Thermal Nitridation of Magnesium at Lower Temperatures and Pressures of the Nitrogen Atmosphere

Abstract

The dependence of the thermal nitridation of polycrystalline magnesium specimens, located in pure nitrogen, on time, temperature, and pressure has been investigated. Parameters of the experiments were chosen with regard to the conditions of nitridation in a d‐c and rf discharge plasma. The temperature dependence was measured up to 500°C and was not detectable below 300°C. The long term kinetic plot at intermediate temperature 450°C, following the initial period, can be approximated by a logarithmic dependence, and the best explanation of the nitridation mechanism seems to be Fehlner and Mott's conception based on boundary diffusion. The value of the activation energy of the process calculated from the linear parts of the nitridation curves at different temperatures was 19.2 kcal/mole. The pressure dependence of the nitridation was measured in the range of 0.2–400 Torr and could best be described by a p¼ dependence.