The synthesis of titanium dioxide (TiO2) powder for cold spray process

Abstract

Titanium dioxide (TiO2) has attracted numerous attentions due to its high photocatalytic property. TiO2 as photocatalyst is best to be coated over large area substrate (walls, windows, etc.). In this case, cold spray process is the most suitable technique, not only because its simplicity and efficiency for large area deposition, but also because it is a low temperature process that would retain the high photocatalytic anatase phase of TiO2 in the coating. However, cold spraying of hard ceramic materials, such as TiO2, is widely known to be difficult. In this study, we are reporting a novel synthesis method of TiO2 powder for cold spray via the hydrolysis of titanyl sulphate (TiOSO4) with addition of ammonium sulphate ((NH4)2SO4). It is a relatively simple synthesis method that can obtain pure anatase structure even without high temperature treatment, although post treatments, such as hydrothermal and calcination further increase the crystallinity and change the morphology of synthesised TiO2. It is believed that the synergetic effect of post treatments and adsorption of NH4+ and SO42- ions on the surface of TiO2 causes the alteration in morphology of TiO2 powder. Finally, the cold spray spot test shows that the TiO2 powders can be cold sprayed. This is a remarkable finding as the difficulty of cold spraying TiO2 is widely known. © 2011 Ceramic Society of Japan.