The use of hydrogen to extract NdFeB magnets and REES from assemblies

Jönsson, Christian Tobias (2018). The use of hydrogen to extract NdFeB magnets and REES from assemblies. University of Birmingham. Ph.D.

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Recycling of end-of-life NdFeB magnet could provide a sustainable supply of the critical elements Nd and Dy. These are found in waste streams of electronic and electric equipment (WEEE) and drive motors of electric vehicles. Hard disk drives have been identified as an ideal recycling candidate, and a promising process has been developed at the University of Birmingham, called HPMS, which uses hydrogen to extract NdFeB in the form of a demagnetized hydrogenated powder. This thesis has identified loudspeakers from laptops and flat screens to have a good recycling potential. They are all coated with Zn meaning that HPMS should be fully applicable. The HPMS process was then successfully applied to large automotive rotors, extracting more than 95% of the NdFeB. However, it was shown that rotor magnets react slower due to the higher Dy content and lower REE content, meaning that higher pressures might be needed. The hydrogenated powder was disproportionated at high temperature in hydrogen to create large spheres of NdH2 in the Fe matrix, opening up for physical separation of NdH2 from NdFeB. The oxidation of various hydrogen-processed powders was also studied, showing that hydrogenation is beneficial for roasting which is used in the pyrometallurgical recycling flowsheet.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Metallurgy and Materials
Funders: None/not applicable
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
T Technology > TP Chemical technology


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