ISOTHERMAL AND NONISOTHERMAL REACTION-KINETICS IN SOLIDS - IN SEARCH OF WAYS TOWARD CONSENSUS

Thermogravimetric data for the decomposition of ammonium dinitramide ( ADN) have been obtained under isothermal and nonisothermal conditions in order to determine the efficacy of different methods for analyzing the kinetics of solid-state reactions. A widely used model-fitting met hod gives excellent fits to the experimental data but yields highly un certain values of the Arrhenius parameters when applied to nonisotherm al data because temperature and extent of conversion are not independe nt variables. Therefore, comparison of model fitting results from isot hermal and nonisothermal experiments is practically meaningless. Conve rsely, model-free isoconversional methods of kinetic analysis yield si milar dependencies of the activation energy on the extent of conversio n for isothermal and nonisothermal experiments. Analysis of synthetic data generated for a complex kinetic model suggests that, in the gener al case; the identical dependencies are unlikely to result from experi ments obtained under isothermal and nonisothermal conditions.