Nucleation heterophase fluctuation

It is supposed that geometry, morphology and crystalline phase nucleation and growth mechanism will be defined to a considerable degree by the nature of heterophase fluctuations in the amorphous state. So, the supposition of heterophase fluctuation from folded chains (Yech model [44]) results in the formation of crystallites with folded chains (CFC). In paper [43], an alternative model of heterophase fluctuation supposes the availability of parallel parts of different chains of macromolecules in it. The use of these models supposes the possibility of formation in the crystallisation process of CFC, crystallites with stretched chains (CSC) or some intermediate morphology... 

By its physical essence the heterophase fluctuation type, proposed in paper [43], is similar to local order domain (cluster) in the cluster model of the amorphous state structure of polymers [7, 8]. The last model application allows a quantitative description of such heterophase fluctuations and, as a consequence, analysis of the change in crystallisation morphology and nucleation mechanism [46]. In papers [47, 48] such analysis was carried out on the example of PCP and LDPE orientational crystallisation. 

When the primary facets of ice are defect free, the relevant step generation mechanism is the formation of two-dimensional nuclei. The process is driven by thermally activated fluctuations of the liquid phase that create two-dimensional heterophase clusters with solid-like structure. The most probable cluster geometry is tiiat of a pillbox, for which the edge-to-surface free energy ratio will favor spreading at a given drive. In analogy with three-dimensions, the nucleation frequency /per unit facet area. 4 is of a Maxwell-Boltzmann form, / exp - n cr /Ap kbT), where [Pg.47]

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