Hydriding and dehydriding kinetics of nanocrystalline and amorphous Mg2Ni1-xMnx(x=0-0.4) alloys prepared by melt spinning

A partial substitution of Ni by Mn was implemented in order to improve the hydriding and dehydriding kinetics of the Mg2Ni-type alloys.The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xMnx(x=0,0.1,0.2,0.3,0.4) alloys were synthesized by the melt-spinning technique.The structures of the as-cast and spun alloys were studied by X-ray diffractometry(XRD),scanning electron microscopy(SEM) and high resolution transmission electron microscopy(HRTEM).The hydrogen absorption and desorption kinetics of the alloys were measured with an automatically controlled Sieverts apparatus.The results show that the as-spun Mn-free alloy holds a typical nanocrystalline structure,whereas the as-spun alloys containing Mn display a nanocrystalline and amorphous structure,confirming that the substitution of Mn for Ni intensifies the glass forming ability of the Mg2Ni-type alloy.The hydrogen absorption and desorption capacities and kinetics of the alloys increase with increasing the spinning rate,for which the nanocrystalline and amorphous structure produced by the melt spinning is mainly responsible.The substitution of Mn for Ni evidently improves the hydrogen desorption performance.The hydrogen desorption capacities of the as-cast and spun alloys rise with the increase in the percentage of Mn substitution.