Controllable Preparation Of 3D Macroscopic Graphene Assembly For Thermally Conductive Composites

As a material for heat transfer filled between heat source and heat sink,thermally conductive composites has a significant influence on the normal operation and service life of the device.Therefore,preparation of thermally conductive composites with high thermal conductivity has become one of most important research topics in the field of thermally conductive composites.Graphene has the highest thermal conductivity of 5300 W /(m·K)among known materials,and graphene possesses light weight,high surface area(2630 m2/g),structural stability,good mechanical properties and other excellent characteristics,all of which make it an ideal thermally conductive filler.However,it is difficult to realize the uniform dispersion of graphene in the polymer matrix by the traditional mixing method,which is not conducive to the construction of the efficient network for thermal conduction.At the same time,the mixing method is also difficult to control the structure based graphene for the construction of thermal network,which can not fully use the anisotropy of the thermal property for graphene.In this thesis,we have proposed to construct a three-dimensional thermal network by selfassembly of graphene in advance to prepare thermally conductive composites with high thermal conductivity.The main research work of this paper is as follows:1.The preparation of three-dimensional thermally conductive network structure based on graphene induced by the evaporation of graphene dispersion in ethanol and water and the preparation of thermally conductive composite after the infusion of epoxy resin.We investigated the effects of the concentration of graphene dispersion,volume ratio of ethanol to water,evaporation temperature on the formation of the graphene three-dimensional assembly,as well as the effects of the microstructure and density of the graphene three-dimensional assembly on the thermally conductive composites.The results show that the method of pre-construction of network based on graphene not only ensures the good dispersion of graphene,but also achieves the orientation of graphene in the polymer matrix,which greatly improves the thermal conductivity of the composites compared with the polymer matrix material itself.2.The three-dimensional structure based on graphene and hexagonal boron nitride were constructed by hydrothermal method using graphene oxide as carrier of boron nitride and using the two as precursors.We studied the effects of the mass ratio between graphene oxide and boron nitride on the three-dimensional structure during preparation process.And the synergistic effect between graphene and boron nitride was also investigated,as well as the effect of the mass ratio of graphene oxide to boron nitride on the thermal conductivity and the insulation properties of composites.The results show that the combination of graphene and boron nitride improves the thermal conductivity of the composites,and compared to the single filler of graphene,the insulation of thermally conductive composite has been obtained.