Browsing by Author "Zeng, G"

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    Hydrogen storage performance and phase transformations in as-cast and extruded Mg-Ni-Gd-Y-Zn-Cu alloys
    (Elsevier, 2023-04-18) Yao, H; Zeng, G; Tan, XF; Gu, QF; Nogita, K; Guo, J; Li, Q
    Thermal-mechanical processing of magnesium-based materials is an effective method to tailor the hydrogen storage performance. In this study, Mg-Ni-Gd-Y-Zn-Cu alloys were prepared by Direct Chill (DC) casting, with and without extrusion process. The influences of microstructure evolution, introduced by DC casting and thermal-mechanical processing, on the hydrogen storage performance of Mg-Ni-Gd-Y-Zn-Cu alloys were comprehensively explored, using analytical electron microscopy and in-situ synchrotron powder X-ray diffraction. The result shows that the extruded alloy yields higher hydrogen absorption capacity and faster hydrogen ab/desorption kinetics. As subjected to extrusion processing, the α-Mg grains in the microstructure were significantly refined and a large number of 14H type long-period stacking ordered (LPSO) phases appeared on the α-Mg matrix. After activation, there were more nanosized Gd hydride/Mg2Ni intermetallics and finer chips. These modifications synergistically enhance the hydrogen storage properties. The findings have implications for the alloy design and manufacturing of magnesium-based hydrogen storage materials with the advantages of rapid mass production and anti-oxidation. © 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
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    Na-modified cast hypo-eutectic Mg–Mg2Si alloys for solid-state hydrogen storage
    (Elsevier B. V., 2022-08-01) Tan, XF; Kim, MJ; Gu, QF; Pinzon Piraquive, J; Zeng, G; McDonald, SD; Nogita, K
    Mg2Si is a promising catalyst for Mg-based H2 storage materials due to its low cost, light weight, and non-toxic properties. This study investigates the effects of Na in hypo-eutectic Mg-1wt.%Si alloys for H2 storage applications. The addition of trace amounts of Na is vital in improving the H2 sorption kinetics, achieving a H2 storage capacity of 6.72 wt.% H at 350 °C under 2 MPa H2, compared to 0.31 wt.% H in the non-Na added alloy. The hydrogen sorption mechanisms were analysed with Johnson-Mehl-Avrami-Kolmogorov models. It was identified that Na affects the surface of the Mg alloys, forming porous Na2O and NaOH in addition to MgO, facilitating the diffusion of H2. Finally, in-situ synchrotron powder X-ray diffraction showed the Mg2Si catalyst is stable during the H2 sorption reactions. This result demonstrates the potential use of Mg–Mg2Si casting alloys for large scale hydrogen storage and transportation applications. © 2022 Elsevier B.V