Refractory Technology
An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture?

Chemically prepared foam
Cork
Saw dust
Sand

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Refractory Technology
What is Thoria?

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

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