Evaluation of kinetic parameters for the thermal decomposition of gamma-irradiated anhydrous lanthanum nitrate

Abstract

The thermal decomposition of gamma-irradiated anhydrous lanthanum nitrate was studied by dynamic thermogravimetry. The decomposition proceeds via three consecutive stages characterized by different activation energies. The reaction order, activation energy, frequency factor and entropy of activation were calculated using the Coats–Redfern, Freeman–Carroll and Horowitz–Metzger methods and were compared with those of the unirradiated salt. Irradiation enhances the decomposition and the effect increases with the irradiation dose. The activation energies of all the three stages decrease on irradiation. The mechanism of the decomposition of unirradiated and irradiated anhydrous lanthanum nitrate follows the Mampel model equation,−ln(1−α) for g(α), and the rate-controlling process is random nucleation with the formation of a nucleus on every particle.