Chemical Engineering - Refractory Technology

11. 

Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of __________ percent respectively.

A. 80 and 20
B. 20 and 80
C. 50 and 50
D. 60 and 40

Answer: Option A

Explanation:

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12. 

Pick out the wrong statement.

A. Refractories used in muffle furnace should have low thermal conductivity.
B. The electrical resistivity of refractories drops rapidly with rise in temperature.
C. For reducing spalling tendency, the refractory should be well fired and its porosity should be more.
D. Refractoriness under load (RUL) of a refractory is always less than its refractoriness.

Answer: Option A

Explanation:

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13. 

__________ bricks should not be used in oxidising atmosphere.

A. Tar dolomite
B. Carbon
C. Silica
D. Fireclay

Answer: Option B

Explanation:

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14. 

Pick out the wrong statement.

A. Insulating refractories used in place of regular refractory bricks are usually called light weight refractories, and they have similar composition as heavy bricks.
B. Graphite refractories are also called plumbago refractories.
C. Superduty fireclay bricks correspond to a pyrometric cone equivalent of 26-28.
D. Calcined magnesite is also called dead burnt magnesite.

Answer: Option C

Explanation:

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15. 

Fusion temperature of pure silica (SiO2) is __________ °C.

A. 1350
B. 1715
C. 2570
D. 2800

Answer: Option B

Explanation:

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