Andalusite-Mullite Transformation - A Unique Kind of Phase Transformation

Written By Bowen Li

The crystal convertion from andalusite to mullite is an inversible phase transformation. Andalusite (Al2O3.SiO2) will decomposed into mullite (3Al2O3.2SiO2) and amorphous silica (SiO2) once temperature is raised to 1300C or above.

3 Al2O3 .SiO2 - 3 Al2O3.2SiO2 + SiO2

What special and unique is that this transformation is started from a single crystal (andalusite), then decomposed into numerous crystals (mullite) and an amorphous phase (SiO2). The application of this phenomenon greatly benefited the productions of high temperature ceramics. For more details, please visit:  B. Li, M. He, H. Wang. Phase Transformation of Andalusite-Mullite and Its Roles to Microstructure and Sinterability of Refractory Ceramic. Metallurgical & Materials Transaction A, 2017, 2017, 48(7), 3188-3192. http://doi.org/10.1007/s11661-017-4092-z. Another paper introduced how the microstructure eveloped: B. Li, R. Weng and J. Li. Experiment and research on the preparation of mullite fibre reinforced material with andalusite. Refractories, 1996, 30(6): 305-307,313

Bowen Li
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