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 others (e.g. kyanite).

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 the significant volume expansion that kyanite does during firing. That makes it better for high-density refractories, crucibles, and sintered ceramics where thermal stability and strength are needed.

Related Information

Links

Oxide	Analysis	Formula	Tolerance

Materials	Kyanite Kyanite is a granular material used in the manufacture of ceramics and abrasives. It is notable for low thermal expansion and one-way expansion on heating.
Materials	Mullite
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

By Tony Hansen
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