Mullitization of Diphasic Aluminosilicate Gels |
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Authors: | Sankaran Sundaresan Ilhan A. Aksay |
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Affiliation: | Department of Chemical Engineering, Princeton University, Princeton, New Jersey 08544–52263;Department of Materials Science and Engineering and Advanced Materials Technology Center, Washington Technology Center, University of Washington, Seattle, Washington 98195 |
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Abstract: | Recent studies have shown that the mullitization of diphasic aluminosilicate matrices comprising transitional alumina and amorphous silica occurs via a nucleation and growth process. Nucleation is preceded by a temperature-dependent incubation period. Following this incubation period, rapid nucleation of mullite occurs, producing about 1.8 × 1011 nuclei/cm3, which remains constant throughout the rest of the transformation. Both incubation and mullite growth are thermally activated processes with apparent activation energies of 987 ± 63 and 1070 ± 200 kJ/mol, respectively. The growth rate of mullite grains under isothermal conditions is time dependent. An interpretation of these results is proposed on the basis of the nucleation and growth concepts of LaMer and Dinegar which supports the concept that the growth rate of mullite grains is controlled by the dissolution of transitional alumina into the amorphous matrix. |
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Keywords: | mullite gels nucleation processing aluminosilicates |
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