Vaporization of uranium-carbon-nitrogen system

The vaporization of species from the uranium-carbon-nitrogen system has been investigated by mass spectrometry with the Knudsen cell technique. After calibration with gold, the vapor pressures of U and N2 have been obtained over UC1−xNx in the temperature range of 1900–2300K. For uranium mono-nitride, values of enthalpies ΔH°298 for overall reaction (1)UN(s) = U(g) + 0.5N2(g) and the partial reactions (2)UN(s) = U(L) + 0.5N2(g) and U(L) = U(g) have been obtained with both second- and third-law treatments. For UC1−xNx the experimental vapor pressures were used to calculate activity of UN in the solutions. For three compositions (x = 0.69, 0.48, 0.30) measured, activity coefficients were found to be slightly smaller than unity.