HOW TO MEASURE PRESSURE-CONCENTRATION-ISOTHERMS REPRESENTATIVE FOR TECHNICAL APPLICATIONS

Pressure-concentration-isotherms (PCI) are one of the most important m aterial characteristics for the design of metal hydride devices. Exper iments show that the results obtained depend strongly on the experimen tal method and the measurement parameters employed. The standard PCI m easuring method is static. The few dynamic PCI presented in the litera ture show a dependence on the hydrogen mass flow rate and generally ha ve a greater hysteresis. PCI for Mg(Ni) and LaNi4.7Al0.3, measured bot h statically and dynamically, are presented, and the most representati ve methods for measuring PCI with respect to specific practical applic ations are discussed. The investigations have shown that there is no i ntrinsic difference between dynamic and static PCI. However, the resul ts depend on different experimental variables like mass flow rate and pressure non-uniformities, respectively.