Refractory Technology

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

1. 80 and 20
2. 20 and 80
3. 50 and 50
4. 60 and 40

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102. Mullite is chemically represented by

1. Al2O₃. 2SiO₂
2. 3Al2O₃. 2SiO₂
3. Al2O₃. SiO₂
4. 2Al2O₃. 3SiO₂

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103. Natural silica

1. Mainly contains quartz
2. Is not stable at high temperature
3. Transforms to other allotropic forms i.e. Tridymite and Cristobalite involving very high volume changes
4. All (A), (B) and (C)

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104. Outer combustion chamber of blast furnace stove is lined with _________ bricks.

1. Fireclay
2. Silica
3. Chrome magnesite
4. Zirconia

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105. Panel test determines the _________ of refractories.

1. Fusion point
2. Spalling resistance
3. Slag penetration resistance
4. Refractoriness under load (RUL)

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106. PCE value (Segar cone) of Superduty refractories is more than 33, which is equivalent to a temperature of _________ °C.

1. 1520
2. 1630
3. 1670
4. 1730

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107. Periclase is

1. Crystalline form of MgO
2. MgCO₃
3. ZrSO₄
4. Amorphous magnesite

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108. Periclase refractory contains mainly

1. CaO
2. MgO
3. Al₂O₃
4. SiO₂

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109. Permeability of bricks is a measure of the

1. Refractoriness
2. Melting point
3. Rate at which a fluid will pass through the pores
4. Expansion during heating

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110. Pick out the wrong statement.

1. Fluxing material like lime is added in clay to reduce the vitrification temperature
2. Main constituents of clay are alumina and silica
3. Addition of sand in ceramic materials makes it non-plastic, increases its fusion point and reduces its shrinkage on burning
4. Vitrification of fireclay material is done to increase its porosity

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