Kinetics of mullite formation in zircon and boehmite mixture
Résumé
The kinetics of zircon decomposition and mullite formation in ZrSiO 4-Al2O3 ceramics were investigated under non-isothermal conditions using differential thermal analysis (DTA). The mullite-zirconia composites were prepared by reaction sintering of the zircon and boehmite mixtures. The DTA conducted at heating rates of 5,10,20 and 30°C.min-1 showed an endothermic peak at about 1500°C associated with zircon dissociation and mullite formation. This crystallization temperature increased slightly with increasing heating rate. The non-isothermal activation energy (Ea) of zircon decomposition and mullite formation, calculated by Johnson-Mehl-Avrami equation and Kissinger's method, were respectively 1272 and 1242 kJ/mol. The growth morphology parameter n was found to be almost equal to 2.6. The analysis of the results indicates that the bulk nucleation was dominant in mullite crystallization followed by three-dimensional growth. © Lavoisier.
Mots clés
Bulk nucleation
Crystallization temperature
Endothermic peaks
Growth morphology
Johnson Mehl Avrami equation
Kissinger
Mullite crystallization
Mullite formation
Non-isothermal condition
Nonisothermal
Reaction sintering
Three-dimensional growth
Zircon decomposition
Activation energy
Crystallization
Heating
Heating rate
Mullite
Sintering
Thermoanalysis
Zircon
Zirconia
Silicate minerals