Refractory Technology

1
Spinel', a refractory mineral is chemically represented as

A. MgAl2O4
B. MgAl2O3
C. MgSO4
D. MgAl2O3.2H2O

2

Mullite is chemically represented by

A. Al2O3 . 2SiO2
B. 3Al2O3 . 2SiO2
C. Al2O3 . SiO2
D. 2Al2O3 . 3SiO2

3

Magnesite chrome refractories

A. have better spalling resistance than chrome magnesite refractories.
B. have very low thermal co-efficient of expansion.
C. are not at all resistant to the corrosive action of iron oxide
D. have very low (50 kg/cm2 ) cold crushing strength (C.C.S.), and can not be used in metalcase form.

4

Which of the following impurities reduces the refractoriness of magnesite bricks ?

A. Al2O3
B. CaO
C. SiO2
D. all (a), (b) & (c)

5

Periclase is

A. crystalline form of MgO
B. MgCO3.
C. ZrSO4.
D. amorphous magnesite.