Structural Transformations of TiO2 during Mechanical Activation and Subsequent Annealing

Abstract

The metastable structure state of the anatase phase of titanium dioxide has been shown to be a favorable basis for a targeted influence on it with the aim of producing new oxide phases consisting of nanoparticles and, accordingly, having a new combination of properties. Mechanical activation and subsequent annealing of the activated powders result in a sequence of phase transformations (anatase–brookite–rutile), thereby ensuring structural ordering of titanium dioxide. Transformations of the titanium oxide phases have been studied in detail by X-ray diffraction. We have evaluated the crystallite (coherent scattering domain) size and internal strain (e) from diffraction line broadening by profile fitting with the pseudo-Voigt function. The average particle size was 20 nm after mechanical activation, whereas heat treatment increased it by almost a factor of 2. Similar results have been obtained for internal strain. The pore system of the particles is formed by mesopores. The hysteresis loop observed in nitrogen sorption–desorption isotherms suggests that the titanium dioxide particles have platelike morphology. The results obtained in this study have been used to develop innovative technology of a special grade of titanium dioxide for the preparation of thermally stable glues with dielectric properties and high tensile and shear strength.