Novel temperature-driven technique to characterize hydrogen sorption properties under vacuum conditions: Method development, experimental setup, and demonstration on the AB5-type metal hydride LaNi4.1Al0.52Mn0.38

Abstract

In this study, a modified temperature-controlled sorption characterization technique based on a Sieverts’ apparatus is presented. The main characteristic of the developed method is the hydrogen mass being constant in the system over individual measurement runs while the thermochemical reaction is controlled by the sample temperature. This allows the sorption properties to be measured in vacuum – even down to high vacuum - without the need for large capturing volumes provided. The method itself, the correspondingly built test rig as well as the measurement procedure are discussed in detail. Sources of uncertainty are discussed and evaluated. By performing reference measurements of the absorption and desorption equilibria of the AB5-type alloy LaNi4.1Al0.52Mn0.38, the method is validated and the corresponding results are demonstrated for the first time. Extensive measurements are performed and complete pressure-composition-isotherms are presented along with repeat measurements series to confirm the results of the novel technique. The obtained PCI data are compared with pressure-concentration isotherms from the literature to validate the measurement method and system. The primary equilibrium data in this work are in very good agreement with both the repeat measurements and the comparison with literature data. It can be shown that the method as well as the experimental design are valid and capable of providing accurate measurements of hydrogen sorption behavior.