Kinetic model of the oxidation of ZrSi2 powders

The oxidation kinetics of Zr-disilicide (ZrSi 2 ) powders up to temperatures of 1550°C were studied in flowing air using non-isothermal and isothermal thermogravimetric (TG) analysis. During the oxidation process two main thermal events were detected. The first stage of the oxidation reaction leads to the formation of elemental silicon as an intermediate reaction product. Upon further temperature increase the newly formed silicon is oxidized. Completely oxidized ZrSi 2 samples consist of ZrSiO 4 , amorphous and crystalline SiO 2 as well as some residual ZrO 2 . The experimental TG data were analysed with a model-fitting kinetic method. The gas-solid reaction is complex and can best be fitted with a multi-step reaction scheme consisting of branching reactions based on 3D diffusion mechanisms and a fractal order reaction.