新型稀土镁基贮氢电极合金的结构与性能

系统研究了La0．7Mg0．3(Ni0．85Co0.15)x(x=2．5，3．0，3．5，4．0，4．5，5．0)贮氢电极合金的结构和储氢性能．该类型合金由(La，Mg)Ni3相(PuNi3型结构)和LaNi5相(CaCu5型结构)组成，两相的a轴参数和晶胞体积都随着x值的增大而减小．(La，Mg)Ni3相的丰度先从x=2．5时的48．4％增加到x=3．5时的78．2％，然后又减小到x=5．0时的12．2％，而LaNi5相的丰度在x=2．5-3．5时基本保持不变(-20％)，在x=4．0时突然增加到71.9％．合金的吸氢量从x=2．5时的0．86％(质量分数)增加到x=3．5时的1．50％然后又减小到x=5．0时的1．19％．合金的放氢平台压力在x=2．5-3．5时保持基本不变(-65．9kPa)，然后逐渐增加到x=5．0时的0．30MPa．随着x的增加，吸放氢过程的滞后效应先增大后减小，而合金的放氢平台变得更加平坦．

Structure and hydrogen storage properties of the rare-earth Mg-based hydrogen storage electrode alloys

The structure and absorption/desorption properties of the La0.7 Mg0.3(Ni0.85Co0.15)x (x = 2.5, 3.0, 3.5, 4.0, 4.5, 5.0) hydrogen storage electrode alloys were studied systematically. All these alloys consisted of (La,Mg)Ni3 phase and LaNi5 phase, and their a-axes and the unit cell volumes decrease with increasing x. Meanwhile, the (La,Mg)Ni3 phase content increases from 48.4% (x=2.5) to 78.2% (x=3.5) and then decreases to 12.2% (x=5.0). However, the LaNi5 phase content first maintains unchanged (-20%) and then increases to 71.9% with increasing x up to 4.0. The hydrogen storage capacity increases from 0.86% (mass fraction, x=2.5) to 1.50% (x=3.5) and then decreases to 1.19% (x=5.0) with increasing x. Furthermore, the plateau becomes flatter and the plateau pressure first maintains almost unchanged and then increases with increasing x from 2.5 to 5.0. The hysteresis of the P-C isotherms increases first and then decreases with increasing x.