KINETICS AND THERMODYNAMICS OF HYDROGEN ABSORPTION IN THE ZR(AL0.1FE0.9)(2) INTERMETALLIC COMPOUND

Thermodynamic and kinetic characteristics of hydrogen absorption in Zr (Al0.1Fe0.9)(2) were investigated at pressures up to 80 atm of H-2 and temperatures between 248 K and 270 K. The heat and entropy of formati on of the Zr(Al0.1Fe0.9)(2) hydride are estimated to be -24.7 kJ/(mole H-2) and -120 J/(Kmole H-2), respectively. Small, well-defined sampl es were utilized for the kinetic research. The experimental kinetic da ta fit a shrinking core (sc) model, in accord with a visual examinatio n of partly hydrided samples. The pressure dependence of the rate cons tants indicates an interface-controlled phase transition as the hydrid e formation rate-determining step. The activation energy for the hydri ding process is estimated from Arrhenius plots of the reaction rates t o be 0.30 eV/H atom. The kinetic data are discussed in view of similar results for additional intermetallic compounds. (C) 1997 Elsevier Sci ence S.A.