Sol-gel synthesis and hydrothermal processing of anatase and rutile titania nanocrystals

The alkoxide sol-gel synthesis of nanostructured TiO2 has been studied systematically to examine the processing parameters that control crystallite size and phase. Nonagglomerated, ultrafine anatase particles have been generated by hydrothermally treating the sol-gel-derived hydrous oxides. The degree of crystallinity and purity of the synthesized materials could affect their structural evolution during heat treatment. It was found that the 10-nm anatase TiO2 sample derived by hydrothermal processing at 180 degrees C underwent neither phase change nor significant grain growth up to 800 degrees C. Nanocrystalline rutile TiO2 particles have also been attained via hydrothermal treatment in an acidic medium. They possessed an ultrafine rutile grain size and a high surface area, which could not be achieved via phase transformation from thermal treatment of anatase particles.