Nucleation of crystallization

Interestingly, this barrier does not depend on chain length. This result coincides with experimental observations on the primary nucleation rate of bulk polymers [128-130]. For secondary nucleation of crystallization on a smooth growth front, a similar free-energy expression can be obtained for 2D nucleation ... 

A better insight into the mechanisms of the individual steps in the formation of crystals would be of great help in explaining the creation and transformation of sedimentary deposits and biological precipitates. Valuable reviews are available on the principles of nucleation of crystals and the kinetics of precipitation and crystal growth (Zhang and Nancollas, 1990 Steefel and Van Cappellen, 1990 Van Cappellen, 1991). Only a few important considerations are summarized here to illustrate the wide scope of questions to be answered in order to predict rates and mechanisms of precipitation in natural systems. 

Examples of the fourth type of changes were described by To and Flink [1.93] and Van Scoik and Carstensen [1.94] according to To and Flink, the change from an amorphous to a crystalline phase is induced either by to high storage temperatures T (T > T) or by water absorption. (Note More water increases the mobility of the amorphous solid, promoting nucleation of crystals and their subsequent growth). 

A pyroceramic material is a special type of glass that has been devitrified by controlled nucleation of crystals. It has certain properties that are like glass and other properties that are like ceramics. Standard round tubing, not square, flat, or distorted walls. 

Swope, W.C., and Anderson, H.C. (1990) 106-Particle Molecular-Dynamics Study of Homogeneous Nucleation of Crystals in a Supercooled Atomic Liquid, Phys. Rev. B, vol. 41, pp.7042-7054. 

A novel idea for the production of water is by the combination of MD and membrane crystallization [ 139], where the salt is concentrated on the feed side to a point close to super-samration, thereby inducing nucleation of crystals. Recently Gryta and Morawski [140] performed experiments using polypropylene capillary membranes with pore diameters ranging between 0.2 and 0.6 p.m, and 70% porosity. They found crystallization to occur at the membrane surface, but by increasing the distillate temperature to 328 K, the problem was eliminated and stable flux restored. 

Crystal nucleation from the melt is but one type of nucleation in the condensed phase. Other processes of interest include the nucleation of salt crystals from aqueous solution, of one crystalline phase from another or from a glass, and of liquid crystal phases from one another or from the isotropic liquid. In this review we discuss only the nucleation of crystals from the melt. The major emphasis will be on single-component systems, although crystallization of alloys and binary mixtures will also be considered. 

NUCLEATION OF CRYSTALS FROM THE MELT D. Density Functional Theories of the Interface... 

There has been little work done to date on the nature of the three-phase substrate-solid-liquid intersection, and there is little guidance in predicting the magnitude of the equilibrium contact angle 9 that enters into classical nucleation theory in the factor f(0). Considerably more work has been done on the contact angle in substrate-liquid-vapor equilibrium, which determines the wetting properties of the liquid for the substrate. It is possible that some of the techniques developed for that problem may be applicable to the study of surface-induced nucleation of crystallization. 

W. C. Swope and H. C. Andersen (1990) 10(6)-Particle molecular-dynamics study of homogeneous nucleation of crystals in a supercooled atomic hquid. Phys. Rev. B 41, pp. 7042-7054... 

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