Diffusion - transfer of mass either within a specific solid or from a liquid, a gas, or another solid phase.
Diffusion couple - formed by joining bars of two different metals together so that there is intimate
contact between the two faces
interdiffusion (impurity diffusion) - The process by which atoms of one metal diffuse into another
self-diffusion - atomic migration in pure metals
vacancy diffusion - one mechanism involves the interchange of an atom from a normal lattice position to
an adjacent vacant lattice site or vacancy
interstitial diffusion - A diffusion mechanism by which atomic motion is from interstitial site to
interstitial site.
-occurs more rapidly than diffusion by the vacancy mode as interstitial atoms are smaller/ more mobile
probability of interstitial diffusion > vacancy diffusion
diffusion flux - how fast the foreign mass can transfer across and area J=M/At
Fick's first law - The diffusion flux is proportional to the concentration gradient. This relationship is used
for steady-state diffusion situations.
Fick's first law equation - dM/dt = -DS (dC/dx)
M = quantity of material
D = Diffusion Coefficient
S = Area of a unit cross section
C = Drug Concentration
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