161. silicon carbide refractories have very low
refractoriness (< 1700°C).
thermal conductivity.
resistance to thermal shock.
none of these.
✅ The correct answer is option D.
Refractory Technology MCQs
162. Si percentage in silica refractories used in the walls of coke oven is about
45
60
80
95
✅ The correct answer is option D.
163. Cold crushing strength of refractories depends upon its
composition
texture
firing temperature
all (a), (b) and (c)
✅ The correct answer is option D.
164. Natural silica
mainly contains quartz.
is not stable at high temperature.
transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes.
all (a), (b) and (c).
✅ The correct answer is option D.
165. Maximum safe working temperature for fireclay bricks is about __________ °C.
1150
1300
1450
1550
✅ The correct answer is option D.
166. Which of the following impurities reduces the refractoriness of magnesite bricks ?
Al2O3
CaO
SiO2
all (a), (b) & (c)
✅ The correct answer is option D.
167. Ceramic recuperators used for waste heat recovery from high temperature flue gas going out of the furnace is made of
fireclay
silicon carbide
corrundum
siliceous fireclay
✅ The correct answer is option B.
168. Porosity of fireclay refractories is __________ percent.
5-Oct
Oct-25
25-35
35-50
✅ The correct answer is option B.
169. Carborundum used for making crucibles for melting non-ferrous metals is chemically
silicon carbide
silicon nitride
crystalline magnesia
zirconium sulphate
✅ The correct answer is option A.
170. Which is the stable form of silica between 1470°C and the melting point 1713°C ?
Cristobalite
Tridymite
Quartz
None of these
✅ The correct answer is option A.