Low-temperature oxidation of ilmenite (FeTiO 3) induced by high energy ball milling at room temperature

Abstract

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 2Ti 3O 9 and γ-Fe 2O 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 2Ti 3O 9 and Fe 2O 3) and the fast high-temperature reactions (> 1000 °C) with the production of the final stable phases(Fe 2TiO 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.