Kinetic behaviour of thermal transformations of kaolinite
Abstract
The kinetic behaviour of kaolinite dehydroxylation and the formation of Al-Si spinel phase is studied using differential scanning calorimetry on powder samples with heating rates from 1 to 10 °C min-1 in a dynamic argon atmosphere. The values of the apparent activation energy and pre-exponential factor were calculated using the Kissinger method. The results show that the dehydroxylation of kaolinite is controlled by several possible mechanisms, including a 1D interface controlled reaction, a 2D diffusion controlled reaction and a diffusion controlled process with zero nucleation rate. The determined values of apparent activation energy and pre-exponential factor of this process are (162 ± 1) kJ mol-1 and (1.99 ± 0.01)×108 s-1, respectively. The results also show that the crystallization of cubic Al-Si spinel phase from metakaolinite is controlled by two possible mechanisms, including grain edge nucleation after saturation and the zero nucleation rate (site saturation). For this process, the determined values of apparent activation energy and pre-exponential factor are (956 ± 1) kJ mol-1 and (4.81 ± 0.11)×1037 s-1, respectively.
The original version of this article supplied to AIP Publishing was missing the explanation of T i and T f points in Fig. 1 and there was a mistake in the axis labels in Fig. 3. The corrected figures appear in the Corrigendum attached to the pdf.- Publication:
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ThermoPhysics 2018: 23rd International Meeting of ThermoPhysics 2018
- Pub Date:
- July 2018
- DOI:
- 10.1063/1.5047627
- Bibcode:
- 2018AIPC.1988b0033O