Produção de po de cobalto via redução de Co3O4 por hidrogenio em leito fluidizado

Dissertação (mestrado) - Universidade Federal de Santa Catarina. Centro TecnologicoO objetivo do presente trabalho foi observar o comportamento cinético na redução por hidrogênio do óxido de cobalto II, III, CO3O4, produzido a partir de minério nacional, em um reator de leito fluidizado, em pequena escala, na faixa de temperatura de 310 - 790oC, visando avaliar a possibilidade de adaptação do sistema reativo para uma escala semi-industrial de produção de pó de cobalto. Além disso, a fluidização do Co3O4 foi acompanhada a temperatura ambiente, com o objetivo de determinar as condições ótimas do processo de fluidização. As constantes cinéticas obtidas (Kso = 0,0039 ± 0,0002 cm/s, e Ea = 5,0 ± 0,3 kcal/gmol) são comparáveis aos valores encontrados na literatura, referentes a redução do pós de Co3O por H2, com área de superfície específica de mesma grandeza, na mesma faixa de temperatura. Por fim, foi elaborada uma estimativa de ampliação de escala do sistema reativo para redução de Co3O4 por hidrogênio em leito fluidizado

Planar Solid Oxide Fuel Cells Using PSZ, Processed by Sequential Aqueous Tape Casting and Constrained Sintering

A process for obtaining planar anode‐supported solid oxide fuel cells was developed. Aqueous‐based slurries were prepared and sequentially deposited via tape casting to form half cell tapes consisting of the electrolyte, functional, and structural anode. Sintering of the three‐layered tapes was done in two stages: presintering circular samples of 25 mm diameter in free conditions first, and then sintering them using zirconium disks as light loads (90 Pa), to obtain half cells having 20 mm and 3.8 m−1 in diameter and curvature, respectively. Active materials for the electrolyte, anode, and cathode were partially stabilized zirconia (PSZ), Ni and LSM, respectively. Finally, thicknesses of complete cells were 400, 30, 30, and 80 μm for the structural anode, functional anode, electrolyte, and cathode, respectively. The cells were tested in a no‐chamber (direct‐flame) setup evaluating electrochemical performance and shock thermal resistance. Open circuit voltage was 830 mV at 560°C using methanol as fuel in a burner with porous media to modify the shape of the flame. Cells were also strong enough to resist the rapid temperature changes during several no‐chamber tests

Caracterização de bauxita ativada antes e depois da saturação com óleo mineral isolante

A characterization of activated bauxite and of activated bauxite impregnated with insulating mineral oil was made. The activated bauxite is used as adsorbent material in percolators during the regeneration of insulating mineral oil. After regeneration an insulating mineral oil is obtained with physical and chemical characteristics similar to those of the new oil. Moreover, saturated activated bauxite impregnated with insulating mineral oil is also produced. It is a dangerous residue according to NBR 10004 (Class I) and, thus, harmful to the environment. An alternative use of this waste in the ceramic industry is discussed

Tecnologia de fabricação de revestimentos cerâmicos

Este livro apresenta princípios científicos e tecnológicos da fabricação de revestimentos cerâmicos, com ênfase no processamento por via úmida. Representa uma contribuição para o aprimoramento e atualização dos que atuam na área e um incentivo para que outros profissionais possam se interessar por esse setor, carente de livros técnicos especializados em língua portuguesa

Processing and characterization of CaTiO3 perovskite ceramics

Calcium titanate (CaTiO3) ceramics with perovskite structure were produced by solid state reaction. Calcium carbonate (CaCO3) and titanium dioxide (TiO2) were mixed (in molar ratios 1/1 and 3/2), and the obtained mixtures were calcined at 1150 °C in successive thermal cycles. The obtained samples were characterized by differential thermal analysis, thermogravimetry, X-ray diffraction, measurement of particle size distribution and linear thermal shrinkage. XRD results indicated that the samples have perovskite CaTiO3 structure with small amount of secondary CaO and TiO2 phases, and their phase composition depends on the heat treatment conditions. The measured values of electrical resistivity were within the characteristic range of insulating materials and approach values corresponding to semiconducting ceramics

Modelización mecánica del enfriamiento rápido en sistemas tipo gres porcelánico

This paper analyses the effect of cooling on mechanical behaviour, in particular, on the residual stresses that appear when materials of the porcelain tile type are involved. However, these compositions have a very complex microstructure, in which there are several crystalline phases and the glassy phase is not homogeneous. In this study a simpler composition was therefore formulated, using sodium feldspar as starting material to which quartz with different particle sizes was added. A viscoelastic model was used to estimate the residual stresses that develop during cooling. The parameters of the model were obtained either from the literature or were determined in laboratory tests. An assembly was designed that allowed non-contact measurement of the temperature at the top and bottom surfaces of the test pieces during cooling. The test pieces were subjected to different types of cooling and their residual stresses were then determined by the strain relaxation slotting metho

Modelling the Influence of Manufacturing Process Variables on Dimensional Changes of Porcelain Tiles

A model to study the influence of main process variables (powder moisture, maximum compaction pressure, and maximum firing temperature) on the intermediate variables (mass, dry bulk density, size, and thickness) and the final dimensions of porcelain tiles is proposed. The properties of dried and fired bodies are basically determined by the process parameters when the physical, chemical, and mineralogical characteristics of the raw material are kept constant. For a given set of conditions, an equation could be sought for each property as a function of raw materials and processing. In order to find the relationship between moisture content and compaction pressure with dry bulk density, springback, and drying and firing shrinkage, a laboratory experimental design with three factors and four levels was applied. The methodology was validated in lab scale for a porcelain tile. The final size and thickness were estimated, and the influence of the main process variables was analysed

Enhanced catalytic performance of CuFeS2 chalcogenide prepared by microwave-assisted route for photo-Fenton oxidation of emerging pollutant in water

In this work, CuFeS2 chalcogenide powders were easily produced by conventional and microwave methods, and for the first time, the influence of synthesis route on their properties and consequent catalytic activity in the photo-Fenton reaction was investigated. X-ray diffraction, N2 adsorption–desorption isotherms, Fourier-transform infrared spectroscopy, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to characterize and point out the main properties and differences among samples. The CuFeS2 particles were used as catalysts for tartrazine dye degradation by the photo-Fenton reaction under visible irradiation. The results showed that the CuFeS2 prepared by microwave-assisted method (CuFeS2–MW) present higher crystallinity, higher concentration of Fe2+ on its surface and remarkable catalytic activity, reaching 99.1% of tartrazine decolorization and 87.3% of mineralization, at a rate twice as fast as CuFeS2 prepared by the conventional method. The catalyst showed high catalytic efficiency and stability during the reaction after five recycles. The hydroxyl radical was revealed to be the reactive species responsible for tartrazine degradation. A mechanism was proposed to elucidate how these free radicals are generated from the catalytic decomposition of H2O2 by CuFeS2–MW