Titania Aggregates Formed by Hydrolysis of Ti(OH)₄-HCl-H₂O Concentrated Solutions

Abstract

Concentrated Ti(OH)₄-HCl-H₂O solutions were prepared from TiCl₄, and adjusted to the composition of Cl^-/Ti⁴⁺=3 in molar ratio. The crystalline phases and particle morphologies were investigated concerning with the hydrolysis conditions. The titania (TiO₂) powders with fine particles were formed from the solution with the concentration ranging from 0.5mol/l to 4.0mol/l. The anatase crystallizes, at first, and then anatase → rutile phase transition takes place. The rate of the phase transition increases with increasing the concentration of the solution. These products were composed of very fine primary particles having large specific surface areas of about 250m²/g for anatase and 87m²/g for rutile, respectively. Aggregates with the size ranging from 0.1 to 0.8μm were formed from the 3.0mol/l solution at 96°C for 24h. The aggregates become larger as decreasing the concentration of the solution. Spherical aggregates of about 3μm in size was formed from 1mol/l solution.