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

Analysis of phase transformation processes observed in hydrogen absorbing materials (pure metals, alloys, or compounds) is still a matter of active research. Using pneumato-chemical impedance spectroscopy (PIS), it is now possible to analyze the mechanism of hydriding reactions induced by the gas phase. Experimental impedance diagrams, measured on activated LaNi5 in single- and two-phase domains, are reported in this paper. It is shown that their shape is mostly affected by the slope of the isotherm at the measurement point. By considering the details of the multistep reaction paths involved in the hydriding reaction, model impedance equations have been derived for single- and two-phase domains, and fitted to experimental impedance diagrams. The possibility of separately measuring surface and phase transformation resistances, hydrogen diffusion coefficient, and hydrogen solubility in each composition domain is discussed.

Pressure-Composition-Isotherm Behavior of Partially Remelted Magnesium Alloys

Partially Remelted Mg alloys focused only to aspect of semi liquid forming until now. In presents study, for the purpose of proposition as economic lightweight hydrogen absorbing materials, the hydrogenation properties of pressure-composition-isotherm (PCI) apparatus. According to the results of experiments, globules (Mg rich solid phase) were regarded the storage system as a hydrogen absorption/desorption and eutectic/liquid droplets (quenched liquid phase) were considered the catalytic system as an improving factor of hydrogenation kinetics. Especially, the hydrogenation properties were depended on properties of globules and liquid fraction.