Navegando por Autor "Ferreira, Erik Alexander Cunha"

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Influence Ca-doped SrIn2O4 powders on photoluminescence property prepared one step by ultrasonic spray pyrolysis
(Elsevier, 2018-05-30) Medeiros, P. N.; Santiago, Anderson de Azevedo Gomes; Ferreira, Erik Alexander Cunha; Li, Maximo Siu; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Crystalline Ca-doped SrIn2O4 structures were prepared by a rapid and efficient Ultrasonic Pyrolysis Spray (USP) method. The Sr1-xCaxIn2O4 (x = 0, 0.1, 0.2, 0.3, 0.4 and 1 mol %) samples were obtained by in a single step at a temperature of 1050oC for 1 min for the formation of particles. The powders were characterized by X-ray diffraction (XRD), field emission electron microscopy (SEM-FEG), optical diffuse reflectance and photoluminescence (PL) measurements. All diffraction peaks present in XRD patterns could be indexed to the orthorhombic structure and that with calcium percentage increments indicates the substitution of Ca2+ in the Sr2+ sites promotes a decrease in its lattice parameters of the structure. MEV-FEG images show that the Sr1- xCaxIn2O4 particles have a spherical predominance, with a porous surface in the form of foam for x = 0 and a surface with low roughness and low porosity with an increase in the percentage of Ca2+ ion, especially for the 1 mol % of Ca2+. The gap energy varied between 4.56 eV and 4.86 eV, being influenced by the structural modifications motivated by increase of Ca2+ ion contained in the SrIn2O4 matrix. The PL emission spectrum of the samples presents a broad band behavior with emission intensity predominant in the blue-green region, having the sample with x = 0.1 the highest PL intensity. The chromaticity coordinates were calculated for the sample based on the PL spectrum and coordinates x and y show that the samples have blue emission. Ultrasonic spray pyrolysis was an effective technique for Ca-doped SrInO4 powder production using short production times with hold great potential for photoluminescent emitters
Influence of solution pH on forming silver molybdates obtained by sonochemical method and its application for methylene blue degradation
(Elsevier, 2019-06-15) Ferreira, Erik Alexander Cunha; Andrade Neto, Nivaldo Freire de; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Catalytic processes such as heterogenous photocatalysis or adsorptions have been extensively studied due to the difficulty in treating organic effluents, mainly textiles. The catalysts stability is essential to enable their ap- plicability, so that the catalytic converter does not turn into secondary residues after the catalytic cycle, enabling its re-employment in the catalytic process. In this work was studied the photocatalytic activity of different phases of silver molybdates obtained by the sonochemical method at different pH in the medium reaction. The powders were characterized by X-ray diffraction (XRD) field emission scanning electron microscopy (FE-SEM), and diffuse reflectance spectroscopy was used to estimate the Egap of the powders. The photocatalytic activity of the powders was measured by varying the degradation of the methylene blue dye (MB). According to the XRD patterns, the crystalline structure of the obtained silver molybdates changes from Ag2Mo3O10. 2H2O at very acidic pH 1 and 2, to pure Ag2Mo2O7 with the values of pH 3 and 4 it is then converted into Ag2Mo2O7 and Ag2MoO4 phases in pH 5, and shifts to pure Ag2MoO4 phase when the pH is increased up to 6. The results indicate that the microstructures of Ag2Mo3O10. 2H2O and Ag2Mo2O7 phases have high adsorbent properties, with the powders obtained at pH 1 and 2 being able to completely remove the MB from the solution in 5 min and the powders of Ag2Mo2O7 phases removing up to 90% of MB after 5 min of exposure without UV irradiation. In contrast, the powders with Ag2MoO4 phase showed high photocatalytic properties, being able to removing up to 90% of MB in less than 20 min and 40 min of ultraviolet exposure to powders obtained at pH 5 and 6, respectively. All presented catalysts maintained their stability and performance after 3 test cycles
