Thermodynamical, structural, hydrogen storage properties and simulation studies of P–C isotherms of (La,Mm)Ni5-yFey

The present work is focussed on the synthesis, structural/microstructural characterization, hydrogenation behaviour and computer simulation studies of P–C isotherms of a new series of alloys represented by LaxMm1-xNi5-yFeyLaxMm1-xNi5-yFey (x=0.0x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 and y=0.1y=0.1), where Mm denotes Ce-rich mischmetal. The alloys have been analysed using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The alloy corresponding to LaNi4.9Fe0.1LaNi4.9Fe0.1 has been found to have high storage capacity of ∼1.68wt% which is one of the highest reported capacity for AB5AB5 type storage systems. A feasible mathematical model has been developed to simulate the P–C isotherms. The model describes the asymmetry of the ‘pressure–composition’ isotherms, temperature-dependent plateau slopes and smooth transitions between αα, α+βα+β and ββ-regions. P–C isotherms, enthalpy and entropy changes (ΔHΔH and ΔSΔS) have been evaluated experimentally for the alloys LaxMm1-xNi4.9Fe0.1LaxMm1-xNi4.9Fe0.1 in order to have input data for the simulation. Special software was developed to simulate the P–C isotherms using the said model. The simulated and experimental curves have been found to match closely.