Study on recycling technology for waste MQ bonded Nd-Fe-B magnets

A simple method is introduced to obtain recycled Nd-Fe-B powders from waste bonded Nd-Fe-B bulk magnets. The main difficulty of the recovery of waste MQ bonded Nd-Fe-B magnets is how to remove the epoxy resins between the magnetic particles and the oxide impurities on the surfaces of the waste magnetic powders. Mixed solvents of acetone, Dimethyl Formamide and N-butyl alcohol were used to dissolve the epoxy resins. Oxide impurities were removed using 0.5% acetic acid/acetone solutions. After these treatments, the carbon and oxygen contents were reduced from 21,200 ppm to 9700 ppm, and from 11,007 ppm to 8177 ppm, respectively. Under optimum processing conditions, the recycled magnetic powders possess improved magnetic properties with M-s of 151.5 emu/g, M-r of 98.0 emu/g, H-cj of 7.1 kOe, and (BH)(max) of 13.7 MGOe. These values, compared to the waste magnetic powders, represent increases of 21.2%, 18%, 0 and 34.3%, respectively.