Photocatalytic activity of TiO2/Ti composite coatings fabricated by mechanical coating technique and subsequent heat oxidation

Abstract

Titanium (Ti) coatings were fabricated on alumina (Al2O3) balls by mechanical coating technique (MCT) with Ti powder. The Ti coatings were then oxidized to titanium dioxide (TiO2) coatings at different temperatures. The oxidation behavior and microstructure evolution of these coatings were investigated. The results showed that the inner and surface layers of the Ti coatings were oxidized simultaneously. When oxidizing at a relatively low temperature for a short time, TiO2/Ti composite coatings were obtained. Increasing the oxidation temperature or time increased the thickness of the TiO2 layer and eventually Ti coatings were totally oxidized to TiO2 coatings. During oxidation, TiO2 needles formed at a lower temperature grew to generate columnar crystals. The photocatalytic activity of these coatings was examined. Compared with TiO2 coatings, the TiO2/Ti composite coatings showed much higher photocatalytic activity. The highest activity was observed for the TiO2/Ti composite coatings prepared by MCT and subsequent oxidation at 1073K for 15h and then the thickness of the TiO2 layer was 27μm.