Pressure-Composition Isotherms of TiC<SUB>1&minus;<I>x</I></SUB>&ndash;H System at Elevated Temperatures

Abstract

Pressure-composition isotherms of TiC 1Àx -H system were measured at 773, 873 and 973 K over a pressure range from 10 À2 to 10 5 Pa. The obtained isotherms could be divided in three concentration regions. In the low concentration region in which ½H=½TiC 1:4 Â 10 À3 , Sieverts' law held, and the solubility of hydrogen clearly increased with decreasing temperature. The enthalpy of solution was À70 AE 5 kJ mol À1 . In the region in which 1:4 Â 10 À3 < ½H=½TiC 8:0 Â 10 À3 , the dependence of hydrogen concentration, C H , on pressure and temperature weakened as pressure increased. Finally, C H was independent of temperature when it reached 8:0 Â 10 À3 . This C H was comparable with the concentration of carbon vacancies in TiC 1Àx . In the high concentration region in which ½H=½TiC ! 8:0 Â 10 À3 , Sieverts' law held again, but the solubility of hydrogen was almost independent of temperature. These observations indicated that hydrogen dissolved in carbon vacancies in the low and middle concentration regions with the above-mentioned value of enthalpy of solution, and also occupied much less stable sites in the high concentration region.

Ti-V-C-Based Alloy with a FCC Lattice Structure for Hydrogen Storage

“…XRD also could not tell Ti from V due to the similar structure factors. In addition, the Ti and V carbides normally could not absorb hydrogen unless there exists so-called long-range ordered carbon vacancies and dislocations [30,31,32,33,34]. Our obtained Ti-V-C alloys, which are very likely to possess much carbon vacancies and dislocations based on the smaller experimental density (5.1 g·cm -3 ) compared to the theoretical one, shows unique hydrogen storage properties.…”

The high-flux effect on deuterium retention in TiC and TaC doped tungsten at high temperatures

“…non-stoichiometry, activation energies for entering the precipitates, and binding energies with the defects inside the precipitates, as well as at their boundaries. Although the H isotope retention in TiC was studied extensively both experimentally [33][34][35][36] and by DFT calculations [25,27], no data on H isotope behaviour is available for TaC.…”