THERMODYNAMIC PROPERTIES OF THE ZRCR2FE0.8-H2, ZRCR2CO0.8-H2, ZRCR2NI0.8-H2 SYSTEMS

The thermodynamic properties of the ZrCr2T0.8-H2 systems (T = Fe, Co, Ni) were studied by measuring the hydrogen equilibrium dissociation isotherms over the temperature range 296-403 K. It was observed that all the host alloys react readily and reversibly and absorb large quantities of hydrogen. Two of these systems exhibit a dissociation pressure plateau at 101.3 kPa. This is observed at 381 K for the ZrCr2Fe0.8-H2 system and at 355 K for the cobalt analogue. It was also found that the dissociation equilibrium pressure considerably increases for all these systems in comparison with the dissociation equilibrium pressure of the prototype ZrCr2-H2 system. The heat of formation, entropy and Gibbs free energy of formation were determined for different hydrogen contents in all the systems investigated.