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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Desemulsificação de emulsões estáveis de água e óleo de girassol por processo de filtração tangencial / Demulsifying of stable emulsions of water and sunflower oil by cross-flow filtration process

Delcolle, Roberta 20 December 2005 (has links)
O processo estudado utilizou tubos cerâmicos porosos fabricados predominantemente com alumina e produzidos pela técnica da colagem de barbotina e sinterizados a temperaturas próximas a 1450 graus Celsius, para seleção de uma temperatura. O meio micro poroso foi caracterizado pela técnica de porosimetria por intrusão de mercúrio, apresentando tamanho médio de poro de 0,5 'mü'm. Os tubos foram submetidos à impregnação com solução de citrato de zircônio (precursor) por capilaridade. Posteriormente, os tubos foram calcinados e tratados termicamente até 600 e 900 graus Celsius, com o objetivo de eliminar componentes orgânicos voláteis e transformar o precursor no óxido metálico. A impregnação foi realizada em diferentes proporções e os tubos microporosos foram testados na bancada de micro-filtração, onde foram variados parâmetros fluidodinâmicos do processo (Reynolds e pressão transmembrana) e analisada as propriedades físico-químicas do volume de permeado, através de medidas da concentração de carbono orgânico total (TOC), condutividade elétrica, pH e a caracterização da mistura (concentrado) através de microscopia óptica. O meio micro poroso impregnado foi caracterizado por microscopia eletrônica de varredura (MEV), para analisar a morfologia do material impregnado e sua composição qualitativa. Os resultados do fluxo de permeado foram analisados e observou-se que os melhores resultados quanto ao fluxo transmembrana foram obtidos para o tubo impregnado a 900 graus Celsius. O tubo impregnado a 600 graus Celsius apresentou melhor desempenho relativo à desemulsificação, por apresentar menores valores de TOC. Em relação ao processo de transferência de massa, o tubo impregnado 900 graus Celsius obteve maiores valores de Sherwood, portanto a temperatura após impregnação influenciou no transporte de massa durante o processo de separação. A retenção da fase óleo analisada através de medidas de TOC foi de até 99%. / The studied process used porous ceramic tubes manufactured predominantly with alumina and produced by the technique of the collage with barbotina and sintered to close temperatures for 1450 Celsius degrees, for selection of a temperature. The microporous enviroment was characterized by mercury porosimetry, presenting medium size of pore of 0,5 'mü'm. The tubes were submitted to the impregnation with solution of citrate of zirconium (precursory) by capillarity. Later on, the tubes were burned and thermally treated up to 600 and 900 Celsius degrees, with the objective of to eliminate volatile organic components and to transform the precursory in the metallic oxide. The impregnation was accomplished in different proportions and the microporous tubes were tested in apparatus of microfiltration process, where were varied fluid dynamics parameters of the process (Reynolds and transmembrane pressure) and analyzed the physical-chemical properties of the volume of permeated, through measures of the concentration of total organic carbon (TOC), electric conductivity, pH and the characterization of the mixture (concentrated) through optical microscopy. The enviroment impregnated microporous was characterized by scanning eletronic microscopy (SEM), to analyze the morphology of the impregnated material and its qualitative composition. The results of the flow of having permeated were analyzed and it was observed that the best results with relationship to the transmembrane flux were obtained for the tube impregnated for 900 Celsius degrees. The tube impregnated for 600 Celsius degrees presented better relative acting to the demulsifying, for presenting smaller values of TOC. In relation to the process of mass transfer, the impregnated tube 900 Celsius degrees obtained larger values of Sherwood, therefore the temperature after impregnation influenced in the mass transport during the separation process. The retention of the phase oil analyzed through measures of TOC was of up to 99%.
2

Desemulsificação de emulsões estáveis de água e óleo de girassol por processo de filtração tangencial / Demulsifying of stable emulsions of water and sunflower oil by cross-flow filtration process

