MAT6665



CANDIDATES ARE ADVISED TO READ THROUGH THE
INSTRUCTIONS GIVEN ON THIS PAGE CAREFULLY BEFORE
ATTEMPTING ANY QUESTIONS




MATERIALS PROCESSING AND CHARACTERISATION


Autumn Semester Exam 2019-2020

Duration of Exam: 3 hours


There are FOUR Sections

Answer ONE Question from EACH of SECTIONS A, B and C
Each Question is worth a possible total of 20 Marks

SECTION D – Compulsory
Answer ALL of Section D which is worth a possible total of 30 Marks



PLEASE WRITE YOUR ANSWERS IN THE ANSWER BOOK PROVIDED
NOT ON THE EXAM PAPER.

ANYTHING WRITTEN ON THIS PAPER WILL NOT BE CONSIDERED.





Department Of
Materials
Science &
Engineering.

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There are FOUR Sections

SECTION A – Answer ONE Question Only

1. (a) A diffracted beam is observed from the {211} planes of bcc K at 2θ = 42.46 °2θ
when Cu Kα1 X-rays (λ = 1.54056 Å) are used.
What is the lattice parameter of bcc K, in Å? [6 marks]

(b) Name the two main types of monochromator system commonly applied in Bragg-
Brentano geometry X-ray diffractometers. Give a brief description of where on
the goniometer they are likely to be mounted, using schematic diagrams if
appropriate, and discuss the functional role(s) that each monochromator system
plays. [6 marks]

(c) Beryllium has a relative atomic mass of 9.01, and a reported density of 1.85 g cm-3.
Given that the mass absorption coefficient of Be for Cu Kα radiation is
1.11 cm2/g, what thickness of Be foil would be required to attenuate a Cu Kα X-
ray beam by 10%? [4 marks]

(d) Name the metal often used for sample and environmental containment, e.g.
sample containers, detector windows, in powder neutron diffraction experiments.
Briefly explain why this element is chosen for this purpose.
[4 marks]


2. X ray fluorescence spectroscopy (XRF) is a powerful analytical technique used in
laboratories and industries worldwide.

(a) As a researcher, for what purpose might one use XRF? What information might
this technique provide about a given sample? [2 marks]

(b) List and briefly describe the four main processes that are likely to occur when X-
rays stroke matter. [5 marks]

(c) Describe how you would prepare a solid, a powder and a liquid sample for XRF
measurement. Give the atmospheric conditions needed with samples prepared
by each method and detail any drawbacks from each preparation method.
[9 marks]

(d) There are 2 common methods of detection in XRF; energy dispersive and
wavelength dispersive detection. How are the intensities traditionally calculated
when using each of these methods? [4 marks]

SECTION B over page – TURN OVER



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SECTION B – Answer ONE Question Only



3. (a) In an electron microscope, when incident electrons collide with atoms in a
material, explain the mechanism by which characteristic X-rays are generated.
Illustrate your answer with a labelled diagram. [8 marks]

(b) Draw a clearly labelled diagram of a typical X-ray spectrum (Number of X-ray
counts collected plotted against the energy of the X-ray) obtained from an X-ray
detector attached to an electron microscope. Explain the key features of the X-
ray spectrum. [6 marks]

(c) Explain how the X-ray spectrum from a sample in a scanning electron microscope
could change if the incident electron energy was reduced from 30kV down to
10kV. [3 marks]

(d) You are given a sample that contains 60%Ti, 45%Al and 5%B to examine in
SEM. When you take an X-ray spectrum you can only detect Ti and Al. Explain
why this might be the case. [3 marks]



4. (a) Explain the functions of the condenser, objective and projector lenses in a TEM.
Illustrate your answer with a sketch of a TEM column, and mark the location of
the lenses and the location of the specimen within the TEM column.
[8 marks]

(b) Explain what a selected area aperture is and what it is used for. Mark the position
of the selected area aperture with respect to the lenses on your diagram from (a).
Why does a microscope usually have 2-4 different selected area apertures?
[6 marks]

(c) You are given a specimen containing two phases, WC and Co. Describe in detail
how you would use a selected area aperture in combination with EDX to
distinguish the two phases, including their chemistry and crystallographic
structure. [6 marks]


SECTION C over page – CONTINUED


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SECTION C – Answer ONE Question Only

5. (a) The graph below shows examples of TG and DTG data. State what the TG and
DTG abbreviations stand for and explain the different information TG and DTG
data can provide.


