MS115a Lecture 12 10-22-2010

MS115a Lecture 12 10-22-2010 - Defects in Solids • 0-D or...

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Unformatted text preview: 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 Diffusional Processes hydrogen separation membrane Pd H 2 + CO + CO 2 H x c H c J D x ∂ = - ∂ c x ∂ < ∂ J Fick’s first law (similar to Ohm’s law) phenomenological Applies under steady state conditions c(x) ≠ f(t) flux diffusion coefficient c J D x ∂ = - ∂ # area time × # vol length response ∝ driving force concentration gradient 2 length time Units of D Diffusional Processes # vol time / 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 ≠...
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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 Lecture 12 10-22-2010 - Defects in Solids • 0-D or...

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