KINETICS AND MECHANISM OF FORMATION OF FINE HYDRATED TIO2 PARTICLES BY HYDROLYSIS OF TI(OC2H5)4

Fine particles of hydrated titanium dioxide were prepared by hydrolysis of titanium tetraethoxide in ethanol solution. Time courses of conversion to solid and size change of the solid particle were measured, and small-angle X-ray scattering measurements were conducted for the solutions from which solid particles were removed by filtration. The initial concentration of titanium tetraethoxide required to produce unagglomerated and monodispersed particles was determined. The effect of addition of a dispersant, hydroxypropylcellulose, on particle formation was also elucidated. Chronomal analysis was applied to clarify the kinetics and the mechanism of particle formation. The rate process was explained by the following kinetic model. 'Nuclei' that contain many titanium atoms are generated in the early stage and subsequently deposit on the surface of particles under the diffusion limited condition. The diameter of the 'nuclei' was calculated from analysis of the small-angle X-ray scattering data.