Hydrogen isotope absorption in Zr(Mn0.5Fe0.5)2

The absorption capacities and rates of hydrogen and deuterium in Zr(Mn0.5Fe0.5)(2) are determined in the range of 5 kPa<p(H2), p(D2)<100 kPa and 373 K<T<473 K by means of a constant volume method. The Sieverts' law holds good in almost the whole range of the Zr(Mn0.5Fe0.5)(2)-H-2 and -D-2 system. The isotopic difference in solubility between H and D becomes smaller with an increase in temperature. The relative partial molar enthalpy per gram atom of H is slightly smaller than that per gram atom of D. The absorption rates of H-2 and D-2 are not explained by previous hydrogenating rate equations but are correlated to a unique dissociation-relating-reaction rate equation regardless of temperature, initial hydrogen pressure and isotopic species. The reaction rates of H, and D-2 are characterized in terms of the time to fill half of the equilibrium absorption amount of the Zr(Mn0.5Fe0.5)(2) particles. The half time is a linens function of the reciprocal of temperature independent of the initial pressure. (C) 1999 Elsevier Science S.A. All rights reserved.