Kinetic study of ZnFe2O4 formation from mechanochemically activated Zn–Fe2O3 mixtures

The kinetics of ZnFe2O4 formation starting from mechanochemically activated Zn–Fe2O3 powders are studied. Mixtures of metallic Zn and hematite were activated under air atmosphere in a high energy mill and thermally treated at temperatures between 500 and 650 °C during several holding times. During the activation, morphological and compositional changes were observed, but ZnFe2O4 formation was not detected. The ZnFe2O4 content in heated samples was determined using quantitative X-ray diffraction analysis. The resulting conversion–time curves were fitted using different kinetic models of solid-state reaction, calculating the kinetic parameters of the studied reaction. The comparison with the conventional synthesis method revealed that the mechanochemical treatment provoked a change of the rate-controlling step and a significant decrease of the activation energy, which was more evident for the more activated mixtures.