Thermodynamic studies of uranium-gadolinium-carbon system through the carbothermic reduction of the oxides

The formation of solid solutions of (U1-yGdy)C2 (where 0.2≤y≤0.8) in the high carbon region, has been studied in the temperature range 1063-1673 K. The solid solutions were prepared by blending the stoichiometric amounts of oxides with graphite and heating the mixture in the form of a pellet to the reaction temperature in a high vacuum chamber. The effusion of CO from the pellet was monitored by means of a quadrupole mass spectrometer. The effusion pressures of CO in the vacuum chamber were correlated to the equilibrium pressure of the system, according to a new method developed in our laboratory [Vidhya (1995)]. The reported solubility [Wallace (1964)] of 'GdC2' in 'UC2' was verified by XRD. The Gibbs energies of formation of the different solid solutions have been calculated. (orig.)