GROWTH AND TRANSFORMATION OF TIO2 CRYSTALLITES IN AEROSOL REACTOR

Rate processes concerning the formation of TiO2 fine crystalline particles by the gas-phase reaction of TiCl4 and O2 are studied using aerosol reactors. Chemical reaction of TiCl4, sintering of particles, mixing of reactants, and transformation from anatase to rutile are evaluated as the system parameters of the simulation model proposed. The crystallite size in the range of 55-65 nm at 1,273 K is predicted well by a model that assumes the maximum fusible particle size, 15 nm in this case. The defect concentration in the TiO2 crystallites strongly affects the transformation rate, and anatase particles produced at 1,173 K are transformed to rutile more rapidly than those produced at 1,373 K. The transformation is simulated quantitatively by the model with the coordinates for elapsed time, particle size fraction. The model can be applied to such particle production processes as collision, sintering and crystal transformation occurring simultaneously.