Application of Non-Isothermal Thermogravimetric Method to Interpret the Decomposition Kinetics of $\hbox {NaNO}_{3}, \hbox {KNO}_{3}$, and $\hbox {KClO}_{4}$

Abstract

The non-isothermal thermogravimetric method was used to study the thermal decomposition of $\hbox {KClO}_{4}, \hbox {KNO}_{3}$, and $\hbox {NaNO}_{3}$ at heating rates of (5, 10, 15, and 20) $\hbox {K}\cdot \hbox {min}^{-1}$. The activation energy of thermal decomposition reactions was computed by isoconversional methods of Ozawa–Flynn–Wall, Kissinger–Akahiro–Sunose, and Friedman equations. Also, the kinetic triplet of the thermal decomposition of salts was determined by the model-fitting method of the modified Coats–Redfern equation. The activation energies of $\hbox {KClO}_{4}, \hbox {KNO}_{3}$, and $\hbox {NaNO}_{3}$ of (293 to 307, 160 to 209, and 192 to 245) $\hbox {kJ}\cdot \hbox {mol}^{-1}$, respectively, are obtained by non–isothermal isoconversional methods. The modified Coats and Redfern method showed that the most probable mechanism functions $g(\alpha )$ of $[-\hbox {ln}(1 - \alpha )]^{1/3}$ (model A3: Arami–Erofeev equation) and $(1 - \alpha )^{-1}- 1$ (model F2: second order) can be used to predict the decomposition mechanisms of $\hbox {KClO}_{4}$, $\hbox {KNO}_{3}$, and $\hbox {NaNO}_{3}$, respectively.