About this previous year paper
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.
Q4. Cupola Furnace
Used for melting cast iron in foundries.
Zones: Crucible → Melting → Combustion → Preheating.
Operation: Coke burns to melt metal; flux removes impurities as slag.
Limitations: Cannot melt high-melting metals; pollution issues.
Q5. Patterns & Pattern Allowances
Pattern: Replica of casting used to prepare mould cavity.
Allowances:
Shrinkage – compensates contraction during cooling.
Machining – extra material for finishing.
Draft – taper for pattern removal.
Rapping – for easy withdrawal.
Distortion – for warping correction.
Summary
The Material Science (CH404) paper comprehensively tests:
Atomic structure and bonding
Crystal geometry and defects
Mechanical properties (stress, strain, fracture)
Metal processing (casting, working, heat treatment)
Modern materials (polymers, ceramics, smart materials)