Exercise 3.3-1

Quick Questions to

3. Point Defects and Diffusion

Here are some quick questions:
The answers are sometimes (and possibly only indirectly) contained in the links.

3.1.1 Diffusion and Point Defects
Give examples of products / processes / technologies that depend in a major way on point defect diffusion.
Write down and discuss Fick's 1st law
Write down and discuss Fick's 2nd law
How do Ficks Laws connect to atomic diffusion? Give the two important equations dermining the diffusion coefficientD i) by atomic jumping, and ii) via the diffusion length L.
What is the geometry factor g concerning jumping point defects in lattices? Can you give numbers for some common lattices?

3.2 Diffusion mechanisms
Describe at least 2 possibilites for the diffusion of a substitutional and interstial impurity atom, respectively.
Which diffusion mechanisms are the most important ones?
For a substitutional impurity atom that diffuses via a vacancy mechanism, the diffusion coefficient D will be proprotional to ....?
How do atoms diffuse in amorphous materials - e.g. glasses and polymers?
What is self diffusion? The self-diffusion coefficient Dself is given by....?
Any given atom in a given crystal will sooner or later leave its original place because of self diffusion. How long - roughly - does it take at high temperatures for all atoms to have changed positions? How about the atoms in your brain?

With frame With frame as PDF

go to Solution to Exercise 3.1-1

go to 3.1.1 Diffusion and Point Defects

go to 3.2.1 Atomic Mechanisms

go to 3.2.2 Self-Diffusion

go to Solution to Exercise 3.2-1

© H. Föll (Defects - Script)