This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Dislocations in Ceramics”.
1. Polymers don’t have dislocations.
a) True
b) False
View Answer
Explanation: Polymers sometimes contain crystalline regions. These regions may contain dislocations.
2. Which bonding is found in ceramic compounds?
a) Ionic
b) covalent
c) metallic
d) ionic and/or covalent
View Answer
Explanation: Metals have metallic bonding. Ceramic compounds have ionic and/or covalent bonding. That’s why crystal structures of ionic ceramics are complex.
3. The Burgers vector in ionic crystal dislocations is _____ as compared to that of metallic solids.
a) Smaller
b) Larger
c) Equal
d) Not specific
View Answer
Explanation: Dislocations in ionic crystals are narrow. Narrow dislocations are difficult to move. Burgers vector in ionic crystal dislocation is larger than metallic solids.
4. Which planes are most densely packed in NiO crystal?
a) {1 0 0}
b) {1 1 0}
c) {1 1 1}
d) {0 0 0 1}
View Answer
Explanation: NiO crystal has NaCl type crystal lattice. It consists 2 ions per lattice positions. {1 0 0} are most dense packed planes.
5. Covalent crystals contain ____ dislocations and show _____ nature.
a) Narrow, ductile
b) Narrow, brittle
c) Wide, ductile
d) Wide, brittle
View Answer
Explanation: covalent crystals are bonded with strong and highly directional forces. The dislocations in these crystals are very narrow. It makes them very brittle.
6. Covalent crystals don’t show ____
a) Plastic deformation
b) Narrow dislocations
c) High P-N stress
d) Brittleness
View Answer
Explanation: Covalent crystals contain narrow dislocations. It makes them brittle and these don’t undergo plastic deformation. These crystals show high P-N stress values.
7. Ionic crystals consist _____ bonds.
a) Weak
b) Strong
c) Directional
d) Non-directional
View Answer
Explanation: Ionic Crystals consists of non-directional bonds. These are of moderate strength. These contain ionic bonding by electron transfer.
8. Simple ionic crystals show no plastic deformation.
a) True
b) False
View Answer
Explanation: Simple ionic crystals generally show very less plastic deformation. These show some plastic deformation when properly oriented with respect to the applied shear stress.
9. What is slip direction in CsCl?
a) <1 1 1>
b) <1 1 0>
c) <1 0 1>
d) <0 0 1>
View Answer
Explanation: CsCl has simple cubic symmetry with two interpenetrating ion lattices. Ions touch along <1 1 1> directions. Slip direction is of the <0 0 1> type.
10. What are slip planes in NaCl crystals?
a) {1 1 1}
b) {1 1 0}
c) {2 1 0}
d) {0 0 0 1}
View Answer
Explanation: NaCl has FCC structure. In FCC structure metals, slip occurs in {1 1 1} planes. But due to Coulombic energy, slip occurs in {1 1 0} planes in NaCl crystal.
11. Layered materials such as graphite and talk _____ deform by ______
a) Elastically, dislocation glide
b) Elastically, twinning
c) Plastically, dislocation glide
d) Plastically, twinning
View Answer
Explanation: Layered materials are crystalline non-metallic. These plastically deform by dislocation glide. Slip occurs by relative displacement of the strongly bonded planes.
12. What is the most commonly observed slip system in covalent crystals?
a) {1 2 3} <1 1 1>
b) {1 1 1} <1 0 0>
c) {1 1 2} <1 1 1>
d) {1 1 1} <1 1 0>
View Answer
Explanation: The most commonly observed slip system is {1 1 1} <1 0 0>. It is found in Si and Ge.
Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.
To practice all areas of Mechanical Behaviour & Testing of Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.
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