Thermodynamics and Hysteresis for Hydrogen Solution and Hydride Formation in Pd-Ni Alloys

Abstract

Pd and its fee substitutional alloys which form hydride phases exhibit hysteresis. If Pd-Ni alloys have been hydrided and then dehydrided a number of times at a moderate temperature, the hysteresis is reduced. The reduction of hysteresis increases with increase of XNi to 0.15 and, if the XNi = 0.15 alloy is hydrided and dehydrided (298 K) a number of times, hysteresis disappears. Hydrogen isotherms have been measured for annealed Pd-Ni alloys from XNi = 0.05 to 0.25 (273 K). These show that the width of the plateau region decreases from XNi = 0 to ≈ 0.15 and then increases again. This trend is not apparent from previous isotherm measurements but it is consistent with the x-ray results available in the literature. Thermodynamic parameters for hydrogen absorption/desorption have been measured in the dilute phase and in the plateau region