Pure oxide refractories are generally monocrystalline in nature and are self bonded _______________ bricks are generally used as moderator in nuclear reactors?

Related Mcqs:

1. Faster rate of drying of moulded refractories results in high _____________ of refractories?

   A. Green strength
   B. Voids
   C. Shrinkage
   D. Both B. and C.

2. The highest melting pure oxide (m.p. > 3000°C)is___________________?

   A. Thoria
   B. Alumina
   C. Beryllia
   D. Zirconia

3. Pure bauxite is the best raw material for the manufacture of high alumina refractories, in which maximum alumina content can be as high as _____________ percent?

   A. 55
   B. 70
   C. 80
   D. 90

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. 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

6. Magnesite refractories are generally not used in the___________________?

   A. Electric furnace walls
   B. Steel melting furnace
   C. Open hearth furnace
   D. Burning zone of cement kilns

7. Tar bonded dolomite bricks__________________?

   A. Are stored under controlled temperature & humidity to avoid hydration
   B. Are used in outer lining of L.D. converters
   C. Have poorer hydration resistance than pitch bonded bricks
   D. All A., B. and C.

8. Refractories are dried in the _______________?

   A. Rotary kilns
   B. Tunnel kilns
   C. Sun
   D. None of these

9. 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

10. Porosity of fireclay refractories is _______________ percent?

    A. 5-10
    B. 10-25
    C. 25-35
    D. 35-50