Síntese e caracterização de vidros fosfatos contendo nanopartículas magnéticas de CdFe2O4, CoPt e Fe3-xO4 protegidas por uma camada de SiO2
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Data
2018-06-07
Autores
Orives, Juliane Resges
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Universidade Estadual Paulista (Unesp)
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 fundida por 15 min manteve o tamanho e forma das nanopartículas com formato estrelado incorporadas. Foram realizados estudos das propriedades estruturais, térmicas, ópticas e magnéticas destes novos materiais utilizando as técnicas de Difração de raios X, Espectroscopia Raman, Ressonância Magnética Nuclear, Microscopia Eletrônica de Varredura, Calorimetria Diferencial Exploratória, Espectroscopia na região UV-Vis-Infravermelho e magnetometria usando SQUID. Foram obtidos vidros transparentes, não higroscópicos e com boa qualidade óptica. Os sistemas contendo CdFe2O4-SiO2 e Fe3-xO4@SiO2 apresentaram um grande aumento da estabilidade térmica, sendo o parâmetro Tx-Tg superior a 200 °C, o que é importante para produção de fibras e dispositivos ópticos. Os vidros fosfatos contendo CdFe2O4-SiO2, CoPt-SiO2 e Fe3-xO4@SiO2 apresentaram comportamentos paramagnéticos, próximo ao ferromagnético e próximo ao superparamagnético, respectivamente, mostrando que é possível incorporar propriedades magnéticas ao vidro diamagnético. Os vidros obtidos são potenciais materiais para aplicações em magneto-óptica. O método de incorporação de nanopartículas utilizado é inédito e abre caminho para incorporação de novos nanomateriais magnéticos aos vidros e também para materiais com outras propriedades além das magnéticas.
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 by 15 min kept the size and stellate shape of the nanoparticles incorporated. The structural, thermal, optical and magnetic properties of these new materials were studied using X - Ray Diffraction, Raman Spectroscopy, Nuclear Magnetic Resonance, Scanning Electr on Microscopy, Exploratory Differential Calorimetry, UV - Vis - Infrared Spectroscopy and magnetometry using SQUID. Transparent, non - hygroscopic glasses with good optical quality were obtained. Systems containing CdFe 2 O 4 - SiO 2 and Fe 3 - x O 4 @SiO 2 showed a large in crease in thermal stability, the Tx - Tg parameter was greater than 200 °C, which is important for the production of fibers and optical devices. The phosphate glasses containing CdFe 2 O 4 - SiO 2 , CoPt - SiO 2 and Fe 3 - x O 4 @SiO 2 presented paramagnetic behavior, close to the ferromagnetic and close to the superparamagnetic behavior, respectively, showing that it is possible to incorporate magnetic properties to the diamagnetic glass. Glasses obtained are potential materials for magneto - optical applications. The nanopart icle incorporation method used is unprecedented and opens the way for the incorporation of new magnetic nanomaterials in glasses and also materials with properties other than magnetic properties.
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 by 15 min kept the size and stellate shape of the nanoparticles incorporated. The structural, thermal, optical and magnetic properties of these new materials were studied using X - Ray Diffraction, Raman Spectroscopy, Nuclear Magnetic Resonance, Scanning Electr on Microscopy, Exploratory Differential Calorimetry, UV - Vis - Infrared Spectroscopy and magnetometry using SQUID. Transparent, non - hygroscopic glasses with good optical quality were obtained. Systems containing CdFe 2 O 4 - SiO 2 and Fe 3 - x O 4 @SiO 2 showed a large in crease in thermal stability, the Tx - Tg parameter was greater than 200 °C, which is important for the production of fibers and optical devices. The phosphate glasses containing CdFe 2 O 4 - SiO 2 , CoPt - SiO 2 and Fe 3 - x O 4 @SiO 2 presented paramagnetic behavior, close to the ferromagnetic and close to the superparamagnetic behavior, respectively, showing that it is possible to incorporate magnetic properties to the diamagnetic glass. Glasses obtained are potential materials for magneto - optical applications. The nanopart icle incorporation method used is unprecedented and opens the way for the incorporation of new magnetic nanomaterials in glasses and also materials with properties other than magnetic properties.
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Vidros magnéticos, Coacervato, Caroço@casca