钛铁矿氧化过程中的离子竞争扩散机制

Competitive Diffusion of Ions during Oxidation of Ilmenite

在600～750℃的温度范围、空气气氛下焙烧攀枝花钛铁矿,通过观察分析钛铁矿氧化后的微观形貌、物相组成以及氧化动力学,对钛铁矿的氧化机理进行了详细地研究。试验结果表明钛铁矿的氧化机制是一种Fe、O离子相互竞争扩散的反应机制。在反应初期,钛铁矿的氧化是通过Fe离子的向外扩散完成,氧化产物是Fe2O3和Fe2Ti3O9,其中Fe2O3会在颗粒表面富集;当反应进行到一定程度后(表面Fe2O3层厚度达到1～2μm),O离子的向内扩散在反应中占主导,颗粒内部逐渐形成Fe2O3和TiO2。由于从Fe离子扩散转变到O离子扩散均发生在表面氧化铁层厚度达到1～2μm时,这一转变时间与温度和钛铁矿颗粒粒径无关,所以Fe离子扩散在整个氧化过程中所占的比重会随着钛铁矿颗粒粒径的减小而增大,而O离子扩散则相反。

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.