Competitive Diffusion of Ions during Oxidation of Ilmenite

The oxidation mechanism of ilmenite was investigated by studying the morphologies,phase compositions and kinetics of Panzhihua ilmenite,which was oxidized in air at the temperature of 600~750℃.The results reveal that the oxidation mechanism of ilmenite is a kind of competitive diffusion of Fe and O ions.At the beginning,as ilmenite is oxidized by the outdiffusion of Fe ions,Fe₂O₃(gathering on the particle surface) and Fe₂Ti₃O₉ are obtained.When the oxidation process proceeds to a certain extent(the hematite layer grows to 1~2 μm),the reaction is dominated by the indiffusion of O ions,which leads to the formation of Fe₂O₃ and TiO₂ in the particle inner.As the transition of Fe ions diffusion to O ions diffusion always happens at the time when the thickness of hematite layer on the surface reaches to 1~2 μm,and the transition time almost has nothing to do with the temperature and particle size of ilmenite,the proportion of Fe ion diffusion increases with the decrease of particle size of ilmenite in a typical oxidation process.But for the O ion,the reverse is true.