nukleaatiopisteitä

Nukleaatiopisteitä refers to nucleation sites. These are specific locations where a phase transition can begin. In the context of crystallization, a nucleation site is a point where the solid phase can start to form from a liquid or gas. These sites can be impurities, defects on a surface, or even random fluctuations in the fluid. Without nucleation sites, a substance might become supercooled or supersaturated, meaning it exists in a state that is not its thermodynamically stable phase.

The process of nucleation can be homogeneous or heterogeneous. Homogeneous nucleation occurs spontaneously within the bulk of the fluid, driven by random molecular collisions forming a stable cluster of the new phase. This is generally less common and requires more energy. Heterogeneous nucleation, on the other hand, occurs on a pre-existing surface, such as the wall of a container or the surface of a dust particle. These surfaces provide a lower energy barrier for the formation of the new phase, making heterogeneous nucleation much more frequent and easier to achieve under typical conditions. The presence and nature of nucleation sites significantly influence the rate and morphology of crystal growth.