Kinetics of cordierite crystallization from diphasic gels

Diphasic cordierite gels were prepared from colloidal silica, aluminum and magnesium nitrates and citric acid. The mechanism of xerogel decomposition was studied by infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The thermal decomposition of the xerogel forms a solid mixture of...

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Bibliographic Details
Published in:Journal of sol-gel science and technology 2008-08, Vol.47 (2), p.140-147
Main Authors: Silva, N. T., Nascimento, N. F., Cividanes, L. S., Bertran, C. A., Thim, G. P.
Format: Article
Language:English
Subjects:
Activation energy
Aluminum oxide
Ceramics
Chemistry
Chemistry and Materials Science
Citric acid
Colloidal gels. Colloidal sols
Colloidal state and disperse state
Composites
Cordierite
Crystallization
Dependence
Differential thermal analysis
Exact sciences and technology
Gels
General and physical chemistry
Glass
Gravimetric analysis
Infrared analysis
Infrared spectroscopy
Inorganic Chemistry
Magnesium oxide
Materials Science
Nanotechnology
Natural Materials
Nucleation
Optical and Electronic Materials
Original Paper
Silicon dioxide
Thermal decomposition
X-ray diffraction
Xerogels
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Summary:Diphasic cordierite gels were prepared from colloidal silica, aluminum and magnesium nitrates and citric acid. The mechanism of xerogel decomposition was studied by infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The thermal decomposition of the xerogel forms a solid mixture of MgO, Al 2 O 3 and SiO 2 at around 250 °C. Cordierite crystallization was studied by X-ray diffraction (XRD) and differential thermal analysis (DTA). Xerogels were initially thermally treated, and this sample crystallized to μ-cordierite at 850 °C, at 900 °C α-cordierite crystallizes and at 1150 °C α-cordierite is the major phase and μ-cordierite is totally consumed. The apparent activation energy for cordierite crystallization process was determined based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, Ligero methods and the Arrhenius law for dependence of activation energy with temperature. The apparent activation energy was (466.8 ± 34.3) kJ/mol, the exponent of Avrami was (1.9 ± 0.2) and the frequency factor was (1.55 × 10 20 ) s −1 . The Avrami value indicates a nucleation controlled process, which can be a consequence of the high xerogel homogeneity, a consequence of the early and simultaneous formation of the MgO, Al 2 O 3 and SiO 2 mixture.
ISSN:0928-0707
1573-4846
DOI:10.1007/s10971-008-1779-z