Research On Magnetic Field Aligned Graphene-based Composites And The Thermal Conductivity

The dense packing density and high-speed operation of multifunctional electronic devices result in a large amount of heat generation.Therefore,effective thermal management at room temperature is crucial for the rapid heat dissipation of highperformance electronic devices.Polymer materials are widely used in the field of electronic packaging due to their low price,strong corrosion resistance and good electrical insulation.However,the thermal conductivity of most polymer materials is very low,only about 0.1-0.3 W/m K,so it is meaningful to find a filler with better thermal conductivity to embed in polymer composites.For example,reinforcing polymer composites with thermally conductive fillers such as graphene is an effective strategy to improve thermal conductivity.However,randomly oriented graphene in polymers is not conducive to improving thermal conductivity due to the thermal conductivity anisotropy of graphene.In this study,a dynamic rotating magnetic field device was employed to exploit the inherent diamagnetism of graphene to vertically align graphene nanosheets to enhance their axial thermal conductivity.The thermal conductivity,thermal stability and mechanical properties of the three composites under the arbitrary orientation of filler,arrangement of static magnetic field and arrangement of dynamic rotating magnetic field were studied.The main work of the thesis is as follows:1.Under the action of a rotating magnetic field,epoxy resin and graphene were mixed to synthesize graphene/epoxy resin composite(R-GE/EP).When the graphene filling amount is 9.2 vol%,the axial thermal conductivity of the epoxy composite under the rotating magnetic field arrangement is increased to 13.36 W/m K,which is 88.5% and47.1% higher than that of the static magnetic field arrangement and the randomly oriented composite,respectively,and is 89.1 times that of pure epoxy resin.The thermal conductivity and heat transport application test results of the composites under different conditions confirm the excellent heat transport properties of the composites.At the same time,the composites under the rotating magnetic field arrangement also showed good flexural modulus,storage modulus and electrical insulation properties.2.Graphene/carbon nanotube/epoxy resin composites were synthesized by combining multi-walled carbon nanotubes and graphene mixed fillers with epoxy resin matrix in different magnetic field arrangements designed to enhance the interaction of the horizontal plane between the filler and the epoxy matrix.The test results show that when the total filler concentration is 10 wt%,the thermal conductivity of the composite under the rotating magnetic field arrangement reaches 6.4 W/m K.The thermal conductivity in the composite is 12.8% and 47.6% higher than the composites under static magnetic field arrangement and random distribution,respectively.In addition,graphene/carbon nanotubes/epoxy composites exhibit superior mechanical properties than graphene/epoxy composites.