Fourier-Domain Analysis of Hydriding Kinetics Using Pneumato-Chemical Impedance Spectroscopy

摘要

Analysis of phase transformation processes observed in hydrogen absorbing materials(pure metals, alloys, or compounds) is still a matter of active research. Using pneumato-chemicalimpedance spectroscopy (PIS), it is now possible to analyze the mechanism of hydridingreactions induced by the gas phase. Experimental impedance diagrams, measured on activatedLaNi5in single- and two-phase domains, are reported in this paper. It is shown that their shape ismostly affected by the slope of the isotherm at the measurement point. By considering the detailsof the multistep reaction paths involved in the hydriding reaction, model impedance equationshave been derived for single- and two-phase domains, and fitted to experimental impedancediagrams. The possibility of separately measuring surface and phase transformation resistances,hydrogen diffusion coefficient, and hydrogen solubility in each composition domain is discussed.