This set of Engineering Materials & Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Ceramic Formation & Clay Ceramics”.
1. Which of the following is a glass forming technique?
a) Powder pressing
b) Hydro-plastic forming
c) Slip casting
d) Fiber forming
Explanation: Glass forming is done by heating the raw materials to elevated temperatures. The common glass forming techniques are Pressing, Blowing, Drawing, and Fiber forming. Glass forming operation does not require drying and firing of the materials.
2. Drawing and firing operations are done on which of these processes?
b) Fiber forming
d) Slip casting
Explanation: Slip casting, along with hydro-plastic forming and powder pressing, is a particulate forming process of ceramic fabrication. All the processes of particulate forming undergo drying and firing operations. Drying process removes the liquid, whereas firing improves its density and strength.
3. Which of the following is not a form of powder pressing?
a) Hot pressing
b) Cold pressing
Explanation: Powder pressing is a ceramic formation technique used to fabricate both clay and non-clay compositions. A powdered substance is added with water and pressure is applied in this process. Uniaxial, Isostatic (hydrostatic), and hot pressing are the three types of powder pressing operations.
4. What is the firing temperature for particulate forming processes?
Explanation: Firing is a process carried out to improve the strength and density of a part, under the application of high temperature. This is generally carried out after the drying process. After drying, the body is fired at a temperature of 900oC to 1400oC. This temperature depends on the composition and properties of the component.
5. What does the term ‘green’ refer to for drying and firing operations?
a) Fired but not dried
b) Dried but not fired
c) Dried then fired
d) Fired then dried
Explanation: Drying and firing are two operations carried out in a particulate forming technique of ceramic fabrication. Usually, the body is dried before it is fired. In some cases, however, the body may be formed and dried but not fired. Such a body is referred to as ‘green’.
6. Which pressing technique employs a rubber envelope and application of pressure by fluid?
a) Hot pressing
b) Uniaxial pressing
c) Isostatic pressing
d) Powder pressing
Explanation: Hot, uniaxial, and isostatic pressing are techniques of the powder pressing method. In the isostatic method, a rubber envelope contains the powdered material which is applied pressure on by a fluid, equally in all directions. This differs from uniaxial pressing as the pressure is only applied in a single direction for that operation, but is similar in the sense that they both require being fired after pressing.
7. Which of these holds true for cementitious bonds?
a) High cost
b) Easy to repair
c) Short curing time
d) Hard to repair
Explanation: Cementitious bonds are advantageous as the molds and equipment are available are a low cost and that they are easy to patch and repair. One of the disadvantages of these is that large castings require a long time for curing.
8. Injection molding can be used for parts of thickness up to __________
a) 4 mm
b) 6 mm
c) 8 mm
d) 12 mm
Explanation: Injection molding forms thin, long, and twisted shapes with good reproducibility. They cannot, however, be used for parts whose thickness is more than 6 mm. Another major disadvantage of injection molding is that the cost of molds is generally high.
9. What is the common name for fired clay wares?
Explanation: Pottery is defined as the generic name for all fired clay ware, where clay is referred to as a ceramic. This has even been defined by the American Society of Testing Materials. These days, however, this term has been often associated with being colored and porous.
10. The shape forming process PIM known as __________
a) Porcelain Injection Molding
b) Plastic Injection Molding
c) Particulate Injection Molding
d) Pottery Injection Molding
Explanation: Porcelain Injection Molding is a shape forming process employed for fabrication of tableware. It is generally used for mass production of parts of intricate shapes. However, this is not a very common method of pottery.
11. What is the firing temperature of structural clay products?
Explanation: Clay products are cut into wires after undergoing the process of crushing, disintegration, and extrusion. They are then dried and fired at a temperature of 980-1095oC. This depends on the maturing temperature of the clay.
12. Which of the following is a property of porcelain?
Explanation: Porcelain is a glazed or unglazed type of whiteware ceramic. They are vitreous in nature (hard and nonabsorbent). They are usually used for their mechanical, electrical, chemical, and thermal properties. Unlike china, it requires only a single firing operation due to which it is cheaper.
13. What is China commonly used for?
a) Electrical insulators
c) Laboratory equipment
Explanation: China is glazed or unglazed vitreous whiteware ceramic used for nontechnical purposes. They are mainly used as dinnerware and artworks as they are available in more colors due to a lower maturing temperature. Porcelain is used for electrical insulators and laboratory equipment.
14. Salt glazing is a manufacturing technique of _______ ceramics.
a) structural clay
Explanation: Salt glazing is a technique of fabrication of structural clay products. The salt is added after the firing process to add a vitreous coating. This is generally used on structural tiles and conduit.
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