Hydrogen absorption kinetics and structural properties of Mg85Ni10Ca5 and Mg90Ni10

Mg85Ni10Ca5 and Mg90Ni10 were prepared by melting mixtures of the elements in mild steel crucibles and pouring them into copper molds. Hydrogen absorption kinetics and structural properties of the alloys were characterized by the volumetric method using a Sievert's apparatus, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size of Mg in Mg85Ni10Ca5, which is evaluated by XRD peak broadening, is about 50% smaller than that in Mg90Ni10. In addition, the nanometer-scale structure composed of Mg, Mg2Ni, Mg2Ca was observed in Mg85Ni10Ca5. Mg85Ni10Ca5 shows better hydrogen absorption kinetics than Mg90Ni10 in the temperature range of room temperature to 573 K. The better absorption kinetics of Mg85Ni10Ca5 is mainly attributed to the nanometer-scale structure.