STABILITIES OF TERNARY CARBIDES UWC1.75 AND UWC2

The methane-hydrogen gas equilibration technique has been used to meas ure the chemical potential of carbon associated with two three-phase f ields of the system U-W-C in the temperature range 973 to 1173 K. By c ombining the values of the chemical potential of carbon in the three-p hase fields UC + W + UWC1.75 and UC + UWC1.75 + UWC2 Obtained in this study with the data on the Gibbs energy of formation of UC available i n the literature, expressions for the Gibbs energies of formation of t he two ternary carbides were derived: Delta(f)G degrees [UWC1.75] = -1 31, 600 - 300 T (+/-8000) J mol(-1) Delta(f)G degrees [UWC2] = -144, 8 00 - 32.0 T (+/- 10,000) J mol(-1) Although estimates of Gibbs energie s of formation of the two ternary carbides TSWC1.75 and UWC2 have been reported, there have been no previous experimental determinations of thermodynamic properties of these compounds.