摘要
The influence of elemental composition on the crystal structure, hydrogen storage and electrochemical properties for Mg-contain- ing alloys was investigated. As La/Mg ratio decreased, the slight change of Ni content was detected. XRD results indicated that these alloys were composed of LaNi5 and Mg-containing phases. The lattice parameters of Mg-containing phases decreased. Meanwhile, the mass fraction of Mg-containing phases varied with the change of La/Mg and Ni. The hydrogen storage capacity reached -1.6 wt.% for La/Mg ≥ 3：1 and de- creased to -0.71 wt.% for La/Mg=1. Two hydrogen absorption processes were observed because of the existence of the multiphases for La/Mg ≥ 3：1. With decreasing La/Mg ratio, the equilibrium pressure rose due to the shrinkage of the lattice parameter. Meanwhile, one hy- drogen absorption process was obviously present. The discharge capacity of these as-cast alloys was higher, but the cyclic stability was poor for La/Mg ≥ 3：1 due to the partial amorphisation. It was better for La/Mg≤2 although the discharge capacity was lower. The polarization re- sistance increased, contrarily the exchange current density decreased with decreasing Mg content.
The influence of elemental composition on the crystal structure, hydrogen storage and electrochemical properties for Mg-contain- ing alloys was investigated. As La/Mg ratio decreased, the slight change of Ni content was detected. XRD results indicated that these alloys were composed of LaNi5 and Mg-containing phases. The lattice parameters of Mg-containing phases decreased. Meanwhile, the mass fraction of Mg-containing phases varied with the change of La/Mg and Ni. The hydrogen storage capacity reached -1.6 wt.% for La/Mg ≥ 3：1 and de- creased to -0.71 wt.% for La/Mg=1. Two hydrogen absorption processes were observed because of the existence of the multiphases for La/Mg ≥ 3：1. With decreasing La/Mg ratio, the equilibrium pressure rose due to the shrinkage of the lattice parameter. Meanwhile, one hy- drogen absorption process was obviously present. The discharge capacity of these as-cast alloys was higher, but the cyclic stability was poor for La/Mg ≥ 3：1 due to the partial amorphisation. It was better for La/Mg≤2 although the discharge capacity was lower. The polarization re- sistance increased, contrarily the exchange current density decreased with decreasing Mg content.
基金
Project supported by National Natural Science Foundation of China (50901030)
Doctoral Science Foundation of Hebei Normal University (L2007B12)
