Fabien Baillon

Titanium dioxide is widely used in the chemical industry, in particular as a powdered pigment. It is prepared by precipitation, and the usual method, based on thermal hydrolysis of a titanyl sulfate solution in a sulfuric medium, preferentially leads to the anatase crystalline form of TiO2.

To identify the mechanisms involved in the apparition of a precipitate, we have studied the chemical structure of titanium-sulfate solutions and have also demonstrated and quantified the existence of titanium sulfato-complexes by Raman spectroscopy. Following this experimental analysis, we propose a model to predict the concentrations of the species in solution leading to the formation of the solid.

It has been shown that the application of ultrasound can accelerate nucleation in supersaturated solutions and we have accordingly studied the influence of sonication on titanyl sulfate solutions during precipitation. It is shown that nucleation can effectively be stimulated by acoustic cavitation and thus eliminate the need to introduce crystal germs. Furthermore it has been shown that the use of ultrasound leads to the rutile structure of titanium dioxide and we have tried to identify the mechanisms which could explain the impact of sonication in the condensation of the solid phase.