Self-Propagating High-Temperature Synthesis of Titanium Oxide Bronzes: Influence of Mechanical Activation

Abstract

M_xTiO₂ (M = Li, Na, K, and Rb; 0 < x < 1) bronzes were prepared via self-propagating high-temperature synthesis (SHS) of mechanically activated and non-activated green mixtures containing TiO₂, MI, and additive CuO + Ti as heat-generating agent. The influence of mechanical activation on the composition and structure of SHS products was studied. TEM investigations revealed the growth of the number of crystal defects after mechanical activation, in particular, the formation of edge dislocations in certain crystallographic directions, leading to an increase in the diffusion speed in the crystal. The beginning of mechanical activation was shown to be accompanied by the formation of unstable interstitial solid solutions without changing the crystal structure of TiO₂. Prolonged grinding generated stable phases with higher content of intercalated atoms and individual structure, which acted as heterogeneous crystallization nuclei during SHS. According to Rietveld refinements preliminary mechanical activation favored a higher yield of target phases with a higher content of intercalated alkali metal ions.