Hydrophobic nanocrystalline glazes based on cassiterite for self-cleaning outdoor power grid insulators

Abstract

Self-cleaning hydrophobic glazes were prepared using a base industrial glaze. A semiconducting component (95SnO2.xSb2O3.(5-x)NiO, where x = 0–5), in which cassiterite nano-sized needles were crystallized was added to the base glaze. The glazes (named SbxNi(5-x)) were applied on a porcelain insulator and gloss fired in an industrial furnace at 1310 °C. The water contact angle (WCA), electrical resistivity and band gap of the glazes were measured. The most decisive factors in the resulted properties were the amount and composition of the semiconducting component and the morphology of the crystallized cassiterite phase. With increasing Sb2O3 content, the crystallinity increased and the needles became shorter and smaller resulting in a higher specific surface area, encouraging air buckets entrapment, and therefore the highest WCA of 147.9˚. This sample also demonstrated the lowest resistivity (28.35 MΩ.cm), due to the presence of maximum Sb ions as electron donors, creating the lowest band gap (2.5 eV). On the contrary, the sample Sb4Ni1 showed the highest resistivity; this was due to the reduction of mobility as a result of the presence of very larger Sb ions in the cassiterite structure with smaller Sn ions, causing charge carrier scattering.