dissipation performance, and meanwhile, the graphene heat dissipation film is obtained by processing the graphene oxide film by two methods, i.e., laser reduction and carbonization, which is complex in process and not beneficial to batch production.
Sodium bismuthate, potassium bismuthate, bismuth chlorate, bismuth nitrate and bismuth subnitrate are oxidic substances, and the suspension thereof can lead Mn to be suspended in acidic condition2+Oxidation to permanganate acid radical MnO-4It has very strong oxidizing property. At present, no prior art discloses that substances with oxidizability of the type are used as oxidants in the process of preparing graphene oxide by chemical oxidation.
Disclosure of Invention
In order to solve the problems that in the prior art, a large number of graphene heat dissipation film carriers are used for a mobile phone, mass preparation is not facilitated, the performance of a graphene heat dissipation film is reduced due to poor quality of graphene oxide raw materials, the preparation process of the graphene heat dissipation film for the mobile phone is complex and the like, the invention aims to provide the graphene heat dissipation film, the graphene heat dissipation film only comprises graphene, and the graphene is obtained by carrying out high-temperature reduction on graphene oxide obtained by carrying out chemical oxidation on graphite through bismuthate under a strong acid condition and then carrying out ultrasonic treatment. The graphene heat dissipation film has good moldability, does not need any carrier, has good heat dissipation performance, has a heat conductivity coefficient of 1700W/mK-2000W/mK, and can be used for heat dissipation films of mobile phones, especially 5G mobile phones.
Preferably, the graphite is selected from crystalline flake graphite with the mesh number of 500 and 1000.
Preferably, the strong acid is selected from concentrated sulfuric acid, and the bismuthate is selected from one or more of the following:
sodium bismuthate, potassium bismuthate, bismuth chlorate, bismuth nitrate and bismuth subnitrate.
Preferably, the high-temperature reduction temperature is 500 ℃ to 2000 ℃. More preferably, the reduction temperature is from 1000 ℃ to 1500 ℃.
The invention also provides a preparation process of the graphene heat dissipation film, and the preparation method comprises the following steps:
s1, chemically oxidizing graphite by using bismuthate under the strong acid condition, washing until the pH value is 5-7, performing ultrasonic treatment to obtain graphene oxide aqueous dispersion liquid, and performing spray drying to obtain graphene oxide powder;
s2, preparing the graphene oxide powder into slurry, and coating the graphene oxide slurry on a substrate material;
s3, drying the substrate material coated with the graphene oxide slurry, and separating the substrate material from the dried graphene oxide film;
and S4, reducing the dried graphene oxide film at high temperature to obtain the graphene heat dissipation film.
Preferably, in step S1 of the preparation process of the graphene heat dissipation film of the present invention, the graphite is selected from crystalline flake graphite, and the mesh number is 500-1000 meshes.
Preferably, in step S1 of the preparation process of the graphene heat dissipation film of the present invention, the strong acid is selected from concentrated sulfuric acid, and the bismuthate is selected from one or more of the following:
sodium bismuthate, potassium bismuthate, bismuth chlorate, bismuth nitrate and bismuth subnitrate.
Preferably, in step S1 of the preparation process of the graphene heat dissipation film of the present invention, the time of the ultrasonic treatment is 0.5 to 1.5 hours.
Preferably, in step S1 of the preparation process of the graphene heat dissipation film of the present invention, the temperature of the spray drying is 100 ℃ to 150 ℃. More preferably, the spray drying temperature is 120 ℃.
Preferably, in step S2 of the preparation process of the graphene heat dissipation film of the present invention, the graphene oxide powder is prepared into a slurry with water, and a solid content of the graphene oxide slurry in the slurry is 1% to 10%. More preferably, the solid content of the graphene oxide slurry is 3% -6%.
Preferably, in step S2 of the preparation process of the graphene heat dissipation film of the present invention, the water is deionized water or distilled water.
