KINETIC-ANALYSIS OF SOLID-STATE REACTIONS BY MEANS OF STEPWISE ISOTHERMAL ANALYSIS (SIA) AND CONSTANT RATE THERMAL-ANALYSIS (CRTA) - A COMPARATIVE-STUDY

The results obtained in this work point out that both SIA and CRTA tra ces, simulated assuming the same values of the reaction rate, are iden tical provided that either 'n order' or diffusion controlled kinetics are concerned. The alpha-T CRTA plots of solid state reactions fitting an Avrami-Erofeev kinetic model show that the temperature decreases w ith increasing alpha until reaching a minimum at a value of the reacte d fraction alpha=alpha(min) characteristic of the Avrami-Erofeev expon ent. The shapes of the corresponding SIA diagrams are quite different and a very long isothermal step is obtained. Moreover, the reaction ra te is not maintained constant during the isothermal period but it show s a maximum at a value of alpha depending on the Avrami-Erofeev coeffi cient. It is important to point out that this alpha(max) value agrees with the corresponding alpha(min) calculated from a CRTA curve by assu ming the same Avrami-Erofeev exponent.