Materials Science Questions and Answers – Classification of Crystallographic Defects

This set of Materials Science Interview Questions and Answers for Experienced people focuses on “Classification of Crystallographic Defects”.

1. Frenkel defect belongs to which of the following classes?
a) Point defect
b) Linear dislocation
c) Interfacial defect
d) Bulk defect
View Answer

Answer: a
Explanation: Frenkel defect occurs when some of the smaller ions shift from their lattice point to interstitial positions.

2. The ratio of the number of vacancies to a total number of lattice points for a metal near melting temperature is of the order of 10-4. For lower temperatures, the ratio:
a) increases
b) decreases
c) remains the same
d) may increase or decrease depending on the metal
View Answer

Answer: b
Explanation: At lower temperature, less energy is available in the system which means less number of atoms are able to leave their lattice sites to create vacancies.

3. Foreign species is present in which of the following defects?
a) Interstitial
b) Vacancy
c) Substitution
d) All of the mentioned
View Answer

Answer: c
Explanation: In substitution defect, particles of other species having similar sizes replace the host particles in a lattice whereas interstitial defect occurs when particles of the same species are present at interstitial voids.
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4. Edge dislocation and screw dislocation are linear crystalline defects.
a) True
b) False
View Answer

Answer: a
Explanation: Edge dislocation and screw dislocations are linear crystalline defects or line defects.

5. Burger vectors are relevant to which of the following crystalline defects?
a) Point defects
b) Line defects
c) Interfacial defects
d) Bulk defects
View Answer

Answer: b
Explanation: Burger vector denotes the magnitude and direction of a line defect.
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6. Pores & cracks in crystalline solids can be classified as bulk defects.
a) True
b) False
View Answer

Answer: a
Explanation: Pores and cracks are not localized to a particular point or edge, but have sizes much larger than atomic dimensions.

7. Ferromagnetic material shows strong para-magnetic behaviour due to the formation of domains. These domains belong to:
a) Point defects
b) Linear defects
c) Interfacial defects
d) Bulk defects
View Answer

Answer: c
Explanation: In ferromagnetic materials, the alignment of magnetic dipoles vary across domain walls. These walls spread across large surfaces but have negligible thickness.
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8. Electrical conductivity of the specimen is a requirement for which of the following microscopic examination techniques?
a) Optical microscopy
b) Transmission electron microscopy
c) Scanning electron microscopy
d) Scanning probe microscopy
View Answer

Answer: c
Explanation: Non-conducting specimen will develop electrostatic charge due to an incident electron beam. This field tends to produce faults in the signal interpretation.

9. Which of the following point defects is non-stoichiometric in nature?
a) Schottky defect
b) Metal excess defect
c) Interstitial defect
d) Impurity defect
View Answer

Answer: b
Explanation: When alkali halides are heated in an atmosphere of the constituent metal, halide ions diffuse to the surface to react with the vapour particles. This results in excess of cations over anions.
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10. The solubility of solute in a solvent in a solid solution is governed by Hume-Rothery rules. The solubility is more if:
a) radii of solute are much smaller than that of solvent
b) solute an solvent have a similar crystal structure
c) solute has low valence
d) all of the mentioned
View Answer

Answer: b
Explanation: For high solubility, the solute-solvent pair should have similar radii, crystal structure, and electronegativity. Moreover, for other factors being equal, a solute with higher valence is more soluble than one having lower valence.

Sanfoundry Global Education & Learning Series – Materials Science.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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