Chapter 5 (Diffusion)
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what are rates governed by
activation energies
define the activation energy
the extra energy required to overcome the energy barrier to allow for movement of atoms
what is inter-diffusion
migration of atoms from [high] to [low]
what is self diffusion
migration of atoms within a single elemental solid
what is substitutional diffusion
solute atoms exchange places with solvent atoms using vacancies
interstitial diffusion
when smaller atoms diffuse between the larger ones in spaces called the interstices
name 2 processes which use diffusion
• case hardening 2. doping
what is steady state diffusion
when the concentration doesn’t change with time
what is non-steady state diffusion
when the concentration changes with both time and distance
what type of energy supplies activation energy?
heat energy
which is more rapid and why, insterstitial or vacancy diffusion?
interstitial diffusion because no vacancies are required so they can move readily, the atoms are generally smaller so they are more mobile
with an increase in temperature, what will happen to the diffusion coefficient
it will increase exponentially