Study On Preparation And Thermal Conductivity Of Graphene Film

The rapid development of electronic devices increases the demand for high thermal conductivity materials in the field of heat dissipation,which makes traditional metal materials have been difficult to meet the increasing demand for heat dissipation.Graphene has excellent thermal conductivity and is a strong competitor of a new generation of heat dissipation materials.However,the current thermal conductivity film prepared from graphene oxide has high cost,high environmental pollution and large performance loss when the film thickness increasing,which limits the application of graphene-based high thermal conductivity film in the heat dissipation field.In this paper,graphene prepared by mechanical stripping method was used as the main raw material.Thermal conductive films were prepared with two different additives,and we have characterized them.The details are as follows:（1）The effect of 5 wt%GO added graphene on thermal conductive film was studied.The addition of GO significantly improved the dispersion effect of graphene in water,makes directivity of GO@G films were better than pure graphene films.GO has different effects on the thermal conductivity of films at different processing temperatures:the thermal conductivity of GO@G films after carbonization is lower than that of pure graphene films.However,after graphitization,its thermal conductivity is up to 29%higher than graphene thermal conductivity film.When the thickness was 30μm,the thermal conductivity of GO@G becoming 423W m^-1 K^-1.Meanwhile,the addition of GO weakened the thermal conductivity loss caused by the thickness increasing:When the film thickness increases from 30μm to 130μm,the thermal conductivity of GO@G film decreased by only 11.3%,which is far less than the performance loss rate of pure graphene film of 28.1%.（2）The modified Hummer’s method was used to oxidize mesophase pitch-based carbon fiber to oxidized carbon fiber sheet（CFO）,which has a high aspect ratio and a structure similar to GO.The influence of G/CFO ratio on the structure and properties of thermal conductive film was studied.CFO’s thin layer can play the same role as GO,so that the thermal conductivity of the thermal conductivity film is significantly improved.CFO’s improvement of thermal conductivity of the thermal conductive film increases first and then decreases with the increase of CFO.When the mass ratio of graphene to CFO is 6:4,a complete thermal conductivity channel is formed in the film,so that the heat in the thermal conductive film spreads through the channel and the matrix at the same time,greatly improving the thermal conductivity.At this time,the thermal conductivity reaches the maximum value of 590 W m^-1 K^-1.