MATS 3011 Lecture Notes - Nerd, Ephemeris Time, Inta
Document Summary
Fick"s 2nd law for unsteady state diffusion in a very thick film on a large objet (composed to diffusion length) concentration at some time, at some places. Note: t = 0 all x, c = 0 --> initial condition t > 0 at x = 0, c = co t > 0 at x --> infinity, c = 0 boundary conditions. -> diffusion length = distance in material where ratio of material becomes about half. Example: the diffusion coefficient of cu in al at 500oc and 600 oc are 4. 8*10-4 & 5. 3*10-13 m2/s. Determine: the approximate time at 500 oc that will produce the same diffusion result as a 10 hr heat treatment at 600oc. *need time greater than 10 hr b/c takes more time to have same result @ lower t. Ans = 110. 41666666 hrs same diffusion result in terms of concentration of cu at some specific point in al.
