Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry
Autor(a) principal: | |
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Data de Publicação: | 2006 |
Outros Autores: | , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UNESP |
Texto Completo: | http://dx.doi.org/10.1103/PhysRevB.74.024208 http://hdl.handle.net/11449/224782 |
Resumo: | Low 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°C min from -120°C up to 30°C. Aerogels were obtained by CO2 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°C up to practically 0°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°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 ξ=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. © 2006 The American Physical Society. |
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Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetryLow 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°C min from -120°C up to 30°C. Aerogels were obtained by CO2 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°C up to practically 0°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°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 ξ=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. © 2006 The American Physical Society.Departamento de Física Unesp-Univerisdade Estadual Paulista IGCE, P.O. Box 178, CEP 13500-970 Rio Claro, SPDepartamento de Física Unesp-Univerisdade Estadual Paulista IGCE, P.O. Box 178, CEP 13500-970 Rio Claro, SPUniversidade Estadual Paulista (UNESP)Vollet, D. R. [UNESP]Donatti, D. A. [UNESP]Ibañez Ruiz, A. [UNESP]Gatto, F. R. [UNESP]2022-04-28T20:08:17Z2022-04-28T20:08:17Z2006-08-03info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://dx.doi.org/10.1103/PhysRevB.74.024208Physical Review B - Condensed Matter and Materials Physics, v. 74, n. 2, 2006.1098-01211550-235Xhttp://hdl.handle.net/11449/22478210.1103/PhysRevB.74.0242082-s2.0-33746554839Scopusreponame:Repositório Institucional da UNESPinstname:Universidade Estadual Paulista (UNESP)instacron:UNESPengPhysical Review B - Condensed Matter and Materials Physicsinfo:eu-repo/semantics/openAccess2022-04-28T20:08:17Zoai:repositorio.unesp.br:11449/224782Repositório InstitucionalPUBhttp://repositorio.unesp.br/oai/requestopendoar:29462024-08-05T15:34:47.930563Repositório Institucional da UNESP - Universidade Estadual Paulista (UNESP)false |
dc.title.none.fl_str_mv |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry |
title |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry |
spellingShingle |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry Vollet, D. R. [UNESP] |
title_short |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry |
title_full |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry |
title_fullStr |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry |
title_full_unstemmed |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry |
title_sort |
Mass fractal characteristics of wet sonogels as determined by small-angle x-ray scattering and differential scanning calorimetry |
author |
Vollet, D. R. [UNESP] |
author_facet |
Vollet, D. R. [UNESP] Donatti, D. A. [UNESP] Ibañez Ruiz, A. [UNESP] Gatto, F. R. [UNESP] |
author_role |
author |
author2 |
Donatti, D. A. [UNESP] Ibañez Ruiz, A. [UNESP] Gatto, F. R. [UNESP] |
author2_role |
author author author |
dc.contributor.none.fl_str_mv |
Universidade Estadual Paulista (UNESP) |
dc.contributor.author.fl_str_mv |
Vollet, D. R. [UNESP] Donatti, D. A. [UNESP] Ibañez Ruiz, A. [UNESP] Gatto, F. R. [UNESP] |
description |
Low 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°C min from -120°C up to 30°C. Aerogels were obtained by CO2 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°C up to practically 0°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°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 ξ=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. © 2006 The American Physical Society. |
publishDate |
2006 |
dc.date.none.fl_str_mv |
2006-08-03 2022-04-28T20:08:17Z 2022-04-28T20:08:17Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://dx.doi.org/10.1103/PhysRevB.74.024208 Physical Review B - Condensed Matter and Materials Physics, v. 74, n. 2, 2006. 1098-0121 1550-235X http://hdl.handle.net/11449/224782 10.1103/PhysRevB.74.024208 2-s2.0-33746554839 |
url |
http://dx.doi.org/10.1103/PhysRevB.74.024208 http://hdl.handle.net/11449/224782 |
identifier_str_mv |
Physical Review B - Condensed Matter and Materials Physics, v. 74, n. 2, 2006. 1098-0121 1550-235X 10.1103/PhysRevB.74.024208 2-s2.0-33746554839 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Physical Review B - Condensed Matter and Materials Physics |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.source.none.fl_str_mv |
Scopus reponame:Repositório Institucional da UNESP instname:Universidade Estadual Paulista (UNESP) instacron:UNESP |
instname_str |
Universidade Estadual Paulista (UNESP) |
instacron_str |
UNESP |
institution |
UNESP |
reponame_str |
Repositório Institucional da UNESP |
collection |
Repositório Institucional da UNESP |
repository.name.fl_str_mv |
Repositório Institucional da UNESP - Universidade Estadual Paulista (UNESP) |
repository.mail.fl_str_mv |
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1808128535272882176 |