Mathematical models for the P–C–T characterization of hydrogen absorbing alloys

This paper presents measured P–C isotherms of an AB5-type alloy (LmNi4.91Sn0.15) and an AB2 alloy (Ti0.99Zr0.01V0.43Fe0.09Cr0.05Mn1.5). The results are compared with the most extended P–C–T models from the literature; the Zhou model, the Lacher–Lototsky model, and the polynomial fitting method. This article presents an overview of the existing models and provides interesting information on their applicability for new metal hydride powders. An extension of the Zhou model has been developed in order to account for the smooth transitions which take place between different phase regions. The best fitting has been obtained with the Zhou model and with the polynomial fitting method. However, the Zhou model presents the main advantage of providing important thermodynamic parameters, and it can be used for the calculation of both the pressure and metal hydride concentration.