1 Among the four atomic diffusion mechanisms what mechanisms

1. Among the four atomic diffusion mechanisms, what mechanisms can assist atomic self-diffusion and what cannot?

2. Why is atomic diffusion called a thermal activation process? What does the thermal activation energy represent? How does the diffusion rate depend on temperature?

3. Heat conduction is a form of exchange in kinetic energy through mutual collisions between microscopic particles. Based on this energy exchange mechanism, please roughly compare the conductivity of gas, liquid and solid. According to your comparison, can you predict what kind of material form produces good thermal insulators?

4. How to choose the material surface to maximize and minimize the heat loss by radiation?

Solution

1. vacancy diffusion , interstitial diffusion can assist and Substitutional diffusion, self-interstitial cannot assist.

2. Atomic diffusion is a diffusion process whereby the random thermally-activated movement ofatoms in a solid results in the net transport of atoms.

3. Thermal conductivity of the gases and liquids increases with the increase in ... the difference between the thermal conductivity of the liquid and solid phases

4. .  select materials that either minimize or maximize the transfer of a thickness of material, in a direction normal (perpendicular) to a surface of area