Effective recycling for Nd-Fe-B sintered magnet scraps

Rare earth sintered magnet scrap powders (Nd₂Fe₁₄B sludge) were melted and solidified with Si or Ti to produce Fe-based intermetallic compounds and coproducts of rare-earth-oxide slugs. After separating them, oxygen content measurements and energy dispersive X-ray analysis (EDX) observations demonstrated that about 60% of the rare earth components in the raw scrap powders were efficiently collected as rare-earth-oxide slugs during the melting process. The former compounds were ground into fine powders and some of them were heated at 100-250 °C for 1-12 h in air. The epoxy resin composites with 80-83 wt% of these powders showed good microwave absorption properties at GHz range. For Fe-Si (18.5 at% Si) and heat-treated (250 °C, 3 h) Laves phase Fe₂Ti intermetallic compound, the minimum reflection loss (RL) values of -38.8 and -39.4 dB were observed at 3.3 and 12.3 GHz, respectively.