Effect of heat transfer on kinetic parameters derived from thermoanalytical curves- decomposition of ammonium uranyl carbonate

Kinetic parameters for the thermal decomposition of ammonium uranyl carbonate were derived from simultaneous TG-DTA data obtained at various heating rates and sample weights. The results indicated that the decomposition reaction followed Mampel unimolecular decay law when the measurements were made at relatively faster heating rates (5-10 K/min) or with small samples (≤ 20 mg). However, when larger samples (50-100 mg) or slower heating rates (2 K/min) were used the thermal decomposition data were explainable by Avrami-Erofeev nuclei growth model with a value of 3/2 for the exponent n in the equation for fraction decomposed, α viz., α 1-exp(-ktn). (author). 9 refs., 1 tab