Formation of mullite phase in diphasic gels consisting of TEOS and boehmite with and without dehydroxylation

• Published in: Journal of the European Ceramic Society Vol. 18; no. 12; pp. 1765 - 1769
• Main Authors: Padmaja, P., Anilkumar, G.M., Warrier, K.G.K.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.1998; Elsevier
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Miscellaneous; Technical ceramics; Colloidal gel; Aluminium Silicates; Sol gel process; Sintering; Mullite; Manufacturing; Experimental study; Ceramic materials; Precursor; Organic silicate
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/S0955-2219(98)00087-9

Mullite (3Al 2O 3 2SiO 2) samples have been prepared from mixture of TEOS and boehmite, with and without dehydroxylation at 400 °C. The precursor samples during the process of phase formation were characterized with respect to TGA, DTA, TMA, and X-ray diffraction at various temperatures. The result shows that by using a partially dehydroxylated boehmite, an enhanced transitional alumina phase is found at a lower temperature (~1000 °C) along with traces of α-Al 2O 3. With an increase in soaking time, the intensity of α-alumina is often found to increase. The formation of mullite takes place at 1225 °C and the α-Al 2O 3 formed at a lower temperature remains unaffected even at 1500 °C. On the other hand, in the samples prepared from boehmite and TEOS, the transitional alumina phase is observed only at 1225 °C and it transforms to phase pure orthorhombic mullite at 1250 °C. Thus while the partially dehydroxylated boehmite appears to be more reactive to transform to transitional alumina phase at lower temperature, the mullite formation temperature does not occur below 1225 °C. The results of investigation are presented and discussed.