The nanocrystalline and amorphous Mg2Ni-type Mg2–xLaxNi (x=0,0.2) hydrogen storage alloys were synthesized by melt-spinning technique.The as-spun alloy ribbons were obtained.The microstructures of the as-spun ribbons were characterized by X-ray diffraction (XRD),high resolution transmission electronic microscopy (HRTEM) and electron diffraction (ED).The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus,and their electrochemical kinetics were tested by an automatic galvanostatic system.The electrochemical impedance spectrums (EIS) were plotted by an electrochemical workstation (PARSTAT 2273).The hydrogen diffusion coefficients in the alloys were calculated by virtue of potential-step method.The obtained results showed that no amorphous phase was detected in the as-spun La-free alloy,but the as-spun alloys substituted by La held a major amorphous phase,con-firming that the substitution of La for Mg markedly intensified the glass forming ability of the Mg2Ni-type alloy.The substitution of La for Mg notably improved the electrochemical hydrogen storage kinetics of the Mg2Ni-type alloy.Furthermore,the hydrogen storage kinetics of the experimental alloys was evidently ameliorated with the spinning rate growing.
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.
