THEORY EXAMINATION (SEM–IV) 2016-17 MATERIAL SCEINCE

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Course: B.Tech (Chemical / Mechanical / Metallurgical Engineering)
Subject Code: CH404
Subject Title: Material Science
Exam Type: Theory (Semester IV, 2016–17)
Duration: 3 Hours
Maximum Marks: 100

SECTION – A (10 × 2 = 20 Marks)

Short and fundamental questions — tests definitions, atomic concepts, and material behavior.

No.	Question	Concept Summary
(a)	What is a Solid Solution?	Homogeneous mixture of two or more elements in a single crystal lattice (e.g., brass = Cu + Zn). Types: substitutional and interstitial.
(b)	Define Unit Cell and Space Lattice.	Unit cell → smallest repeating structure; Space lattice → 3D arrangement of atoms representing crystal geometry.
(c)	Applications of Aluminum and Its Alloys.	Used in aircraft, packaging, heat exchangers, and lightweight structures due to low density and corrosion resistance.
(d)	Concept of Magnetism.	Property by which materials exert attractive or repulsive forces; classified as diamagnetic, paramagnetic, ferromagnetic, and antiferromagnetic.
(e)	Superconductivity.	Phenomenon of zero electrical resistance below a critical temperature (e.g., NbTi, Hg). Used in MRI, maglev trains.
(f)	Different Types of Lattices.	7 crystal systems, 14 Bravais lattices (Cubic, Tetragonal, Orthorhombic, etc.).
(g)	Atomic Mass and Atomic Number.	Atomic mass = total mass of protons + neutrons; Atomic number = number of protons (defines element).
(h)	Phase in Metals.	A region of material with uniform composition and structure (e.g., α, β phases in alloys).
(i)	Importance of Alloys.	Enhance mechanical, thermal, and corrosion resistance properties.
(j)	Atomic Model.	Describes atom’s structure — Thomson, Rutherford, Bohr, and Quantum models.

SECTION – B (5 × 10 = 50 Marks)

Detailed conceptual questions on metallurgy, defects, and material processing.

(a) Polymerization Techniques

Methods: Addition (chain-growth) and condensation (step-growth).

Techniques:

Bulk Polymerization – pure monomer, no solvent; produces clear polymer but risk of overheating.

Solution Polymerization – monomer dissolved in solvent; better heat control.

Suspension Polymerization – monomer droplets in water; forms beads.

Interfacial Polymerization – polymer forms at boundary between two immiscible liquids; used in thin-film membranes.

(b) Terms Explanation

Quenching: Rapid cooling from high temperature to increase hardness.

Poisson’s Ratio: ν=−lateral strainlongitudinal strain\nu = -\frac{lateral \ strain}{longitudinal \ strain}ν=−longitudinal strainlateral strain (typical metals ≈ 0.3).

Plastic Deformation: Permanent deformation beyond elastic limit due to dislocation motion.

(c) Carbon Steels

Type	Carbon %	Example	Properties
Low Carbon	< 0.25%	Mild steel	Ductile, malleable
Medium Carbon	0.25–0.6%	Structural steel	Good strength
High Carbon	0.6–1.5%	Tool steel	Hard, brittle, high wear resistance

(d) Investment Casting

Process: Wax pattern → ceramic coating → molten metal poured → shell broken → casting obtained.

Advantages: High precision, smooth finish.

Limitations: Costly, small part size.

(e) Hot & Cold Working

Aspect	Hot Working	Cold Working
Temperature	Above recrystallization	Below recrystallization
Strength	Lower	Higher
Ductility	High	Reduced
Surface Finish	Poor	Good
Example	Forging	Rolling, drawing

(f) Defects in Solids

Point Defects: Vacancies, interstitials, substitutionals.

Line Defects: Dislocations (edge, screw).

Surface Defects: Grain boundaries, twin boundaries.

Volume Defects: Voids, cracks, inclusions.

(g) Fracture in Metals

Types: Ductile (cup-and-cone) & Brittle (cleavage).

Causes: Overload, stress concentration, temperature drop, impurities.

(h) Crystalline vs Glass Ceramics

Property	Crystalline	Glass-Ceramic
Structure	Ordered	Partially crystalline
Strength	Moderate	High
Thermal Shock Resistance	Low	Excellent
Applications	Tiles, bricks	Cookware, insulators

SECTION – C (2 × 15 = 30 Marks)

Analytical and application-based questions on advanced materials and processes.

Q3. Smart Materials & Optical Fiber

Smart Materials: Materials that respond to external stimuli (stress, temperature, field).
Examples: Shape-memory alloys (Ni-Ti), piezoelectric ceramics, magnetostrictive materials.

Optical Fiber Principle: Total internal reflection — transmits light signals through a core surrounded by cladding.

Applications: Telecommunications, medical endoscopy, sensors, data transfer.