[3 marks]

(b) The graph in question (a) above shows TG and DTG data for three different
concrete samples with the following formulation.

Sample 1: 25 wt% cement paste with 75 wt% aggregate
Sample 2: 78 wt% cement paste with 22 wt% aggregate
Sample 3: 100 wt% cement paste with no aggregate

Based on the data, calculate the amount of calcium hydroxide in wt% for each
concrete sample when the dehydroxylation of calcium hydroxide can take place
according to Reaction 1 shown below at any temperatures in the range of 300-
600oC. The molecular masses of Ca, H, O are 40 g/mol, 1 g/mol and 16 g/mol,
respectively.

Ca(OH)2 →CaO + H2O ----- (1)
[5 marks]


SECTION C, Question 5 continued over page – TURN OVER

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(c) Assuming the amount of calcium hydroxide represents the degree of hydration in
cement, estimate which sample has the most hydrated cement paste based on
the calculation in question (b). [4 marks]

(d) Pure aluminium metal melts at 660 °C. Draw a graph of the DSC curves you
would expect to see if you heated aluminium from 400 °C to 800 °C and then
cooled it from 800 °C back to 400 °C. Label the axes and the curves.
[4 marks]

(e) In the graph a DTA curve for a glass on heating is shown. Explain what is
happening to the glass at the events labelled A and B. Explain why the shape of
the curve at the two events is different. [4 marks]





6. (a) The following are abbreviations of some of the commonly used techniques for
thermal analysis. Specify what the following abbreviations stand for and explain
what kind of information is recorded in each technique.

i. LFA
ii. TMA
iii. DSC
iv. DTA
[4 marks]



SECTION C, Question 6 continued over page – CONTINUED





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(b) The Tin-Bismuth phase diagram is shown below. DSC was used to analyse three
samples in the Sn-Bi system. Sample 1 has the composition 40 wt% Bi – 60 wt%
Sn, Sample 2 has the composition 57 wt% Bi – 43 wt% Sn, and Sample 3 has
the composition 100 wt% Sn. Using the information from the phase diagram,
draw graphs of the expected DSC curves for the three samples on heating from
50°C to 300°C. Label the axes and curves.
[5 marks]

(c) Sample 1 (40wt% Bi – 60wt% Sn) and Sample 2 (57wt% Bi – 43wt% Sn) from
question (b) are heated in a furnace until they melt. The samples are removed
from the furnace and the temperatures of the molten mixtures are measured
using a thermocouple as the samples cool to room temperature and solidify.
Example cooling curves (Time – Temperature curves) are shown below. Select
the cooling curve you would expect to measure for Sample 1 and Sample 2 from
the three choices below. Explain why the curves selected have this shape and
the reason for the change in the rate of cooling.


[5 marks]

SECTION C, Question 6 continued over page – TURN OVER

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(d) A TG and DTG curve for a cement sample is shown. The events A and B
indicated in the figure are due to the reactions below.

Event A: Ca(OH)2 → CaO + H2O ----- (1)
Event B: CaCO3 → CaO + CO2 ----- (2)

Based on the data, state the temperature range of Event A and Event B and
estimate the amount in milligrams (mg) of CO2 and H2O released during Event A
and Event B if there was originally 35 mg of cement.


[4 marks]

(e) What would you expect the TG curve for the cement in Question (d) to look like
on cooling from 1000°C? Explain why the cooling curve would look like this.
[2 marks]



SECTION D, over page – CONTINUED

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SECTION D – Compulsory – Answer ALL of SECTION D


Give the correct answer in the blue answer book.

