High temperature oxidation of rare earth permanent magnets. Part 2-Kinetics

Oxidation is an integral part of some high temperature recycling routes for rare earth permanent magnets. This paper deals with a study of oxidation kinetics of commercial permanent (Nd,Pr)FeB magnet samples, re-sized to 5 × 5 x 10 mm, in the temperature range 700-1500 K. The results show that the oxidation behaviour follows a parabolic rate law and that the kinetics can be described using the Ginstling-Brounshtein diffusion model. In line with the microstructure study that shows three different oxidation mechanisms, the kinetics study also reveals that there are probably three different rate-controlling mechanisms in the temperature range studied.