Assuming steady-state diffusion, calculate the diffusion flux of carbon at 650o
ID: 815240 • Letter: A
Question
Assuming steady-state diffusion, calculate the diffusion flux of carbon at 650o C through a 3 cm iron sheet if the concentration gradient is -0.66 kg/m4 . The activation energy is 0.79 eV/atom, and D0 = 6.510-7 m 2 /s. a. 2.110-11 kg/(m2 s) b. 3.510-14 kg/(m2 s) c. 7.410-10 kg/(m2 s) d. 5.210-12 kg/(m2 s)
Assuming steady-state diffusion, calculate the diffusion flux of carbon at 650o C through a 3 cm iron sheet if the concentration gradient is -0.66 kg/m4 . The activation energy is 0.79 eV/atom, and D0 = 6.5 x 10^-7 m^2/s.Explanation / Answer
Diffusion flux J = -D dC/dx where D is diffusion coefficient and dC/dx is concentration gradient (given) -0.66 kg/m^4.
D = Do exp(-QD/RT) where Do = 6.5 x10-7 m2/s, QD= 0.79eV/atom = 0.79 / 6.022x1023 eV/mol, R = 8.313 J/mol.K and given T = 650+273 = 923K.
Substitue the values in given formual and obtain the flux value.