Tese (doutorado)—Universidade de Brasília, Instituto de Física, 2006. / Submitted by Raquel Viana (tempestade_b@hotmail.com) on 2009-11-16T16:17:31Z
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Previous issue date: 2006-09 / Nessa tese foram investigadas as propriedades magnéticas e fotoacústicas de nanopartículas de maghemita dispersas em microesfera de BSA (bovine serum albumine), nanopartículas de ferrita de cobalto dispersas em microesfera de PLA (polylactic acid), nanopartículas de ferrita de cobalto peptizadas na forma de fluido magnético iônico e nanopartículas de magnetita coberta com dextrana e DMSA (dimercaptosuccinic acid) e peptizadas na forma de fluido magnético biocompatível. Foram realizadas medidas de microscopia eletrônica de transmissão (MET) e medidas de difração de raios-X para obtenção das micrografias, difratogramas, diâmetros médios e polidispersão das nanopartículas investigadas. Medidas Mössbauer permitiram a caracterização da fase magnética dos nanocompósitos (maghemita em BSA e ferrita de cobalto em PLA). Medidas de fotoacústica foram realizadas e analisadas em termos de três bandas (L, S e C). Medidas de susceptibilidade dinâmica foram realizadas na faixa de freqüência de 2 a 80 MHz, em temperatura ambiente e de nitrogênio líquido. Finalmente, a técnica de ressonância magnética foi empregada na investigação das propriedades magnéticas das amostras. As medidas de ressonância magnética foram realizadas em um espectrômetro comercial Bruker ESP-300 operando em banda-X (9,6 GHz), permitindo a investigação das amostras em função da temperatura (100 a 300K) e concentração das nanopartículas. As dependências do campo de ressonância e largura de linha de ressonância com a temperatura foram analisadas usando a aproximação proposta por Morais e colaboradores [98, 110, 112]. __________________________________________________________________________________________ ABSTRACT / In this thesis the magnetic and photoacoustic properties of maghemite nanoparticles dispersed in BSA (bovine serum albumine) microsphere, cobalt ferrite nanoparticles dispersed in PLA (polylactic acid) microsphere, cobalt ferrite nanoparticles peptized as ionic magnetic fluid and magnetite nanoparticles surface-coated with dextran and DMSA (dimercaptosuccinic acid) and peptized as biocompatible magnetic fluids were investigated. Transmission electron microscopy and X-ray diffraction measurements were performed in order to obtain the micrographs, diffractograms, average diameter and polydispersity of the investigated nanoparticles. Mössbauer measurements allowed characterization of the nanocomposites magnetic phase (maghemite in BSA and cobalt ferrite in PLA). Photoacoustic measurements were performed and analyzed in terms of three bands (L, S, and C). Dynamic susceptibility measurements were performed in the frequency range of 2 to 80 MHz, at room temperature and liquid nitrogen temperature. Finally, the magnetic resonance technique was employed in the investigation of the magnetic properties of the samples. Magnetic resonance measurements were carried out in a commercial Bruker ESP-300 spectrometer operating in the X-band (9.6 GHz), allowing investigation of the samples as a function of the temperature (100 to 300K) and nanoparticle concentration. The temperature dependence of both resonance field and resonance linewidth were analyzed within the approximation proposed by Morais and coworkers [98, 110, 112].
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.unb.br:10482/2201 |
| Date | 09 1900 |
| Creators | Silveira, Luciene Batista da |
| Contributors | Morais, Paulo César de |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | Portuguese |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UnB, instname:Universidade de Brasília, instacron:UNB |
| Rights | info:eu-repo/semantics/openAccess |
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