Which is the stable form of silica upto 1470°C ?

Related Mcqs:

1. Which is the stable form of silica between 1470°C and the melting point 1713°C ?

   A. Cristobalite
   B. Tridymite
   C. Quartz
   D. None of these

2. Which is the most stable crystalline form of silica at room temperature ?

   A. Quartz
   B. Cristobalite
   C. Tridymite
   D. None of these

3. Which is the stable form of silica below 870°C ?

   A. Tridymite
   B. Cristobalite
   C. Quartz
   D. None of these

4. Semi-silica bricks compared to silica bricks have_______________?

   A. Less fusion point
   B. Better spalling resistance
   C. Both A. and B.
   D. Neither A. not B.

5. Which form of silica has the highest specific gravity ?

   A. Quartz
   B. Cristobalite
   C. Tridymite
   D. All have the same specific gravity

6. An indication of degree of firing in silica brick is its____________________?

   A. Specific gravity
   B. Fusion point
   C. RUL
   D. None of these

7. Silica refractories are not used in _________________?

   A. Coke oven walls
   B. Beehive coke ovens
   C. Dome and upper portion of B.F. stoves
   D. Open hearth furnace roof

8. Porosity of silica bricks varies from ______________ percent?

   A. 5 to 10
   B. 20 to 30
   C. 45 to 60
   D. 60 to 75

9. Silica bricks have low spalling resistance below 600°C, due to its________________?

   A. Very high thermal conductivity
   B. High co-efficient of expansion upto this temperature
   C. High thermal diffusivity
   D. Low refractoriness

10. Use of higher percentage of lime for bonding silica bricks, reduces their__________________?

    A. Strength
    B. Abrasion resistance
    C. Both A. & B.
    D. Neither A. nor B.