Effect of Solvent on Titania Particle Formation and Morphology in Thermal Hydrolysis of TiCl4

Titania powders were synthesized by the thermal hydrolysis of titanium tetrachloride with the yield of above 85% in a mixed solvent of n -propanol and water. The morphology of the precipitates was controlled by adjusting the volume ratio of n -propanol to water (RH ratio) of the mixed solvent. Precipitates obtained with an RH ratio of 0 were fine, and highly agglomerated. In contrast, an RH ratio of 3 resulted in precipitates consisting of uniform and discrete particles. According to observations of the zeta potentials of precipitates and the dielectric constants of solvents, the discrete particles obtained with an RH ratio of 3 resulted from the low zeta potential and dielectric constant. The result of Fourier transform infrared (FTIR) spectroscopy showed the chemical interaction of particle surface with the solvent alcohol, which decreased the zeta potential of precipitates with an increase of RH ratio. Adding hydroxypropyl cellulose (HPC) as a steric dispersant made it possible to reduce the size of particles to the submicrometer range. Effects of the solvent on the formation and morphology of the resulting particles were investigated.