Roberta Delcolle 20 December 2005 (has links)
O processo estudado utilizou tubos cerâmicos porosos fabricados predominantemente com alumina e produzidos pela técnica da colagem de barbotina e sinterizados a temperaturas próximas a 1450 graus Celsius, para seleção de uma temperatura. O meio micro poroso foi caracterizado pela técnica de porosimetria por intrusão de mercúrio, apresentando tamanho médio de poro de 0,5 'mü'm. Os tubos foram submetidos à impregnação com solução de citrato de zircônio (precursor) por capilaridade. Posteriormente, os tubos foram calcinados e tratados termicamente até 600 e 900 graus Celsius, com o objetivo de eliminar componentes orgânicos voláteis e transformar o precursor no óxido metálico. A impregnação foi realizada em diferentes proporções e os tubos microporosos foram testados na bancada de micro-filtração, onde foram variados parâmetros fluidodinâmicos do processo (Reynolds e pressão transmembrana) e analisada as propriedades físico-químicas do volume de permeado, através de medidas da concentração de carbono orgânico total (TOC), condutividade elétrica, pH e a caracterização da mistura (concentrado) através de microscopia óptica. O meio micro poroso impregnado foi caracterizado por microscopia eletrônica de varredura (MEV), para analisar a morfologia do material impregnado e sua composição qualitativa. Os resultados do fluxo de permeado foram analisados e observou-se que os melhores resultados quanto ao fluxo transmembrana foram obtidos para o tubo impregnado a 900 graus Celsius. O tubo impregnado a 600 graus Celsius apresentou melhor desempenho relativo à desemulsificação, por apresentar menores valores de TOC. Em relação ao processo de transferência de massa, o tubo impregnado 900 graus Celsius obteve maiores valores de Sherwood, portanto a temperatura após impregnação influenciou no transporte de massa durante o processo de separação. A retenção da fase óleo analisada através de medidas de TOC foi de até 99%. / The studied process used porous ceramic tubes manufactured predominantly with alumina and produced by the technique of the collage with barbotina and sintered to close temperatures for 1450 Celsius degrees, for selection of a temperature. The microporous enviroment was characterized by mercury porosimetry, presenting medium size of pore of 0,5 'mü'm. The tubes were submitted to the impregnation with solution of citrate of zirconium (precursory) by capillarity. Later on, the tubes were burned and thermally treated up to 600 and 900 Celsius degrees, with the objective of to eliminate volatile organic components and to transform the precursory in the metallic oxide. The impregnation was accomplished in different proportions and the microporous tubes were tested in apparatus of microfiltration process, where were varied fluid dynamics parameters of the process (Reynolds and transmembrane pressure) and analyzed the physical-chemical properties of the volume of permeated, through measures of the concentration of total organic carbon (TOC), electric conductivity, pH and the characterization of the mixture (concentrated) through optical microscopy. The enviroment impregnated microporous was characterized by scanning eletronic microscopy (SEM), to analyze the morphology of the impregnated material and its qualitative composition. The results of the flow of having permeated were analyzed and it was observed that the best results with relationship to the transmembrane flux were obtained for the tube impregnated for 900 Celsius degrees. The tube impregnated for 600 Celsius degrees presented better relative acting to the demulsifying, for presenting smaller values of TOC. In relation to the process of mass transfer, the impregnated tube 900 Celsius degrees obtained larger values of Sherwood, therefore the temperature after impregnation influenced in the mass transport during the separation process. The retention of the phase oil analyzed through measures of TOC was of up to 99%.
3

Hierarchical Assembly of Polymeric Nanofibers for Advanced Material Applications

Wang, Ji 27 March 2015 (has links)
Polymer nanofibers are gaining importance due to their wide applicability in diverse fields, such as tissue engineering, fuel cells, photonics and sensors. For these applications, manufacturing aligned polymer nanofibers with precisely controlled morphology and well characterized mechanical properties in a bottom up configuration is essential. In this work, we developed an isodiametric design space for fabrication of aligned polystyrene nanofibers (diameter 60-800nm) using non-electrospinning Spinneret based Tunable Engineered Parameter (STEP) technique. By adjusting the processing parameters such as relative humidity, solvent volatility and polarity, porous polymer tubes are demonstrated having large specific surface areas. Combining STEP with sol-gel process, aligned inorganic nanofibers, such as Titanium Oxide (TiO2) with varied morphologies can be conveniently obtained. Mechanical properties of aligned polymer nanofibers (diameter from 50nm to several hundred nanometers) with fixed-fixed boundary conditions were estimated using a lateral force microscope (LFM). We find that the tension in the fiber caused during fabrication process scales with fiber diameter and it dominates fiber stiffness. Our studies demonstrate isotropic arrangement of polymer chains in the fibers and anisotropic arrangement in the necking region for fibers undergone deformation. Finally, this study demonstrates development of force sensors capable of measuring single cell forces, which scale with the fiber structural stiffness. The ability to measure cell forces during cell division, migration and apoptosis provides new insights in cell mechanobiology. / Ph. D.

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