Crystallization Kinetics of 2CaO·Fe<sub>2</sub>O<sub>3</sub> and CaO·Fe<sub>2</sub>O<sub>3</sub> in the CaO–Fe<sub>2</sub>O<sub>3</sub> System

Abstract

In this study, the non-isothermal crystallization kinetics of 2CaO·Fe2O3 and CaO·Fe2O3 were investigated by DSC measurement. Crystallization of CaO–Fe2O3 system includes three reactions and can be explained using Fe2O3–CaO phase diagram. The mechanisms of 2CaO·Fe2O3 and CaO·Fe2O3 crystallization were analyzed using Avrami and Mo models. Results of the Avrami model analysis indicated that growth of 2CaO·Fe2O3 and CaO·Fe2O3 include two stages, which are controlled first by a fibril-like mechanism followed by a spherulitic-type mechanism. The Mo model analysis yielded results similar to those of the Avrami model and further concluded that Avrami exponent/Ozawa exponent is constant despite the changes in cooling rate. Calculations using Kissinger method revealed that the activation energy of 2CaO·Fe2O3 and CaO·Fe2O3 crystallization were −464.16 kJ·mol−1 and −172.61 kJ·mol−1, respectively. Moreover, 2CaO·Fe2O3 crystallization occurs in a difficult manner but proceeds at a faster rate than CaO·Fe2O3 crystallization. Increasing the cooling rate promotes CaO·Fe2O3 crystallization but inhibits 2CaO·Fe2O3 crystallization, which is beneficial during sintering.