Effects of nano-alumina hydrate coating for conductive fillers on dielectric properties of epoxy composite materials

The present study aims to put to profit a newly developed insulating nano-alumina (Al2O3) hydrate coating technique applied to electrically conductive particles. This paper deals with the morphology of the nano-alumina hydrate coating and its impact on dielectric properties of the composite materials. For the base polymer, a bisphenol-A type epoxy resin and an alicyclic polyamine hardener were used. The following four kinds of micro particles were used as conducting or semi-conducting core materials; Aluminum, Graphite, Zinc, and Silicon carbide. The particles were coated by a nano-alumina hydrate using a hydrothermal synthesis method. Alumina micro particle was also used as a reference. Dielectric properties were characterized by broadband dielectric spectroscopy (10^-2-10⁶ Hz) and volume resistivity measurements.