Thermodynamics of solid solution of hydrogen in M2C type carbides of vanadium and niobium

Equilibrium hydrogen pressures in the systems V2C--H2 and Nb2C--H2 have been determined at several temperatures in the range 400 to 6500C. Hydrogen pressure data were treated to obtain various thermodynamic quantities for the solutions of hydrogen in V2C and Nb2C. It has been found that the enthalpies of the reaction H(S.S.) = 1/2H2(g) are similar but slightly less endothermic compared with the respective metal hydrogen solid solutions. Entropies of dissolved hydrogen in V2C and Nb2C are also found to be similar to those of hydrogen in the respective metals