Refractory Technology

211. With increase in the porosity, thermal spalling resistance of fireclay brick

1. Increases
2. Decreases
3. Remain same
4. May increase or decrease

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212. With increasing alumina content, the fusion point of high alumina refractories

1. Increases
2. Decreases
3. Remain constant
4. May increase or decrease; depends on its alumina content

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213. Zircon refractories have

1. Low co-efficient of expansion
2. High RUL (1600°C) and refractoriness (> 2000°C)
3. High spalling resistance
4. All (A), (B) and (C)

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214. Zirconia refractories are not used in

1. Making sheaths for thermocouple
2. Lining high temperature ceramic kilns
3. Furnaces subjected to fluctuating temperature
4. High frequency induction furnaces in the form of inductors

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215. Zirconia refractory

1. Does not react with basic slags
2. Is produced from baddeleyite
3. Cannot be used as an insulator
4. Has poor electrical conductivity at high temperature

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