Effects of Substituting Ni with Mn on Structure and Hydrogen Storage Characteristics of as-Spun Mg<sub>2</sub>Ni-Type Alloys

Abstract

A partial substitution of Ni by Mn has been implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys. The nanocrystalline and amorphous Mg2Ni-type Mg20Ni10-xMnx (x = 0, 1, 2, 3, 4) alloys were synthesized by the melt-spinning technique. The structures of the as-cast and spun alloys were studied by x-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). The hydrogen absorption and desorption kinetics of the alloys were measured by using an automatically controlled Sieverts apparatus. The results show that the as-spun Mn-free alloy holds typical nanocrystalline structure, whereas the as-spun containing Mn alloys display a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass forming of the Mg2Ni-type alloy. The hydrogen absorption capacity of the alloys first increases and then decreases with the rising of Mn content, but the hydrogen desorption capacity of the alloys grows with the increasing of Mn content.