Tuning of thermal and dielectric properties for epoxy composites filled with electrospun alumina fibers and graphene nanoplatelets through hybridization

Epoxy resin is widely used for electrical and electronics packaging in various forms due to its excellent adhesion, low cure shrinkage and good electrical insulation. However, the low thermal conductivity and mismatched dielectric properties limit its application in highly integrated circuits. In this work, alumina fibers (AFs) were firstly prepared via electrospinning with sol-gel precursor. Epoxy (EP) composites with graphene nanoplatelets (GNPs) and AFs were fabricated using a hot-pressing process. Microstructures, thermal conductivity and dielectric properties of EP hybrid composites were studied. Scanning electron microscopy images reveal that the modified AFs and GNPs were uniformly dispersed in the epoxy matrix and the thermal conductive reticular structures were formed. The AFs can not only link the GNPs and epoxy but also reduce the interfacial thermal resistance so that a high thermal conductivity of 1.62 W m^-1 K^-1 is realized in the EP-GNP-AF composite, which is about 8 times higher than pure EP. The decomposition temperature of the epoxy composites with 2 vol% GNP and 50 vol% AF loading was enhanced by about 100 degrees. Dielectric properties of EP composites have a strong dependence on frequency and a weak dependence on temperature, which gives rise to the potential in different electronic/electrical field applications.