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

Solution to Exercise 3.1-1

3.1.1 Diffusion and Point Defects

3.2.1 Atomic Mechanisms

3.2.2 Self-Diffusion

Solution to Exercise 3.2-1

© H. Föll (Defects - Script)