Influence of oxidation process on photocatalytic activity of photocatalyst coatings by mechanical coating technique

Titanium (Ti) coatings on alumina (Al2O3) balls fabricated by mechanical coating technique (MCT) were oxidized in air at a series of relatively low temperatures with the oxidation time of 3 h and 50 h. Crystal structure and microstructure of the coatings were investigated. Photocatalytic activity of the coatings was evaluated and discussed. The results showed that titanium dioxide (TiO2) films on Ti or Ti/TiO2 coatings were fabricated by the MCT and subsequent heat oxidation. The oxidized coatings started to show the mixed-phase of anatase and rutile, at the temperature of 873 K for 3 h and 773 K for 50 h. With extending the oxidation time from 3 h to 50 h, the oxidative effect of relatively lower temperatures of 773 K to 973 K almost reached to that of higher temperatures, which is similar to the time–temperature equivalence principle. Photocatalytic activity of anatase TiO2 at 673 K is higher than that of mixed-phase or rutile TiO2 under UV irradiation.