Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry

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dc.contributor.authorVollet, D. R.
dc.contributor.authorDonatti, D. A.
dc.contributor.authorRuiz, A. Ibanez
dc.contributor.authorGatto, F. R.
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.date.accessioned2014-05-20T15:21:03Z
dc.date.available2014-05-20T15:21:03Z
dc.date.issued2006-07-01
dc.description.abstractLow density silica sonogels were prepared from acid sonohydrolysis of tetraethoxysilane. Wet gels were studied by small-angle x-ray scattering (SAXS) and differential scanning calorimetry (DSC). The DSC tests were carried out under a heating rate of 2 degrees C/min from -120 degrees C up to 30 degrees C. Aerogels were obtained by CO(2) supercritical extraction and characterized by nitrogen adsorption and SAXS. The DSC thermogram displays two distinct endothermic peaks. The first, a broad peak extending from about -80 degrees C up to practically 0 degrees C, was associated to the melting of ice nanocrystals with a crystal size distribution with pore diameter ranging from 1 or 2 nm up to about 60 nm, as estimated from Thomson's equation. The second, a sharp peak with onset temperature close to 0 degrees C, was attributed to the melting of macroscopic crystals. The DSC incremental nanopore volume distribution is in reasonable agreement with the incremental pore volume distribution of the aerogel as determined from nitrogen adsorption. No macroporosity was detected by nitrogen adsorption, probably because the adsorption method applies stress on the sample during measurement, leading to a underestimation of pore volume, or because often positive curvature of the solid surface is in aerogels, making the nitrogen condensation more difficult. According to the SAXS results, the solid network of the wet gels behaves as a mass fractal structure with mass fractal dimension D=2.20 +/- 0.01 in a characteristic length scale below xi=7.9 +/- 0.1 nm. The mass fractal characteristics of the wet gels have also been probed from DSC data by means of an earlier applied modeling for generation of a mass fractal from the incremental pore volume distribution curves. The results are shown to be in interesting agreement with the results from SAXS.en
dc.description.affiliationUniv Estadual Paulista, Dept Fis, IGCE, BR-13500970 Rio Claro, SP, Brazil
dc.description.affiliationUnespUniv Estadual Paulista, Dept Fis, IGCE, BR-13500970 Rio Claro, SP, Brazil
dc.format.extent7
dc.identifierhttp://dx.doi.org/10.1103/PhysRevB.74.024208
dc.identifier.citationPhysical Review B. College Pk: Amer Physical Soc, v. 74, n. 2, 7 p., 2006.
dc.identifier.doi10.1103/PhysRevB.74.024208
dc.identifier.fileWOS000239426600038.pdf
dc.identifier.issn1098-0121
dc.identifier.lattes2661573794233385
dc.identifier.lattes3538107401166553
dc.identifier.lattes5890636096105376
dc.identifier.urihttp://hdl.handle.net/11449/32240
dc.identifier.wosWOS:000239426600038
dc.language.isoeng
dc.publisherAmer Physical Soc
dc.relation.ispartofPhysical Review B
dc.relation.ispartofsjr1,604
dc.rights.accessRightsAcesso restrito
dc.sourceWeb of Science
dc.titleMass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetryen
dc.typeArtigo
dcterms.licensehttp://publish.aps.org/authors/transfer-of-copyright-agreement
dcterms.rightsHolderAmer Physical Soc
unesp.author.lattes2661573794233385
unesp.author.lattes3538107401166553
unesp.author.lattes5890636096105376
unesp.campusUniversidade Estadual Paulista (Unesp), Instituto de Geociências e Ciências Exatas, Rio Claropt

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Artigos - Física - IGCE