Preferably, in step S2 of the preparation process of the graphene heat dissipation film of the present invention, the base material is selected from any one of the following base materials:
high temperature resistant polyester film (PET membrane), polyimide film (PI membrane), polytetrafluoroethylene film (PTFE membrane), aluminium foil.
Preferably, in step S3 of the preparation process of the graphene heat dissipation film of the present invention, the drying temperature is between room temperature and 100 ℃. Preferably, the drying temperature is from 50 ℃ to 70 ℃. Preferably, the drying is performed by using a drying device, and preferably, the drying device is a forced air oven.
Preferably, in step S4 of the preparation process of the graphene heat dissipation film of the present invention, the temperature of the high-temperature reduction is 500 ℃ to 2000 ℃. More preferably, the temperature of the high temperature reduction is 1000 ℃ to 1500 ℃.
The graphene heat dissipation film takes common graphite (such as crystalline flake graphite) as a raw material, and has wide raw material source and low price. The preparation method comprises the steps of carrying out chemical oxidation on graphite by using concentrated sulfuric acid as strong acid and bismuthate as an oxidant (under an acidic condition, pentavalent bismuth has oxidability stronger than potassium permanganate), then carrying out ultrasonic treatment to obtain graphene oxide with high oxidation degree, high single-layer rate (the lower the number of layers of graphene is, the higher the heat conductivity is), and good water solubility, drying the graphene oxide, preparing slurry, coating, reducing and the like to obtain a graphene heat dissipation film with high heat conductivity coefficient, wherein the graphene heat dissipation film can be used for heat dissipation of mobile phones, such as 5G mobile phones. The usability of the mobile phone can be improved, and the service life of the mobile phone can be prolonged.
The graphene heat dissipation film has the characteristics of low cost, high yield, high quality, strong heat dissipation performance and the like. And no carrier is required to be added to the graphene film, and complex operation in the preparation process is required, and meanwhile, the preparation method is low in production cost, high in production efficiency and convenient for large-scale production and application.
Drawings
Fig. 1 is a flow chart of a process for preparing a graphene heat dissipation film according to the present invention.
Fig. 2 is a Scanning Electron Microscope (SEM) image of graphene oxide prepared in example 1 of the present invention.
Detailed Description
In the description of the present invention, "graphite" includes, but is not limited to, flake graphite.
In the context of the present invention, strong oxidizing agents for chemical oxidation of graphite include, but are not limited to, one or more of sodium bismuthate, potassium bismuthate, bismuth chlorate, bismuth nitrate, and bismuth subnitrate.
In the description of the present invention, the substrate material does not affect the properties of graphene oxide, and is easily separated from the graphene oxide after drying. The substrate material includes, but is not limited to, any one of the following substrate materials: high temperature resistant polyester film (PET membrane), polyimide film (PI membrane), polytetrafluoroethylene film (PTFE membrane), aluminium foil.
In the description of the present invention, "room temperature" means 25 ℃.
In the description of the present invention, "solution" generally refers to an aqueous solution unless otherwise specified.
In the description of the present invention, "plural" means two or more.
"thermal conductivity" as used herein means the heat transferred in watts/meter.degree (W/m.K, where K can be replaced by C.) within 1 second through a 1 square meter area of 1 degree (K,. degree.C.) temperature difference across a 1m thick material under stable heat transfer conditions. For anisotropic materials, the horizontal thermal conductivity differs from the vertical thermal conductivity.
Referring to fig. 1, the preparation method of the graphene film of the present invention includes the following four steps: the first step, carrying out chemical oxidation on crystalline flake graphite by using bismuthate under a strong acid condition, washing until the pH value is 5-7, carrying out ultrasonic treatment to obtain graphene oxide aqueous dispersion liquid, and carrying out spray drying to obtain graphene oxide powder; secondly, preparing the graphene oxide powder into slurry, and coating the graphene oxide slurry on a substrate material; thirdly, drying the substrate material coated with the graphene oxide slurry, and separating the substrate material from the dried graphene oxide film; and fourthly, reducing the dried graphene oxide film at high temperature to obtain the graphene heat dissipation film.
