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A SAXS study of kinetics of aggregation of TEOS-derived sonogels at different temperatures

dc.contributor.authorVollet, D. R.
dc.contributor.authorDonatti, D. A.
dc.contributor.authorRuiz, A. I.
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.date.accessioned2014-05-20T15:26:48Z
dc.date.available2014-05-20T15:26:48Z
dc.date.issued2001-08-01
dc.description.abstractThe kinetics of aggregation of tetraethoxysilane (TEOS)-derived silica sols, produced by acid-catalyzed and ultrasound-stimulated hydrolysis, were studied by 'in situ' measurements of small-angle X-ray scattering (SAXS) at the temperatures 40 degreesC, 60 degreesC and 70 degreesC. The results were analyzed in terms of the evolution with time (t) of the SAXS intensity probing the mass fractal characteristics of the system, the average radius of gyration (Rc,) of the clusters and the number of primary particles per cluster. The aggregation process yields mass fractal structures which exhibit a scattering exponent (alpha) practically equal to 2, in the probed length scale range (5.3 nm < 1/q < 0.22 nm), beneath and even far beyond the gel point. This suggests that a is a direct measure of the real mass fractal dimension (D) of the structure. The precursor sol (pH = 2) exhibits I nm mean sized clusters with mass fractal dimension D similar to 1.9. Increasing the pH to 4.5, the cluster mean size and the number of primary particles per cluster increase but the system keeps a more opened structure (D similar to 1.4). In the first aggregation stages, D increases up to similar to2 by incorporating primary particles to the clusters without changing their mean size. From this stage, the aggregation progresses following a thermally activated scaling law well described by R-G similar tot(1/D) in all cases. This is indicative of a diffusion-controlled cluster-cluster aggregation process. The activation energy of the process was found to be 91.7 kJ/mol. (C) 2001 Elsevier B.V. B.V. All rights reserved.en
dc.description.affiliationUNESP, IGCE, Dept Fis, BR-13500970 Rio Claro, SP, Brazil
dc.description.affiliationUnespUNESP, IGCE, Dept Fis, BR-13500970 Rio Claro, SP, Brazil
dc.format.extent81-87
dc.identifierhttp://dx.doi.org/10.1016/S0022-3093(01)00607-X
dc.identifier.citationJournal of Non-crystalline Solids. Amsterdam: Elsevier B.V., v. 288, n. 1-3, p. 81-87, 2001.
dc.identifier.doi10.1016/S0022-3093(01)00607-X
dc.identifier.issn0022-3093
dc.identifier.lattes2661573794233385
dc.identifier.lattes3538107401166553
dc.identifier.lattes5890636096105376
dc.identifier.urihttp://hdl.handle.net/11449/36885
dc.identifier.wosWOS:000170260500010
dc.language.isoeng
dc.publisherElsevier B.V.
dc.relation.ispartofJournal of Non-Crystalline Solids
dc.relation.ispartofjcr2.488
dc.relation.ispartofsjr0,722
dc.rights.accessRightsAcesso restrito
dc.sourceWeb of Science
dc.titleA SAXS study of kinetics of aggregation of TEOS-derived sonogels at different temperaturesen
dc.typeArtigo
dcterms.licensehttp://www.elsevier.com/about/open-access/open-access-policies/article-posting-policy
dcterms.rightsHolderElsevier B.V.
unesp.author.lattes2661573794233385
unesp.author.lattes3538107401166553
unesp.author.lattes5890636096105376
unesp.author.orcid0000-0001-8154-9692[1]
unesp.campusUniversidade Estadual Paulista (Unesp), Instituto de Geociências e Ciências Exatas, Rio Claropt
unesp.departmentFísica - IGCEpt

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