7. (a) The minimum temperature at which reformation of crystal grains occurs is called:
i. Work hardening temperature
ii. Reformation temperature
iii. Transformation temperature
iv. Recrystallisation temperature
v. Recovery temperature [1 mark]

(b) If you were to roll very thin products, like aluminium foil, which of the following
techniques would you choose?
i. Two high hot rolling mill
ii. Three high reversible hot rolling mill
iii. Tandem rolling mill
iv. 20-High Sendzimir mill
v. Shape rolling mill [1 mark]

(c) Which of the following processes can only be carried out in either hot or cold
state?
i. Rolling
ii. Wire/Tube Drawing
iii. Deep Drawing
iv. Stretch Forming
v. Swaging [1 mark]

(d) Which of the following activities typically carries the major part of the costs in the
making of a product?
i. Engineering design
ii. R & D
iii Manufacture
iv. Administration
v. Sales & Marketing [1 mark]

(e) Cold Working is normally performed at:
i. Room temperature
ii. Below 0.3 Tm
iii. Above 0.3 Tm
iv. Between 0.3-0.6 Tm
v. Above 0.6 Tm [1 mark]

SECTION D, Question 7 continued over page – TURN OVER



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(f) Which of the following processes is carried out in the liquid state?
i. Casting
ii. Forging
iii. Extrusion
iv. Machining
v. Rolling
[1 mark]
(g) Which of the following metal alloys cannot be die-cast?
i. Zn
ii. Al
iii. Mg
iv. Cu
v. Fe
[1 mark]

(h) Which is the most common alloy used in current additive manufacturing
applications?
i. Al
ii. Cu
iii. Zn
iv. Ti
v. Fe
[1 mark]
(i) Which of the following is not a bulk deformation process?
i. Rolling
ii. Extrusion
iii. Thermoforming
iv. Machining
v. Forging
[1 mark]

(j) Which of the following forging technique would you choose for a precision
forging?
i. Open die forging
ii. Impression die forging
iii. Upset forging
iv. Flashless forging
v. Hot forging
[1 mark]


SECTION D, Question 8 over page – CONTINUED





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8. Complete the paragraphs below by selecting the choice which you believe to be
correct. You must write your choices in the answer book.

(a) i. In extrusion blow moulding, the mould is filled with a
1. parison,
2. heated preform,
which is inflated resulting in a moulded product in which the level of biaxial
orientation of the polymer chains is
3. low.
4. medium.
5. high.

ii. In injection blow moulding, the mould is filled with a
1. parison,
2. heated preform,
which is inflated resulting in a moulded product in which the level of biaxial
orientation of the polymer chains is
3. low.
4. medium.
5. high.

iii. In stretch blow moulding, the mould is filled with a
1. parison,
2. heated preform,
which is inflated resulting in a moulded product in which the level of biaxial
orientation of the polymer chains is
3. low.
4. medium.
5. high.

iv. The technique most suited to manufacturing larger containers where the
liquid contents are not pressurised is
1. extrusion blow moulding
2. injection blow moulding
3. stretch blow moulding

v. The technique most suited to manufacturing smaller containers where the
liquid contents are pressurised is
1. extrusion blow moulding
2. injection blow moulding
3. stretch blow moulding
[8 marks]

SECTION D, Question 6 continued over page – TURN OVER

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(b) From the list of composite processing techniques given below, choose the one
which typically gives the lowest fibre volume fraction in the final part.

i. Hand Lay-up
ii. Spray Lay-up
iii. Compression Moulding
iv. Filament Winding
v. Resin Transfer Moulding
vi. Vacuum Assisted Resin Transfer Moulding
vii. Pultrusion
viii. Pre-preg
[1 mark]


(c) From the list of composite processing techniques given below, choose the one
which is typically used where the final part has a constant cross-section.

i. Hand Lay-up
ii. Spray Lay-up
iii. Compression Moulding
iv. Filament Winding
v. Resin Transfer Moulding
vi. Vacuum Assisted Resin Transfer Moulding
vii. Pultrusion
viii. Pre-preg

[1 mark]


9. (a) Draw a simple flow chart to illustrate the four main stages involved in ceramic
processing. Briefly describe the main objective of each step. [6 marks]

(b) Pyrochlore structured ceramics such as gadolinium titanate (Gd2Ti2O7) have
been proposed as potential materials for application as thermal barrier coatings.
Using Gd2O3 and TiO2 as starting materials calculate the amount of each required
to form 20 grams of Gd2Ti2O7.

Element Relative atomic mass
Gd 157.250
Ti 47.867
O 15.999
[4 marks]

END OF QUESTION PAPER

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