No abstract

Direct Ethanol Fuel Cells DEFCs are considered one of the promising renewable energy sources, as they can produce electrical energy directly from the ethanol electrooxidation reaction. The efficiency of ethanol electrooxidation is a big question from research point of view. In this work, Pd is used as catalyst for the electrooxidation in alkaline media aiming to improve the catalytic activity for ethanol electrooxidation reaction, and consequently the DEFC performance, more than using a Pt-based catalyst. In this research, Pd was used as an alternative for Pt-based catalyst. Additionally, it can be recorded that the alloying of Pd with Sn will enhance the efficiency through increasing the surface area of the PdSn catalysts.

The modified SAE 10B22 steel has high hardenability, which provides its use in special engineering applications, such as in self-drilling screws, with carbonitrided layer, quenched and tempered. However, these components are susceptible to hydrogen embrittlement, which can cause damage to structural components. In addition, the study of the behavior regarding to hydrogen embrittlement of components with carbonitrided layer has not been done hitherto. In this work the tempering temperature influence on hydrogen embrittlement of modified SAE 10B22 steel, was evaluated after a carbonitriding process. Standard samples and M4 Â 50 screws were tested. A galvanostatic circuit was used for hydrogen charging of the samples, which were characterized by low-strain tensile test and the samples fracture were analyzed by SEM. The obtained results demonstrate that by lowering tempering temperatures, the hydrogen-loaded samples presented a greater loss of mechanical properties and greater changes of the micromechanics of fracture. In addition, the geometry of the screw was more prone to the deleterious effects of the hydrogen charging than the conventional specimens.

Hydrogen has been seen as one of the most valuable options regarding renewable energy storage and conversion. However, its production is still mostly based on fossil fuels, in part because of the high cost of alternative production routes, as is the case of water electrolysis for example. This fact is explained by the energy consumed during the process of hydrogen evolution from water. Nevertheless, the research on water electrolysis is justifiable by the advantages that the process offers, as high produced hydrogen purity, possible association with other renewable energy sources such as solar, hydro and wind power generation, no CO 2 emissions during the evolution, simplicity of the process, as so many others. With the purpose of increasing the hydrogen-producing device (electrolysers) performance, great scientific efforts have been directed to the electrodes base materials and their surface technology. In this way, the present work propose powder metallurgy based processes as production routes of nickel porous electrodes, i.e., relatively low cost and high active superficial area electrodes for hydrogen production.

In order to restrain the high temperature oxidation on metallic interconnects, a ceramic coating is deposited on its surface. For this study a AISI 430 stainless steel was coated with perovskite (La 0,6 Sr 0,4 CoO 3 ) film using the spray pyrolysis technique. Therefore, in this work, the coating morphology and composition was evaluated through X-Ray diffraction and scanning electron microscopy/energy dispersive spectroscopy analyses. The oxidation behavior was also investigated by a high temperature oxidation test. The results obtained showed that the technique employed for the coating deposition was effective, and the resultant crystalline perovskite layer acted significantly in decreasing the oxidation of the AISI 430 stainless steel. An enrichment of Sr and Cr was also observed on the alloy-coating interface, indicating a possible perovskite coating decomposition.