1100-1450C (2012-2642F)
Kyanite decomposition and volume expansion
The exact range depends strongly particle size, firing rate, soak time and purity of the kyanite. Fine particles convert earlier and more completely; coarse particles convert more gradually. Associated specific gravity change from 3.6 to about 3.0. As the Kyanite crystal structure breaks down mullite crystals form in their place and free silica is released. The crystal rearrangement creates a volume increase of 4-8%.
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Kyanite
A refractory aluminum silicate mineral notable for low thermal expansion and one-way volume expansion as it converts to mullite at high temperatures. |