Ti-Coated Al₂O₃ Balls Prepared by Fine Particle Bombardment and Their Reductive Properties

Abstract

Ti-coated Al₂O₃ balls with a proposed structure of TiO₂/TiO_x/Al₂O₃ (0<x<2) prepared by fine particle bombardment (FPB) had previously been reported to possess a catalytic effect for durability improvement of oils or mileage increase of diesel fuels due presumably to the well-known oxidative effect of titanium dioxide. On the contrary, we believed that the durability improvement of oils can more reasonably be explained by reductive properties (i.e. antioxidant) of the Ti-coated Al₂O₃ balls. For this reason, reductive properties of Ti-coated Al₂O₃ balls have been studied in the present investigation in terms of electrical measurements of the balls, X-ray photoelectron spectroscopy (XPS) analysis of the surface, as well as reduction indicator using a viologen compound. The reductive properties are found to arise from a thin TiO_x layer which can gradually be dissolved into water-containing media, leaving behind electrons on the Al₂O₃ balls. These electrons may serve as the antioxidant (i.e. reducing agent: electron donor) for durability improvement of oils or mileage increase of diesel fuels.