Effect of stirring and heating rate on the formation of TiO2 powders usingsupercritical fluid

The crystalline TiO2 powders were prepared by highly reactive supercritical fluid with unique properties of both liquid and vapor phases. In this rese arch, the effects of stirring and heating rates on the crystallization beha vior of the TiO2 powders were investigated. The crystalline size of the TiO 2 powders decreased from 90 to 60 nm as the stirring rate increased from 0 up to 150 rpm but increased to 160 nm with a further increase of the stirri ng rate to 400 rpm. The TiO2 crystals tend to develop into spherical shape at a stirring rate below 50 rpm. The morphology of the TiO2 particles chang ed from spherical to platelet shape as the stirring rate increased from 400 to 600 rpm. The particle size of the TiO2 powders increased from 200 to 40 0 nm as the heating rate increased from 3 to 12 degreesC/min, but the shape of the TiO2 powder became more spherical.