1985 Volume 11 Issue 3 Pages 317-323
Fine particles of TiO2 were prepared by chemical vapor deposition from titanium tetraisoproxide (TTIP) as a starting material. Due to the catalytic effects of TiO2 deposited on the reactor wall; the chemical vapor deposition occurred at temperatures as low as around 510 K. The properties of TiO2-particles changed from amorphous to crystalline (anatase) and from porous to nonporous, depending on the reaction temperature and the initial concentration of TTIP. The particles were spherical, ranging in average diameter from 0.1 to 0.5 μm. The reaction rates of TiO2 deposited on the reactor wall were well expressed by the Langmuir-Hinshelwood type of rate forms. The mechanism of particle formation, being different from the mechanism of homogeneous nucleation generally believed to be followed by the growth of the nuclei, is considered to consist of the initiation reaction of TiO2 deposited on the reactor wall, uniform nucleation and growth, and coagulation. The coagulation step plays an important role in the formation of the spherical particles of specific surface area as high as 300 m/g.
