C c b x0 0072 mol cm 3 x 0 0 mol cm 3 x

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Unformatted text preview: s the analysis from the “B” point of view. Because the change of molar volume is assumed as constant throughout, the analysis from the “A” point of view would yield the same result. (b) Assuming D D(C B ) , C B A Berf x 2 Dt 0.036 0.036 erf x 2 Dt CB/moles·cm -3 0.072 increasing time 0 x/cm (c) D* / D* 4 and system obeys Raoult’s law (ideal mixing). A B d ln B ~ D ( N A D* N B D* )(1 ) B A d ln N B d ln B Ideal mixing N B a B B N B B 1 0 d ln N B ~ D N A D* N B D* B A N A D * 4 N B D * (1 N B )D * 4 N B D * B B B B D * (1 3N B ) B ~ i) According to above equation, D is no longer constant, so The composition profile ~ is not symmetric, and the erf solution is no longer valid. D is lower at the pure A side of the diffusion couple than A-B side. It is expected that the concentration ~ gradient at A-side is steeper compared with erf curve. In the contrary, D at A-B side is higher, thus a shallower concentration gradient. CB 0.072 X ii) 1 2 3 4 At t=0, the Matano interface is at the original weld. After s...
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This document was uploaded on 11/26/2013.

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