Estimation of reaction conditions for synthesis of nanosized brookite-type titanium dioxide from aqueous TiOCl2 solution

Ti O2 nanoparticles with a mixture of brookite and rutile phases were prepared from aqueous TiOCl2 solution at 80–150◦C and pure rutile phase at 200◦C. The volume fraction of brookite was gradually increased with increase of HCl concentration in the range of about 4.43 M to 6.28 M. The maximum volume fraction of brookite in the as-prepared TiO2 particles was obtained when oxidation of Ti4+ to TiO2 was completed but it was gradually decreased with increase of reaction time. The reaction time for complete oxidation of Ti4+ to TiO2 was about 15 h at 80◦C, about 5 h at 100◦C, about 2 h at 120◦C, and about 1 h at 150◦C, respectively, showing that the kinetics of oxidation is very dependent on the reaction temperature. Brookite phase was not transformed directly to rutile phase but to anatase phase by heat-treatment at about 750◦C, which finally converted to rutile phase at 1100◦C. C 2005 Springer Science + Business Media, Inc