Understanding the Kirkendall Effect and Its Impact on Diffusion in Materials

[mhill]

could someone explain me this effect ??

i know that , is due to the diffusion of atoms by the existence of 'vacancies' deffects that allow the diffusion.

the problem is that this is what i know, for example in the German Wikipedia there is a good image but i do not how to interpret (image of Kirkendall effect)

http://upload.wikimedia.org/wikipedia/commons/4/4c/KirkendallSceme1.png

if someone can help, thank you.

 

[DiffusionGuy]

In essence, the Kirkendall effect describes the differing diffusion rates that exists between two or more dissimilar layers (e.g. thin films). If one is able to insert markers on the interface between the layers of a sample (call it an A/B thin film system), one would see that the markers migrate into one layer, depending on the difference of the diffusion coefficient of element A in B and B in A. So, if A diffuses faster into B, the markers will move into layer A.

One way to described this effect is with Darken's equation, D_effective = X_AD_B + X_BD_A, where D_A is the diffusion coefficient of element A in B, D_B is the diffusion coefficient of B in A, and D_effective is the effective diffusion coefficient.