Instituto Nacional de Ciências dos Materiais em Nanotecnologia

SrTiO 3 crystalline nanoparticles were prepared using the microwave-assisted hydrothermal method at 140 °C with synthesis times varying from 4 to 160 min. Sample characterization showed that the method is effective in obtaining nanoparticles in a relatively short time, which have the highest photoluminescence emission. The crystalline phase of perovskite-type SrTiO 3 is not significantly influenced by synthesis time. However, the SrTiO 3 phase is already obtained with a 4 min synthesis time. Also, all samples exhibited photoluminescence at room temperature in the blue-green region, where intensity decreased with increasing synthesis time and particle size. The samples synthesized with the shortest time showed higher photoluminescence emission and smaller particle sizes. The morphology obtained based on FE-SEM showed cubic nanoparticles with inhomogeneous grain growth at higher temperatures of synthesis in addition to the formation of new architectures.

ResumoA versatilidade de materiais naturais como as argilas tem chamado a atenção para a sua aplicação em estudos científicos. Neste trabalho foi avaliado o enriquecimento dessas propriedades com a impregnação de SnO2 na superfície desse material, e seu comportamento como catalisador para a reação de transesterificação de óleo de soja. Para isso, uma bentonita foi selecionada, considerando os valores de capacidade de troca catiônica e teor de quartzo. A bentonita foi utilizada na forma pura e impregnada com SnO2 por dois métodos: solvotermal assistido por micro-ondas e Pechini modificado. Para avaliar a eficiência da impregnação, foram realizadas algumas caracterizações, como difração de raios X, adsorção de N2 e microscopia eletrônica de varredura, que mostraram uma melhor dispersão do SnO2no suporte utilizando o método Pechini modificado, o qual também apresentou melhor eficiência no teste catalítico para obtenção de biodiesel, reduzindo em 41,3% a viscosidade do óleo utilizado.

Dados obtidos durante e após processamento em reômetro de torque do polímero (PLA) modificado com a adição de Vitamina E, sendo esses dados referentes às análises térmicas do material (DSC e TGA), reológicas (reometria de placas e MFI), Análise Colorimétrica, Tempo de Indução da Oxidação (OIT) e Espectroscopia de Infravermelho por Transformada de Fourier (FTIR).

Most of the Brazilian oil production comes from offshore fields in deep and ultra-deep waters where the intrinsic characteristics of the oil combined with the high pressures and low temperatures of the environment can compromise production by obstructing the flow of oil through problems such as precipitation of hydrates and accumulation of paraffin and asphaltenes inside the transport tubes.The main objective of this work was to investigate the use of supermagnetic nanoparticles and the phenomenon of hyperthermia as a way to increase the oil temperature in the pipes, minimizing these problems and consequently increasing oil production.For this, 8 nm iron oxide (Fe 3 O 4 ) nanoparticles (NPs) were dispersed in an oil of 20.3 API.The NPs were characterized in terms of morphology, crystallinity, and size distribution.Stable colloids were initially prepared from the dispersion of NPs in diesel, and then added to crude oil.The final mixture was exposed to an alternating magnetic field and the specific absorption rate (SAR) and temperature differential (∆T) were measured.Hyperthermia tests were also carried out with static fluid and with fluid in flow in an experimental bench.∆T, mass flow (m ) and specific mass (ρ) were measured.It was concluded from the results that, although this is a new technology still in the development stage and several phenomena that have occurred still need to be investigated more deeply, NPs can indeed heat the fluid when subjected to an alternating magnetic field.The best result obtained for the fluid at rest was ∆T= 36.8 ℃ for a field of 28 kA/m, with an intensity of 770 kHz after 2 minutes of testing.As for the flowing fluid, a ∆T= 16 ℃ was found for a magnetic field of intensity of 14 kA/m and frequency of 553 kHz after 50 minutes of testing.

Ba1-xCaxTiO3, Ba1-xSrxTiO3 and Sr1-xCaxTiO3 (x = 0, 0.25, 0.50, 0.75 and 1) nanoparticles were synthesized using the microwave-assisted hydrothermal method. Samples were prepared for 40 minutes at 140°C under a pressure of 3 MPa using an adapted domestic microwave oven. The samples were characterized by X-Ray diffraction (XRD), scanning electron microscopy (FE-SEM), and Raman, photoluminescence (PL) and ultraviolet-visible (UV-Vis) spectroscopies. XRD data show that ceramic powders have crystalline phases associated with a short-range structural disorder. This structural disorder is confirmed by Raman spectral bands indicating multi-phonon processes and the presence of defects or impurities. Such defects account for a broad band in the photoluminescence spectrum in the green light (460 nm) region for all samples. Gap energy variation, obtained from UV-Vis spectra, suggest a non-uniform band structure of these titanates in accordance with the PL results. The morphology of each sample is changed with doping and varies from a spherical to cubic appearance for energy minimization.