Konferans 2020-2029 yılları

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Browsing Konferans 2020-2029 yılları by ORCID "0000-0002-0826-7880"

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    Influence of Different Temperatures on Hydrogen Decrepitation of Scrap Hard Disk Drive NdFeB Magnets
    (Turkish Energy, Nuclear and Mineral Research Agency (TENMAK), 2026-01-15) KAPLAN, Cansu; KAPLAN, Gizem; ÇAKIR, Öznur
    Demand for rare earth elements (REEs) in NdFeB permanent magnets used in wind energy and EV necessitates efficient recycling to address supply chain vulnerabilities and environmental concerns. Hydrogen decrepitation (HD), hydrogen-assisted decrepitation process, offers a promising method for processing end-of-life Hard Disk Drive (HDD) NdFeB magnets by converting them into demagnetised powders while preserving microstructural integrity. This study investigates the impact on hydrogenation temperature (room temperature, 50°C, 75°C) on the recycling process at 4 bar hydrogen pressure and 2 hours. Chemical composition was determined by ICP-OES, oxygen and hydrogen contents by LECO analysis, phase identification by XRD with Rietveld refinement, and microstructure by SEMEDS. Results indicate that reduced temperatures promote hydrogen absorption, diminish oxidation, and produce finer particles characterised by typical intergranular fractures. XRD confirmed the formation of Nd₂Fe₁₄BHₓ phases with decreasing hydrogen content at elevated temperatures, along with an increased presence of Nd₂O₃ due to the exposure of reactive surfaces. According to these results, HD at room temperature under 4 bar is optimal for the effective and sustainable recycling of NdFeB magnets, eliminating the need for further heat treatment.
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    Temperature Effects on Phase Evolution and Particle Morphology in Ce-Rich Commercial NdFeB Magnets During High-Pressure Hydrogen Decrepitation
    (Turkish Energy, Nuclear and Mineral Research Agency (TENMAK), 2026-01-14) BILGIN, Salih; ARIK, M. Nasuh; SARITAS, Senem; ÇAKIR, Öznur
    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.