Interface diffusion and reaction between TiO 2 film photocatalyst and aluminium alloy substrate

A compact TiO 2 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 TiO 2 layer but also reacted with O 2 that diffused from the air to form an interface layer of Al 2 O 3 species on the interface between the TiO 2 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 TiO 2 layer and existed as a metallic in the layer, it did not interact chemically with the TiO 2 layer. Because it was only a physical mixture of metallic Al and TiO 2 species in the layer, Al did not enter the lattice of TiO 2 . The interface diffusion only influenced the ultraviolet absorbency of the TiO 2 film photocatalyst and had no influence on the peak position. The diffusion and existence of metallic Al in the TiO 2 layer did not influence the formation of a TiO 2 layer with the anatase structure. Copyright © 2001 John Wiley & Sons, Ltd.