Effect of hydrolysis conditions on morphology and crystallization of nanosized TiO2 powder

Nanosized titania powders were prepared by controlling the hydrolysis of TiCl4 in aqueous solution. The powders were characterised by TEM, HREM, XRD, ED, and BET techniques. In the presence of a small amount sulphate ions, when TiCl4 solution hydrolysed at 70°C, the obtained powder was pure anatase and its primary particle size was 3.5 nm, which is finer than that of alkoxide-derived powders, moreover, its anatase-rutile transformation was retarded. However, at the same temperature, in the absence of SO42− the synthetic powder was a mixture of the anatase and rutile, the primary particle size in the rutile phase was 4.3 nm. When TiCl4 solution hydrolysed at 20°C, the prepared TiO2 powder was amorphous and its BET surface area was as high as 501 m2/g. The results of UV–Vis absorption spectra indicate that the presence of sulphate ions accelerated the growth of TiO2 clusters to anatase.