JNTU
JNTU B.Tech IV MECHANICAL BEHAVIOUR OF NANO MATERIALS Previous Question Paper (November/December - 2018 - R15)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Part B consists of 5 Units. Answer any one full question from each unit.
PART - A
What are different types of nanostructures.
Answer
Nanostructures are classified based on their dimensionality: zero-dimensional (0D) structures (e.g., nanoparticles, quantum dots), one-dimensional (1D) structures (e.g., nanowires, nanotubes, nanorods), two-dimensional (2D) structures (e.g., nanosheets, thin films, graphene), and three-dimensional (3D) structures (e.g., bulk nanostructured materials, nanocomposites).
Explain the Heterogeneous nucleation phenomena in the processing of nano material.
Answer
Heterogeneous nucleation occurs when a new phase forms on existing surfaces, such as impurities, container walls, or grain boundaries. These sites reduce the activation energy barrier required for nucleation compared to homogeneous nucleation, allowing the process to occur at lower levels of supersaturation or undercooling by providing a pre-existing interface that lowers the surface energy penalty.
Give few examples for two dimensional nano materials.
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Define Ductility.
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What are the thin film nano composite materials application?
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What are the advantages of grain refinement.
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Give few examples for wear characteristics materials.
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Explain the Fatigue and Creep in nano materials.
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Define hardness.
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Explain the terms of Bending and Curvature in indentation.
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PART - B
Explain any Top-down method for the synthesis of nanomaterials with few examples.
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Explain any Bottom-up method for the synthesis of nanomaterials with few examples.
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Discuss the plastic deformation methods:
ECAP
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ball milling.
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Discuss the advantages and disadvantages of Shear bands formation in Bulk materials.
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Discuss the theory of Hall-Petch effect.
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Write a short note on grained and nanocrystalline materials.
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Explain the significance of Strain Hardening in nanomaterials.
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Explain:
Dispersion strengthening
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Precipitation hardening
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Why is strain hardening also called cold working? What kind of microstructure develops after cold working?
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What are the different stages of precipitation hardening? And explain what kind of alloy system hardens by precipitation?
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Describe the Fatigue behavior of nanocrystalline materials with few examples.
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How the wear characteristics differ in bulk and nano.
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Briefly discuss and describe the Nabarro–Herring creep.
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Explain the advantages of wear resistance characteristics in nano.
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How to measure the mechanical behavior using Nanoindentation instrument?
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Discuss the tools to probe the nano-mechanical behavior with associated mechanics in bulk materials.
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Briefly discuss about Carbon material for the manufacturing of MEMS/NEMS devices.
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Discuss the tools to probe the nano-mechanical behavior with associated mechanics in thin films.
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