Preparation and thermal treatment of titania aerogels

TiO₂ aerogels were prepared by sol-gel process and supercritical carbon dioxide drying. The influence of thermal treatment temperature on the crystalline structures and pore structures of TiO₂ aerogels was investigated by X-ray diffraction and N₂ adsorption-desorption. The results showed that the fresh prepared TiO₂ aerogels were amorphous. After thermal treatment, the samples still possessed high surface areas and pore volumes, and the amorphous TiO₂ gradually transforms to anatase and further to rutile. The crystallite sizes presented a persistent increase with the rise of temperature. The light absorption and the band gap of samples treated at different temperatures were also surveyed by diffuse reflection ultraviolet-visible (UV-vis) spectroscopy.