Which is not an alumino-silicate refractory ?

Related Mcqs:

1. Presence of MgO in alumino-silicate refractories _______________ its refractoriness?

   A. Increases
   B. Lowers
   C. Does not affect
   D. Either A. or B.; depends on its quantity

2. Sillimanite (Al2O3.SiO2) refractory, which is a neutral refractory, is not used in________________?

   A. Pottery furnace
   B. Glass melting furnace
   C. Crucibles
   D. Gas retorts

3. An ideal refractory should have high__________________?

   A. Spalling rate
   B. Fusion point
   C. Shrinkage ability
   D. None of these

4. _____________ is not a single oxide-refractory?

   A. Zirconia
   B. Silicon carbide
   C. Magnesia
   D. None of these

5. Which refractory must have controlled atmosphere (temperature and humidity) for its safe storage ?

   A. Tar bonded dolomite bricks
   B. Fireclay bricks
   C. Mullite bricks
   D. Magnesite bricks

6. High porosity refractory bricks have _______________?

   A. Poor resistance to the penetration of molten slag, metal & flue gases
   B. Poor heat conductivity & low strength
   C. Better thermal spalling resistance
   D. All A., B. and C.

7. To resist spalling tendency, a refractory should have________________?

   A. Greater diffusivity
   B. Low specific heat
   C. Low thermal co-efficient of expansion
   D. All A., B. and C.

8. Which is a basic refractory ?

   A. Fireclay
   B. Silica
   C. Chrome magnesite
   D. None of these

9. Which is required in an insulating refractory ?

   A. High thermal conductivity
   B. Low porosity
   C. Both A. and B.
   D. Neither A. nor B.

10. Thoria is an expensive refractory material and is radioactive in nature. Thorium oxide is used in the manufacture of______________?

    A. Segar cones
    B. Muffles for muffle furnaces
    C. Insulating bricks
    D. Crucibles used for melting of high purity metals