Homogeneous nucleation kinetic unit

The Kinetic Limit. To initiate homogeneous nucleation, a vapor embryo is required that has the critical radius r. In principle, the formation of just one such embryo would be sufficient to initiate the nucleation process, but in practice it is found that conditions must be such that J, the number of vapor embryos formed in a unit volume per unit time, has a high value (typically J > 1012). Carey [4] derives the following expression for J ... 

In the process of homogeneous nucleation taking piace without any mechanical shock, friction, rapid cooling, etc., molecules, atoms or ions join together to form a crystal nuclei called a kinetic unit (McCabe and Smith, 1976). Individual kinetic units whose volumes are of the order of 10 nm can come together or collide combinations of a few such kinetic units lead to a cluster formation in the manner of a chain reaction (an addition mechanism) ... 

There are two basic rate phenomena of interest in crystallization (1) the nucleation rate (2) the growth rate. Let us start with the nucleation rate. We have observed via equations (3.3.99) how the addition mechanism ieads from kinetic units to a cluster, to an embryo, and then to a nucleus finally, a critical size is achieved by the nucieus. From the theory of activated process in chemicai kinetics, the rate of nucleation in homogeneous nucleation is described by an Arrhenius type expression... 

In general, the number of latex particles per unit volume of water determined at the end of polymerization and the slope obtained from the least-squares best-fitted linear portion of the monomer conversion versus time curve are taken as the Np and Rp data in the study of polymerization mechanisms and kinetics. In traditional emulsion polymerization, monomer droplet nucleation, can be neglected and only naiceflar nucleation, homogeneous nucleation and flocculation of latex particles need to be taken into consider-... 

With this model in mind we may adapt the Volmer-Stranski-Becker-Doring theory of homogeneous nucleation in a supersaturated vapor to the problem of nucleation of a new crystalline phase II in the interior of an unstable crystalline phase I. Progressive clustering of kinetic units occurs to form embryos ... 

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