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metadata.dc.type: Artigo de Periódico
Artigo de Periódico
Title: Diffusion coefficients for crystal nucleation and growth in deeply undercooled glass-forming liquids
Authors: Fokin, Vladimir Mihailovich
Schmelzer, Jurn Williard P.
Nascimento, Marcio Luis Ferreira
Zanotto, Edgar Dutra
metadata.dc.creator: Fokin, Vladimir Mihailovich
Schmelzer, Jurn Williard P.
Nascimento, Marcio Luis Ferreira
Zanotto, Edgar Dutra
Abstract: We calculate, employing the classical theory of nucleation and growth, the effective diffusion coefficients controlling crystal nucleation of nano-size clusters and the subsequent growth of micron-size crystals at very deep undercoolings, below and above Tg, using experimental nucleation and growth data obtained for stoichiometric Li2O 2SiO2 and Na2O 2CaO 3SiO2 glasses. The results show significant differences in the magnitude and temperature dependence of these kinetic coefficients. We explain this difference showing that the composition and/or structure of the nucleating critical clusters deviate from those of the stable crystalline phase. These results for diffusion coefficients corroborate our previous conclusion for the same glasses, based on different experiments, and support the view that, even for the so-called case of stoichiometric (polymorphic) crystallization, the nucleating phase may have a different composition and/or structure as compared to the parent glass and the evolving macroscopic crystalline phase. This finding gives a key to explain the discrepancies between calculated (by Classical Nucleation Theory) and experimentally observed nucleation rates in these systems, in particular, and in deeply undercooled glass-forming liquids, in general.
Keywords: Vidro
Crescimento de Cristais
Issue Date: 1-Jan-2007
Appears in Collections:Artigo Publicado em Periódico (PEI)

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