The Effect Of Multi-scale Synergistic Enhancement On Thermal Conductivity Of Epoxy Resin With Two-dimensional Thermal Conductive Fillers

Two-dimensional thermally conductive fillers such as graphene,h-BN can offer many phonons transport paths thanks to the planar structure.But their composite would face some challenges like poor interfacial bonding and dispersibility.In addition,the increased contents of fillers result in the deterioration of mechanical and processing properties of composites.Therefore,how to balance the amount of added fillers and the construction of the conductive network become the key to effectively improve the thermal conductivity.In this paper,graphene oxide(GO),hexagonal boron nitride,and graphitic carbon nitride(GCN)were treated based on a solvent-assisted exfoliation method.The BNNS@GCN and BNNS@RGO hybrid fillers were synthesized by electrostatic absorption and the hydrothermal reduction separately,realizing the amelioration of thermal conductivity for epoxy-based composite.The main works done in this topic were as follows:(1)GCN powders were prepared by three synthetic routes,and one was selected as a thermally conductive filler,the solvent-assisted exfoliation method was applied to optimize a kind of solvent and obtain GCN dispersion,which mixed with epoxy to explore the impact on thermal conductivity and other properties.Through various characterizations and testing methods,it was shown that the GCN powders synthesized by the two-stage heating procedure at termination of 550℃ and 600℃ was more suitable for the role of thermally conductive fillers because of their regular structure.With the assisted of IPA solvent,GCN powders can be brought down of 4～5 nm.Meanwhile,thermal conductivity reached 0.318 W/m·K by adding 10wt%fillers.The composites maintained low dielectric constant and loss,but bending strength presented lower than pure resin,.(2)The BNNS and GCN sheets can be self-assembly into BNNS@GCN mixed fillers through electrostatic adsorption.The dispersion and interfacial combination kept well with 10wt%hybrid fillers since BNNS still had some remained oxygen-containing groups,and The thermal conductivity reached 0.54 W/m·K,which was significantly improved compared with pure resin and single-filler.The synergistic effect of hybrids optimized the thermal stability,bending strength,and dielectric loss.(3)BNNS@RGO aerogels were synthesized by the process of hydrothermal reduction and freeze-drying process.The aerogel was vacuum-impregnated with epoxy resin to prepare composites.The interaction between BNNS and RGO was explored and the effect of the aerogel on the thermal conductivity of the composite was investigated.The results indicated that BNNS can be assembled to the RGO aerogel network by electrostatic adsorption,the thermal conductivity of the composite was 0.252 W/m·K when the aerogel mass fraction was 2.5wt%and BNNS:RGO=4:1,which was 76.2%and 108%higher than pure RGO aerogel and pure resin,respectively.