{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/27801"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/27801","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Structure Evolution of Silica Aerogel under a Microwave Field","abstract":"Structure evolution of silica aerogel was studied in microwave- and conventionally processed samples over the temperature range from 25 to 1200â °C. The samples were produced using sol-gel processing and dried under carbon dioxide supercritical conditions. After drying, the monolithic samples received a thermal treatment at different programmed temperatures in two different ovens, conventional and microwave. The microwave process was performed using a single mode microwave oven at 2.45GHz. Dielectric properties were measured using the cavity perturbation method, and structural characterization was carried out using a variety of techniques, including absorption surface analysis, Helium pycnometry, Archimedes principle, Fourier transform infrared spectroscopy, X-ray diffraction, and high resolution microscopy. The data obtained revealed that structural differences do exist between microwave- and conventionally processed samples. Three different regions were identified from the structural characterization of the samples. Regions I exhibited a structure densification at temperatures between 25 and 850â °C. Region II was characterized by a bulk densification in the temperature range from 850 to 1200â °C. Region III was represented by the onset of crystallization above 1200â °C. Explanation and possible causes behind the structural differences observed in each region are provided. In general, the structure evolution observed in microwave- and conventionally processed samples followed the same order, but occurred at lower temperature for the microwave process.","abstract_html":"Structure evolution of silica aerogel was studied in microwave- and conventionally processed samples over the temperature range from 25 to 1200â °C. The samples were produced using sol-gel processing and dried under carbon dioxide supercritical conditions. After drying, the monolithic samples received a thermal treatment at different programmed temperatures in two different ovens, conventional and microwave. The microwave process was performed using a single mode microwave oven at 2.45GHz. Dielectric properties were measured using the cavity perturbation method, and structural characterization was carried out using a variety of techniques, including absorption surface analysis, Helium pycnometry, Archimedes principle, Fourier transform infrared spectroscopy, X-ray diffraction, and high resolution microscopy. The data obtained revealed that structural differences do exist between microwave- and conventionally processed samples. Three different regions were identified from the structural characterization of the samples. Regions I exhibited a structure densification at temperatures between 25 and 850â °C. Region II was characterized by a bulk densification in the temperature range from 850 to 1200â °C. Region III was represented by the onset of crystallization above 1200â °C. Explanation and possible causes behind the structural differences observed in each region are provided. In general, the structure evolution observed in microwave- and conventionally processed samples followed the same order, but occurred at lower temperature for the microwave process.","abstract_has_math":false,"creators":["Folgar, Carlos Eduardo"],"institution":"Virginia Tech","degree_name":"Ph. D.","degree_level":"doctoral","degree_discipline":"Materials Science and Engineering","degree_department":"Materials Science and Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Clark, David E."],"committee_members":["Viehland, Dwight D.","Suchicital, Carlos T. A.","Pickrell, Gary R."],"year":2010,"date_issued":"2010-05-10","date_published":"2010-05-10","updated_at":"2026-07-22T22:19:04Z","subjects":["silica gel","single mode microwave oven","dielectric measurements","microwave process"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-05192010-013744"],"render_values":[{"text":"etd-05192010-013744","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/27801","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Clark, David E."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Viehland, Dwight D.","Suchicital, Carlos T. 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The samples were produced using sol-gel processing and dried under carbon dioxide supercritical conditions. After drying, the monolithic samples received a thermal treatment at different programmed temperatures in two different ovens, conventional and microwave. The microwave process was performed using a single mode microwave oven at 2.45GHz. Dielectric properties were measured using the cavity perturbation method, and structural characterization was carried out using a variety of techniques, including absorption surface analysis, Helium pycnometry, Archimedes principle, Fourier transform infrared spectroscopy, X-ray diffraction, and high resolution microscopy. The data obtained revealed that structural differences do exist between microwave- and conventionally processed samples. Three different regions were identified from the structural characterization of the samples. Regions I exhibited a structure densification at temperatures between 25 and 850â °C. Region II was characterized by a bulk densification in the temperature range from 850 to 1200â °C. Region III was represented by the onset of crystallization above 1200â °C. Explanation and possible causes behind the structural differences observed in each region are provided. In general, the structure evolution observed in microwave- and conventionally processed samples followed the same order, but occurred at lower temperature for the microwave process."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:title","label":"Title","values":["Structure Evolution of Silica Aerogel under a Microwave Field"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Clark, David E."],"dc:contributor.committeemember":["Viehland, Dwight D.","Suchicital, Carlos T. 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Dielectric properties were measured using the cavity perturbation method, and structural characterization was carried out using a variety of techniques, including absorption surface analysis, Helium pycnometry, Archimedes principle, Fourier transform infrared spectroscopy, X-ray diffraction, and high resolution microscopy. The data obtained revealed that structural differences do exist between microwave- and conventionally processed samples. Three different regions were identified from the structural characterization of the samples. Regions I exhibited a structure densification at temperatures between 25 and 850â °C. Region II was characterized by a bulk densification in the temperature range from 850 to 1200â °C. Region III was represented by the onset of crystallization above 1200â °C. Explanation and possible causes behind the structural differences observed in each region are provided. 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