Preparation, characterization, and kinetic and thermodynamic studies of mixed-phase TiO2 nanoparticles prepared by detonation method

Although detonation method has been reported to prepare TiO2 nanoparticles, phase transformation and crystal growth of detonation-prepared TiO2 nanoparticles have not been explored extensively. In this study, mixed-phase TiO2 nanoparticles, consisting of anatase (34.8 wt%, similar to 9.4 nm) and rutile (65.2 wt%, similar to 18.2 nm), were prepared by the detonation method. The phase transformation in the TiO2 sample at different annealing temperatures was modeled to understand the transformation behaviors. Thermal treatment experiments of the detonation-prepared TiO2 nanoparticles indicated that the initial process involved an anatase-to-rutile transformation. The TiO2 grains coarsened drastically after thermal treatment at 600 degrees C for 1 h. In contrast to a normal transformation, the anatase-to-rutile transformation was followed by conversion of rutile to anatase in large crystals. Moreover, smaller TiO2 particles could gain more kinetic energy and combine rapidly with the increase in temperature, forming larger particles. Anatase was transformed completely to rutile after thermal treatment at 720 degrees C for 3.5 h. The transformation temperature from anatase to rutile of the detonation-prepared TiO2 nanoparticles was approximately 80 degrees C lower than that of TiO2 prepared by conventional methods. Therefore, thermal treatment may be employed to control the particle size and phase content of detonation-prepared TiO2 nanoparticles. (C) 2016 The Authors. Published by Elsevier B. V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).