Studied On The Preparation And Thermal Conductivity And Electric Thermal Performance Of Ultra-thin Flexible Graphite Paper And Its Graphene Composite Film

Thermal interface materials(TIM)are used to fill in the pores produced during the joint or contact between two kinds of materials,which improve the heat dissipation of the material.With the development of lighter,thinner and smaller of all kinds of devices,the working temperature of each device is also increased significantly,and the requirement of heat dissipation is more and more rigorous.Traditional thermal interface materials can meet the cooling requirement,but all sorts of problems are presented in the process of preparation,which restrained the development and the application in many areas.Graphite paper has great property of thermal conductivity and electric thermal performance and graphene also has the same advantages,but there are little researches on their thermal conductivity and electric thermal performance.In this paper,the preparation of flexible graphite paper,its graphene composite film,graphene film and their property of thermal conductivity and electric thermal performance are mainly studied.In this thesis,the preparation of flexible graphite paper and different parameter which influence the property of the material are firstly researched.Then the preparation of ultra-thin flexible graphite paper/graphene composite material and the influence of the thickness and composite methods on the thermal conductivity and electric thermal performance of materials are discussed.Finally,the preparation of graphene film is simply researched and the thermal conductivity is tested.The experiment results show that many closing pores exsit inside the flexible graphite paper,which lead to the bound resilience.After the test,it is found that when the thickness increases,the thermal conductivity and electric thermal performance decline.When the density increases,these two properties also increase.And the thickness and density of the flexible graphite paper is 0.03 mm and 1.5 g/cm3,respectively,has the best thermal conductivity and electric thermal performance.The thermal conductivity can be up to 588 W/m·k.After 5 minutes of electricity under the voltage of 2.8 V,the surface temperature can be up to 64 degrees centigrade and the power can be up to 7 W.After the study of flexible graphite paper/graphene composite film,the optimum preparation conditions are given.Ethyl alcohol is considered to be the solution of the graphene dispersion,the concentration is 2.5wt%,the shearing speed is 10000r per minute and keeping 15 minutes is the best,then ultrasonic 2 hours.And the graphene coating made by spraying is the best.The appropriate substrate is 0.4 mm with low density of 0.078 g/cm3.After the research on the property of composite film,the thickness of the substrate and graphene coating is 0.4 mm and 0.2 mm,respectively,when performing to 0.08 mm,has the best thermal conductivity and electric thermal performance,the thermal conductivity can be up to 917 W/m·k.After 5 minutes of electricity under the voltage of 3.5 V,the surface temperature is 70 degrees centigrade,the power is up to 10 W.By contrasting with the pure graphite paper,the properties of composite film are better than those of the pure graphite paper.The study of pure graphene film shows that when remove the water of the GO solution at the temperature of 60 degrees centigrade,GO film is obtained.After heat-treatment and microwave reduction,graphene film is finally made.The structure of the film is intact,few defects exist on the surface of the film.The thermal conductivity can be up to 3290 W/m·k.