Analysis of the structure of titanium tetrachloride derived precipitates

Titania nanoparticles were prepared by the hydrolysis of titanium tetrachloride (TiCl4) solution at different temperatures and characterized by differential scanning calorimetry (DSC), TG/DTA, TEM, FT-Raman spectroscopy and X-ray diffraction. XRD results indicate the precipitates obtained from TiCl4 hydrolysis at room temperature are amorphous with no long range ordering. The Raman spectra of precipitate obtained at room temperature show three broad bands, consisting of multiple components, at Raman shifts of 160, 407, 613 cm(-1), which is anatase-like and is different dynamically from alkoxide-derived amorphous titania. A small amount of sulfate ions is very effective to promote the formation of anatase even at room temperature, e.g. in the presence of sulfate ions as low as 1/20th, DSC result shows its crystallinity is 17.8%. This effect is also in agreement with the deconvoluted Raman spectra. Strong, broad exothermic peaks are observed in the DSC curves of amorphous precipitates in the 325-485 degreesC temperature range, which are attributable to the transformation heat and the position of DSC peak is sensitive to the crystallinity of as-prepared titania precipitates. (C) 2002 Elsevier Science B.V. All rights reserved.