Fabrication of Mullite and Mullite-Matrix Composites by Transient Viscous Sintering of Composite Powders |
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Authors: | Michael D. Sacks Nazim Bozkurt Gary W. Scheiffele |
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Affiliation: | Ceramics Division, Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 |
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Abstract: | Mullite was fabricated by a process referred to as transient viscous sintering (TVS). Composite particles which consisted of inner cores of α-alumina and outer coatings of amorphous silica were used. Powder compacts prepared with these particles were viscously sintered to almost full density at relatively low temperatures (∼1300°C). Compacts were subsequently converted to dense, fine-grained mullite at higher temperatures (∼1500°C) by reaction between the alumina and silica. The TVS process was also used to fabricate mullite/zirconia/alumina, mullite/silicon carbide particle, and mullite/silicon carbide whisker composites. Densification was enhanced compared with other recent studies of sintering of mullite-based composites. This was attributed to three factors: viscous flow of the amorphous silica coating on the particles, avoidance of mullite formation until higher temperatures, and increased threshold concentration for the development of percolation networks. |
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Keywords: | mullite composites sintering powders |
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