SYNTHESIS, CHARACTERIZATION, AND REACTION KINETICS OF NANO-STRUCTURED Mg-V-Ni COMPOSITES FOR SOLID-STATE HYDROGEN STORAGE

摘要

In this study, we have developed and characterized various Mg-V-Ni compositions with respect to hydrogen storage. The study was conducted using magnesium as the base material with additions of 5 atomic% of nickel and vanadium in the range of 2.5-10 atomic%. The various compositions were synthesized using high-energy ball milling with different milling times. The compositions were characterized using scanning electron microscopy, energy-dispersive X-ray spectrometry, and X-ray diffraction, and the hydriding-dehydriding characteristics studied using the Sievert method. It was found that the maximum reversible hydrogen storage capacity in the Mg-V-Ni system is 5.71 mass %. Furthermore, it was found that 6 mass% of hydrogen is absorbed within the first 5 min at 210℃. This lowered hydriding temperature is associated with the presence of vanadium as a catalyst. The hydriding enthalpy of the optimized (highest storage capacity) Mg-V-Ni composition has been measured using differential scanning calorimetry as 79.15 ± 3.56 kJ/mol of H_2 and the hydriding entropy was obtained as 141.18 ± 6.35 J/mol of H_2 K.