Refractory Technology
Natural silica

Mainly contains quartz
All of these
Transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes
Is not stable at high temperature

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Refractory Technology
Thermal conductivity of refractory bricks

Is independent of its porosity and is maximum for insulating bricks
Increases with decrease in porosity
Decreases with decreases in porosity
Increases with the amount of air entrapped in pores

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