Coercivity enhancement of recycled Nd-Fe-B sintered magnets by grain boundary diffusion with DyH3 nano-particles

The waste VCM magnets were disassembled from hard disk. After removing the coating of nickel by electrochemical method, the waste VCM magnets were recycled by grain boundary diffusion with DyH3 nano-particles. Compared to that of the original magnet, the coercivity of recycled magnets increases by 11.81 kOe, while the remanence keeps almost invariant. investigation shows that Dy is preferentially enriched as (Nd,Dy)(2)Fe14B phase in the surface region of the Nd2Fe14B matrix grains indicated by the remarkable enhancement of the magneto-crystalline anisotropy field of the magnet. As a result, the magnet diffused with a small amount of DyH3 nano-particles possesses enhanced coercivity without remarkably sacrificing its magnetization. (C) 2015 Elsevier B.V. All rights reserved.