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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

Síntese e caracterização de vidros fosfatos contendo nanopartículas magnéticas de CdFe2O4, CoPt e Fe3-xO4 protegidas por uma camada de SiO2 /

Orives, Juliane Resges. January 2018 (has links)
Orientador: Marcelo Nalin / Banca: Sidney Jose Lima Ribeiro / Banca: Paulo Noronha Lisboa Filho / Banca: Hellmut Eckert / Banca: Cleber Renato Mendonça / Resumo: O trabalho apresenta a obtenção de vidros fosfatos contendo nanopartículas de CdFe2O4, CoPt e Fe3-xO4, com diâmetros médios de 3,9, 16,1 e 20 nm, respectivamente, as quais foram recobertas por uma camada de sílica com a finalidade de protege-las durante a fusão dos precursores vitreos. As nanopartículas de CdFe2O4 foram sintetizadas pelo método de coprecipitação enquanto as nanopartículas de Fe3-xO4 foram obtidas por decomposição térmica, ambas apresentaram comportamento superparamagnético à 300 K. As nanopartículas de CoPt foram sintetizadas por redução dos precursores metálicos em solvente orgânico em alta temperatura, e após tratamento térmico a 900 °C apresentaram comportamento ferromagnético à 300 K. As nanopartículas foram primeiramente incorporadas no coacervato de polifosfato de cálcio, o qual foi o precursor dos vidros fosfatos, e em seguida o material foi transformado em vidro pelo método de fusão seguido de choque térmico. Foram preparadas amostras de vidro fosfato com 1, 4 e 8 % em massa de CdFe2O4-SiO2 e vidros com 0,5, 1 e 2 % de CoPt-SiO2, fundidos por 15 min a 1000 °C. Também foram preparadas três amostras contendo 8% em massa de nanopartículas monodispersas de Fe3-xO4@SiO2, as quais foram fundidas por 15, 45 e 75 min a 1050 °C. Em todos os casos a incorporação das nanopartículas se mostrou viável, e foram observadas nas imagens de Microscopia Eletrônica de Transmissão que as nanopartículas foram incorporadas satisfatoriamente. A amostra contendo Fe3-xO4@SiO2 ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The work presents the obtaining of phosphate glasses containing nanoparticles of CdFe 2 O 4, CoPt and Fe 3 - x O 4, with average diameters of 3.9, 16.1 and 20 nm, respectively, which were covered by a layer of silica in order to protect them during the melting of vitreous precursors. The nanoparticles of CdFe 2 O 4 were synthesized by the coprecipitation method, while the nanoparticles of Fe 3 - x O 4 were obtained by thermal decomposition, both p resented superparamagnetic behavior at 300 K. CoPt nanoparticles were synthesized by reduction of the metal precursors in organic solvent at high temperature, and after heat treatment at 900 °C the particles presented a ferromagnetic behavior at 300 K. The nanoparticles were first incorporated into the calcium polyphosphate coacervate, which was the precursor of the phosphate glasses, and then the material was transformed into glass by melt - quenching method. Samples of phosphate glass with 1, 4 and 8 % in m ass of CdFe 2 O 4 - SiO 2 and glasses with 0.5, 1 and 2 % of CoPt - SiO 2, melted for 15 min at 1000 °C, were prepared. Also, three samples containing 8 % in mass of monodisperse nanoparticles of Fe 3 - x O 4 @SiO 2 were prepared, and were melted by 15, 45 and 75 min at 1050 °C. In all cases the incorporation of the nanoparticles was shown to be feasible, and it was observed in the transmission electron microscopy images that the nanoparticles were satisfactorily incorporated. The sample containing Fe 3 - x 4 @SiO 2 melted b... (Complete abstract click electronic access below) / Doutor

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