Efficient thermal transport network construction within epoxy composites with hybrid ceramic fillers

Abstract Polymer composites with superior thermal conduction and low dielectric constant are urgently required for thermal management applications of modern electrical devices. However, the performances of traditional polymer composites usually suffer from either low thermal transfer efficiency or high dielectric loss. Herein, we prepared a series of epoxy composites using a binary system of beta-silicon nitride (β-Si3N4) rod-like crystals and aluminum oxide (Al2O3) spheres fillers via a gravity mixing process and investigated the effect of the mass ratio and solid content of hybrid fillers on their thermal conductivity. Al2O3 spheres played a role of “hot spots” and small size β-Si3N4 rod-like crystals were homogenously dispersed between Al2O3 spheres acting as “bridges”, which constructed an efficient thermal transport network in the epoxy matrix for propagating heat flow. The thermal conductivity was efficiently increased up to 2.2 Wm−1K−1 for β-Si3N4/Al2O3 loading of 52.5 vol% at an optimum mass ratio of 3/4 in the composite, which demonstrated 899% thermal conductivity enhancement with the preservation of a low dielectric constant and dielectric loss. Moreover, a 67.3% reduction of the thermal expansion (CTE) coefficient in cryogenic temperature was achieved at the same time. The highly desirable multifunctional features of the epoxy composites were potential for the heat-dissipation demand in many fields.