Microwave absorption properties of the nano-composite powders recovered from Nd–Fe–B bonded magnet scraps

Abstract Nd–Fe–B bonded magnet scraps were recovered as the nano-composite powders composed of α-Fe, Fe x B and Nd 2 O 3 by a disproportionation method and their electromagnetic wave absorption properties at the GHz range were characterized to recycle them as efficient absorbers. The bonded magnet scraps decomposed to NdH 2 , Fe x B and α-Fe at 873 K for 30–60 min in H 2 , of which NdH 2 was converted to the corresponding fine particles of Nd 2 O 3 by the subsequent oxidation at room temperature for 120 min in air. Resin-bonded discs prepared from the composites powders of α-Fe/Fe x B/Nd 2 O 3 (mean diameter ≅ 20 nm), Fe x B (amorphous) and Nd 2 O 3 particles showed the excellent electromagnetic wave absorption ability in a frequency range of 4.0–6.7 GHz, which shifted to the high GHz region side compared with binary composite ones of α-Fe/rare earth oxide.