Thermal Dissociation Kinetics of Solid and Liquid Ammonium Nitrate

Thermogravimetry has been used to study the kinetics of the thermal dissociation of solid and liquid ammonium nitrate. Model-fitting and model-free kinetic methods have been applied to the sets of isothermal and nonisothermal measurements to derive kinetic characteristics of the processes. The application of the model-fitting method to the isothermal data has demonstrated that both solid- and liquid-phase kinetics are characterized by a single activation energy of ∼90 kJ mol-1 and by the model of a contracting cylinder. A model-free isoconversional method has also been applied to isothermal and nonisothermal data and has yielded an activation energy of ∼90 kJ mol-1, which is essentially independent of the extent of conversion. The obtained kinetic characteristics have been assigned to the process of dissociative sublimation/vaporization.