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16 Cards in this Set
- Front
- Back
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What is Diffusion?
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The phenomenon of material transport by atomic motion
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What is Interdiffusion or Impurity Diffusion?
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The process by which atoms of one metal diffuse into another metal.
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What is Self-Diffusion?
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Atomic migration in pure metals.
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For atoms to be in constant motion in solid materials, what two conditions must be met?
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1. There must be an empty adjacent site
2. The atom must have sufficient energy to break bonds with its neighbor atoms and be able to cause some lattice distortion during the displacement. |
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What is Vacancy Diffusion?
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The diffusion mechanism in which net atomic migration is from a lattice site to an adjacent vacancy.
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What is Interstitial Diffusion?
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A diffusion mechanism by which atomic motion is from interstitial site to interstitial site.
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What is Diffusion Flux?
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The quantity of mass diffusing through and perpendicular to a unit cross-sectional area of material per unit time.
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In Diffusion Flux, what is M?
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Mass (or the # of atoms) diffusing through
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What is Steady-State Diffusion?
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The diffusion of atoms of a gas through a plate of metal for which the concentrations of the diffusion species are held constant.
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What is Fick's First Law?
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Diffusion flux for steady-state diffusion is J = -D(dC/dx)
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What are the 3 assumptions of Fick's Second Law?
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1. Before diffusion, any of the diffusing solute atoms in the solid are uniformly distributed with concentration of C
2. The value of x at the surface is 0 3. Time is 0 the instant before diffusion begins |
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As temperature increases, does the fraction of atoms who's vibrational energy is high, increases or decrease?
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Increases!
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If Diffusion Flux does not change with time, what does this mean?
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It means that steady-state condition exists.
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What are 2 factors that influence Diffusion?
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1. Diffusing species AND host material
2. Temperature dependence of diffusion coefficient |
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What is D?
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The Temperature Dependence of the Diffusion Coefficients
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What is the driving force for steady-state diffusion?
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Concentration Gradient
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