As pilhas a combustível permitem a geração de energia elétrica de forma limpa e eficiente. Dentre seus diferentes tipos destaca-se a pilha a combustível do tipo óxido sólido (PaCOS). O óxido de cério dopado com samário (SDC) tem sido amplamente estudado, visando sua aplicação como eletrólito sólido e na elaboração do anodo tipo cermet. Inicialmente, este trabalho descreve a síntese, através do método do precursor, de nanopartículas de óxido de cério dopado com 20% mol de samário (Ce0,8Sm0,2O1,9). Posteriormente, é analisado o efeito do óxido de níquel (NiO) e do óxido de níquel dopado com 10% de cobalto (CoNiO) na sinterização de pastilhas de SDC, a 1200 ºC, visando à obtenção de porcentuais de sinterização superiores a 90%. Os materiais foram caracterizados por Difração de Raios X (DRX), Espectroscopia do Infravermelho (IV), Análise Térmica (TG/DTA), Microscopia Eletrônica de Transmissão (MET) e Espectroscopia Raman. Observou-se um aumento no percentual de sinterização de 83,1 % (pastilha de SDC pura) para 98,6% (pastilha de SDC com CoNiO). Portanto, a SDC preparada pelo método do precussor permite a obtenção de pastilhas com alta densificação, o qual é um dos pré-requisitos para sua utilização na elaboração de componentes de pilhas a combustível do tipo PaCOS.

Fuel cells allow generation of electric energy in a clean and efficient way. Among the different types of fuel cells, solid oxide fuel cell (SOFC) stands out. Samarium doped cerium oxide (SDC) have been widely studied for its application as solid electrolyte and as a component of cermet type anode. Initially, this work describes synthesis of nanoparticles of 20% mol samarium doped cerium oxide (Ce0,8Sm0,2O1,9), by the precursor method. Subsequently, we analyze the effect of nickel oxide (NiO) and 10% cobalt-doped nickel oxide (CoNiO) on the sintering at 1200 °C of SDC pellets, aiming to attaining a sintering degree higher than 90%. Materials were characterized by X-ray Diffraction (XRD), Infrared Spectroscopy (IR), Thermal Analysis (TG/DTA), Transmition Electron Microscopy (TEM) and Raman Spectroscopy. We observed an increase in percentage of sintering from 83.1% (pure SDC pellet) to 98.6% (SDC pellet with CoNiO). Therefore, SDC prepared by the precursor method allows obtaining pellets with high density, which is a prerequisite for their use in preparation of components of SOFC type fuel cells.

Os óxidos mistos SiO2/MxOy obtidos pelo processo sol-gel, designados de compósitos, normalmente aliam as propriedades mecânicas e químicas da sílica gel com as propriedades químicas do óxido metálico (MxOy), apresentando propriedades tais como: elevado grau de dispersão e homogeneidade das partículas do óxido metálico na matriz de sílica, assim como elevada resistência mecânica e química. O objetivo deste trabalho foi o de preparar e caracterizar materiais do sistema SiO2/Mn xOy, obtidos pelo processo sol-gel, utilizando diferentes concentrações dos precursores de Mn (II), acetato ou nitrato. A técnica de fluorescência de raios X (FRX) mostrou que a concentração do óxido metálico nos materiais é dependente do precursor utilizado e da sua concentração no meio reacional, variando de 9,4% até 20,9% em massa. A maior concentração de óxido de manganês foi obtida quando se utilizou como precursor o (CH3CO2)2Mn.4H2O. Os espectros de infravermelho indicam que a rede de SiO2 é pouco perturbada pelo aumento da quantidade de óxido de manganês, sugerindo que o Mn xOy está disperso na superfície da matriz de sílica. Os difratogramas de raiosX (DRX) mostram que os materiais apresentam baixa cristalinidade. No entanto, observa-se uma mudança no DRX em 2θ = 35,7º quando o material é aquecido a 400 0C, provavelmente devido à formação de cristalitos de Mn3O4. O método de síntese proposto para os materiais SiO2/Mn xOy é reprodutível. A aplicação destes materiais como eletrodos para a redução de O2 foi avaliada e observou-se que a atividade eletrocatalítica desses materiais pode ser aumentada através do seu aquecimento a 400 0C.

The mixed oxides SiO2/MxOy obtained by the sol-gel process, designated as composites, usually combine both mechanical and chemical properties of silica gel with the chemical properties of metal oxide (MxOy), showing properties such as: high degree of dispersion and homogeneity of metal oxide particles in the silica matrix, as well as high mechanical and chemical resistance. The goal of this work was to prepare and characterize materials in the system SiO2/Mn xOy obtained by the sol-gel process, using different concentrations of Mn (II) precursors (acetate or nitrate). The technique of X-ray fluorescence showed that the concentration of metal oxide in the materials is dependent on the precursor used and its concentration, ranging from 9.4% up to 20.9% by mass. The highest concentration of manganese oxide was obtained when (CH3CO2)2Mn.4H2O was used as precursor. The infrared spectra indicate that the network of SiO2 is not disturbed by the increase in the quantity of manganese oxide, suggesting that the Mn xOy is dispersed on the surface of the silica matrix. The X-ray diffraction showed the low crystallinity of these materials. However, there is a change in the XRD on 2θ = 35.7(0) when the material is heated to 400 0C, probably due to the formation of Mn3O4 crystallites. The proposed synthesis method for materials SiO2/Mn xOy is reproducible. Application of these materials as electrodes for the reduction of O2 was evaluated and it was found that the electrocatalytic activity of these materials can be increased by heating them at 400 0C.

The mineral waste studied was host rock from a chromite mine located in Andorinha/Bahia, extracted and stockpiled in yards without specific application. Host rock was submitted to chemical analysis, XRD, SEM-EDS, IR and TGA and classified according to ABNT standards for solid waste classification. Analyses confirmed that this host rock, classified as ultrabasic, consists mainly of dolomite, calcite and diopside. Hazard assessment results showed this host rock should be classified as class II B - inert waste, important for its potential application in agriculture as a soil acidity correction agent.

Samples of Kaolin from different regions in Brazil were characterized by XRD, SEM and chemical analysis. A chemical bleaching study with pH adjustment was accomplished with the fractions below 37 μm, after classification by screening. The main objective was to evaluate the conditions of chemical bleaching that most increase the brightness of these kaolin's samples. Increases between 2.63 and 2.98% in the brightness (ISO) were observed after the chemical bleaching. We could say that the reduction of Fe3+ to Fe2+ during the chemical bleaching promoted an increase in the brightness, based on the Pourbaix Diagrams.

In this paper the current status of fuel cells is described with particular emphasis on high (T > 800 ºC) and intermediate (T < 800 ºC) temperature solid oxide fuel cells. Also the importance of the fuel cell technology is shown. Reviewed are the fundamental features, the basic principles, types of fuel cell, fabrication methods, cell configurations and the development of components (cathodes, anodes, electrolytes, interconnect) and materials.

Combinatorial chemistry refers to techniques to rapidly fabricate tens, hundreds or even thousands of different micro samples. The analysis of the large number of samples generated by combinatorial methods requires highly efficient analytical methods. In this case, the challenges are due not only to the large number of samples to be analyzed, but also to the small amount of sample available for analysis. This paper describes the fundamentals of combinatorial chemical methods applied to discover of materials and the development in x-ray diffraction to analyze micro samples.