Structural alterations during mechanochemical activation of a titanium–magnetite mixture

In this work, mechanochemical activation and thermal behaviour of (Ti + Fe3O4) mixtures in Ti/Fe3O4 molar ratios 0.5, 1, and 1.5, are studied. The samples were activated under Ar atmosphere, thermally treated at temperatures ranging between 400 and 700 °C, and analyzed by XRD and Rietveld analysis, SEM and EPMA. By XRD, a progressive decrease in crystallinity with the activation time of was observed. For the samples with lower Ti contents, the system evolved towards the formation of a ulvospinel (Fe2TiO4)–magnetite (Fe3O4) solid solution, while for higher Ti contents the major phase obtained was ilmenite (FeTiO3). During the activation at room temperature, low crystalline intermediate phases (FeO + TiO, FeO, pseudobrookite [Fe2TiO5]) were generated, depending on the initial mixture composition. Thermal treatments resulted in a progressive structural ordering, with lattice parameters slightly greater than those of the original spinel.