Effect of rotation rate on the recovery of Nd–Fe–B sludge via rotation-reduction diffusion method

In recent years, calcium reduction diffusion has emerged as a new method for in situ regeneration of Nd–Fe–B sludge. In this work, rotation calcium thermal reduction diffusion technology was used for the first time to solve the issue of batch regeneration of Nd–Fe–B sludge to a certain extent, and regenerated Nd–Fe–B powder with uniform size and good dispensability was prepared. The effect of rotation rate on the properties of regenerated Nd–Fe–B powder was mainly studied. We found that the magnetic properties of the regenerated magnetic powder initially increased and then decreased with increasing rotation rate. When the rotation rate was 10 rpm, the magnetization of regenerated magnetic powder reached 138.22 emu/g, which was 10.2% higher than that of the purified sludge. The regenerated magnetic powder was doped with rare earth-rich alloy powder and high remanence alloy powder to control the composition, where the regenerated sintered magnet was prepared. The density reached 7.51 g/cm3 and the maximum magnetic energy product reached 42.87 MGOe, laying a foundation for the short-process in situ regeneration of Nd–Fe–B sludge.