Thermodynamic data of the hydrogen-niobium system

Abstract

Ultrahigh vacuum techniques have been used to investigate the equilibrium pressure-composition-temperature relationships of hydrogen-niobium solutions up to gas concentrations of H/Nb=0.5, and from these relationships the variations of the thermodynamic properties of the solution with composition have been determined. The variation of the entropy of solution indicates that gas concentrations in interstitial solutions of this type are limited to low nonstoichiometric ratios by the blocking of interstitial sites by neighbouring solute atoms rather than by any nonequivalence of the sites themselves. The measurements were made in the ranges: pressure p=10-6-1 Torr, concentration H/Nb=0.017-0.502, temperature T=295-523 K.