Preferably, in the first step, the water used in the sonication process is deionized or distilled water.
Preferably, in the first step, the chemical oxidation is carried out at a temperature of 30 to 50 ℃ for a time of 1 to 3 hours.
Preferably, in the first step, the mass ratio of the graphite to the bismuthate in the chemical oxidation process is 1:1-1: 10. In a preferred embodiment of the invention, the mass ratio of graphite to bismuthate is 1: 4.
Preferably, in the first step, the amount of concentrated sulfuric acid (98%) used in the chemical oxidation process is 1g of graphite dissolved with 25-35mL of concentrated sulfuric acid. In a preferred embodiment of the invention, 1g of graphite is dissolved with 30mL of concentrated sulfuric acid (98%).
In a preferred embodiment of the present invention, in the fourth step, the temperature for the high-temperature reduction of the graphene oxide film is 1000 ℃ to 1500 ℃.
In a preferred embodiment of the present invention, the thermal conductivity of the graphene heat dissipation film obtained by the preparation method of the graphene heat dissipation film of the present invention is 1992W/mK.
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, for which specific conditions are not indicated in the following examples, are generally carried out under conventional conditions, or under conditions recommended by the manufacturer. Percentages are by weight unless otherwise indicated.
The scanning electron microscope used in the following examples was manufactured by Tessin (China) Inc. under the model MIRA 3.
The vendor of flake graphite used in the following examples is Qingdaoshengda graphite, Inc.
The manufacturer of the graphite heat-dissipating film used in the following comparative example 1 is Shenzhen, K.K. K.K.
Example 1
Putting 10g of crystalline flake graphite (600 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of sodium bismuthate at 10 ℃, stirring at 40 ℃ for 2h at a high speed, pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 3%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 3h, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30min to obtain the graphene heat dissipation film with thickness of 30 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high. See fig. 1.
And (3) testing the heat conduction performance of the finally obtained graphene heat dissipation film by using a hot plate method, wherein the heat dissipation coefficient of the heat dissipation film reaches 1992W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 2
Putting 10g of crystalline flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of sodium bismuthate at 10 ℃, stirring at 40 ℃ for 2h at a high speed, pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 3%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 3h, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30min to obtain the graphene heat dissipation film with thickness of 33 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1813W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 3
Putting 10g of crystalline flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate at 10 ℃, stirring at 40 ℃ for 2h at a high speed, pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 3%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 3h, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30min to obtain the 5G mobile phone graphene heat dissipation film with thickness of 32 microns.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1773W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 4
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and bismuth chlorate (with the weight ratio of 2:1) at 10 ℃, stirring at a high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 3%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 3h, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30min to obtain the graphene heat dissipation film with the thickness of 35 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1786W/mK, and the heat dissipation requirement of a 5G mobile phone is completely met.
Example 5
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and bismuth nitrate (with the weight ratio of 4:1) at 10 ℃, stirring at a high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 3%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 3h, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30min to obtain the graphene heat dissipation film with thickness of 33 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
The finally obtained graphene heat dissipation film is subjected to heat conduction performance test by using the determination method described in example 1, the heat dissipation coefficient of the heat dissipation film reaches 1798W/mK, and the heat dissipation requirement of a 5G mobile phone is completely met.
Example 6
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of sodium bismuthate and bismuth subnitrate (with the weight ratio of 4:1) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 3%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 3h, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30min to obtain the graphene heat dissipation film with thickness of 30 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1759W/mK, and the heat dissipation requirement of a 5G mobile phone is completely met.
Example 7
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 3%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 3h, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30min to obtain the graphene heat dissipation film with thickness of 31 microns.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1725W/mK, and the heat dissipation requirement of a 5G mobile phone is completely met.
