Estudo experimental da indução magnética

This work will discuss how magnetic fields can be produced, either generated by magnets, natural, artificial, or even by an electric current going through a wire, as discovered by Oersted. Besides the theoretical content, experimental studies on magnetic induction and on the Laws of Faraday and Lenz will be performed. In the Magnetic Induction experiment, the electromotive force generated by varying the flow of the field B in a solenoid, depending on the variation of the current intensity and frequency associated with it will be measured; the experiment on the Laws of Faraday and Lenz the electromotive force produced by the relative movement of the magnet in relation to a coil. Thus, this study experimental verification of magnetic induction using solenoids and magnets; analysis of magnetic induction by Faraday's Law and Lenz's Law

Desenvolvimento de catalisadores sem platina: estudos comparativos da oxidação de metanol em 'PD''RU'/'C' e 'PT''RU'/'C' em meio alcalino

Pós-graduação em Química - IQ

Tratamento térmico de filmes supercondutores do sistema BSCCO utilizando forno de micro-ondas doméstico

Pós-graduação em Ciência dos Materiais - FEIS

Electrochemical oxidation of landfill leachate in a flow reactor: optimization using response surface methodology

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação dos parâmetros tempo, corrente e pressão na soldagem por resistência elétrica de compósitos PEI/fibras contínuas: influência na resistência mecânica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fabrication and structural characterization of bismuth niobate thin films grown by chemical solution deposition

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Anodization mechanism on SiC nanoparticle reinforced al matrix composites produced by power metallurgy

Specimens of aluminum-based composites reinforced by silicon carbide nanoparticles (Al/SiCnp) produced by powder metallurgy (PM) were anodized under voltage control in tartaric-sulfuric acid (TSA). In this work, the influence of the amount of SiCnp on the film growth during anodizing was investigated. The current density versus time response and the morphology of the porous alumina film formed at the composite surface are compared to those concerning a commercial aluminum alloy (AA1050) anodized under the same conditions. The processing method of the aluminum alloys influences the efficiency of the anodizing process, leading to a lower thicknesses for the unreinforced Al-PM alloy regarding the AA1050. The current density versus time response is strongly dependent on the amount of SiCnp. The current peaks and the steady-state current density recorded at each voltage step increases with the SiCnp volume fraction due to the oxidation of the SiCnp. The formation mechanism of the anodic film on Al/SiCnp composites is different from that occurring in AA1050, partly due the heterogeneous distribution of the reinforcement particles in the metallic matrix, but also to the entrapment of SiCnp in the anodic film.

Nonlinear angle control of a sectioned airfoil by using shape memory alloys

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thin films produced on 5052 aluminum alloy by plasma electrolytic oxydation with red mud-containing electrolytes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Numerical tests of an adaptive sectioned airfoil actuated by shape memory alloys

The main objective of this work is to illustrate an application of angular active control in a sectioned airfoil using shape memory alloys. In the proposed model, one wants to establish the shape of the airfoil profile based on the determination of an angle between its two sections. This angle is obtained by the effect of the shape memory of the alloy by passing an electric current that modifies the temperature of the wire through the Joule effect, changing the shape of the alloy. This material is capable of converting thermal energy into mechanical energy and once permanently deformed, the material can return to its original shape by heating. Due to the presence of nonlinear effects, especially in the mathematical model of the alloy, this work proposes the application of a control system based on fuzzy logic. Through numerical tests, the performance of the fuzzy controller is compared with an on-off controller applied in a sectioned airfoil model.

The changes on microstructure and electrical properties of Bi:2223/Ag composite as a function of the granulation and the content of the added silver powder

The Bi-Sr-Ca-Cu-O system has been one of the most studied superconducting ceramic materials for industry applications. The most of the studies with this aim are on silver/ceramic composites, due to the benefits and great compatibility of this metal with the oxide. In this paper we describe a systematic and comparative study on Ag/BSCCO composite, made by the citrate route, in which the ceramic pellets are sintered in the presence of silver powder using several proportions and having several granulations. It was observed that the introduction of fine (0.5 and 2 μm) silver powder in the proportions of 5 wt. % always implies in a better critical current density compared to the no silver pellet. According to the results, the silver powder in excess of 5 wt.% may not promote best electrical properties, depending on the size of the silver particles.

A novel single-phase ZCS-PWM high power factor boost rectifier

This paper presents a novel single-phase high power factor PWM boost rectifier, featuring soft commutation of the active switches at zero-current (ZCS). It incorporates the most desirable properties of the conventional PWM and the soft-switching resonant techniques. The input current shaping is achieved with average current mode control, and continuous inductor current mode. This new PWM converter provides ZCS turn-on and turn-off of the active switches, and it is suitable for high power applications employing IGBTs. Principle of operation, theoretical analysis, a design example, and experimental results from a laboratory prototype rated at 1600 W with 400 Vdc output voltage are presented. The measured efficiency and power factor were 96.2% and 0.99 respectively, with an input current THD equal to 3.94%, for an input voltage THD equal to 3.8%, at rated load.

Eletro-oxidação de metanol e etanol sobre PtAu/C em meio alcalino

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.

Estudo do efeito do transporte de massa nas curvas de polarização potenciodinâmica em ligas de alumínio da série 7XXX de aplicação aeronáutica

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.

Influência de tratamentos a plasma na resistência à corrosão e na propriedade de adesão de uma camada protetiva sobre a superfície de ligas de alumínio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)