Thermal transformations of titania hydrolysates prepared from tetraisopropoxytitanium(iv)

Titania hydrolysates prepared from the hydrolysis of both unmodified and modified tetraisopropoxytitanium(iv) are shown by both FT-Raman spectroscopy and X-ray diffraction to be amorphous with no long range ordering. The Raman hydrolysate spectra show three broad bands, consisting of multiple components, at Raman shifts of ~210, 440 and 570cm. These bands do not correspond with any known phase of titania. Thermal analysis shows broad endothermic peaks centred at 106-136°C and extending to ≥200°C for each of the hydrolysates and is attributed to dehydration and loss of water. Strong, broad exothermic peaks are observed in the modified hydrolysate curves, in the 310-340°C temperature range and are attributed to the combustion of the residual surface adsorbed organics. Weight loss occurred during these exotherms. Crystallisation of the disordered hydrolysates into anatase occurs in the 500-600°C temperature range. The anatase→rutile phase transition was found between 665°C and 691°C