Preparation of TiO2 Powder by Modified Two-Stage Hydrolysis

Nano-sized TiO₂ powders were synthesized by modified hydrolysis reaction using two-stage treatments of acid/base catalyst. Using an acidic catalyst, the primary particle size of assynthesized TiO₂ was smaller than using basic catalyst, but rutile ratio and the particle size were increased after heat treatment due to the dense packing of particles. However, in the synthesized TiO₂ powder using a basic catalyst persist the anatase phase and a loosely aggregation of particle after heat treatment. It was found that the catalyst used in the first stage determines the primary particle size. However the phase, the packing density and degree of dispersion of TiO₂ powder were determined by the secondly applied catalyst. Therefore, the addition sequence of catalysts is the most important key to prepare fine powders for photocatalytic use and solar cell. In this study, an acid treatment followed by a base is suggested as best route to obtaining fine size and distribution of particles and high content of anatase phase.