Microstructures And Electrochemical Performances Of (Mg_2.4Ni)_100-xRE_x（RE=Nd,Sm;x=0～20） Alloys Prepared By Casting And Rapid Quenching

Mg2Ni hydrogen storage alloys are considered as one of the most promising candidates,because of their high theory discharge capacity1000mAh/g, abundant resources and lower cost.However, the practical application of Mg2Ni alloys is prevented by their higher dehydrogenationtemperature and poor anti-corrosion ability in KOH solutions. Mg_2.4Ni alloys displays betterproperties due to the presence of Mg and Mg2Ni phases. In view of this fact, this paper try to addrare earth elements Nd or Sm into Mg_2.4Ni alloys to improve the hydrogen storage properties.The experimental alloys were (Mg_2.4Ni)_100-xRE_x（RE=Nd, Sm; x=0,5,10,15,20） include the as-cast and quenched alloys. Corresponding with Nd or Sm content x, the alloys were represented byREx. The effects of Nd or Sm additive on the microstructures and absorption/desorption propertieswere discussed. The microstructures were detected by XRD and SEM, electrochemicalcharacteristic by LAND battery tester, electrochemical kinetics properties by electrochemicalPARSTAT2273and the hydrogen absorption/desorption properties.The XRD and SEM results revealed that the as-cast Mg_2.4Ni alloys with Mg2Ni phase gotmulti-phase structure when Nd content increase, such as NdNi, Mg₆Ni, Nd₂Ni₇.And dischargecapacity of alloys with Nd got advantagement from Nd046.3mAh/g to Nd20115.0mAh/g. For theas-spun alloy, Nd elements added, resulting in the amorphous alloys, and the Nd content in the moreamorphous the greater the degree. With the increase of Nd content, the decrease in dischargecapacity slightly, but the cycle stability is improved. Nd of the cast and quenched alloys of high ratedischarge performance as follows: In no more than15at%Nd content, the monotonously increasingtrend. Impedance quenched alloy are larger than the cast alloy, the diffusion coefficient of the twostates the same trend, have reached the maximum at the Nd15.For the as-cast alloys, Sm content increases gradually with the emergence of multi-phasestructure, electrochemical capacity monotonically increasing from the Sm0of46.3mAh/g increasedto Sm20of192.9mAh/g; high rate discharge performance and electrochemical conductance releaseto the same place at the Sm5slightly decreased, then gradually increased; polarization current thendecreases. The quenched alloys with the addition of Sm element gradually amorphous, and in theSm10department have fully amorphous. Discharge capacity decreased with Sm content increasingthen increased, and the high rate and hydrogen diffusion coefficient is a monotonically increasing.Finally, the relatively good performance of all aspects of cast alloy Sm added gaseous hydrogenabsorption and desorption were measured, and after hydrogen absorption and desorption, XRD analysis of alloys. Found in the200oC,3MPa hydrogen volumes within the next60min or more inthe3.0at%, Sm10even up to3.88%, while the hydrogen Sm5put the best,85min released35.3%ofthe total intake volume.