Demagnetization followed by remagnetization of waste NdFeB magnet for reuse

Abstract

New recycling process was proposed to reuse the waste NdFeB magnet scrap powder from the manufacturing process of NdFeB magnet and disc from motor of waste washing machine. The feasibility study was carried out to examine demagnetizing followed by remagnetizing the waste NdFeB magnets. The X-ray diffractometer patterns showed that the peaks of Fe were observed and those of NdFeB disappeared with increasing temperature to more than 500°C under the Ar atmosphere. The weight increased more under the air atmosphere than under the Ar atmosphere in TG-DTA test. After the waste NdFeB magnets were demagnetized at 300-500°C under the air and Ar atmospheres, they were remagnetized, and the magnetic power was measured. All remagnetization ratios showed more than 100% except the waste NdFeB magnet demagnetized at 500°C under the air atmosphere. The remagnetization ratio decreased with increasing the demagnetization temperature, and the decrease is faster under the air atmosphere than under the Ar atmosphere, which would result from the metal crystal structure change.