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

摘要

Nd-Fe-B bonded magnet scraps were recovered as the nano-composite powders composed of a-Fe, Fe,B and Nd_2O_3 by a disproportionation method and their electromagnetic wave absorption properties at the GHz range were characterized to recycle them as efficient absorbers. The Donded magnet scraps decomposed to NdH_2, Fe_xB and a-Fe at 873 K for 30-60 min in H_2, of which NdH_2 was converted to the corresponding fine particles of Nd_2O_3 by the subsequent oxidation at room temperature for 120 min in air. Resin-bonded discs prepared from the composites Dowders of a-Fe/Fe_x-B/Nd_20_3 (mean diameter = 20 nm), FeTB (amorphous) and Nd203 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 x-Fe/rare earth oxide.