Mg3Cd: A model alloy for studying the destabilization of magnesium hydride |
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Authors: | V.M. Skripnyuk E. Rabkin |
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Affiliation: | Department of Materials Engineering, TECHNION – Israel Institute of Technology, 32000 Haifa, Israel |
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Abstract: | We prepared an ordered Mg3Cd alloy by high energy ball milling of elemental powders. The synthesized alloy exhibited good hydrogenation kinetics and reversibly absorbed about 2.8 wt. % of hydrogen. The temperature dependence of hydrogenation kinetics of the alloy measured in the range of temperatures covering the order-disorder phase transformations in the Mg3Cd and MgCd phases did not exhibit any anomalies and could be fitted with a single Arrhenius line. The measured apparent activation energy (69 ± 2 kJ/mol) hinted that hydrogenation process was controlled by diffusion of Cd in metallic phase. The pressure-composition isotherms exhibited negligible pressure hysteresis and sloping pressure plateau. Based on microstructural evidence obtained with the aid of X-ray diffraction and scanning electron microscopy, we built a thermodynamic model predicting the plateau hydrogen pressure for partially hydrogenated alloy. The predictions of the model were in a good agreement with the experimental data. Finally, we discussed the origins and the growth mechanisms of Cd whiskers observed in the alloys after full hydrogenation cycle. |
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Keywords: | Magnesium alloys Hydrogen storage properties Hydride destabilization High energy ball milling Thermodynamics of alloys |
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