MATERIALS SCIENCE AND TECHNOLOGY IKMU 396
Name
Instructor: Dr. Selis Önel
Midterm Examination, Friday, April 30, 2010
You are allowed to use an A4 size information sheet, which you have to return with the exam paper.
Please use English and give brief answers to the following questions:
Question 1. (12 pts)
Circle the correct word in the following sentence or fill in the blank:
a) Materials that have high binding energy have high/low strength and melting temperature.
b) Materials with ionic bonding have a particularly large/small binding energy due to the large/small electronegativity
difference between the ions. Metals have relatively higher/lower binding energies as the electronegativities of the atoms
are similar.
c) A steep slope on the force-distance curve or the stress-strain curve in the elastic region correlates with a higher/lower
binding energy and higher/lower melting point, which means that a greater/smaller force is required to stretch the bond.
d) Smaller grain size higher/lower structural disorder
e) Smaller grain size harder/lower to move dislocations across grain boundaries due to more barriers for slip
f) More barrier for slip higher/lower material strength
g) Adding “impurity” atoms to Cu increases/decreases electrical resistivity and deforming Cu increases/decreases its
resistivity.
Question 2. (16 pts)
Your boss asked you to select a material for the electrical contacts in an electrical switching device which opens and closes
frequently and forcefully.
a) What are the most important properties that this contact material should have?
b) What type of material might you recommend?
c) Would Cu be a good choice, why or why not?
d) Would Al2O3 be a good choice? Explain briefly.
