Preparation and hydrogen storage properties of nanostructured Mg-Ni BCC alloys

Nanostructured Mg-Ni system alloys - Mg90Ni10, Mg80Ni20, Mg67Ni33 (Mg2Ni), Mg60Ni40, Mg50Ni50, Mg40N60, Mg33Ni67 (MgNi2) and Mg30Ni70 were prepared by mechanical alloying (MA) method. Body centered cubic (BCC) structure is obtained in Mg60Ni40, Mg50Ni50, Mg40N60 and Mg33Ni67 composition alloys after the milling. Mg30Ni70 alloy shows face centered cubic (FCC) structure. The BCC and FCC structures are confirmed by electron diffraction patterns of the samples. From the X-ray diffraction (XRD) patterns and transmission electron microscope (TEM) image observation results, the crystallite size of the alloys is calculated into nanometer scale. Hydrogen absorption kinetics and storage properties of these alloys were studied by hydrogen absorption rate and pressure-composition isotherm (PCT) measurements at 373 K. Mg50Ni50 BCC alloy shows the best kinetics and absorption efficiency among these Mg-Ni system alloys. It can absorb 1.85 mass% hydrogen at 373 K in a hydrogen pressure up to 7 MPa without any activation process.