Property enhancement of bonded Nd-Fe-B magnets by composite adhesive design

Bonded neodymium iron boron (Nd-Fe-B) magnets with excellent properties were prepared by using waterborne-epoxy resin/sodium silicate composite binder (W-EP/SS). The results show that this composite binder can endow the bonded magnets with high temperature resistance as well as strong corrosion resistance. In addition, the compressive strength of W-EP/SS bonded magnet is higher than other types of bonded magnets. W-EP/SS composite binder has excellent homogeneity, which can coat the magnetic powders uniformly during mixing and curing, and therefore forms a protective thin film on the surface of the magnet to prevent thermal oxidation under high temperature conditions as well as corrosion during chemical treatments. Moreover, the W-EP/SS composite binder, which combines the toughness of epoxy resin with the rigidity of sodium silicate, endows bonded magnets better mechanical properties. It is attributed to the co-existence of Si-O-Si and C-O-C network structure in the W-EP/SS. Therefore, it is expected that W-EP/SS composite binder will provide a broader application prospects for future bonded magnets. (C) 2020 The Authors. Published by Elsevier Ltd.