Effect of Hydrogen Decrepitation Temperature and Milling on Crystal Structure and Particle Size of End-of-Life NdFeB Magnets
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Date
2024-08-16
Journal Title
Journal ISSN
Volume Title
Publisher
Türkiye Enerji, Nükleer ve Maden Araştırma Kurumu (TENMAK)
Abstract
Recycling NdFeB magnets from secondary sources is a vital strategy for addressing the
supply risks associated with critical raw materials such as Neodymium (Nd) and Dysprosium
(Dy). Among various recycling methods, Hydrogen Decrepitation (HD) is recognized as an
efficient process for recovering the end-of-life (EoL) magnets. This study aims to examine the
impact of different HD temperatures on the crystal structure and particle size of milled HDNdFeB. End-of-Life (EoL) NdFeB magnets were subjected to HD process at ambient
pressures and varying temperatures between 30°C to 200°C. It was observed that increasing
the HD temperature up to 50°C exhibits a shift to lower 2θ angles in XRD crystal patterns
while further increasing the HD temperature resulted in reversed behavior. The optimum HD
process, according to the XRD results, showed 92.7% Nd₂Fe₁₄BH (Neodymium Iron Boride
Hydride) along with some oxide phases.
It was revealed that following milling of the optimum HD powders, the crystallite size
decreased from 12.512 Å to 302 Å and this reduction is accompanied by a dramatic shift to
higher angles. Overall, the milling resulted in a particle size distribution of 10µm (Dv50)