| Abstract Scope |
In a hydrothermal synthesis of TiO2, TiO2 polymorphs are formed via condensation reaction of [Ti(OH)h(H2O)6-h]4-h (h, the hydrolysis ratio) monomers. In this study, the formation mechanism was proposed that the hydrolysis ratio h determines the crystal structure of TiO2. The detailed nucleation process of TiO2 has been derived. The corresponding relationship between the hydrolysis ratio and the crystal structure has been investigated. When the h is in the intervals of h≤ 2, 2 < h < 3, 3 ≤ h < 5 and h ≥ 5, the predicted crystal structures of TiO2 are rutile, a mixed crystal (rutile, brookite and anatase), anatase and brookite, respectively. In addition, the hydrolysis ratio under different hydrothermal conditions was modified by introducing the ionic product correction. And, the dynamical change of the hydrolysis ratio during the hydrothermal crystallization has been investigated. The theoretical predictions of crystal structure of TiO2 has been experimentally verified. |