Microstructures And Electrochemical Performances Of (Mg_2.4 Ni) _100-x RE_x(RE= Nd,Sm; X=0²0) 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 capacity 1000mAh/g, abundant resources and lower cost. However, the practical application of Mg₂Ni alloys is prevented by their higher dehydrogenation temperature and poor anti-corrosion ability in KOH solutions. Mg_2.4Ni alloys displays better properties due to the presence of Mg and Mg₂Ni phases. In view of this fact, this paper try to add rare earth elements Nd or Sm into Mg_2.4Ni alloys to improve the hydrogen storage properties.The experimental alloys were (Mg_2.4Ni)100-xREx(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 by REx. The effects of Nd or Sm additive on the microstructures and absorption/desorption properties were discussed. The microstructures were detected by XRD and SEM, electrochemical characteristic by LAND battery tester, electrochemical kinetics properties by electrochemical PARSTAT 2273 and the hydrogen absorption/desorption properties.The XRD and SEM results revealed that the as-cast Mg_2.4Ni alloys with Mg₂Ni phase got multi-phase structure when Nd content increase, such as NdNi, Mg6Ni, Nd2Ni7.And discharge capacity of alloys with Nd got advantagement from Nd0 46.3 mAh/g to Nd20 115.0 mAh/g. For the as-spun alloy, Nd elements added, resulting in the amorphous alloys, and the Nd content in the more amorphous the greater the degree. With the increase of Nd content, the decrease in discharge capacity slightly, but the cycle stability is improved. Nd of the cast and quenched alloys of high rate discharge performance as follows: In no more than 15at% Nd content, the monotonously increasing trend. Impedance quenched alloy are larger than the cast alloy, the diffusion coefficient of the two states the same trend, have reached the maximum at the Nd15.For the as-cast alloys, Sm content increases gradually with the emergence of multi-phase structure, electrochemical capacity monotonically increasing from the Sm0 of 46.3mAh/g increased to Sm20 of 192.9 mAh/g; high rate discharge performance and electrochemical conductance release to the same place at the Sm5 slightly decreased, then gradually increased; polarization current then decreases. The quenched alloys with the addition of Sm element gradually amorphous, and in the Sm10 department have fully amorphous. Discharge capacity decreased with Sm content increasing then 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 hydrogen absorption and desorption were measured, and after hydrogen absorption and desorption, XRD analysis of alloys. Found in the 200 oC, 3 MPa hydrogen volumes within the next 60 min or more in the 3.0at%, Sm10 even up to 3.88%, while the hydrogen Sm5 put the best, 85 min released 35.3% of the total intake volume.