Study of the phase transitions and crystallization Kinetic Parameters of mixtures Al2O3-MgO-SiO2
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Date
2020-10-07
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UNIVERSITE MOHAMED BOUDIAF - M’SILA
Abstract
The mullite-cordeirite composites was prepared by Sol-Gel method, using magnesium nitrate powder, aluminum nitrate powder and tetraethyl orthosilicate solution as raw materials, these materials were mixed in various ratios according to stoichiometric formula of the wanted composite, in order to analyze the prepared materials we used several techniques, including Thermogravimetry and Differential Thermal Analysis (TG/DSC), also Dilatometry analysis to observe the phases transformation, and to confirm it we used X-ray diffraction analysis (DRX) which it been used to identify the formed phases of M50C50 which is mullite and cordierite, we also tracked the stages of phase transformations for M50C50 powder that has been treated by Dilatometry at various temperatures using the analysis technique by X-ray diffraction, where we were able by means of the ASTM cards , to identify the formed phase in various temperatures, and activation energy and Avrami parameters for cordierite phase in the non-isothermal and isothermal treatment, and for Al-Si spinal phase in the non-isothermal, were calculated based on Dilatometry analysis results, we found that the energy as the following: 1210.91 kJ/mol and 1190.06 kJ/mol respectively for cordierite and 719.93 kJ/mol for spinel, as for the morphological growth parameters n and m are approximately 1.5 which indicating that the dominant crystallization volume mode in cordierite phase formation followed by three dimensional growth of spinal crystals with a polyhedral-like shape controlled by diffusion from fixed number of nuclei, As for the spinal, it is approximately 0.5, indicating that the dominant crystallization volume mode in a spinal phase formation followed by one-dimensional (needles) diffusion, and bulk nucleation with constant number of nuclei.
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Keywords
Mullite, Cordierite, Sol-Gel, Activation Energy, Avrami parameters.