Example 8
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 5%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 4 hours, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30 minutes to obtain the graphene heat dissipation film with the thickness of 49 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1867W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 9
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 6%, coating the graphene oxide slurry on a PET (polyethylene terephthalate) film by using a film coating machine, drying the PET film in a 50 ℃ oven for 5 hours, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30 minutes to obtain the graphene heat dissipation film with thickness of 57 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1926W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 10
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) carrying out spray drying on the graphene oxide aqueous dispersion liquid at the temperature of 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 6%, coating the graphene oxide slurry on a PI film by using a film coating machine, drying in a 50 ℃ oven for 5h, taking down the graphene oxide film, and reducing at high temperature of 1200 ℃ for 30min to obtain the graphene heat dissipation film with thickness of 60 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1818W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 11
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) spray-drying the graphene oxide aqueous dispersion liquid at 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 6%, coating the graphene oxide slurry on a PTFE (polytetrafluoroethylene) film by using a film coating machine, drying the PTFE film in a 50 ℃ oven for 5 hours, taking down the graphene oxide film, and reducing the graphene oxide film at high temperature of 1200 ℃ for 30 minutes to obtain a graphene heat dissipation film with thickness of 62 microns.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1807W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 12
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) carrying out spray drying on the graphene oxide aqueous dispersion liquid at the temperature of 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 6%, coating the graphene oxide slurry on an aluminum foil by using a film coating machine, drying in a 50 ℃ oven for 5h, taking down a graphene oxide film, and reducing at high temperature of 1200 ℃ for 30min to obtain a graphene heat dissipation film with thickness of 60 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
The finally obtained graphene heat dissipation film is subjected to heat conduction performance test by using the determination method described in example 1, the heat dissipation coefficient of the heat dissipation film reaches 1797W/mK, and the heat dissipation requirement of a 5G mobile phone is completely met.
Example 13
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) carrying out spray drying on the graphene oxide aqueous dispersion liquid at the temperature of 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 6%, coating the graphene oxide slurry on an aluminum foil by using a film coating machine, drying in a 70 ℃ oven for 3h, taking down a graphene oxide film, and reducing at high temperature of 1200 ℃ for 30min to obtain a graphene heat dissipation film with thickness of 57 mu m.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
And (3) performing a heat conduction performance test on the finally obtained graphene heat dissipation film by using the determination method described in example 1, wherein the heat dissipation coefficient of the heat dissipation film reaches 1827W/mK, and the heat dissipation requirement of the 5G mobile phone is completely met.
Example 14
Putting 10g of flake graphite (1000 meshes) into 300mL of concentrated sulfuric acid (with the mass concentration of 98%), mechanically stirring for 30min, then putting 40g of potassium bismuthate and sodium bismuthate (with the weight ratio of 1:2) at 10 ℃, stirring at high speed for 2h at 40 ℃, then pouring the reaction solution into 300mL of deionized water, filtering by using ceramic membrane filtering equipment, washing the obtained solid until the pH value is 5-7, and then adding the solid into 1000mL of deionized water for ultrasonic treatment for 1h to obtain the graphene oxide aqueous dispersion liquid.
And (3) carrying out spray drying on the graphene oxide aqueous dispersion liquid at the temperature of 120 ℃ to obtain graphene oxide powder. Dispersing graphene oxide powder in deionized water to prepare graphene oxide slurry with solid content of 6%, coating the graphene oxide slurry on an aluminum foil by using a film coating machine, drying in a 70 ℃ oven for 3h, taking off a graphene oxide film, and reducing at 1500 ℃ for 30min to obtain a graphene heat dissipation film with thickness of 60 microns.
The graphene oxide aqueous dispersion liquid obtained by ultrasonic treatment is observed by using a scanning electron microscope, and the result shows that the graphene oxide monolayer rate obtained by the method is high.
The finally obtained graphene heat dissipation film is subjected to heat conduction performance test by using the determination method described in example 1, the heat dissipation coefficient of the heat dissipation film reaches 1980W/mK, and the heat dissipation requirement of a 5G mobile phone is completely met.
