Chapter 5_Part_2

Chapter 5_Part_2 - Diffusion Flux The flux of diffusing...

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6 MSE 2090: Introduction to Materials Science Chapter 5, Diffusion The flux of diffusing atoms, J, is used to quantify how fast diffusion occurs. The flux is defined as either the number of atoms diffusing through unit area per unit time (atoms/m 2 -second) or the mass of atoms diffusing through unit area per unit time, (kg/m 2 - second). For example, for the mass flux we can write Diffusion Flux J = M / At (1/A) (dM/dt) (Kg m -2 s -1 ) where M is the mass of atoms diffusing through the area A during time t. A J
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7 MSE 2090: Introduction to Materials Science Chapter 5, Diffusion Steady state diffusion: the diffusion flux does not change with time. Concentration profile: concentration of atoms/molecules of interest as function of position in the sample. Concentration gradient: dC/dx (Kg m -4 ): the slope at a particular point on concentration profile. Steady-State Diffusion B A B A x x C C x C dx dC = Δ Δ
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8 MSE 2090: Introduction to Materials Science Chapter 5, Diffusion Fick’s first law:
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This note was uploaded on 02/14/2012 for the course MSE 2090 taught by Professor Leoindzhiglei during the Fall '10 term at UVA.

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Chapter 5_Part_2 - Diffusion Flux The flux of diffusing...

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