摘要
The effect of Mn substitution on phase structure,hydrogen hydriding/dehydriding properties(plateau pressure and slope)and reaction heat enthalpy of LaNi_(4.25-x)Al_(0.75)Mn_(x)alloys(x=0,0.25,0.35,0.45,0.55 and 0.65)were studied.The experimental results show that all LaNi_(4.25-x)Al_(0.75)Mn_(x)alloys have single phase and have the same hexagonal structure as that of LaNi5 alloy(CaCu_(5)type,P6/mmm).With increasing Mn substitution content,the cell parameters of LaNi_(4.25-x)Al_(0.75)Mn_(x)alloy greatly increase,but the maximum hydrogen storage capacity and the equilibrium absorption pressure of LaNi_(4.25-x)Al_(0.75)Mn_(x)alloy decrease from 1.38 wt.%to 1.18 wt.%and from 1.61 to 0.0712 MPa,respectively.Moreover,the hydrogen pressure plateau slope factorσincreases from 0.014 to 0.18,but the hysteresis factor is nearly constant.The heat enthalpy absolute value|ΔH_(plat)|increases from 46.7 kJ·mol^(-1)H2 to 56.1 kJ·mol^(-1)H_(2)as the Mn content x increases from 0 to 0.65.
