Does viscosity describe the kinetic barrier for crystal growth from the liquidus to the glass transition?

Autor(es)

Ferreira Nascimento, Marcio Luis ^{[1, 2]} ; Zanotto, Edgar Dutra ^[3]

Afiliação do(s) autor(es)

^[1] Univ Fed Bahia, Inst Humanities Arts & Sci, BR-40170115 Salvador, BA - Brazil

^[2] Univ Fed Bahia, PROTEC PEI Postgrad Program Ind Engn, Polytech Sch, BR-40210630 Salvador, BA - Brazil

^[3] Univ Fed Sao Carlos, Dept Mat Engn, Vitreous Mat Lab, BR-13565905 Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Chemical Physics; v. 133, n. 17 NOV 7 2010.
• Citações Web of Science: 49

Resumo

An analysis of the kinetic coefficient of crystal growth U(kin), recently proposed by Ediger et al. {[}J. Chem. Phys. 128, 034709 (2008)], indicates that the Stokes-Einstein/Eyring (SE/E) equation does not describe the diffusion process controlling crystal growth rates in fragile glass-forming liquids. U(kin) was defined using the normal growth model and tested for crystal data for inorganic and organic liquids covering a viscosity range of about 10(4)-10(12) Pa s. Here, we revisit their interesting finding considering two other models: the screw dislocation (SD) and the two-dimensional surface nucleated (2D) growth models for nine undercooled oxide liquids, in a wider temperature range, from slightly below the melting point down to the glass transition region T(g), thus covering a wider viscosity range: 10(1)-10(13) Pa s. We then propose and use normalized kinetic coefficients (M(kin)) for the SD and 2D growth models. These new kinetic coefficients restore the ability of viscosity to describe the transport part of crystal growth rates (M(kin) similar to 1/eta and xi similar to 1) from low to moderate viscosities (eta < 10(6) Pa s), and thus the SE/E equation works well in this viscosity range for all systems tested. For strong glasses, the SE/E equation works well from low to high viscosities, from the melting point down to Tg! However, for at least three fragile liquids, diopside (kink at 1.08T(g), eta=1.6 x 10(8) Pa s), lead metasilicate (kink at 1.14T(g), eta=4.3 x 10(6) Pa s), and lithium disilicate (kink at 1.11T(g), eta=1.6 x 10(8) Pa s), there are clear signs of a breakdown of the SE/ E equation at these higher viscosities. Our results corroborate the findings of Ediger et al. and demonstrate that viscosity data cannot be used to describe the transport part of the crystal growth (via the SE/ E equation) in fragile glasses in the neighborhood of T(g). (C) 2010 American Institute of Physics. {[}doi:10.1063/1.3490793] (AU)

• Processo FAPESP: 04/10703-0 - Crescimento de cristais em vidros óxidos: testes de modelos e do possível desacoplamento entre difusão iônica e fluxo viscoso
• Beneficiário: Marcio Luis Ferreira Nascimento
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 07/08179-9 - Processos cinéticos em vidros e vitrocerâmicas
• Beneficiário: Edgar Dutra Zanotto
• Modalidade de apoio: Auxílio à Pesquisa - Temático