Influência da concentração das partículas cristalinas nas propriedades dielétricas do híbrido PVAl/Cds
Carregando...
Data
2011-05-31
Autores
Oliveira, Milena Souza [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho foram obtidos e caracterizados filmes de polivinil álcool (PVAl) puro e híbrido polivinil álcool/sulfeto de cádmio (PVAl/CdS). A síntese foi realizada usando o método “hidrotérmico in situ”. O híbrido é composto pela matriz orgânica o PVAl e a outra fase inorgânica é o CdS. As amostras foram obtidas na forma de filmes pelo método “casting” a partir de soluções de PVAl/CdS sintetizadas, as quais possuem concentrações de (0.05 %); (0.1 %); (0.2 %); (0.4 %) e (0.7 %) em peso de CdS. A morfologia e as propriedades ópticas, térmicas e elétricas do filme de PVAl e do híbrido PVAl/CdS foram caracterizadas pelas técnicas de Difração de Raios –X (DRX), Espectroscopia na Região do Ultravioleta-visível (UV-vis), Calorimetria Diferencial Exploratória (DSC) e Espectroscopia de Impedância. A análise de DRX utilizando o software composto por um banco de dados de cristalografia indicou a formação de nanopartículas de CdS que possuem estrutura hexagonal. Através de cálculos usando a equação de Scherrer obteve-se o tamanho das nanopartículas que variaram entre (70 e 113 nm). As medidas de UV-vis também confirmaram que as partículas possuem diferentes tamanhos. A presença das nanopartículas é indicada por um pequeno deslocamento da banda de absorção característica do material em determinado comprimento como o CdS “bulk” (490 nanômetro (nm)). O deslocamento desta banda, característica para comprimento de onda menor (de 490 para 485 nm) indica que os tamanhos das partículas são suficientemente pequenos para produzir o chamado efeito quântico. A análise térmica de DSC indicou o comportamento térmico e a influência das partículas CdS sobre os tipos de transformações básicas do polímero como a temperatura de transição vítrea (Tg), temperatura de fusão (Tm), temperatura...
In this work were obtained and characterized films of pure polyvinyl alcohol (PVAl) and hybrid PVAl/CdS. The synthesis was performed using the “hydrothermal in situ” method. The hybrid is composed by one organic part, called matrix polyvinyl alcohol (PVAl) and an inorganic phase, cadmium sulfide (CdS). The samples were obtained as films by the casting method from PVAl/CdS solutions with (0.05 %); (0.1 %); (0.2 %); (0.4 %) and (0.7 %) concentration of CdS. The morphology, optical properties, thermal properties and electrical properties of pure PVAl film and hybrid PVAl/CdS were characterized by techniques such as X-ray diffraction (XRD) spectroscopy in the ultraviolet-visible (UV-vis), Differential Scanning Calorimetry (DSC) and impedance spectroscopy. The analysis of XRD using programs with crystallography data stored shows the formation of CdS nanoparticles which have hexagonal structure. Through calculation using the Scherrer equation, the sizes of the nanoparticles were obtained in a gap between (70 and 113 nm). The measurements of UV-vis also showed that the particles have different sizes and that the CdS particles have dimensions in nanometric scale. The presence of nanoparticles is indicated by a small shift of the absorption band of the material characteristic as in the CdS bulk, (490 nm). When such characteristic band shift occurs to shorten wavelength from (490 to 485 nm), it indicates that the particle size decreased due to quantum effects. It is confirmed by the XRD technique. The thermal analysis of DSC studied the thermal behavior and the influence of CdS particles on the types of transformations as the basic polymer glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc). The external factor that most affect the T m and Tg is the presence of plasticizers. It could be noted when intentionally added the CdS... (Complete abstract click electronic access below)
In this work were obtained and characterized films of pure polyvinyl alcohol (PVAl) and hybrid PVAl/CdS. The synthesis was performed using the “hydrothermal in situ” method. The hybrid is composed by one organic part, called matrix polyvinyl alcohol (PVAl) and an inorganic phase, cadmium sulfide (CdS). The samples were obtained as films by the casting method from PVAl/CdS solutions with (0.05 %); (0.1 %); (0.2 %); (0.4 %) and (0.7 %) concentration of CdS. The morphology, optical properties, thermal properties and electrical properties of pure PVAl film and hybrid PVAl/CdS were characterized by techniques such as X-ray diffraction (XRD) spectroscopy in the ultraviolet-visible (UV-vis), Differential Scanning Calorimetry (DSC) and impedance spectroscopy. The analysis of XRD using programs with crystallography data stored shows the formation of CdS nanoparticles which have hexagonal structure. Through calculation using the Scherrer equation, the sizes of the nanoparticles were obtained in a gap between (70 and 113 nm). The measurements of UV-vis also showed that the particles have different sizes and that the CdS particles have dimensions in nanometric scale. The presence of nanoparticles is indicated by a small shift of the absorption band of the material characteristic as in the CdS bulk, (490 nm). When such characteristic band shift occurs to shorten wavelength from (490 to 485 nm), it indicates that the particle size decreased due to quantum effects. It is confirmed by the XRD technique. The thermal analysis of DSC studied the thermal behavior and the influence of CdS particles on the types of transformations as the basic polymer glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc). The external factor that most affect the T m and Tg is the presence of plasticizers. It could be noted when intentionally added the CdS... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Cadmio - Síntese, Polivinil álcool, Compósito híbrido, Poly (vinyl alcohol), Cadmium sulfide
Como citar
OLIVEIRA, Milena Souza. Influência da concentração das partículas cristalinas nas propriedades dielétricas do híbrido PVAl/Cds. 2011.. 81 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Engenharia de Ilha Solteira, 2011..