Preparation Of Graphene/Silicone Rubber Composites And Thermally Conductive Properties

As the applications of electrical equipment with high energy density increases widely and rapidly,the thermal management of electrical components have become an urgent need,which makes the research and development of thermally conductive materials become increasingly significant and valuable.Thermally conductive composites with silicone rubber as the matrix were prepared by using graphene(GNP)in combination with alumina and multi-morphological thermally conductive fillers.Three dimensional network of GNP and alumina for thermal conduction was prepared by hydrothermal method and sintering method,respectively.The dispersion of GNP,alumina and other thermally conductive fillers in composites was studied by optical microscope(RPM)and scanning electron microscopy(SEM).The thermal conductivity of the composites was evaluated in term of thermal diffusivity by means of a laser thermal conductivity meter.The relationship between thermal conductivity and dispersion of fillers was studied.The influences of morphology,particle size and compounding on the thermal conductivity of the composites were discussed.The function of three-dimensional network for thermal conduction was revealed.Accordingly,the method was proposed for constructing effective thermally conductive network,which provided possible solutions for the development of silicon rubber composites with excellent thermal conductivity.The following results were obtained.(1)GNP improved the thermal conductive properties of silicon rubber based composites.A percolation relationship was revealed between thermal diffusivity and GNP loading content.The composites with 1.5 wt.%GNP showed a thermal diffusivity of 0.194 mm~2/s.(2)The alumina mixed fillers were prepared according to closely packing theory,which greatly enhanced thermal conductive properties of the composites in combination with GNP.As a result,the silicone composites with 0.5 wt.%GNP and 85 wt.%mixed filler showed a thermal diffusivity of 0.796 mm~2/s.(3)The multi-morphological fillers were found to be helpful in forming effective structure for thermal conduction,which was further improved with introduction of GNP.A thermal diffusivity of 0.492 mm~2/s was achieved by using 0.5 wt.%GNP and 80 wt.%multi-morphological fillers.(4)Three dimensional networks of GNP and alumina foams as well as GNP deposited alumina network were revealed to enhance the thermal conductive properties while decreasing the content of fillers.A thermal diffusivity of 0.588 mm~2/s was obtained for the composites with 41 wt.%alumina foams deposited with 0.8 wt.%GNP.