Hydrogen solubility studies in Zr0.2Tb0.8Fe1.5Co1.5

The hydrogen solubility studies in a PuNi3-type alloy Zr0.2Tb0.8Fe1.5Co1.5 are performed in the ranges 75≤T (°C)≤150 and 0.1≤P (bar)≤30. The hydrogen solubility properties are compared with those of Zr0.2Tb0.8Fe3 and Zr0.1Tb0.9Fe1.5Co1.5. The plateau pressure of Zr0.2Tb0.8Fe1.5Co1.5–H at any given temperature is higher than that of Zr0.1Tb0.9Fe1.5Co1.5–H. The lattice is accompanied by an expansion of about 17% upon hydriding the alloy, retaining its parent alloy (PuNi3-type) structure. The thermodynamical parameters (ΔHH and ΔSH) of the dissolved hydrogen are evaluated and compared with those of Zr0.2Tb0.8Fe3–H and Zr0.1Tb0.9Fe1.5Co1.5–H. The different phases of the alloy–hydrogen system are identified from the variation of ΔHH, ΔSH with y, which agree well with those seen in the hydrogen absorption isotherms. These phases are further confirmed through powder X-ray diffraction studies at appropriate hydrogen concentrations. From the studies on kinetics of hydrogen absorption, it is found that the rate of reaction in Zr0.2Tb0.8Fe1.5Co1.5 is faster than that in Zr0.1Tb0.9Fe1.5Co1.5, and slower than that in Zr0.2Tb0.8Fe3.