MS115a Lect 13 10 24 2011

MS115a Lect 13 10 24 2011 - Defects in Solids 0-D or point...

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Defects in Solids 0-D or point defects vacancies, interstitials, etc. control mass diffusion 1-D or linear defects dislocations control deformation processes 2-D or planar defects grain boundaries, surfaces, interfaces 3-D or volume defects voids, secondary components (phases) concentrations
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Diffusional Processes hydrogen separation membrane Pd H 2 + CO + CO 2 H x c H c J D x = - 0 c x < 0 J Fick’s first law (similar to Ohm’s law) phenomenological Applies under steady state conditions c(x)   f(t) flux diffusion  coefficient response driving force concentration gradient
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Diffusional Processes Continuity requirements Non steady-state: c(x) = f(t) Fick’s second law B A t = 0 C A C B t > 0 C A C B c J t x = - c D x x = ÷ if D   f(x) c c D t x x = ÷ 2 2 c c D t x = c J D x = - Steady-state: c(x)   f(t)
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This note was uploaded on 01/03/2012 for the course MS 115a taught by Professor List during the Fall '09 term at Caltech.

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MS115a Lect 13 10 24 2011 - Defects in Solids 0-D or point...

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