Kinetic analysis of solid state reactions by means of stepwise isothermal analysis (SIA) and constant rate thermal analysis (CRTA). A comparative study

Article abstract of DOI:10.1023/A:1010172821020

The results obtained in this work point out that both SIA and CRTA traces, simulated assuming the same values of the reaction rate, are identical provided that either `n order' or diffusion controlled kinetics are concerned. The α-T CRTA plots of solid state reactions fitting an Avrami-Erofeev kinetic model show that the temperature decreases with increasing α until reaching a minimum at a value of the reacted fraction α = α_min characteristic of the Avrami-Erofeev exponent. The shapes of the corresponding SIA diagrams are quite different and a very long isothermal step is obtained. Moreover, the reaction rate is not maintained constant during the isothermal period but it shows a maximum at a value of α depending on the Avrami-Erofeev coefficient. It is important to point out that this α_max value agrees with the corresponding α_min calculated from a CRTA curve by assuming the same Avrami-Erofeev exponent.