PART A (40%)
Attempt any FIVE of following questions ( 8%
each)
| 1. |
Consider an edge dislocation within a crystal
with a cubic lattice structure. If the extra-plane ending on the edge is
(010), what is the Burger vector?
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| 2. |
Name two common examples, each
of (i) 0-dimentional and (ii) 2-dimentional defects in a crystal. Draw
a schematic diagram to illustrate one such defect.
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| 3. |
Calculate the resolved shear stress on
the {110} < 111> slip system, resulting from an applied stress
of 10 MPa along the [010] direction.
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| 4. |
Give a physical explanation as to why,
in the Brinell hardness test, the hardness number is 
where P represents the applied load, D the diameter of the spherical indentor,
and d the diameter of indentation mark.
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| 5. |
Name three processes by which a polycrystalline
metal may be made stronger, i.e. may attain greater yield strength. Briefly
describe how any one such process works.
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| 6. |
How is tempered glass produced?
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| 7. |
The resonance frequency of a Quartz plate is
given by f=Vp/(2w), where Vp designates the transverse elastic waves velocity
along the plate thickness w. This property may be utilized to monitor thin
film deposition. Show, mathematically, how the deposition rate depends
on the rate of change in resonance frequency, df/dt.
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| 8. |
Point out the major difference, in operation
principle, between differential scanning calorimetry and differential
thermal analysis. Cite one advantage and one disadvantage of each technique
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PART B (60%)
Answer ALL questions in this Part B ( 15% each).
| 9. |
A substance is known to change from the bcc
to the fcc crystal structure above 67.8?. Also
known are its density and lattice constant at 20?,
namely 1.36 Å and 2.8gcm-3. Its lattice constant at 68.0?
, a*, needs, however, to be determined.
One student finds a* by measuring its density at 68.0?,
which turns out to be 2.6 gcm-3. Another is able to perform
a power X-ray diffraction experiment on a sample at 68.0?,
and abserves the first diffraction peak at q
= 38.6? using X-ray of =1.54 Å.
Whose result should be more accurate? What is the percentage error in
the less accurate value of a*?
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| 10. |
With the help of a schematic diagram, explain
how a rotary pump ( of a particular type chose by you) generates
vacuum.
You have been asked to purchase additional vacuum components, to build
an rf triode sputtering system for the gold coating of jewellary.
Draw a schematic diagram for the whole system, clearly labelling all parts.
Specify the types of pump, etc.
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| 11. |
Show in details why a four-point probe
measurement leads to a more exact value of the electrical resistance of
a conductor, than a two-point probe measurement.
The quality control of some products involve the test of whether their
resistances do not exceed 1 mW . Two models
of constant current source are rated at 10mA(max) and 50mA (max) but cost
$1,000 and $2,000, respectively, whilst three voltmeters offer resolutions
of 100m V, 20m V
and 10m V for the prices of $2,000 , $3,000
and $5,000 respectively. Which current source and which voltmeter will
you buy to do the job most economically?
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| 12. |
Explain why photoelectron spectroscopy measurements,
are sensitive to the surface but not to the bulk.
Draw the electron binding energy diagram for a hypothesis metal.
Then sketch the expected (i) X-ray and (ii) ultraviolet photoelectron spectra
from this metal, with the photoelectron kinetic energy to scale ( by assuming
certain photon energies.)
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