Yaqin Li

Hydrogen storage thermodynamic and kinetic characteristics of PrMg12-type alloys synthesized by mechanical milling

To improve the hydrogen storage performance of PrMg12-type alloys, Ni was adopted to replace partially Mg in the alloys. The PrMg11Ni+x wt. % Ni (x = 100, 200) alloys were prepared via mechanical milling. The phase structures and morphology of the experimental alloys were investigated by X-ray diffraction and transmission electron microscopy. The results show that increasing milling time and Ni content accelerate the formation of nanocrystalline and amorphous structure. The gaseous hydrogen storage properties of the experimental alloys were determined by differential scanning calorimetry (DSC) and Sievert apparatus. In addition, increasing milling time makes the hydrogenation rates of the alloys augment firstly and decline subsequently and the dehydrogenation rate always increases. The maximum capacity is 5.572 wt. % for the x = 100 alloy and 5.829 wt. % for the x = 200 alloy, respectively. The enthalpy change (ΔH), entropy change (ΔS) and the dehydrogenation activation energy (

Structures and Electrochemical Performances of As-spun RE-Mg-Ni-Mn-based Alloys Applied to Ni-MH Battery

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Structures and electrochemical hydrogen storage properties of melt-spun RE-Mg–Ni–Co–Al alloys

) markedly lower with increasing the milling time and the Ni content due to the generation of nanocrystalline and amorphous structure.

Hydrogen storage properties of nanocrystalline and amorphous Pr–Mg–Ni-based alloys synthesized by mechanical milling

The La-Mg-Ni-Mn-based AB2-type La1-xCexMgNi3.5Mn0.5 (x = 0, 0.1, 0.2, 0.3, and 0.4) alloys were fabricated by melt spinning technology. The effects of Ce content on the structures and electrochemical hydrogen storage performances of the alloys were studied systematically. The XRD and SEM analyses proved that the experimental alloys consist of a major phase LaMgNi4 and a secondary phase LaNi5. The variation of Ce content causes an obvious change in the phase abundance of the alloys without changing the phase composition. Namely, with the increase of Ce content, the LaMgNi4 phase augments and the LaNi5 phase declines. The lattice constants and cell volumes of the alloys clearly shrink with increasing Ce content. Moreover, the Ce substitution for La results in the grains of the alloys clearly refined. The electrochemical tests showed that the substitution of Ce for La obviously improves the cycle stability of the as-spun alloys. The analyses on the capacity degradation mechanism demonstrate that the improvement can be attributed to the ameliorated anti-corrosion and anti-oxidation ability originating from substituting partial La with Ce. The as-spun alloys exhibit excellent activation capability, reaching the maximum discharge capacities just at the first cycling without any activation treatment. The substitution of Ce for La evidently improves the discharge potential characteristics of the as-spun alloys. The discharge capacity of the alloys first increases and then decreases with growing Ce content. Furthermore, a similar trend also exists in the electrochemical kinetics of the alloys, including the high rate discharge ability (HRD), hydrogen diffusion coefficient (D), limiting current density (IL) and charge transfer rate.