Hydrogen isotherms for annealed, un-activated LaNi5 (273–333 K)

Abstract

Hydrogen absorption isotherms (273–333K) have been measured for closely stoichiometric, annealed, un-activated LaNi5, i.e., a virgin un-activated LaNi5 sample was employed at each temperature. This is the first time that such isotherms have been measured for annealed, un-activated LaNi5 at such low temperatures ⩽298K. After measurement of the initial absorption isotherms, the second absorption and desorption isotherms have been measured at each temperature. Van’t Hoff plots have been made from these absorption and desorption plateau pressure data and, from these, ΔHplat values have been obtained for the initial and subsequent absorption and desorption reactions. The ∣ΔHplat∣ determined from the van’t Hoff plot is smaller for the initial isotherm for the annealed, un-activated form of LaNi5 than it is for activated LaNi5.