Hydrogen storage behavior of ZrNi 70/30 and ZrNi 30/70 composites

The Zr-Ni compositional alloys, namely (i) ZrNi 70/30 and (ii) ZrNi 30/70 (both by weight) have been investigated for the reversible hydrogenation behavior. These composites show Zr-Ni intermetallic multi-phase formation as explored by X-ray diffraction studies. The sorption kinetics of ZrNi 70/30 seems much faster (∼3-4 times) than that of ZrNi 30/70 alloys. The initial desorption rate increasing with an increase in temperature. A well-defined plateau region was obtained for the ZrNi 70/30 with an equilibrium pressure range from <1 bar (300 deg. C) to 10 bars (390 deg. C). For ZrNi 30/70, the sloppy plateau region extends to higher equilibrium pressures. It is estimated that the total effective hydrogen concentration for ZrNi 70/30 (∼1.0 wt.%) is at least 2 times that of ZrNi 30/70 (∼0.5 wt.%) composites. From the PCT isotherms, the enthalpy of reaction (ΔH) has been calculated to be ∼39 kJ/mol H2 for the ZrNi 70/30. The surface morphologies of the hydrogenated materials exhibit the presence of cracks and particle size pulverization in comparison to the pristine alloys