09-25-Lecture

09-25-Lecture - 1 Diffusion ENGR 213 DIFFUSION material...

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Unformatted text preview: 1 Diffusion ENGR 213 DIFFUSION material transport by atomic motion Movement of atoms from site to site Requires sufficient vibrational energy Can change structure in solids DIFFUSION - Cu/Ni Example TIME & TEMP 4 DIFFUSION TYPES interdiffusion concentration changes w/ time impurity atoms diffusing into host self-diffusion host atoms swapping places No change in concentration 5 DIFFUSION MECHANISMS - 1 vacancy/substitutional vacancies required holes and fillers move in opposite direction interstitial small atoms many interstices more rapid than vacancy mechanism other paths (rapid, minor) dislocations, grain boundaries (gb), surfaces D surf > D gb > D disc > D matrix 6 DIFFUSION MECHANISMS - 2 Vacancy Interstitial 7 DIFFUSION & TEMPERATURE 8 Diffusion transports material - mass Flow is from high to low concentration Measure flow using Flux, J: mass/area/time Steady state means no change with time STEADY-STATE DIFFUSION - 1 9...
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This note was uploaded on 03/26/2008 for the course ENGR 213 taught by Professor Dr.stubbs during the Fall '04 term at Texas A&M.

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09-25-Lecture - 1 Diffusion ENGR 213 DIFFUSION material...

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