Adjusting the crystal phase and morphology of titania via a soft chemical process

The successful adjustment of phase composition and morphology of anatase/rutile TiO₂ nanocomposites is achieved via a soft chemical strategy, which involves no templates, hydrothermal treatments, or calcinations. The process consists of a NaOH treatment of the hydrolysate of titanium tetra-n-butoxide and a subsequent acidic peptization of the H-titanate intermediate. The effects of the acid peptization time, acid volume, and the NaOH-treatment time on the properties of products are systematically investigated. For the first time, the two-way phase transition between anatase and rutile is realized through adjusting the acid peptization time, which provides a promising way to control the phase ratio in preparing TiO₂ anatase/rutile composites. The mechanism of the phase transitions and crystal growth under such soft chemical processes is discussed in detail, and the evolution of the phase composition is illustrated according to dissolution-reassembly equilibrium.