Investigation of the influence of the annealing atmosphere on the structure of powders after recycling Nd-Fe-B magnets by solvothermal process
A. Chetouani, F. Richomme, J.M. Le Breton, Jefry Samson Thonikuzhiyil, P. Bernstein, Jacques Noudem
Abstract
The effect of annealing under vacuum and argon atmospheres on the structure of a Nd-Fe-B powder recycled by a solvothermal treatment was investigated by means of X-ray diffraction and Mössbauer spectrometry. The results show that vacuum annealing at 300 °C is accompanied by the complete desorption of hydrogen from the magnetic Nd2Fe14BHx phase that was obtained after the solvothermal treatment. Vacuum annealing above 650 °C leads to the decomposition of Nd2Fe14B into iron and Fe2B. Annealing in argon atmosphere at 300 °C has almost no effect on the powder and the desorption of hydrogen from the Nd2Fe14BHx phase is partial. Argon annealing above 650 °C leads to the oxidation of the Nd2Fe14B phase.