Effect of hydrolysis conditions on morphology and phase content in the crystalline TiO2 nanoparticles synthesized from aqueous TiCl4 solution by precipitation

Nanosized TiO2 particles with a size of about 5-20 nm and the specific surface area of about 188.5 m2 g−1, in which two polymorphs of TiO2, brookite and rutile, are present, were obtained by heating aqueous TiCl4 solution with not more than 1.0 M of Ti4+ at 80-150 °C for 15 h. The volume fraction of brookite in TiO2 particles was about 60-70% at 0.1-0.5 M Ti4+, about 80-81% at 0.6-0.8 M Ti4+ and about 69% at 1.0 M Ti4+, respectively. The molar ratio of Cltotal− to Ti4+ for brookite formation ranged between 6.4 and 33. Reaction temperature, reaction time and HCl concentration in the solution are the decisive factors in determining phase content in TiO2 particles. Brookite in the mixture phase was directly transformed to rutile with increase in reaction time after complete oxidation of Ti4+ to TiO2 whereas it to rutile via anatase through heat treatment.