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Materials for Ceramics

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Sillimanite

Notes

An aluminum silicate mineral ground for use in high-temperature refractory bodies (e.g. crucibles, kiln shelves). It is not as widely used as its polymorphs kyanite and andalusite.

Sillimanite, like kyanite, transforms into mullite and silica when heated to high temperatures. Partial transformation can begin as low 1000°C but higher temperatures (e.g. 1400°C) accelerate it. Sillimanite is more thermally stable than kyanite, taking more firings and higher temperatures to transform. Once transformed, its thermal expansion properties are similar to those of mullite derived from kyanite. The untransformed material has a thermal expansion more similar to mullite than kyanite does.

Sillimanite sinter bonds better than kyanite because it has a more stable crystal structure and does not undergo as significant a volume expansion as does kyanite during firing. That can make it better for some high-density refractories, crucibles, and sintered ceramics.

Related Information

Links

Oxide	Analysis	Formula	Tolerance

Materials	Kyanite A refractory aluminum silicate mineral notable for low thermal expansion and one-way volume expansion as it converts to mullite at high temperatures.
Materials	Mullite A highly refractory low-expansion alumino-silicate crystal formed naturally only rarely but produced industrially and within fired kaolin bodies.
Materials	Andalusite A low expansion aluminum silicate mineral that converts to mullite on repeated firings.
Typecodes	Refractory Materials that melt at high temperatures. These are normally used for kiln bricks, furniture, etc. or for ceramics that must withstand high temperatures during service.
Minerals	Sillimanite A low expansion aluminum silicate mineral that converts to mullite on repeated firings.
URLs	http://en.wikipedia.org/wiki/Sillimanite Sillimanite at Wikipedia
URLs	http://www.handbookofmineralogy.org/pdfs/Sillimanite.pdf Sillimanite mineralogy

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