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

Abstract

Nanostructured Mg–Ni system alloys – Mg 90Ni 10, Mg 80Ni 20, Mg 67Ni 33 (Mg 2Ni), Mg 60Ni 40, Mg 50Ni 50, Mg 40N 60, Mg 33Ni 67 (MgNi 2) and Mg 30Ni 70 were prepared by mechanical alloying (MA) method. Body centered cubic (BCC) structure is obtained in Mg 60Ni 40, Mg 50Ni 50, Mg 40N 60 and Mg 33Ni 67 composition alloys after the milling. Mg 30Ni 70 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. Mg 50Ni 50 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.