1000 resultados para Polarização eletro térmica
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Zootecnia - FCAV
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Pós-graduação em Odontologia Restauradora - ICT
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The development of electrocatalysts for the oxidation of methanol and ethanol is very important, because these alcohols may be used in the anode fuel cells which convert chemical energy directly into electrical energy with high efficiency, cleanly and with low noise. Thus, this study reports to the synthesis of nanocatalysts of PtAu supported on carbon by microemulsion method. The physical characterization of these catalysts is performed through the techniques of X-ray diffraction and transmission electron microscopy. The catalytic activity of the prepared materials was studied using conventional electrochemical techniques and also the technique of spectro-electrochemical in situ FTIR, which allows identification of intermediates and products of the reactions. From the x-ray diffraction, it was observed that the thermal treatment applied to catalysts favored incorporation of Au into the crystal lattice of Pt,that is, increased the formation of PtAu alloy. Micrographs indicated particle size about 3 nm to materials not heat treated and 9 nm to materials subjected to thermal treatment (heating at 150 ° C for 1h and 30 min in argon atmosphere). Current density oxidation of methanol on PtAu / C were superior to pure platinum. Spectroscopic results indicated the presence of formate in solution in 50:50 and the composition showed bands for CO2, indicating complete oxidation, in lower potential. During ethanol oxidation on the catalyst PtAu, the main product formed was acetate, product of incomplete oxidation. The good performance for methanol oxidation can be attributed to large amounts of oxygen species adsorbed on the catalyst surface, or an electronic effect.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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This study has as main objective to identify the complains occurrences about pain in the spine segments, that are related to work standing posture, adopted by the collaborators in the production section of a food industry, in the city of Marília São Paulo state. A descriptive research and studying case was made, using 30 employees as a sample. It was used as methodological procedure, a questionnaire to obtain information on professional and personal data, posture to remain standing, the most uncomfortable postures in the work environment (signed by the form of Ranney, 2000) and pain (pointed out by Corllet and Manenica Diagram, 1980). It was also used the Nordic questionnaire (Kuorioka et al.,1986), validated in the Brazilian culture by Barros e Alexandre (2003) and adapted for the study, the direct evaluation and, a direct observation was made in the production work, a posture analysis using the OWAS Method. It was noticed that the posture of standing up is adopted during work, and 73.3% of the people that was interviewed said that they felt tired in consequence of this posture, especially when associated with trunk twists, trunk inclination and elevation of their arms above their heads. Most complains regarding pain through their bodies, by Corllet e Manenica (1980) pointed to the lumbar region, followed in the dorsal area and legs and in the neck area, shoulders and right thigh. The adapted Nordic questionnaire reveled the lumbar area, in 10 interviewed people (33.3%) as the area mostaffected by musculoskeletal symptoms, next in the dorsal area, with five people interviewed (16.7%) and one of them (3.3%) felt pain in the cervical area, none reported pain in the hips area. The postural analysis was applied using OWAS method, and it was identified the postures that demanded more effort in the four levels of musculoskeletal injuries. As conclusion, the standing up posture and the asymmetric and incorrect movements are related to pain in the spine, mostly in the lumbar area.
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Aluminum Alloys are widely used as structural materials in the aerospace industry due to low weight, high mechanical strength and enduring corrosion resistance. Their resistance to corrosion is attributed to the rapidly formed stable oxide film (Al2O3) which spontaneously forms itself on the surface of the material. However, in the presence of aggressive ions, such as halide, Aluminum Alloys are subject to a localized process of corrosion. The electrochemical behavior of 7081-T73511 and 7050-T7451 Aluminum Alloys employed in the aerospace industry was investigated using a 0.6 M NaCl solution under the conditions of a controlled mass transport employing a rotating disk electrode. The theoretical limiting current density was determined by the Kouteki-Levich equation. The results confirmed that the inter-metallic Al7Cu2Fe acts as preferential cathode generating the galvanic coupling and the dissolution of the Aluminummatrix around it.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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The photopolimerization it is be widely used nowadays in different fields as materials, medicine and dentistry. To occur that synthesis is utilized dimethacrylates monomers and photoinitiators, the photoinitiator system more usual is camphorquinone/tertiary amine (ethyl-p-dimethylamino benzoate). However is knowledge that tertiary amines are toxics, so the aim of this work is replace toxic amine compounds to non-toxic compounds as glycerol and inositol. Therefore was used the FTIR technic to calculate the monomers conversion degree as well as Thermogravimetric Analysis-simultaneous differential thermal analysis (TG-DTA) and Differential Scanning Calorimetry (DSC) to evaluate thermal stability, combustion rate, degradation steps, oxidation and volatilization of all samples. The study shown no significant difference about thermal behavior of all polymers, the initiators system for efficient and more fastness was camphorquinone /tertiary amine system followed by ca mph o r quinone/glycerol system