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

The alkoxide sol-gel synthesis of nanostructured TiO2 has been studied syst ematically to examine the processing parameters that control crystallite si ze and phase. Nonagglomerated, ultrafine anatase particles have been genera ted by hydrothermally treating the sol-gel-derived hydrous oxides. The degr ee of crystallinity and purity of the synthesized materials could affect th eir structural evolution during heat treatment. It was found that the 10-nm anatase TiO2 sample derived by hydrothermal processing at 180 degrees C un derwent neither phase change nor significant grain growth up to 800 degrees C. Nanocrystalline rutile TiO2 particles have also been attained via hydro thermal treatment in an acidic medium. They possessed an ultrafine rutile g rain size and a high surface area, which could not be achieved via phase tr ansformation from thermal treatment of anatase particles.