Deuterium absorption properties of V85Ni15 and evidence of isotope effect

The pressure-composition absorption isotherms of deuterium in an alloy with nominal composition V85Ni15 were measured between 87 and 400 °C for pressures up to ?17 bar. For T <= 144 °C one observes the occurrence of a solid solution ? phase for D/M < 0.15, the coexistence of ? and ? phase up to D/M ? 0.5 and a subsequent change to a different phase for higher deuterium concentrations. For temperatures higher than 200 °C only a solid solution with a deuteration enthalpy ?Hdeutr = 47 ± 2 kJ/mol is detected. The critical temperature of this V-Ni alloy (144 °C <= T*<=200 °C) is much higher than that of pure V (100 °C). Moreover, well above the critical temperature, one can observe a "normal" isotope effect, i.e. the equilibrium pressure of the V85Ni15-H system is higher than that of V85Ni15-D.