TY - JOUR
T1 - Thermodynamic and structural aspects of hydrogen absorption in the Zr(AlxCo1-x)2 system
AU - Bereznitsky, M.
AU - Jacob, I.
AU - Bloch, J.
AU - Mintz, M. H.
N1 - Funding Information:
This work was supported by a grant of the Israeli Council of Higher Education and the Israeli Atomic Energy Commission. The help of Dr D. Mogilyanski in the X-ray work is gratefully acknowledged.
PY - 2002/11/18
Y1 - 2002/11/18
N2 - Hydrogen absorption and desorption isotherms have been measured for Zr(AlxCo1-x)2 (0.1≤x≤0.5) compounds at pressures up to 60 atm and temperatures between -30 and 100 °C. Enthalpies and entropies of hydride formation have been derived from desorption isotherms for x=0.1, 0.167, 0.25 and 0.35. Below these x values the pressures, necessary for hydrogen absorption, are higher than 60 atm. The critical temperatures for hydride formation of the x=0.35 compounds are lower than the experimental temperatures employed in the present work. In general, the hydride stability increases while the critical temperature decreases as a function of x. Consequently, we suggest that a competition between two opposing factors, namely the metal-hydrogen interaction and the hydrogen-hydrogen interaction (or hydrogen-induced long range elastic strain interaction), accounts for the anomalous hydrogen sorption behavior in this and other Al-containing systems. The hydrogen equilibrium pressure for ZrCo2 is estimated by extrapolation. The estimation compares fairly with available experimental information. The volume occupied by a single hydrogen atom is obtained for all the investigated compounds, and supports the idea of approximately constant value for this quantity.
AB - Hydrogen absorption and desorption isotherms have been measured for Zr(AlxCo1-x)2 (0.1≤x≤0.5) compounds at pressures up to 60 atm and temperatures between -30 and 100 °C. Enthalpies and entropies of hydride formation have been derived from desorption isotherms for x=0.1, 0.167, 0.25 and 0.35. Below these x values the pressures, necessary for hydrogen absorption, are higher than 60 atm. The critical temperatures for hydride formation of the x=0.35 compounds are lower than the experimental temperatures employed in the present work. In general, the hydride stability increases while the critical temperature decreases as a function of x. Consequently, we suggest that a competition between two opposing factors, namely the metal-hydrogen interaction and the hydrogen-hydrogen interaction (or hydrogen-induced long range elastic strain interaction), accounts for the anomalous hydrogen sorption behavior in this and other Al-containing systems. The hydrogen equilibrium pressure for ZrCo2 is estimated by extrapolation. The estimation compares fairly with available experimental information. The volume occupied by a single hydrogen atom is obtained for all the investigated compounds, and supports the idea of approximately constant value for this quantity.
KW - Gas-solid reactions
KW - Hydrogen absorbing materials
KW - Transition metal compounds
UR - http://www.scopus.com/inward/record.url?scp=0037131860&partnerID=8YFLogxK
U2 - 10.1016/S0925-8388(02)00670-9
DO - 10.1016/S0925-8388(02)00670-9
M3 - Article
AN - SCOPUS:0037131860
SN - 0925-8388
VL - 346
SP - 217
EP - 221
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
IS - 1-2
ER -