Thermal stability of TiO2-anatase: Impact of nanoparticles morphology on kinetic phase transformation

TiO2 is a material of great interest for many technological applications among which, as catalyst support. As this specific application requires a good thermal stability of the material, the phase transition between the two most commonly used titania polymorphs, anatase and rutile, has been extensively studied over the past decade. However not much importance has been given to the initial and final particles morphologies. In this study, anatase nanoparticles with an elongated shape were synthesized and their kinetic phase transformation was studied. The thermal treatments were conducted at temperatures ranging from 500 to 700°C. The morphology evolution and the phase transition were characterized by X-ray diffraction and transmission electron microscopy. The phase transformation kinetics is best described by the interface nucleation models. The values of the measured kinetic parameters are significantly lower than those proposed in the literature for isotropic particles, with an activation energy of Ea=345kJmol−1. The influence of morphology and, as a consequence, the influence of exposed faces on anatase particles, are presented and discussed.