Epoxy-alumina nanocomposites: Advanced materials for high-voltage insulation?

In this paper, vacuum-cast epoxy-alumina nanodielectrics are reported with particular attention to the formulation and processing of the samples. Four grades of alumina nano-fillers with different particle size and surface treatments were compared. The samples were fully characterised in terms of their structure, mechanical, thermal and dielectric properties. The characterisations included: nano/micro-structure (optical and electron microscopy), mechanical properties (tensile, flexural and fracture properties), thermal properties (glass transition temperature, thermal expansion coefficient and thermal conductivity), and dielectric properties (dielectric constant, dielectric losses, DC volume conductivity and dielectric strength). Resistance to surface discharges was also evaluated. The results are discussed and compared to results commonly known for conventional epoxy composites. It is concluded that despite the initial benefits shown by nanotechnologies, there are still some challenges to overcome and more systematic research must be carried out in the choice of the nano-fillers, their size, their surface treatment and their dispersion. Materials selection, formulation and dispersion are the key steps to improve the consistency and reproducibility of nano-dielectrics.