Effects of hydrothermal conditions on the morphology and phase composition of synthesized TiO2 nanostructures

We investigate the effects of synthetic parameters on the morphologies during hydrothermal process and the crystal structural transitions from intermediate titanate to final TiO2 products by transmission electron microscopy (TEM) and X-ray diffraction (XRD). It reveals that hydrothermal duration, temperature and reactant amount play important roles in controlling the morphologies and crystal structures of titanate products. Anatase nanotubes, anatase nanorafts, TiO2–B nanoribbons, and anatse/TiO2–B nanoribbons were synthesized by modifying these synthetic parameters. We found that the crystal structures of intermediate titanate products influence on the transitions from titanate to TiO2. Our results show that anatase and TiO2–B derive from the orthorhombic and monoclinic titanate, respectively. We suggest that the crystallographic relationships between the intermediate products (hydrogen titanate) and the final TiO2 products play important roles in heat treatment.