Effects and mechanism of filler surface coating strategy on thermal conductivity of composites: A case study on epoxy/SiO2-coated BN composites

Abstract

In order to make a systematic understanding of the effects and mechanism of the filler surface coating strategy on the thermal conductivity of composites, the silica coated BN was synthesized via Stöber sol-gel method and then incorporated into epoxy. The thermal conductivities of epoxy/BN@SiO2 composites were investigated experimentally, and it was found that increasing the coating thickness or filler content would decrease the enhanced effect of the strategy on thermal conduction. Fitting the thermal conductivities of composites with the EMA model indicates that the interfacial thermal resistance in the formed BN@SiO2 thermal conduction networks will increase with the increase of filler content, and then deteriorates the thermal conduction enhancement factor. Thus, the concept of the effective filler volume fraction was introduced in the strategy for the first time. Reducing the coating thickness will expand the effective filler volume fraction, but the upper limit of the effective filler volume fraction will not exceed the maximum random packing volume fraction of the fillers. The mechanism research provides an efficient guideline for further studying core-shell particles to improve the thermal conductivity of composites.