Low-temperature oxidation of ilmenite (FeTiO3) induced by high energy ball milling at room temperature

The mineral ilmenite (FeTiO 3 ) has been ball milled at room temperature in air. The oxidation of ilmenite in the process of milling was investigated by examining the milled samples with powder X-ray diffractometry, X-ray fluorescence spectrometry and thermal analysis. The ilmenite was fully converted to thermally metastable Fe 2 Ti 3 O 9 and γ-Fe 2 O 3 phases after 100 h of ball milling in air. The oxidation process of an ilmenite in a pure thermally activated process consists of a slow low-temperature reaction (600°C-1000°C) with the formation of intermediate phases (Fe 2 Ti 3 O 9 and Fe 2 O 3 ) and the fast high-temperature reactions ( > 1000°C) with the production of the final stable phases(Fe 2 TiO 5 and TiO 2 ). The observed oxidation reaction during ball milling at room temperature corresponds to the low-temperature reaction in a thermally activated process. The high-temperature reactions were not observed during milling, even during a prolonged milling or under a higher milling intensity. It seems that the process of the oxidation of ilmenite induced by high energy ball milling is a non-equilibrium process and is favourable for the formation of thermally metastable phases. © 1997 Elsevier Science S.A.