Refractory Technology
Thermal conductivity of refractory bricks

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

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Refractory Technology
What is Thoria?

Which is expensive & radioactive, is used in crucibles for melting high purity metals
Thoria Has high fusion temperature (> 3000°C) but poor resistance to thermal shock
Thoria Has high resistance to basic slags
All of these

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Refractory Technology
Carbon refractories

Are not attacked by slags, as they are not wetted by melts
Do not resist temperature fluctuations
Have extremely low thermal & electrical conductivities
Do not burn/oxidise, when exposed to air on heating

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