ABSTRACT
This chapter discusses the mullite formation by various chemical methods and study the phase evolution behavior by differential thermal analysis and X-ray diffractometry. Mullite is synthesized by the aqueous sol-gel method by the gelation of a water-soluble silica component in the presence of Al salt. The colloidal system of alumina-silica-water is synthesized on the basis of adsorption of aluminum hydroxide on the silicon hydroxide gel surface. The spectroscopic measurement shows that alumina incorporation likely takes place to the extent of 30% in the silica framework. As a result, the surface properties of silica-alumina combinations differ to some extent. Mullite was synthesized by the monophasic gel method by the hydrolysis and gelation of the organic silicon component in the presence of a water-soluble component in absolute alcohol and an acidic medium. Mullite can be synthesized by the polymeric and colloidal gel methods involving hydrolysis and subsequent cogelation of organic Al and Si compounds in a neutral to a slightly acidic medium.
