The Effect of Ni Impurities on HDDR Processing of Scrap Sintered NdFeB Magnets

Richard Sheridan, Vicky Mann, Allan Walton, Ivor Harris, Alexander Campbell, Matthew Farr, Andrew Bradshaw

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The Magnetic Materials Group (MMG) at the University of Birmingham have demonstrated previously that it is possible to use hydrogen to extract sintered NdFeB magnets from electronic waste [1] and to re-use the extracted alloy powders to form both sintered and resin bonded magnets [2,3,4]. One of the challenges in using scrap NdFeB magnets is that this material is likely to contain a number of impurities, for example, nickel from the protective coating. In this paper the effects of Ni contamination on the magnetic properties of HDDR NdFeB powders has been investigated. Nickel powder was blended with hydrogenated NdFeB powder in varying fractions from 1wt%-5wt% prior to processing using a modified version of the HDDR processing route developed by Sheridan et al (2012)[2] to produce anisotropic material. It has been shown that powders can be produced from voice coil magnets (VCM), which exhibit significant anisotropy and the anisotropy of the HDDR powder was shown to diminish with increasing Ni content. The Ni additions have been shown to lower the pressure at which the disproportionation reaction starts and ends, which, under the current conditions, could lead to over processing of the material.
Original languageEnglish
Title of host publicationProceedings of the 23rd International Workshop on Rare Earth Permanent Magnets and their Applications
Place of PublicationAnnapolis, USA
Number of pages3
Publication statusPublished - Aug 2014


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