Abstract
Nucleation is a fundamental process in materials processing. The well-known theory is the classical nucleation theory. The theory contains two fundamental approximations, that is, (1) the equilibrium distribution of nucleating clusters and (2) the treatment of small clusters as though they had bulk properties. The former approximation transforms a kinetic nature of nucleation into a thermodynamic one. The latter, often called capillarity approximation, oversimplifies the microscopic treatment of interfacial energy of nucleates. Recently, experimental studies on the nucleation of macro-molecular crystals, such as proteins and colloids showed the new aspects of nucleation dynamics that is different from the pictures predicted by the classical nucleation theory. The study on nucleation of those materials is promising from the viewpoint of industrial and scientific interests. The future microgravity experiments are suggested to overcome the fundamental approximations of the classical nucleation theory using the materials.
