Mullite (3Al₂O₃−2SiO₂) Synthesis with Aluminosiloxanes

Abstract

High-yield mullite (3Al2O3−2SiO2) precursors consist of aluminosiloxanes synthesized from mixtures of aluminum and silicon alkoxides. Atomic level mixing of the aluminum and silicon oxides is demonstrated by the low-temperature conversion (<1000 °C) of the aluminosiloxanes to phase-pure mullite. The proper selection of monomeric side groups serves several functions: (i) controlling reactivity of the silicon and aluminum monomers, thereby favoring atomic-level mixing; (ii) maintaining the tractability of the resulting aluminosiloxane; (iii) improving the yield during mullitization of the aluminosiloxane through easy thermolytic removal. The tractability of the aluminosiloxane compounds permits these materials to be used in fiber spinning, the casting of thin films and monoliths, and as impregnants to powder compacts.