TEST 2 (TAKE HOME TEST)

Question 1(a) Give ONE (1) application example each of following material.

i. Smart materialsii. Shape memory alloys

iii. Metal alloyiv. Ceramicv. Polymer alloy

(5 marks)

(b) Draw a schematic representation of the Bohr atomic model for Cobalt (Atomic number =27). Write down its quantum number notation.

(5 marks)(c) State two commonly used atomic models; explain the difference between

the theories. (10 marks)

Question 2

(a) Draw in unit cubes of the crystal planes that have the following and calculate the planar density if the following are all BCC structure with a=0.33007

( i)(001 )( ii )(111 )

(8 marks)

(b) All material system has its imperfections or defects. What is the relationship between defects and entropy? Explain briefly.

(8 marks)

(c) State two types of point defects and two types of line defects.

(4 marks)

(Total: 20 marks)

Question 3

(a) Corrosion is defined as the destructive and unintentional attack of a metal; it is

electrochemical and begins at the surface.

i) Explain about electrochemical corrosion of metal. (10 marks)

ii) Provide THREE (3) types of corrosion. (6 marks)

iii) A mild steel tank 82 cm high with a 33 cm × 33 cm square bottom is filled with

aerated water up to the 77 cm level and shows a corrosion loss of 126.91 g over

a four-week period. Calculate

(a) corrosion current

(b) corrosion density

(F= 96,500 A.s/mol, M = 55.85 g/mol)

(b) In 80 gram of alloy containing 90 at% of zinc and 10 at% of copper, find how many gram of zinc and copper it contains?

(4 marks)

(Total: 20 marks)

Question 4

(a) Colored gemstones are usually more valuable than colorless stones of the same

type and quality. Colorless sapphires (single-crystal alumina, Al2O3) can be

embedded in a powder mixture of TiO2 and Fe2O3, and then heated for 500 hours

at 2000°C. These oxides diffuse into the gemstones to a depth of approximately

0.4 mm, giving the gems a deep blue color.

This diffusion process is a non-steady state.

ME1205/ECE3132 2

i. Estimate how long will it takes for a layer at 0.4 mm to form at the same

processing temperature mentioned above.

ii. How long would it take to achieve the diffusion depth of 0.4 mm at 1500 °C?

Assume that the apparent activation energy for the diffusion of these

impurities in sapphire is 500 kJ/mol. The gas constant, R = 8.314 J/mol K.

(Total: 20 marks)

Question 5

(a) An x-ray diffractometer recorder chart for an element that has either the BCC or the

FCC crystal structure showed diffraction peaks at the following 2 angles:

41.069o, 47.782o, 69.879o, and 84.396o. (The wavelength of the incoming

radiation was 0.15405nm)

(i) Determine the crystal structure of the element

(ii) Determine the lattice constant of the element

(10 marks)

A fatigue test was conducted in which the mean stress was 80MPa, and the stress

amplitude is 200MPa.

i. Compute the maximum and minimum stress levels.

ii. Compute the stress ratio

iii. Compute the magnitude of stress range

(10 marks)

(Total: 20 marks

APPENDIX

ME1205/ECE3132 3

Table 1:

ME1205/ECE3132 4