Structure Evolution of Silica Aerogel under a Microwave Field

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dc.contributor.authorFolgar, Carlos Eduardoen
dc.contributor.committeechairClark, David E.en
dc.contributor.committeememberViehland, Dwight D.en
dc.contributor.committeememberSuchicital, Carlos T. A.en
dc.contributor.committeememberPickrell, Gary R.en
dc.contributor.departmentMaterials Science and Engineeringen
dc.date.accessioned2014-03-14T20:12:18Zen
dc.date.adate2010-06-01en
dc.date.available2014-03-14T20:12:18Zen
dc.date.issued2010-05-10en
dc.date.rdate2010-06-01en
dc.date.sdate2010-05-19en
dc.description.abstractStructure 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.en
dc.description.degreePh. D.en
dc.identifier.otheretd-05192010-013744en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05192010-013744/en
dc.identifier.urihttp://hdl.handle.net/10919/27801en
dc.publisherVirginia Techen
dc.relation.haspartFolgar_CE_2010.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectsilica gelen
dc.subjectsingle mode microwave ovenen
dc.subjectdielectric measurementsen
dc.subjectmicrowave processen
dc.titleStructure Evolution of Silica Aerogel under a Microwave Fielden
dc.typeDissertationen
thesis.degree.disciplineMaterials Science and Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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