Magnetic Properties and Stability of Bonded magnets Produced from Zn Metla-sorbed Nd-Fe-B HDDR Powders

摘要

Corrosion resistance and thermal stability of the anisotropic Nd-Fe-B HDDR powders were improved by forming a unifor coating film (thickness=-2 mum) of zinc metal on their surface via the vapor sorption process. Magnetic properties of the resultant Zn metla-sorbed Nd-Fe-B powders were little depressed even after the surface coating and maintained at the high level as same as those of the original Nd-Fe-B powders, viz. (BH)_max = -320 kJ/m~3. Compression-type anisotropic resin-bonded magnets produced from the Zn metal-coated powders gave the superior magnetic performance, B_r=approx 1.0 T, H_cj=approx 1.01 MA/m and (BH)_max=approx 176 kJ/m~3, than MQA-T. Moreover, the Zn metla-sorbed Nd-Fe-B bonded magnets showed excellent corrosion resistance adn thermal stability: The permanent flux loss observed on the mafter aging treatments in air at 80 and 120 deg C for 1000 h was about 4 percent and typical thermal parameters were alpha (B_r)=-0.042 percent/K and beta(H_cj)=-0.52 percent/K.