GIBBS ENERGIES OF FORMATION OF UMOC1.7 AND UMOC2

The chemical potentials oi carbon associated with two three-phase fiel ds in the system U-Mo-C were measured by using the methane-hydrogen ga s equilibration technique in the temperature range 973 to 1173K. The t echnique was validated by measuring the standard Gibbs energy of forma tion of Mo2C. From the experimentally measured values of the chemical potential of carbon in the ternary phase fields UC+Mo+UMoC1.7 and UC+U MoC1.7+UMoC2 and data for UC from the literature, the Gibbs energies o f formation of the two ternary carbides were derived: Delta(f)G(o)(UMo C1.7) = - 146 632 - 15.OT(+/-8200)J mol(-1) (973 - 1173 K) Delta(f)G(o )(UMoC2) = - 151 961 - 13.7T(+/-8100)J mol(-1) (973 - 1173 K) Experime ntally determined values of the Gibbs energy of formation of UMoC1.7 a re reported for the first time.