Diffusion
What is needed for diffusion to occur?
Vacancies
What drives the formation of vacancies?
Increase in entropy
What is the equation that shows the relationship between temperature and the diffusion coefficient? List the meaning and units of each variable.
Diffusion of Matter equation
What is the linear density of [110]?
1/2R
How are the Boltzmann constant (k) and Ideal Gas Constant (R) related?
Boltzmann Equation:
S = k_B ln Omega
Use R when using mol quantities
Use k when using atom quantities
What is steady-state diffusion and why is it important?
Constant concentration gradient and Fick's First Law assumes steady-state
What type of defect is this? (Slide 7)
Line Defect
What is the equation that shows the formation of vacancies in crystals? List the variables and their meaning.
Equation for formation of vacancies in crystals :)>
How do you draw a (111) plane?
Draw it on the board
How do dislocations move?
Like a carpet, slipping
High to low concentration
What type of defect is this? (Slide 8)
Grain Boundaries
What is the equation that relates temperature to viscosity? List the variables and their meaning.
The Arrhenius equation related to viscosity
A 5-mm-thick sheet of palladium (Pd) with a cross-sectional area of 0.2 m² is used as a steady-state diffusional membrane for purifying hydrogen. The hydrogen concentration on the high-pressure (impure gas) side of the sheet is 1.5 kg/m³ and the concentration on the low-pressure side is 0.3 kg/m³. Assume the diffusion coefficient of H in Pd is given by: DPd=10−9 m2/s. (https://www.youtube.com/watch?v=FuevAkamXNc)
1.73x10^-4 kg/hr
What does an FCC unit cell look like?
Draw it on the board
What is the driving force of diffusion of atoms in the crystal?
Increase in entropy
What type of defect is this? (Slide 9)
Point Defect (left to right: substitution, interstitial, vacancy)
What equation explains the rate of diffusion? List the variables and their meaning.
Fick's first law of diffusion
Calculate the energy for vacancy formation in nickel (Ni), given that the equilibrium number of vacancies at 850°C (1123 K) is 4.7 × 10²² m⁻³ and the number of atomic sites is 9.03 x 10^28 m-3 . (Textbook question 5.5)
2.23 x 10^-19 m^-3
What is the miller indices of these planes?