Thermal and kinetic analysis of uranium salts

Thermal decomposition of U(C₂O₄)₂·6H₂O was studied using TG method in nitrogen, air, and oxygen atmospheres. The decomposition proceeded in five stages. The first three stages were dehydration reactions and corresponded to removal of four, one, and one mole water, respectively. Anhydrous salt decomposed to oxide products in two stages. The decomposition products in nitrogen atmosphere were different from those in air and oxygen atmospheres. In nitrogen atmosphere UO_1.5(CO₃)_0.5 was the first product and U₂O₅ was the second product, while these in air and oxygen atmospheres were UO(CO₃) and UO₃, respectively. The second decomposition products were not stable and converted to stable oxides (nitrogen: UO₂, air–oxygen: U₃O₈). The kinetics of each reaction was investigated with using Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa methods. These methods were combined with modeling equations for thermodynamic functions, the effective models were investigated and thermodynamic values were calculated.