Kinetic and thermodynamic investigations of non-isothermal decomposition process of a commercial silver nitrate in an argon atmosphere used as the precursors for ultrasonic spray pyrolysis (USP): The mechanistic approach

Abstract

The non-isothermal decomposition process of commercial silver nitrate used as the precursor for the USP procedure was investigated by simultaneous TGA–DTA measurements at different heating rates, in an argon atmosphere. Detailed kinetic and thermodynamic analyses, with special emphasis on the formation of a complete mechanistic scheme of the process were performed. It was found that the process under study can be described by the acceleratory power law kinetic model (P2), in the range of the extent of conversion (α) values (0.15≤α≤0.85), where the value of the apparent activation energy (Ea) can be considered as the constant (141.3kJmol−1). The kinetic prediction analysis was shown that only the power law kinetic model (f(α)=2α1/2) gives the value of Ea which is consistent with the value obtained from the isothermal conditions. The critical temperature (Tc) of decomposition process was determined. The resulting value of Tc was in fairly good agreement with the starting temperature of thermal decomposition of silver oxide (Ag2O). The thermodynamic functions of decomposition process are calculated by the activated complex theory and showed that the silver–oxygen bond secession can be interpreted as a “slow” stage of the decomposition process.