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 less than or equal to T (degrees C) less tha n or equal to 150 and 0.1 less than or equal to P (bar) less than or equal to 30. The hydrogen solubility properties are compared with those of Zr0.2T b0.8Fe3 and Zr0.1Tb0.9Fe1.5Co1.5. The plateau pressure of Zr0.2Tb0.8Fe1.5Co 1.5-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 t he alloy, retaining its parent alloy (PuNi3-type) structure. The thermodyna mical parameters (Delta N-H and Delta S-H) of the dissolved hydrogen are ev aluated 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 t he variation of Delta H-H, Delta S-H with y, which agree well with those se en in the hydrogen absorption isotherms. These phases are further confirmed through powder X-ray diffraction studies at appropriate hydrogen concentra tions. From the studies on kinetics of hydrogen absorption, it is found tha t the rate of reaction in Zr0.2Tb0.8Fe1.5Co1.5 is faster than that in Zr0.1 Tb0.9Fe1.5Co1.5, and slower than that in Zr0.2Tb0.8Fe3. (C) 2000 Internatio nal Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.