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homework6solution - Solutions to Homework#6 1 Problem 1 To...

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Solutions to Homework #6 1. Problem 1 To study the diffusion of nickel in the grain boundaries of nickel oxide NiO in the temperature range between 500 o C and 800 o C, polycrystalline nickel oxide samples were prepared by oxidation of pure nickel foils. The material thus obtained had equiaxed grains with an average diameter of about 10 µ m. A thin layer of tracer ( 63 Ni) was deposited on the surface. After diffusion annealing, the penetration profile was determined by a sectioning technique based on RF sputtering. The anneals were carried out at 4 different temperatures (500, 600, 700, 800 o C) under a pressure of one atmosphere of pure oxygen. The data are given in table below T o C t (s) D (cm 2 /s) D δ (cm 3 /s) 800 6.6x10 2 2.1x10 -14 1.4x10 -16 700 7.2x10 3 1.2x10 -15 600 6.05x10 5 3.7x10 -17 1.8x10 -18 500 8.6x10 5 4.5x10 -19 5.6x10 -20 D and D ' are the diffusion coefficients of nickel in the volume and the grain boundaries, respectively. δ is the width of the grain boundaries, taken as δ = 7x10 -8 a. Show that these experiments are indeed in the Harrison B kinetics regime b. The experimental values for the average concentration as a function of depth found at 700 o C, are given in table below z(cm)x10 4 0.1 0.12 0.14 0.16 0.18 0.22 0.24 0.30 0.50 cx10 3 550 340 160 100 29 30 25 15 9 0.68 0.90 1 1.15 1.4 1.6 2.1 2.6 3.1 3.6 5.2 4.6 4 3.8 3.1 3 2.2 1.6 1.05 0.85 Obtain D' δ and the grain boundary diffusion coefficient D '. Is the condition β > 10 fulfilled?
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This note was uploaded on 01/19/2010 for the course MAT SCI 503 taught by Professor Chen during the Spring '02 term at Penn State.

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homework6solution - Solutions to Homework#6 1 Problem 1 To...

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