Effect of the addition of rare earths in conjunction with the nodularizing agent FeSiMg in the microstructure and mechanical properties of the ductile cast iron J434 D4512

O objetivo deste trabalho foi avaliar o efeito da adição de duas ligas FeSiMg tipo 4 em diferentes concentrações de terras raras, nomeadas como liga A e B, na microestrutura e propriedades mecânicas de um ferro fundido nodular da norma SAE J434 classe D4512. Para o desenvolvimento, foi utilizado o mesmo percentual do insumo avaliado em diferentes reações para verificar sua repetibilidade e posteriormente avaliados os corpos de prova de nodularização via microscopia óptica. As propriedades mecânicas foram avaliadas através de ensaios de tração e dureza Brinell. Os resultados mostraram que a liga A apresentou melhores resultados nas propriedades mecânicas em função no acréscimo de 15% de perlita na matriz metálica e aumentou o tamanho da grafita esferoidal proporcionado pelo menor percentual de terras raras presente nesta liga.The objective of this work was to evaluate the effect of the addition of two FeSiMg type 4 alloys at different concentrations of rare earths, named as alloy A and B, on the microstructure and mechanical properties of a ductile cast iron SAE J434 class D4512. For the development, the same percentage of the evaluated input was used in different reactions to check its repeatability and later the test bodies of nodularization were evaluated by optical microscopy. The mechanical properties were evaluated through tests tensile and hardness Brinell. Results showed that alloy A presented better results in the mechanical properties due to the addition of 15% of perlite in the metal matrix and increased in the size of the spheroidal graphite provided by the lower percentage of rare earths present in this alloy

Sistema para avaliação de resistência à corrosão de revestimentos, método para a avaliação de resistência à corrosão de revestimento e uso da liga magnetoelástica

Universidade Federal do Rio Grande do SulEngenhariaDepositad

Produção de hidrogênio a partir de glicerina em eletrodos de Ni-Zn

The interest associated with the use of hydrogen is not only related to the fact that it is an alternative fuel and renewable, depending on the process, but it is also related to the use of it as an important raw material in industrial processes, for example refining oil and ammonia production. The water electrolysis presents itself as an excellent alternative for hydrogen production, because it is a technically tested method of easy technological transfer and good efficiency. This paper proposes the development of Ni-Zn leached electrodes efficient, stable and cheap for hydrogen production from electrolysis process in aqueous medium, providing system development for the use of waste from the production of biodiesel (glycerol) process. We evaluated the chemical composition, morphology and the electrochemical behavior of the electrodes. The results showed that the developed electrodes showed a more efficient behavior for HER in comparison to the Ni electrode. The high electrocatalytic activity was mainly attributed to the high surface area of the electrodes that increased the number of active sites for Hads.Keywords: glycerol, hydrogen electrodes, Ni-Zn.O interesse associado ao uso do hidrogênio não está apenas relacionado com o fato de ser um combustível alternativo, e dependendo do processo renovável, mas também está relacionado com o emprego do mesmo como uma importante matéria-prima em processos industriais, como, por exemplo, refino do petróleo e produção de amônia. A eletrólise da água apresenta-se como uma excelente alternativa para a produção de hidrogênio, pois é um método tecnicamente testado, de fácil transferência tecnológica e boa eficiência. Este trabalho propõe o desenvolvimento de eletrodos de Ni-Zn lixiviados eficientes, estáveis e baratos para produção de hidrogênio a partir do processo de eletrólise em meio aquoso, prevendo o desenvolvimento do sistema para uso de resíduos oriundos do processo de produção do biodiesel (glicerina). Avaliou-se a composição química, a morfologia e o comportamento eletroquímico dos eletrodos. Os resultados obtidos mostraram que os eletrodos desenvolvidos apresentaram um comportamento mais eficiente para a HER quando comparados ao eletrodo de Ni. A alta atividade eletrocatalítica foi atribuída principalmente à alta área superficial dos eletrodos desenvolvidos que aumentaram o número de sítios ativos para o Hads.Palavras chave: glicerina, hidrogênio, eletrodos, Ni-Zn.

Preparation and characterization of yttria stabilized zirconia (YSZ) films deposited by dip-coating on LSM-YSZ substrate with different proportions

In this work, sol-gel/dip-coating process for obtaining yttria stabilized zirconia (YSZ, ZrO2–8% Y2O3) films deposited onto LSM-YSZ (lanthanum strontium manganite (LSM, La0.7Sr0.3MnO3) mixed with YSZ) with different proportions (20/80, 50/50, 80/20) was investigated. The films were deposited on substrate varying the number of layers deposited. LSM powders were obtained by the combustion method using metal nitrates and urea and YSZ was commercial. LSM-YSZ composite powders were obtained by the solid state method, through ball-milling of a mixture of LSM-YSZ (mass ratio) powder for 4 h with 500 rpm using ZrO2 balls as milling media. For LSMYSZ substrate a study of sintering temperature was performed, where the optimum sintering temperature for each LSM-YSZ studied proportion was obtained. According to our results, it was found that 1100 ºC is the optimum sintering temperature for 20/80, 950 ºC is the optimum sintering temperature for 50/50 and 900 ºC is the optimum sintering temperature for 80/20 because of the good phase formation. The films were characterized by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The films showed LSM, YSZ, SrZrO3 and La2O3 phases. Crack-free, homogeneous and well adhered films were obtained with a thickness between 3 and 38 μm. In this work, YSZ films with appropriate thickness were obtained for application as SOFC electrolyte

Human embryonic stem cell-derived mesenchymal progenitor (hESCs-MP) growth on nanostructured Ti6Al4V surfaces

Nanotexturing processes that focus on enhancing the bone-implant contact, such as electropolishing, have been proposed. The aim of this work was to evaluate the influence of Ti6Al4V surface morphology on human embryonic stem cell-derived mesenchymal progenitor (hESCs-MP) growth. Three surface treatments were used in this study: mechanically polished samples and two types of electropolished samples that were treated for 4 min and 12 min, respectively. The systems were characterized by atomic force microscopy, contact profilometry, X-ray diffraction, and wettability. Each system was submitted to a cell culture containing hESCs-MP cells for 14 days, and the resultant cell growth on each system was then evaluated. The results indicated that surfaces with higher nanometric and micrometric roughnesses experienced greater hESCs-MP cell growth in osteogenic media. The same behavior was not observed for cell growth in non-osteogenic media due to the absence of dexamethasone, which is responsible for controlling protein adsorption on the surface

Deposition of nanostructured LSM perovskite thin film on dense YSZ substrate by airbrushed solution combustion (ASC) for application in SOFC cathodes

[EN] To make SOFC high efficiency energy generation devices, thin ceramic films are proposed as their main components. The rate of the oxygen reduction reaction is relevant for the overall performance of the SOFC, hence a lot of attention is given to the cathodes and their interfaces. The airbrushed solution combustion (ASC) method was used to fabricate an LSM thin film on a dense YSZ substrate. A single phase LSM perovskite was obtained with very thin and interconnected porosity, and a small average grain size (55 nm). The nanostructured LSM thin film electrode showed a low total activation energy (1.27 eV) at high temperatures, but a high area specific resistance at 850°C (55 Ω.cm²). The activation energy for the dissociative adsorption and diffusion of oxygen was significantly low (1.27eV), while the charge transfer and oxygen ion migration activation energy at the LSM/YSZ interface (1.28 eV) was closer to those usually reported.The authors would like to thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNpQ) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) in Brazil and Instituto de Cerámica y Vidrio (ICV) and Consejo Superior de Investigaciones Científicas (CSIC) in Spain.Peer reviewe