TiO2-derived titanate nanotubes by hydrothermal process with acid treatments and their microstructural evaluation.

In this study, the effect of post acid treatments with HCl aqueous solutions after the hydrothermal process on the microstructure of TiO2-derived titanate nanotube was investigated. Especially, the relationship between local structural changes with the HCl treatment and their thermal stability were investigated by X-ray absorption fine structure (XAFS). Consequently, it revealed that the replacement of Na+ with H+ (proton exchange) in TiO2-derived titanate nanotubes was caused by the acid treatment with HCl aqueous solutions and the excess acid treatment led to the disordering. Moreover, it was confirmed that the minor change of TiOx polyhedra in TiO2-derived titanate nanotubes was also related with this disordering.