Temperature Effects on Phase Evolution and Particle Morphology in Ce-Rich Commercial NdFeB Magnets During High-Pressure Hydrogen Decrepitation
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Date
2026-01-14
Journal Title
Journal ISSN
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Publisher
Turkish Energy, Nuclear and Mineral Research Agency (TENMAK)
Abstract
NdFeB magnets are essential to clean energy and advanced technological applications due to their superior magnetic properties. However, the availability
of rare earth elements is susceptible to geopolitical and environmental challenges. The recycling of NdFeB permanent magnets from secondary sources
represents a strategic approach to mitigate this supply risks associated with critical raw materials, particularly Neodymium (Nd) and Dysprosium (Dy).
Among the available recycling techniques, Hydrogen Decrepitation (HD) has demonstrated significant potential for the efficient recovery of these
elements from commercial magnets. This study investigates the effect of temperature during high pressure hydrogen decrepitation on the structural,
microstructural, and compositional evolution of a commercial NdFeB magnet with relatively high Ce content, which is confirmed by inductively coupled
plasma (ICP-OES) analysis provided baseline compositional data for the starting material. Experiments were performed at 9 bar hydrogen pressure under
constant conditions of time, with three processing temperatures investigated (25 °C, 50 °C, and 75 °C). Scanning electron microscopy (SEM) of the initial
magnet illustrated Ce-rich phases, while X-ray diffraction (XRD) confirmed the presence of CeFe2. According to XRD results, main RE2Fe14B phase
transformed RE2Fe14BHx hydride phase after hydrogenation process. However, the CeFe2 peaks disappeared, indicating amorph phase transformation. In
addition to hydride phase and CeFe2 phase, the presence Nd2O3 phase was detected. LECO elemental analysis was performed to quantify the amount of
the oxygen and hydrogen inside hydrogenated powders. These results confirm the presence of oxide and hydrides with different amount. The results
demonstrated that powders processed at 75 °C retained higher oxygen levels compared to those treated at 25 °C and 50 °C. This behaviour is attributed to
less efficient hydrogen desorption and increased surface oxidation caused by extensive fragmentation. Furthermore, higher processing temperatures
produced more agglomerated morphologies with limited cracking, lowering surface reactivity. Overall, the study highlights the effect of temperature on
particle morphology, particle fragmentation, and oxidation behaviour during HD. These insights provide valuable guidance for the optimization of NdFeB
magnet recycling and reprocessing strategies.
Description
Keywords
NdFeB magnets, hydrogen decrepitation, recycling