Superior thermal transport and electrically insulating properties of epoxy composites with waxberry-like calcined alumina/poly diallyldimethylammonium chloride/diamond

This work reported a novel preparation of waxberry-like calcined alumina/poly diallyldimethylammonium chloride/diamond (AO*@ND) via a facile self-assembly of cationic polymer, electrostatic adsorption of nano-sized diamonds and calcination process. The incorporation of hybrid particles into an epoxy matrix significantly enhanced the thermal conductivity and dielectric properties. For example, the thermal conductivity of epoxy composite with 10 wt% calcined AO*@ND in air at 500 °C soars to a remarkable level of 0.70 W/(m·K) and 1.83 W/(m·K) at room temperature and 100 °C, respectively. In addition, its dielectric breakdown strength was 59.6 kV/mm, only showing a decrease of 11 % compared to that of epoxy. More importantly, the epoxy composites with the calcined AO*@ND showed an ultralow dielectric loss. The modification strategy of hybrid filler provides a new insight on the development of thermally conductive yet electrically insulating materials for future power modules and electrical equipment.