Topochemical approach of kinetics of the reduction of hematite to wüstite

The kinetics of hematite (Fe₂O₃) to wüstite (FeO) reduction has been investigated. Kinetic parameters have been estimated based on the thermogravimetric data. The Avrami-Erofe'ev equation of coupled nucleation and growth processes was successfully applied to describe the initial stages of the process, while four diffusion equations were tested to model the final stages of the process. It was found that the initial stage can be interpreted theoretically as the crystals' nucleation and 1D growth at the gas/iron oxide(s) interface, which gradually shifts to diffusion control. Kinetic and diffusion regions for various temperatures (within the 700-900 °C range) were identified. The value of activation energy ΔE_a of the reaction was estimated and compared with the literature data.