Review Sheet for Quiz #2

Review Sheet for Quiz #2 - Quiz 2: Lecture 9: Diffusion in...

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Quiz 2: Lecture 9: Diffusion in Solids Interdiffusion – In an alloy, atoms tend to migrate from regions of large concentration. Self-Diffusion – In an elemental solid, atoms also migrate Substitutional Diffusion: - Applies to Substitutional impurities - Atoms exchange with vacancies - Rate depends on - - Number of vacancies - - Activation energy to exchange - - Frequency of jumping Case Hardening: - Diffuse carbon atoms into the host iron atoms at the surface - Result: - Hard to deform carbon atoms, lock planes from shearing - Hard to crack, carbon atoms put the surface in compression - Processing using diffusion - - Dope Silicon with P for n-type semiconductors ****oops, looks like I erfed the rest of the lecture***** Lecture 10: Steady State Diffusion Steady State – The concentration doesn’t change with time (Jx[left] = Jx[right]) Fick’s First Law: Jx = -D(dC/dx), slope must be constant Non Steady-State Diffusion – Conc. Profile, C(x) changes with time Fick’s Second Law: dC/dt = D{d^2C/dx^2) Using 2 nd law, Co – initial conc. In material Cs – initial conc. At surface Cx – conc. At position x.
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This note was uploaded on 05/01/2008 for the course MAT 33 taught by Professor Keith during the Spring '07 term at Lehigh University .

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Review Sheet for Quiz #2 - Quiz 2: Lecture 9: Diffusion in...

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