Hydrogen Absorption and Temperature Programmed Desorption (TPD) Studies of Iron- and Chromium-Substituted ZrV sub 2

摘要

The hydrogen absorption proterties of the alloys Zr(V/sub 1-x/Cr/sub x/) sub 2 , x = 0.4 and 0.5, were studied at 450 exp 0 C from 10 exp -3 atm to 10 atm. the alloy ZrV/sub 0.8/Cr/sub 1.2/ was studied at 350 exp 0 , 400 exp 0 , and 450 exp 0 C from 10 exp -3 atm to 10 atm, and from these data partial molar enthalpies and entropies of solution were calculated for several hydride compositions. A free energy against cell volume plot of the cubic chromium-containing materials compared with earlier data on hexagonal as well as cubic iron-substituted alloys shows that electronic factors are probably more important than structural factors in determining the free energies of the ternary Zr(V/sub 1-x/B/sub x/) sub 2 systems. Temperature-programmed desorption (TPD) of several hydride compositions in the systems ZrV/sub 1.6/Fe/sub 0.4/H/sub y/ and ZrV/sub 1.2/Cr/sub 0.8/H/sub y/ revealed two distinct peaks. The TPD results appear to correlate with changes in the pressure-composition isotherms when plotted on a log-log plot. These changes may be related to thermodynamic changes in the desorption of hydrogen. The so called trapping model (Pfeiffer and Wipf, 1976; Flanagan, Wulff, and Bowerman, 1980) is presented as a possible explanation of the observed TPD behavior. 7 figures, 2 tables. (ERA citation 08:023214)