Obtenção de molibdatos de prata através do método sonoquímico para catálise do azul de metileno
(2018-08-30) Ferreira, Erik Alexander Cunha; Motta, Fabiana Villela da; ; ; Nascimento, Rubens Maribondo do; ; Godinho Júnior, Mario;
Os semicondutores a base de prata pertencente ao grupo de óxidos de metais de transição têm atraído atenção significativa devido à sua fotossensibilidade única, o que fornece a estes materiais uma excelente atividade fotocatalítica devido principalmente, aos efeitos de ressonância plasmônica. Para aplicabilidade desses matérias, a estabilidade durante o reuso é fundamental para se evitar a geração de resíduos secundários. Esta dissertação, propôs-se a realizar o estudo das propriedades estruturais e morfológicas dos molibdatos de prata obtidos pelo método sonoquímica para o meio reacional entre pH 1 a pH 8. Avaliando a aplicação dos molibdatos através do reuso dos pós obtidos na catálise do corante azul de metileno. Os pós de molibdatos de prata foram obtidos através do método sonoquímico e caraterizados por difração de raios-X (DRX), microscopia eletrônica por emissão de campo (MEV-FEG), e espectroscopia do UV-Visível por refletância difusa para estimar o valor de band-gap óptico. A atividade catalítica sobre o corante azul de metileno, assim como estabilidade dos pós avaliados também foram avaliados. Observou-se que os materiais sintetizados se cristalizam nas estruturas Ag2Mo3O10.2H2O, Ag2Mo2O7 e Ag2MoO4, em função do pH do meio reacional. Com as estruturas de Ag2Mo3O10.2H2O e Ag2Mo2O7 apresentando morfologia de nanobastões, enquanto as estruturas de Ag2MoO4 apresentam morfologia irregular micrométrica, com ambas estruturas obtidas após o método sonoquímico apresentando elevado teor de precipitados de prata superficial. A completa descolorização da solução contendo o corante foi obtida após 5 minutos de exposição dos pós de Ag2Mo3O10.2H2O e 15 minutos de exposição do Ag2Mo2O7 sem atuação de irradiações externas. A degradação do corante de azul de metileno sob irradiação UV foi observada para estrutura Ag2MoO4, onde observou-se a completa descoloração do corante MB após 60 minutos. Não foi observado perda de eficiência catalítica dos pós após 3 ciclos de reuso. Indicando que o método sonoquímico é eficaz na obtenção de pós de molibdatos de prata estáveis para aplicação catalítica do corante azul de metileno.
Synthesis and characterization of α-Ag2MoO4/β-Ag2MoO4 heterostructure obtained by fast and simple ultrasonic spray pyrolysis method at diferent temperatures
(Springer, 2020-01-30) Paskocimas, Carlos Alberto; Ferreira, Erik Alexander Cunha; Andrade Neto, Nivaldo Freire de; Santiago, Anderson de Azevedo Gomes; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
In this work, microspheres of α-Ag2MoO4/β-Ag2MoO4 were obtained by ultrasonic spray pyrolysis (USP) at temperatures of 400, 500, 600, and 700 °C. Characterizations of X-ray difraction (XRD), feld emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), Raman scattering, and ultraviolet–visible spectroscopy (UV–Vis) were performed on the samples. The beta phase is present in all samples, while the alpha phase forming α/β-Ag2MoO4 appears from 500 to 700 °C. FE-SEM images indicate the tendency of micrometric sphere formation, in which the increase of temperature promotes a smoothing on the surface. The α/β-Ag2MoO4 heterostructure was a better photocatalytic performance on methylene blue dye (MB) degradation than the pure beta phase. The MB was 87% reduced by the pure beta phase and 100% reduced by the α/β-Ag2MoO4 after 45 min of photocatalysis

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Navegando por Autor "Ferreira, Erik Alexander Cunha"