Still Unsolved Puzzle is the Growth of Colloidal Crystal(<Special Issue>Crystal Growth in Space part 2)

Abstract

Colloidal crystal is a name of spatially ordered aggregates composed of monodispersed colloids. Since colloids are often negatively charged in aqueous media, the understanding of the formation of colloidal crystal and its stability has been deeply related to the development of the DLVO theory. In 1930s, Langmuir ingeniously criticized the deficiencies of the DLVO theory taking the case of colloidal aggregations of charged colloids in aqueous solvent and pointed out an aspect of the theoretical oversimplification of colloidal phenomena in its pair potential treatment. The DLVO theory explains the colloidal interaction by a repulsive coulombic potential and supports the Alder-Kirkwood transition of colloidal liquid to crystalline state. In spite of Langmuir's criticism, the DLVO theory became the basic understanding of treating colloidal crystallization. According to the progress of the statistical treatment of the charged colloids in salt solutions, the like-charge attraction of colloidal particles again became the hottest problem when colloidal phase diagrams, such as gas-liquid and liquid-solid transitions are evaluated both experimentally and theoretically. In this report, we discuss a new space experiment that enables the evaluation of phase transition phenomena of various colloids, e.g. polystyrene, silica, titania, etc.