Production of anisotropic injection moulded NdFeB magnets from end-of-life sintered magnets

Farr, Matthew (2018). Production of anisotropic injection moulded NdFeB magnets from end-of-life sintered magnets. University of Birmingham. Ph.D.

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In this work, the hydrogenation-disproportionation-desorption-recombination (HDDR) processing conditions were optimised for scrap sintered NdFeB magnets from hard disk drives (HDDs). The HDDR process was then performed on scrap sintered NdFeB magnets, which were separated from HDD assemblies using hydrogen, on a large scale in order to produce anisotropic NdFeB alloy powder. The HDDR powder was then used to produce injection moulded magnets on pilot scale equipment (5 kg load) at Kolektor Magnet Technology GmbH, Germany. Sintered NdFeB magnets were separated from cropped hard disk drive corners as a hydrogenated powder, before being purified to remove any contaminants. The material was then HDDR processed using parameters optimised for this material (900 °C and 1200 mbar). The powder was compounded with polyamide 12 at a 90/10 ratio of HDDR powder to binder before injection moulding in a 500 mT field to form bonded magnets. The best bonded magnets produced had a remanence of 0.64 T, a coercivity of 623 kA/m and a BHmax of 61.7kJ/m\(^3\). Despite the mixed composition input feed, there was very little variation in the magnetic properties between 5 randomly selected magnets where a standard deviation for BHmax of 0.34 kJ/m\(^3\) was observed.

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 > TN Mining engineering. Metallurgy


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