Polymer-bonded magnets III. Effect of surface modification and particle size on the improved oxidation and corrosion resistance of magnetic rare earth fillers

We studied the effect of surface modification and particle size on the oxid ation and corrosion behavior of neodymium-iron-boron (Nd-Fe-B) magnetic all oy powders by using thermal analysis to accelerate efforts to develop usefu l poLy(phenylene sulfide) bonded Nd-Fe-B magnets. The results indicate that coating the Nd-Fe-B powders with 3 coupling agent provides the required ox idation and corrosion resistance for the targeted processing conditions. Th e coated rare earth powders are thermally and environmentally stable at ele vated temperatures and in a 100% humid environment, where commercial rare e arth alloy magnets are not usable. The coating treatment more significantly affects the small particle powders. A mechanism accounting for the improve d thermal end environmental stability is presented and discussed. Magnetic measurements were performed to verify the thermal analysis results. (C) 200 0 Elsevier Science S.A. All rights reserved.