
#1
Feb2811, 04:33 PM

P: 2

I have a problem with calculating the concentration gradiant. Here is the question and the solution from the solution manual and the numbers don't add up.
A 1mm sheet of FCC iron is used to contain nitrogen in a heat exchanger at 1200℃. The concentration of N at one surface is 0.04 atomic percent and the concentration at the second surface is 0.005 atomic percent. Determine the flux of nitrogen through the foil in atoms/cm2−s. solution (a) Ac/Ax = [.00005  .0004]*4 atoms/cell(3.589E8)^3  .1cm =3.03 x 1020 N atoms/cm3cm (b) J=D(Ac/Ax) = 0.0034 exp[34,600/(1.987)(1473)](3.03 x 1020) = 7.57 x 1012 N atoms/cm2s I would like to know how they get the answer in part a. 



#2
Mar111, 07:20 AM

P: 2

I figured it out. the volume of the cell needs to be in the denominator. Our professor takes everything out of the solutions manual and never checks it.



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