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The current work reviews the importance of engineering the interface between nanofillers and polymers to achieve unique dielectric properties in nanocomposites. Although many improved dielectric properties of nanocomposites have been attributed to the presence of the interface, the interface can also be an attractive location for water to accumulate, which may otherwise jeopardize the dielectric properties of nanocomposites. Consequently, the use of surface functionalization and calcination techniques in removing water-related moieties on nanofillers is highlighted. Specifically, the effects of nanofiller calcination on two exemplar oxide-based nanocomposite systems, namely, silica-based nanocomposites and zirconia-based nanocomposites, are discussed. Evidence suggests that nanofiller calcination influences not only the water-related chemistry, but also the structure of oxide-based nanofillers. Significantly, for detailed interfacial chemistry of nanofillers to become relevant in engineering the dielectric properties of nanocomposites, effective removal of interfacial water on nanofillers is crucial.

The current work investigates the effects of filler calcination on the structure and dielectric properties of polyethylene/zirconia (ZrO 2 ) nanocomposites. Calcination temperatures of 600 and 900 °C have been applied to ZrO 2 in an attempt to modify its surface chemistry and structure. Calcination results in a slight reduction in the concentration of physically adsorbed water on ZrO 2 and, in addition, structural reorganization of the ZrO 2 nanopowder. Consequently, the real permittivity of nanocomposites containing calcined ZrO 2 is reduced compared to nanocomposites containing uncalcined ZrO 2 . Furthermore, the DC breakdown strength of nanocomposites containing calcined ZrO 2 improves compared to nanocomposites containing uncalcined ZrO 2 . Since the removed water content is minimal, we primarily attribute the observed dielectric results to structural changes in ZrO 2 rather than water-related effects. As such, calcining can have positive effects in enhancing the dielectric properties of ZrO 2 -based nanocomposites.

This paper reports on an investigation of the effects of calcination on the structure and dielectric properties of polyethylene/silica (SiO 2 ) nanocomposites. Calcination temperatures of 600 and 900 °C have been used in order to modify the surface chemistry and surface structure of the SiO 2 . The results show that, after calcination, the concentration of surface hydroxyl groups and water molecules around SiO 2 and within resulting nanocomposites is reduced. The real permittivity of nanocomposites containing calcined SiO 2 decreases compared to nanocomposites based on uncalcined SiO 2 . The DC breakdown strength of nanocomposites containing calcined SiO 2 becomes higher than those containing uncalcined SiO 2 . In contrast, AC breakdown was found not to be significantly affected by addition of any of the silicas considered here. The use of calcined nanofillers can have positive effects akin to the use of chemically functionalized nanofillers in enhancing the dielectric properties of nanocomposites; both approaches remove polar surface hydroxyl groups.