Group A
1 a) Draw schematic to show different types of Bravis lattices in crystalline material. calculate the atomic packing factor (APF)of FCC and BCC crystal structure.
b) Explain the types of defects in crystalline material in brief .
c) Differentiate between the edge and screw dislocation in term of burger’s vector .
d) Find the equilibrium concentration of vacancies in aluminium at 0k and 900 k . Enthalpy of formation of vacancies in aluminium , ∆Hf=68kj mol-1;R=8.314 jmol-1
2. a)Mention and explain Nernst-Einstein relation in diffusion.
b) Describe Fick’s second law of diffusion.the diffusion coefficient for copper in aluminium at 500 0 C and 600 0 C are 4.8*10-4 m2/s and 5.3x10-13 m2/s respectively . calculate the time required at 500 0 C to produce diffusion depth equal to that at 6000 C for 10 hr.
c) Explain Gibb’s phase rule . Find the degrees of freedom when FCC and BCC iron co exist in equilibrium.
d) Draw an eutectic phase diagram and explain it.
3. a) Draw and Explain Fe-Fe3C phase diagram. Indicate the carbon percentage range of steel.
b) Define peritectic reaction. Explain with a suitable phase diagram .
c) Explain the mechanism of working of zone refining process with the help of a diagram.
4. a) Differentiate between true and engineering stress – strain curve. Indicate the elastic zone ,plastic zone and yield point in stress strain curve of mild steel.
b) Describe viscoelastic behaviour of materials.Explain Maxwell element and voigt- Kelvin model
c) Explain Griffiths theory of brittle fracture ? why has silicate glass a relativelylow fracture strength.?
GROUP-B
5. a) Discuss different method of carburising ,nitriding and carbo-nitriding .
b) Define harden ability of metals . Describe jominy’s harden ability test in brief.
c) Discuss different mechanism of hardening in metals and allys
6. a) Explain the working principle of bimetallic thermo stat in regulating temperature.
b) Define thermal stress . Discuss stresses due to restrained thermal expansion and contraction ?
c) Define high temperature materials. Name some of the high temperature material .
d) What are ceramics? What is the range of thermal expansion coefficient in ceramics? Explain why ceramics have low coefficient of thermal expansion . 5
7 a) what are polymers? Describe briefly in terms ‘saturated polymer’ and ‘un saturated polymer’.
b) Differentiate between thermoplastic and thermosetting polymers .
c) Define the terms ‘composites’ . Describe the briefly about different types of composites and their application.
8. a) What are nano materials ? mention important application of nano materials .
b) Define curie temperature .what is spontaneous magnetisation ? write about characteristics of ferromagnetism material .
c) Discuss band theory of solids . Differentiate between metals semiconductor andinsulator on the basis of band theory.
Group-C
9 Answer the following in brief:
i) At high temperature,the mechanical strength is high or low ? Give answer with proper reasoning .
ii) Draw the binary phase diagramof Al2O3-Cr2O3. Clearly showing the tie line
iii) Why thoria dispersed nickel retains very good mechanical strength up to 0.9Tm , where Tm is its melting point ?
iv) Mention relative magnitudes of enthalpy of motion for the atoms moving on the surface along the boundary and within the lattice .
v) Explain how surface cracks can be made ineffective.
vi) Find the fractional amount of ferrite (α) and cementite (Fe3C)using lever’s rule and placing the fulcrum at 0.8% Carbon in iron-iron carbide phase diagram
vii) What is glass ? mention its important characteristics .
viii) Explain the degree of polymerisation.
ix) Draw the schematics of a) linear b) branched c) cross linked d)networked polymer structures
x) Define a) susceptibility b)permeability c)magnetisation of magnetic material
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