Is the structural relaxation of glasses controlled by equilibrium shear viscosity?

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dc.contributor.authorLancelotti, Ricardo Felipe
dc.contributor.authorCassar, Daniel Roberto
dc.contributor.authorNalin, Marcelo [UNESP]
dc.contributor.authorPeitl, Oscar
dc.contributor.authorZanotto, Edgar Dutra
dc.contributor.institutionUniversidade Federal de São Carlos (UFSCar)
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.date.accessioned2021-06-25T10:20:29Z
dc.date.available2021-06-25T10:20:29Z
dc.date.issued2021-05-01
dc.description.abstractKnowledge of relaxation processes is fundamental in glass science and technology because relaxation is intrinsically related to vitrification, tempering as well as to annealing and several applications of glasses. However, there are conflicting reports—summarized here for different glasses—on whether the structural relaxation time of glass can be calculated using the Maxwell equation, which relates relaxation time with shear viscosity and shear modulus. Hence, this study aimed to verify whether these two relaxation times are comparable. The structural relaxation kinetics of a lead metasilicate glass were studied by measuring the refractive index variation over time at temperatures between 5 and 25 K below the fictive temperature, which was initially set 5 K below the glass-transition temperature. Equilibrium shear viscosity was measured above and below the glass-transition range, expanding the current knowledge by one order of magnitude. The Kohlrausch equation described very well the experimental structural relaxation kinetics throughout the investigated temperature range and the Kohlrausch exponent increased with temperature, in agreement with studies on other glasses. The experimental average structural relaxation times were much longer than the values computed from isostructural viscosity, as expected. Still, they were less than one order of magnitude higher than the average relaxation time computed through the Maxwell equation, which relies on equilibrium shear viscosity. Thus, these results demonstrate that the structural relaxation process is not controlled by isostructural viscosity and that equilibrium shear viscosity only provides a lower boundary for structural relaxation kinetics.en
dc.description.affiliationGraduate Program in Materials Science and Engineering Federal University of São Carlos
dc.description.affiliationDepartment of Materials Engineering Center for Research Technology and Education in Vitreous Materials Federal University of São Carlos
dc.description.affiliationInstitute of Chemistry São Paulo State University UNESP
dc.description.affiliationUnespInstitute of Chemistry São Paulo State University UNESP
dc.description.sponsorshipConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
dc.description.sponsorshipFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
dc.description.sponsorshipIdCNPq: 130495/2019-0
dc.description.sponsorshipIdFAPESP: 2013/07793-6
dc.description.sponsorshipIdFAPESP: 2017/12491-0
dc.description.sponsorshipIdFAPESP: 2019/15108-8
dc.format.extent2066-2076
dc.identifierhttp://dx.doi.org/10.1111/jace.17622
dc.identifier.citationJournal of the American Ceramic Society, v. 104, n. 5, p. 2066-2076, 2021.
dc.identifier.doi10.1111/jace.17622
dc.identifier.issn1551-2916
dc.identifier.issn0002-7820
dc.identifier.scopus2-s2.0-85099398899
dc.identifier.urihttp://hdl.handle.net/11449/205743
dc.language.isoeng
dc.relation.ispartofJournal of the American Ceramic Society
dc.sourceScopus
dc.subjectglass
dc.subjectrefractive index
dc.subjectviscosity
dc.titleIs the structural relaxation of glasses controlled by equilibrium shear viscosity?en
dc.typeArtigo
unesp.author.orcid0000-0002-6111-6520[1]
unesp.author.orcid0000-0001-6472-2780[2]
unesp.author.orcid0000-0003-4931-4505[5]

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