Effect of Sm on the cyclic stability of La–Y–Ni-based alloys and their comparison with RE–Mg–Ni-based hydrogen storage alloy

The LaY2Ni9.7Mn0.5Al0.3 and LaSm0.3Y1.7Ni9.7Mn0.5Al0.3 alloys have been synthesized to investigate the effect of Sm partial substitution for Y on the cyclic stability of A2B7-type La–Y–Ni-based alloys. Their cyclic properties were also compared with the A2B7-type (RE0.85Mg0.15)2(NiAl)7 (RE = Rare Earth) alloys. The gas-solid and electrochemical cycle lives were tested. The structural stability, pulverization, and oxidation/corrosion performances were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical methods. The partial substitution of Sm for Y improves anti-corrosion and anti-pulverization performances, thereby increasing the cycle life of A2B7-type La–Y–Ni-based hydrogen storage alloys. The A2B7-type RE–Y–Ni-based alloys exhibit better crystal structure stability, but the gas-solid and electrochemical cyclic stability is worse than A2B7-type (RE0.85Mg0.15)2(NiAl)7 alloys due to easier pulverization of particles and the oxidation of Y elements.