Comparative example 1
The difference from example 1 is that the heat dissipation film of graphene material has better performance when tested for thermal conductivity by the measurement method described in example 1 (1507W/mK. shows the heat dissipation coefficient of the heat dissipation film).
Comparative example 2
The difference from example 1 is that the method for preparing the heat dissipation film for the mobile phone is the method of chinese patent publication No. CN110255538A, "a method for preparing graphene heat dissipation sheet", and the obtained heat dissipation film was tested by the measurement method described in example 1, and the obtained heat dissipation coefficient was 1673W/mK, which is lower than 1992W/mK. The graphene heat dissipation film for the mobile phone prepared by the method is better in heat dissipation performance.
The reason for this is probably that the oxidation degree of graphite oxide of the crystalline flake graphite is higher than that of the existing graphite oxide when the oxidation process is carried out by using bismuthate under the condition of strong acid, the graphene oxide obtained after the graphite with high oxidation degree is subjected to ultrasonic treatment has higher single-layer rate and good water solubility, and the finally prepared graphene heat dissipation film after high-temperature reduction has better heat dissipation coefficient.
The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.

Claims (12)

1. The graphene heat dissipation film is characterized by only consisting of graphene, wherein the graphene is obtained by carrying out high-temperature reduction on graphene oxide obtained by carrying out chemical oxidation on graphite by bismuthate under a strong acid condition and then carrying out ultrasonic treatment.
2. The graphene heat dissipation film according to claim 1, wherein the graphite is flake graphite with a mesh size of 500-1000 meshes.
3. The graphene heat spreading film according to claim 1, wherein the strong acid is selected from concentrated sulfuric acid, and the bismuthate is selected from one or more of the following:
sodium bismuthate, potassium bismuthate, bismuth chlorate, bismuth nitrate and bismuth subnitrate.
4. The graphene heat dissipation film according to claim 1, wherein the temperature of the high-temperature reduction is 500 ℃ to 2000 ℃.
5. The preparation process of the graphene heat dissipation film is characterized by comprising the following steps:
s1, chemically oxidizing graphite by using bismuthate under a strong acid condition, washing until the pH value is 5-7, performing ultrasonic treatment to obtain graphene oxide aqueous dispersion liquid, and performing spray drying to obtain graphene oxide powder;
s2, preparing the graphene oxide powder into slurry, and coating the graphene oxide slurry on a substrate material;
s3, drying the substrate material coated with the graphene oxide slurry, and separating the substrate material from the dried graphene oxide film;
and S4, reducing the dried graphene oxide film at high temperature to obtain the graphene heat dissipation film.
6. The method as claimed in claim 5, wherein the graphite is selected from crystalline flake graphite with a mesh size of 500-1000 mesh.
7. The preparation method according to claim 5, wherein in step S1, the strong acid is selected from concentrated sulfuric acid, and the bismuthate is selected from one or more of the following:
sodium bismuthate, potassium bismuthate, bismuth chlorate, bismuth nitrate and bismuth subnitrate.
8. The preparation method according to claim 5, wherein in step S2, the graphene oxide powder is prepared into slurry by using water, and the solid content of the graphene oxide slurry in the slurry is 1% -10%.
9. The method according to claim 1, wherein the drying temperature in step S3 is between room temperature and 100 ℃.
10. The method according to claim 1, wherein the temperature of the high-temperature reduction in step S4 is 500 to 2000 ℃.
11. The graphene heat dissipation film according to any one of claims 1 to 4 or the graphene heat dissipation film obtained by the preparation method according to any one of claims 4 to 10, wherein the thermal conductivity of the graphene heat dissipation film is 1700W/mK to 2000W/mK.
12. The graphene heat dissipation film according to any one of claims 1 to 4 or the graphene heat dissipation film obtained by the preparation method according to any one of claims 4 to 10 is used as a 5G mobile phone heat dissipation film.
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