This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Types of Glasses and their Properties”.
1. How much SiO2 does Pyrex contain?
a) 70.3%
b) 73%
c) 80.5%
d) 91%
View Answer
Explanation: Pyrex is a borosilicate glass having a low thermal expansion. It consists of 80.5% SiO2 along with B2O3 (11.9%), and small quantities of Na2O, K2O, CaO, and Al2O3. This glass is mainly used in laboratory equipment and kitchenware.
2. How does the addition of magnesia and alumina affect soda lime glass?
a) Enhances mechanical strength
b) Reduces porosity
c) Increases softening temperature
d) Improves chemical durability
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Explanation: Sodium carbonate is added to fused quartz glass to lower glass transition temperature. However, this results in water solubility. In order to prevent this, magnesia (MgO) and alumina (Al2O3) are added, which increases chemical durability of the glass.
3. What is the melting temperature of fused quartz?
a) 1112oC
b) 1328oC
c) 1525oC
d) 1723oC
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Explanation: Fused quartz is a glass made of chemically-pure silica. It has tremendous resistance to thermal shock and has a melting temperature of about 1723oC. However, it has a low thermal expansion and is generally hard.
4. What is the maximum usable temperature of soda like glass?
a) 860 F
b) 941 F
c) 1084 F
d) 1324 F
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Explanation: Soda lime glass is regarded as the most preferred form of glass due to its low cost and ease of use. Annealed glass can be used up to 860 F whereas tempered form may be usable up to 480 F. These glasses are used in ordinary windows and bottles.
5. What is the Kovar type of glass?
a) Low expansion type
b) Low electrical loss type
c) Sealing type
d) Ultraviolet transmitting type
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Explanation: Kovar glass is a well-known type of sealing grade of borosilicate glass. These are used in glass-to-metal sealing applications.
6. What is the crown type of glasses?
a) Laboratory apparatus grade
b) Optical grade
c) Sealing type
d) Ultraviolet transmitting type
View Answer
Explanation: Optical grade is one brand of borosilicate glass illustrated by high light transmission (HLT). They also possess good corrosion resistance. The optical grade of glass is otherwise known as the crown.
7. What are lead glasses used for?
a) Kitchenware
b) Optical components
c) Electronic tubes
d) Temperature thermometers
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Explanation: Lead glasses are known as lead-alkali glasses which contain lead as its primary constituent. They have high electrical resistivity and are moderately economical. These glasses are used in optical applications, neon-sign tubing, and electrical bulb stems.
8. Which type of glass is regarded as the most heat resistant?
a) Fused silica
b) Aluminosilicate
c) 96% silica
d) Borosilicate
View Answer
Explanation: Fused silica is characterized as 100% silicon dioxide and is known as fused quartz in its naturally occurring state. It has a high level of transparency owing to its purity. This glass is heat resistant up to 1650 F in continuous service, and up to 4172 F in short-term service, making it the most heat-resistant glass.
9. What is 96% silica glass used for?
a) Heat shield
b) Combustion tubes
c) Electronic tubes
d) Temperature thermometers
View Answer
Explanation: Ninety-six-percent silica glasses are similar to fused silica, but are easier to fabricate and have a higher coefficient of expansion. These can be used as heat shields in space vehicles and other chemical glassware. Aluminosilicate glasses can be used in high-temperature thermometers and combustion tubes.
10. What is the maximum service temperature of aluminosilicate glass?
a) 220oC
b) 460oC
c) 650oC
d) 1200oC
View Answer
Explanation: Aluminosilicate glasses are generally expensive and have more thermal shock resistance. Their maximum service temperature in the annealed state is 650oC. The maximum service temperatures for soda lime and fused silica are 460oC and 1200oC correspondingly.
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