Interface diffusion and reaction between TiO2 film photocatalyst and aluminium alloy substrate

A compact TiO2 film of thickness ??300 nm was deposited on aluminium alloy substrates by using the sol-gel method with Ti(OBu)4 as a precursor. It was found that Al in the alloy substrate not only diffused into the TiO2 layer but also reacted with O2 that diffused from the air to form an interface layer of Al2O3 species on the interface between the TiO2 layer and the aluminium alloy substrate during the annealing treatment. With annealing temperature and time increasing, the diffusion of Al was promoted significantly. Although Al diffused into the TiO2 layer and existed as a metallic in the layer, it did not interact chemically with the TiO2 layer. Because it was only a physical mixture of metallic Al and TiO2 species in the layer, Al did not enter the lattice of TiO2. The interface diffusion only influenced the ultraviolet absorbency of the TiO2 film photocatalyst and ha d no influence on the peak position. The diffusion and existence of metallic Al in the TiO2 layer did not influence the formation of a TiO2 layer with the anatase structure. Copyright ? 2001 John Wiley & Sons, Ltd.EI