Hydriding/dehydriding behavior of Mg-Ni systems

To fabricate high efficiency, light-weight hydrogen storage materials in an economical way, a hydrogen induced mechanical alloying (HIMA) and an advanced melting/casting process were employed in a Mg-Ni hydride alloy system. The hydrogenation properties of the synthesized or/and cast specimen were evaluated with an automatic PCI (pressure-composition-isotherm) apparatus and TGA (thermo-gravimetric analysis). To produce Mg2NiHx. intermetallics in an economical way, especially, Mg and Ni chips were mechanically alloyed under 2 MPa of hydrogen atmosphere by planetary ball milling. Adopting 66:1 BCR (ball to chips mass ratio) for HIMA process, fully hydrogenated alloys were obtained after 96 firs of milling, resulting in total hydrogen content of 2.25 mass%. The dehydriding temperature was found to be 453 similar to 493 K. The composite phase obtained after 96 hrs of HIMA appeared to be composed of nanocrystalline and amorphous phases, of which structure was believed to enhance hydriding and dehydriding kinetics. The condition of BCR seemed to affect strongly the synthesis of the Mg2NiHx. In addition, the minimized Ni content specimens in Mg-Ni hydrides were successfully manufactured by Rotation-Cylinder method (RCM) without any heat treatments.