Definition - What does Nucleation mean?
Nucleation is a process that occurs when a new material phase begins to form. This can be a crystal formation that develops as a material begins to solidify, or what occurs as a gas transitions to its liquid form. Nucleation is important for understanding metals and crystallization.
Corrosionpedia explains Nucleation
When talking about crystalline structures, nucleation occurs as a liquid begins to solidify and a nucleus of solidified material forms and grows. It continues to undergo nucleation until it comes into contact with another volume of material undergoing nucleation. Grain boundaries form when the two volumes come into contact if the solidifying nuclei are not of the same orientation.
There are two basic types of nucleation:
- Heterogeneous nucleation occurs when nuclei begin to form on some sort of impurity and grow outward from the impurity. An example is a molten metal solidifying on the walls of a crucible. Some of the metal nucleation will occur on the crucible wall and grow outward from there.
- Homogeneous nucleation occurs when crystals form in the absence of impurities. This includes nuclei that form in the center of a volume of gas or liquid, apart from any contaminants.