Sol-hydrothermal synthesis and hydrothermally structural evolution of nanocrystal titanium dioxide

A sol-hydrothermal method has been proposed to prepare uniform and unaggregated nanocrystals of pure anatase and rutile from various acidic mediums. The phase formation, particle sizes, and morphologies varying with different acids and their concentrations at different reaction temperatures and times have been investigated using X-ray diffraction and transmission electron microscopy. The use of HCl and the effect of its concentrations on the formation of rutile phase at different temperatures for various reaction times have been described in detail. The effect of the addition of NaCl salt on particle sizes and rutile fractions has also been studied. In this work, the phase transformation from anatase to rutile in the presence of and the absence of NaCl salt has been considered both in neutral and in acidic mediums, The presence of a trace rutile in starting materials of anatase can show obvious effects on the phase transformation under hydrothermal conditions.