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Nucleation, environmental conditions

The environmental conditions for each of the cases considered below are summarized in Table III all these parameters are constant in time. The build up of the nucleation mode of the stable particles and the build up of both the nucleation and accumulation modes of the radon decay products is calculated, and the results are given after a process time of one hour. Figures 1 to 5 show the size distributions of stable and radioactive particles, and Table IV gives the disequilibrium, the equilibrium factor F, the "unattached fraction" f and the plate-out rates for the different daughters. [Pg.332]

The general considerations above highlight the importance of nucleation and the role of environmental conditions (e.g. solvent, temperature) in the crystallization of polymorphs as well as their interconversions. These areas continue to be the subject of intense interest especially in the context of polymorphic control in crystallization. [Pg.167]

Silica enhances the crystallinity of a polymer (and hence reduces clarity) during ageing, by acting as a nucleating agent. This is moderated, however, when the stabilizers are bound to the silica. Distinct differences in the stabilization performance of anti-oxidants and HALSs when pre-bound to silica are attributed to the ability of the stabilizers to desorb selectively, depending on the environmental conditions. [Pg.100]

The same statement holds for the nucleation of corrosion pits. Here three main mechanisms have been discussed. Again, it depends on the experimental or environmental conditions which one is the most effective and dominates the nucleation step. [Pg.283]

The difficulty with each of the theoretical approaches to date, however, is that they cannot yet predict crystal growth rate coefficients and exponents for a particular substance a priori. Thus as with nucleation kinetics, crystal growth rate data from industrial crystallizers are usually correlated empirically with environmental conditions, such as concentration and temperature using a power law model of the form... [Pg.129]

In this context, cooperativity does not necessarily mean that different parts of the system depend on and need to interact with each other to change the macrostate (or the phase). Rather, local parts of the system can react individually in the same way upon a weak change of the environmental conditions. In the freezing transition of water, nucleation cores form independently and attract other molecules in the local environment of each nucleus to join. This leads to macroscopic crystalline structures which finally bind to each other in order to reduce instabilities due to surface effects. However, the individual growth of the nucleation centers also causes dislocations that typically appear at the boundaries of these crystalline substructures,... [Pg.53]

The overall set of partial differential equations that can be considered as a mathematical characterization of the processing system of gas-liquid dispersions should include such environmental parameters as composition, temperature, and velocity, in addition to the equations of bubble-size and residence-time distributions that describe the dependence of bubble nucleation and growth on the bubble environmental factors. A simultaneous solution of this set of differential equations with the appropriate initial and boundary conditions is needed to evaluate the behavior of the system. Subject to the Curie principle, this set of equations should include the possibilities of coupling effects among the various fluxes involved. In dispersions, the possibilities of couplings between fluxes that differ from each other by an odd tensorial rank exist. (An example is the coupling effect between diffusion of surfactants and the hydrodynamics of bubble velocity as treated in Section III.) As yet no analytical solution of the complete set of equations has been found because of the mathematical difficulties involved. To simplify matters, the pertinent transfer equation is usually solved independently, with some simplifying assumptions. [Pg.333]


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