Kinetic Studies of Fluorination of Uranium Carbides by Fluorine, (II)

The fluorination reaction of uranium dicarbide with fluorine to form UF6 has been studied in the temperature range between 220° and 300°C using a thermobalance. The overall mechanism of reaction is similar to the case of uranium monocarbide, i.e. in the first step, UC2 is rapidly converted to UF4, polymeric fluorocarbon and gaseous fluorocarbon, while in the second step, UF4 and polymeric fluorocarbon are converted rather slowly to UF6 and gaseous fluorocarbon. The amount of polymer is much larger than the case of uranium monocarbide, its weight ratio to UF4 being 0.2 to 0.25 in the early stages of the reaction. The fluorination of 4 to UF6 always follows the linear law derived from the diminishing sphere model. The apparent activation energy was determined to be 19.5 kcal/mole. Differences in the fluorination between UC and UC2 are discussed, with the effect of polymer taken into consideration.