Abstract
Cadmium vapor pressures were determined over Ce–Cd samples by an isopiestic method. The measurements were carried out in the temperature range from 690 to 1080 K and over a composition range of 48–85 at% Cd. From the vapor pressures thermodynamic activities of Cd were derived for all samples at their respective sample temperatures, and partial molar enthalpies of Cd were obtained from the temperature dependence of the activities. With these partial molar enthalpies the Cd activities were converted to a common temperature of 823 K. By means of a Gibbs–Duhem integration Ce activities were calculated, using a corresponding literature value for the two-phase field (CeCd11+L) as integration constant. Finally integral Gibbs energies were calculated for the composition range 48–100 at% Cd with a minimum value of −37 kJ g-atom−1 at 823 K in the phase CeCd. Phase boundaries of the intermetallic compounds CeCd, CeCd2, Ce13Cd58, and CeCd11 were estimated from the vapor pressure measurements and from SEM analyses.
Highlights
The nuclear waste disposal is one of the key issues for future use of nuclear energy
During traditional aqueous methods some restrictions occur like limited solubility of fuel materials in acidic aqueous solutions and poor radiation stability of the organic solvents employed in the extraction process [1]
Existence and stability of intermetallic compounds in the various binary phase diagrams rare earth (RE)-Me are important. Thermodynamic properties such as the stability of the intermetallic compounds are of high interest, both for a thermodynamic assessment of the binary system based on the CALPHAD1 method [4], and for an optimization of the extraction process itself
Summary
The nuclear waste disposal is one of the key issues for future use of nuclear energy. Existence and stability of intermetallic compounds in the various binary phase diagrams RE-Me are important Thermodynamic properties such as the stability of the intermetallic compounds are of high interest, both for a thermodynamic assessment of the binary system based on the CALPHAD1 method [4], and for an optimization of the extraction process itself. This was the starting point for the present study which wants to provide partial and integral thermodynamic properties of binary Ce– Cd alloys, mainly based on Cd vapor pressure measurements with an isopiestic method [5,6]. Together with calorimetric measurements to determine enthalpies of formation of several intermetallic compounds and a careful experimental phase diagram reinvestigation (both currently under way) this will serve as input for a CALPHAD optimization of the binary Ce–Cd system
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