Mechanochemistry of Titanium Dioxide

Abstract

Mechanochemical processing of solids is a relatively new application of using mechanical energy (i.e., impact) to affect a chemical change. The process has been successfully used to alter natural minerals into different crystalline materials. Thermodynamic models can be a good way to predict the probability of two substances forming new compounds through mechanical impacting. A study was initiated to look into the mechanical alloying of titanium dioxide with various reactants and conditions in a dry ball mill. Using free energy models to look at reaction spontaneity, aluminum, bismuth(III) oxide, and barium peroxide were selected as candidates to react with the TiO2. Each was individually added to a ball mill with titanium dioxide and allowed to roll for up to 24-hours to investigate the possibility of recovering metals or spinels from the blend. X-ray diffraction (XRD) was used to evaluate the effectiveness of the reactions by comparing the XRD scans of the feed material with the “reacted” blends to see if new crystalline structures could be made.The resulting XRD scans showed that the peaks for the resulting product had almost identical peaks with the head scans, suggesting no reactions took place. Although thermodynamic models predicted spontaneous reactions, little effect was noted when TiO2 was impacted with Al, Bi2O3 or BaO2. The blends were impacted in air, and in a vacuum to no avail. The absence of a reaction could be due to a number of factors. The most likely is that the mechanical energy was not sufficient to overcome the activation energy required to complete the reaction.