Dobson+CH6+Diffusion+2011

Dobson CH6 Diffusion - DIFFUSION ISSUES TO ADDRESS How does diffusion occur Why is it an important part of processing How can the rate of diffusion

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ISSUES TO ADDRESS. .. How does diffusion occur? Why is it an important part of processing? How can the rate of diffusion be predicted for some simple cases? How does diffusion depend on structure and temperature? DIFFUSION
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Difusion - Mass transport by atomic mo9on Mechanisms Solids – vacancy difusion or inters99al difusion Difusion http://www.youtube.com/watch?v=STLAJH7_zkY&feature=related
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Interdiffusion : In an alloy, atoms tend to migrate from regions of high concentration to regions of low concentration Initially Adapted from Figs. 5.1 and 5.2, Callister & Rethwisch 8e. After some time Difusion Ni Cu
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Self-diffusion : In an elemental solid, atoms also migrate. Label some atoms A B C D After some time A B C D Difusion
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Vacancy Diffusion : atoms exchange with vacancies applies to substitutional impurities atoms rate depends on: -- number of vacancies -- activation energy to exchange. increasing elapsed time Difusion Mechnaisms
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• Simulation of interdiffusion across an interface: Rate of substitutional diffusion depends on: -- vacancy concentration -- frequency of jumping (Courtesy P.M. Anderson) Difusion Simula9on
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Inters99al difusion – smaller atoms can difuse between atoms. *More rapid than vacancy diffusion Adapted from Fig. 5.3(b), Callister & Rethwisch 8e. Difusion Mechanisms
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What about our Cu/Ni example? -> Vacancy or Interstitial? -> Why? Difusion
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•Food marinating •Carburization for Surface Hardening of Steels •Food packaging, beverage bottles •Mylar Balloons Applica9ons of DiFusion
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chapter-opening photograph, Chapter 5, Callister & Rethwisch 8e. (Courtesy of Surface Division, Midland-Ross.) Case Hardening : -- Diffuse carbon atoms into the host iron atoms at the surface. -- Example of interstitial
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This note was uploaded on 02/28/2012 for the course EMA 3010 taught by Professor Unknown during the Fall '08 term at University of Florida.

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Dobson CH6 Diffusion - DIFFUSION ISSUES TO ADDRESS How does diffusion occur Why is it an important part of processing How can the rate of diffusion

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