A. Alumina
B. Thoria
C. Zirconia
D. Magnesia
Related Mcqs:
- The highest melting pure oxide (m.p. > 3000°C)is___________________?
A. Thoria
B. Alumina
C. Beryllia
D. Zirconia - _____________ is not a single oxide-refractory?
A. Zirconia
B. Silicon carbide
C. Magnesia
D. None of these - 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 - 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 - Fusion point of a basic refractory material is__________________?
A. Reduced by the addition of acid oxides
B. Increased by the addition of acid oxides
C. Not affected by the addition of acid oxides
D. Always less than 1000°C - Pure oxide refractories are generally monocrystalline in nature and are self bonded _______________ bricks are generally used as moderator in nuclear reactors?
A. Beryllia
B. Carborundum
C. Corundum
D. Thoria - Beryllia (which is used in making crucibles for melting uranium & thorium) is superior to alumina in all respects for high temperature (> 1900°C ) use, except ?
A. Cost
B. Electrical conductivity
C. Thermal conductivity
D. Fusion point - 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 - Carborundum used for making crucibles for melting non-ferrous metals is chemically________________?
A. Silicon carbide
B. Silicon nitride
C. Crystalline magnesia
D. Zirconium sulphate - Firing of refractory brick is done to __________________?
A. Dehydrate the dried refractory
B. Develop stable mineral forms in them
C. Form ceramic bonds necessary for development of high crushing strength in the finished
product
D. All A., B. and C.
