• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.545-551
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• 2007

HCl concentration, reaction temperature, and $Ti^{4+}$ concentration are the decisive factors in determining the structure of precipitates in the process of synthesis of $TiO_2$ particles from aqueous $TiCl_4$ solution by precipitation and the volumetric proportion of brookite phase in $TiO_2$ particles can be controlled by these factors. Pure brookite-type $TiO_2$ nanoparticles were synthesized by heating the aqueous $TiCl_4$ solution with no more than 1.0 M of $Ti^{4+}$, in which the concentration of HCl was kept in the range of about 2.53~6.41 M during reaction, at the temperature below $70^{\circ}C$ for 20 h. Also, Pure brookite was finally transformed to a rutile phase via an anatase phase through heat-treatment.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.785-789
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• 2005

$TiO_2$ powders with rutile and brookite phases were synthesized through homogeneous precipitation of the aqueous $TiOCl_2$ solution, prepared from $TiCl_4$ and HCl solution, and their properties were characterized. Based on the analytical results appropriate molar ratios of ${Cl^-}_{total}:Ti^{+4}$ in precipitating solution for synthesis of pure rutile phase and a mixture of rutile and brookite phases were proposed. The volumetric proportion of brookite increased with increasing HCl concentration under a typical condition obtaining mixed phase of rutile and brookite. The brookite phase in the mixture was transformed to anatase phase by heat treatment at about $800^{\circ}C{\sim}850^{\circ}C$, and finally converted to rutile phase at $1000^{\circ}C$.