Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6660294 | The Journal of Chemical Thermodynamics | 2015 | 10 Pages |
Abstract
The vaporization behavior and decomposition mechanism of NaUO3 were studied using Knudsen effusion mass spectrometry. The temperature dependence of the sodium partial pressure over the ternary phase field NaUO3-Na2U2O7-UO2 was measured for the first time: log(PNa/Pa)=10.98(±0.04)-14,999(±50)/(T/K). The enthalpy of formation of α-Na2U2O7 was moreover derived from second law analysis of the data at ÎfHmo(α-Na2U2O7,cr,T=298.15K) = â(3208.4  ± 5.5) kJ · molâ1, in very good agreement with the value reported in the literature from solution calorimetry. The existence of three polymorphs for Na2U2O7 (α, β, and γ) was confirmed using high temperature X-ray diffraction. The two phase transitions occur above about T = 600 K, and around T = 1323 K, respectively. Our results were finally assessed with respect to similar vaporization studies carried out in neighboring ternary phase fields of the Na-U-O phase diagram.
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Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
A.L. Smith, J.-Y. Colle, P.E. Raison, O. Beneš, R.J.M. Konings,