Kinetic analysis of nonisothermal decomposition of (Mg5(CO3)4(OH)2·4H2O/5Cr2O3) crystalline mixture

Pure MgCr2O4 spinel was synthesized from crystalline mixture of (Mg5(CO3)4(OH)2·4H2O/5Cr2O3) by heating at 900 °C for 27 h. TG, DTA, FT-IR and XRPD techniques were used to follow the reactions and identify the products. Nonisothermal kinetics of thermal decomposition of un-irradiated and γ-irradiated physical crystalline mixtures were studied in static air. The kinetic parameters were obtained through model-fitting and model-free methods, and artificial isokinetic relationship (IKR) for multi-step processes. The results show that the decomposition for both un-irradiated and γ-irradiated mixtures proceed through two steps with different reaction mechanisms. The first is a third-order reaction (F3) mechanism followed by one-dimensional diffusion (D1) as a second step.