1. The diffusion condition for which the flux is independent of time is known as

Random Diffusion

Non-Steady State Diffusion

@ Steady State Diffusion

Patterned Diffusion

2. Concentration gradient is the slope of the concentration profile curve at some specific point.

Tue

@ False

3. Oxygen gas is flowing through a 12m long circular pipe with a radius of 20cm. The concentrations of oxygen at the ends of the pipe are 30 kg/m? and 10 kg/m. Given that the diffusion constant for the oxygen gas at 20C is 1.8 x1075 m2/s, what must be the diffusion rate of the gas?

@ 6.91x 10^-6kg/s

O 3.77 x 10^-6 kg/s

O 4.22% 10^-6 kg/s

2.90% 10^-6 kgs

4. Which of the following processes does not involve diffusions of atoms in a material?

Addition of impurity atom in semiconductors

Cutting a copper wire into two

Annealing of steel

Adsorbing a cesium atom anto a molybdenum surface

5. A plate of iron is exposed to a carbon-rich atmosphere on one side and a carbon-deficient atmosphere on the other side at 700 C. If a steady-state diffusion is achieved, what must be the diffusion flux of the carbon through the plate given the concentrations of carbon at 5 mm and 10 mm beneath the surface are 1.2 kg/m? and 0.8 ke/m3, Assume that the diffusion coefficient at the given temperature is 3 x 10^-11 m2/s,

1.2% 10^-9 kg/m2s

4.8 10^-12 kg/m2s

5.3x10^-12 kg/m2s

@ 2.4% 10^-9 kg/m2s

6. The concentration profile is represented as a plot of area versus distance into the solid material.

@ False

O True

7. The mathematics for non-steady state in a single (x) direction (and when the diffusion coefficient is independent of concentration) are described by

@ Fick's 2nd Law

Fick's Ist Law

Diffusion Coefficient Equation

Gaussian Error Equivalence

8. This term refers to the diffusion occurring for pure metals, but all atoms exchanging positions are of the same type.

@ Self Diffusion

Vacancy Diffusion

External Diffusion

Internal Diffusion

9. Using the diffusion coefficient equation wrt temperature, find the diffusion coefficient of a proton onto a germanium surface with a temperature-independent preexponential equal to 2 cm/s at 800 C with an activation energy of 57500 cal/mol.

O 1.25x10^-12 cm2/s

O 2.96x10^-12 cm2/s

@ 3.88x10^-12 cm2/s

O 2.60% 10^-12 cm2/s

10. The diffusion coefficient equation as shown below

D= D₀e ^(Qd/RT)

@ The diffusion coefficient is a function of temperature,

The diffusion coefficient is zero in extreme environments.

The diffusion coefficient is constant for all materials,

The diffusion coefficient is varying with respect to time.

11. R is known as the ideal gas constant which is equal to

8.31 J/mol-K

9.81 J/mol-K

O 11.48 J/mol-K

12.65 J/mol-k

12. What is the mathematical relationship between diffusion flux and diffusion elapsed time?

directly proportional

equal

inverse square law

@ Inversely proportional

13. For steady-state diffusion, diffusion flux is proportional to the negative of the concentration gradient according to

Diffusion Coefficient Equation

Gaussian Error Equivalence

@ Fick's 1st Law

Fick's 2nd Law

14. The figure below shows the motion of a substitutional atom. What type of diffusion occurred here?

Internal Diffusion

Vacancy Diffusion

Interstitial Diffusion

Self Diffusion

15. The figure below shows the motion of a substitutional atom. What type of diffusion occurred here?

@ Vacancy Diffusion

Interstitial Diffusion

Thermal Diffusion

Self Diffusion