Navegando por Autor "Silva, Elson Longo da"

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Heterogeneous Fenton reactants : a study of the behavior of iron oxide nanoparticles obtained by the polymeric precursor method.
(2009) Giraldi, Tânia Regina; Arruda, Cezar Carvalho de; Costa, Geraldo Magela da; Silva, Elson Longo da; Oliveira, Cauê Ribeiro de
Nanoparticles composed of iron oxides and iron salts were obtained from polymeric resins produced by polymerizing Fe2?-citrate and Fe3?-citrate complexes with ethylene glycol. The citric acid:Fe molar ratio was varied to obtain different synthesis conditions. The materials were treated at 450 C for 2 h to obtain nanoparticles, which were characterized by XRD, Mo¨ssbauer spectroscopy, FEG, CHNS, atomic absorption and surface area through N2 physisorption. Rhodamine B photo degradation in the presence of these nanoparticles and hydrogen peroxide was carried out to analyze the possible behavior of nanoparticles as heterogeneous Fenton reactants. UV–visible spectroscopy revealed that the catalytic activity in the presence of nanoparticles obtained with a citric acid:Fe molar ratio of 12:1 was the condition that provided the best results in this work.
Influence of deposition parameters on the structure and microstructure of Bi12TiO20 films obtained by pulsed laser deposition.
(2019) Gorup, Luiz Fernando; Bouquet, Valérie; Députier, Stéphanie; Dorcet, Vincent; Guilloux-Viry, Maryline; Santos, Iêda Maria Garcia dos; Silva, Adão Antônio da; Nogueira, André Esteves; Kubo, Andressa Mayumi; Silva, Elson Longo da; Camargo, Emerson Rodrigues de
The structure, morphology and surface roughness of Bi12TiO20 (BTO) thin films grown on R-sapphire by pulsed laser deposition (PLD) were studied at different substrate temperatures, target-substrate distances, oxygen pressures and laser-pulse repetition rates. Although the substrate temperature seems to be the most important experimental parameter, the gas pressure and the target–substrate distance played important role on the phase formed and film thickness, with a significant effect of the laser-pulse repetition rate on the films thickness and preferred orientation of the deposited film. Single-phase γ-Bi12TiO20 was obtained on substrates at 650 °C, while several BTO metastable phases were observed in films deposited on substrates at temperatures between 500 and 600 °C. By the first time, thin films of pure and textured δ-Bi12TiO20 were successfully growth on substrates at 450 °C. When annealed, all the films deposited at lower temperatures resulted in the thermodynamically stable γ-Bi12TiO20.
Rapid microwave-assisted hydrothermal synthesis of CuBi2O4 and its application for the artificial photosynthesis.
(2020) Ribeiro, Lucas da Silva; Pinatti, Ivo Mateus; Torres, Juliana Arriel; Giroto, Amanda Soares; Lesse, Fabiana; Silva, Elson Longo da; Oliveira, Cauê Ribeiro de; Nogueira, André Esteves
Strategies for CO2 reforming for hydrocarbon production using ultraviolet or visible radiation are promising to mitigate environmental impacts from other human activities. Semiconductors act as photocatalysts for light-to-fuel conversion, but a rigorous control of their structure and morphology is crucial for high efficiency and selectivity. Thus, CuBi2O4 semiconductors have been synthesized by the microwave-assisted hydrothermal method and studied for the CO2 photoreduction process. This method produced crystalline materials with controlled morphology using low temperatures and short processing time. Moreover, the semiconductors showed excellent catalytic performance and selectivity, approximately 90% in the conversion of CO2 to CH4. Therefore, our new synthesis approach was adequate for CuBi2O4 preparation, providing an essential indication of activity in the CO2 photoreduction process.