Diffusion Post-Session

Diffusion is defined as mass transport of atoms

• True

• False

Which is NOT a mechanism of diffusion?

• Interstitial diffusion

• Substitutional diffusion

• Interfacial diffusion

Diffusion can occur slowly or rapidly. Which is NOT a condition for slow diffusion?

• Close-packed system

• Low density of atoms

• High density of atoms

• Large atoms

Diffusion can occur slowly or rapidly. Which is NOT a condition for fast diffusion?

• Open system

• Small atoms

• Secondary bonding

• Covalent bonding

Ficke's First Law of Diffusion shows a concentration gradient in space.

• True

• False

Ficke's Second Law of Diffusion shows a concentration gradient in time.

• True

• False

Diffusivity of a material is assumed to be independent of species concentration.

• True

• False

Which arrhenius equation is used to determine the diffusivity / diffusion coefficient?

• $N_V=N\exp\left(-\frac{Q_V}{kT}\right)$

• $D=D_0\exp\left(-\frac{Q_D}{RT}\right)$

• $D_0=D\exp\left(-\frac{Q_D}{RT}\right)$

• $D=D_0\exp\left(-\frac{Q_D}{kT}\right)$

Calculate the diffusivity of carbon in iron at 1050^oC.

NOTE: Use Equation Booklet to find D₀, Q_D, and R.

• 9.419x10^-11 m²/s

• 3.276x10^-11 m²/s

• 8.114x10^-9 m²/s

• 3.880x10^-10 m²/s

Calculate the flux of carbon through a plate. The high concentration area has a concentration of 1.0 kg/m³, while the low concentration area has a concentration of 0.2 kg/m³. The thickness of the plate is 7 mm and it has a diffusivity of 3.5x10^-11 m²/s.

• 4.67x10^-9 kg/m²s

• 2.625x10^-13 kg/m²s

• 1.08x10^-8 kg/m²s

• 4.00x10^-9 kg/m²s