Mechanical processing of nanometric magnesium titanate precursors

The influence of mechanical treatment could be assessed on mixtures of two unary or coprecipitated binary xerogel precursors of magnesium titanates. The precursors in various stoichiometric ratios were subjected to milling action, at room temperature, for periods ranging from 0 to 24 h, followed by heating at 600°C for 3-4 h. After a short mechanical processing to ensure good mixing of unary xerogel precursors, small yields were obtained of nanocrystalline geikielite, accompanied by periclase and anatase. After prolonged milling one of the latter two phases disappeared, however, the other one persisted and yields of magnesium titanates were far form being quantitative. The reason for this is failure of the mechanical treatment to totally comminute the single component aggregates and produce intimate binary mixtures, that could convert into titanates in a few hours at 600°C. Mechanical treatment of coprecipitated precursors yielded after heating less well developed crystallites than those obtained from the same precursors without mechanical treatment. A possible reason for this behavior is mechanochemical dehydration of hydroxyl group pairs belonging to different metals and leading to a disordered polymeric structure that crystallizes more slowly.