Development of a Sieverts-type apparatus for the characterization of hydrogen storage materials

While traditional hydrogen storage methods have primarily focused on liquefied or gaseous hydrogen, selected metal hydrides present a promising alternative due to their comparatively low storage pressure and high volumetric hydrogen storage capacities. Characterizing metal hydride-forming materials is a crucial step in advancing hydrogen storage research. For this purpose, a volumetric gas sorption apparatus (Sieverts-type apparatus) was developed, including piping, instrumentation, an automated experimental control program, and a data evaluation script. Material performance was assessed using pressure-composition isotherms (PCI) at various temperatures and resulting thermodynamic data. Validation of the apparatus was carried out using the well-characterized lanthanum pentanickel powder (LaNi_5). Additional studies were performed on powder samples of magnesium and one magnesium-based metal alloy with different manufacturing and activation histories. The PCI curves and formation enthalpy derived from LaNi_5 sorption experiments showed consistency with literature data, confirming the capability of the apparatus to generate reliable research data. Furthermore, the enthalpy and entropy of formation for the magnesium samples were in good agreement with literature values and did not show significant dependence on the activation route. From the experimental data and the resulting PCI curves, further improvement suggestions regarding the apparatus and the experimental procedure are derived.