Eduardo A. Ponzio

Sensor development exploiting graphite-epoxy composite as electrode material

This study presents some results regarding the development and characterization of graphite-epoxy composites for use as working electrodes in electroanalysis. Such composites were preliminary assessed by TGA-DTA, AFM, XDR and cyclic voltammetry (CV), standing for a suitable stable and low cost material for electroanalytical purposes. The described material was used, in its best proportion (65% graphite m/m), to build a cell electrochemistry.

Melt sonoquenching: an affective process to obtain new hybrid material and achieve enhanced electrochromic performances based on V2O5/2,4,5-tris(1-methyl- 4-pyridinium)-imidazolide tetrafluoroborate nanofibers

Hybrid electrochromic materials are a very important class of compounds, because they enable new and/or better optical and electrochemical properties to be unfolded. This paper reports the synthesis of the new V2O5.1.26H2O([C3N2(C6H7N)3])0.07 using the combination of two traditional methods, melting quenching and sonochemistry. The new material was characterized by several methods in order to verify the physical and chemical characteristics and its possible use as an electrochromic electrode. The organic guest provokes an interlayer spacing decrease of the inorganic matrix and the electrostatic interaction between the oxo groups of the V2O5 matrix and the pyridinium rings of the organic guest demonstrate a strong interaction. The new hybrid nanostructure presented good reversibility and cyclability during 50 cycles, electrochromic efficiency of 22 cm2 C-1 (410 nm) and 96 % color retention after 50 cycles of color changing.

Influence of Deleterious Phases Precipitation in the Corrosion Resistance Measured by Double Loop Electrochemical Polarization Reactivation Test in Superduplex Stainless Steel

This work investigates the influence of deleterious phases precipitation on the corrosion resistance of two wrought superduplex stainless steels UNS S32750 with similar composition, but different grain sizes. Isothermal treatments were carried out to introduce different amounts of deleterious phases, such as chi (χ), sigma (σ) and secondary austenite (γ2). The specimens were tested by double loop electrochemical potentiodynamic reactivation test (DL-EPR). The kinetics of precipitation in the two steels was different due to the difference of the grain sizes. The results show a correlation between the sensitization degrees, measured by DL-EPR, with the amount of deleterious phases precipitated.

Development and application of a routine robust graphite/poly(lactic acid) composite electrode for the fast simultaneous determination of Pb2+ and Cd2+ in bijou by square wave anodic stripping voltammetry

A handcrafted, low cost sustainable electrochemical sensor based on graphite/PLA was developed and applied for the simultaneous quantification of Pb2+ and Cd2+ in jewelry (metallic ores) on the basis of square-wave anodic stripping voltammetry (SWASV). The proposed electrode was characterized by different complementary strategies such as cyclic voltammetry (CV), thermogravimetric analysis (TGA), Raman spectroscopy, X-ray Micro Computed Tomography (μCT), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental results showed that the developed electrode exhibits excellent electrochemical performance, with accurate and well-resolved voltammetric responses for the analytes assessed. Under optimized conditions, experiments led to linear ranges from 0.9 to 35.0 μg L−1 for Cd2+, and from 1.2 to 35.0 μg L−1 for Pb2+, with detection limits estimated as 0.3 μg L−1 and 0.4 μg L−1, respectively. The fabricated electrode was successfully applied to the fast simultaneous quantification of Pb2+ and Cd2+ in jewelry samples and the findings were in agreement to those reached by graphite furnace atomic absorption spectrometry (GF AAS).

Recuperação Avançada de Petróleo: Potencialidades da Injeção WAG (Water Alternating Gas)

The increase in the recovery factor in an oil reservoir is an essential goal in the oil industry and in this sense, complementary and alternative methodologies have been developed, for example, the alternating injection of water and gas (WAG), which has been used ever as a more advanced method of recovering oil. This method combines the best gas displacement and swept the water efficiencies. Recent discoveries of oil reserves in the Pre-Salt layer, with a significant amount of gas whose CO 2 content is in the range 8-12%, the use of CO 2 gas in WAG injection (WAG-CO 2 ) has emerged as an opportunity for Brazil. Besides the good prospect of increased oil recovery factor of these reservoirs, this process is in line with mitigation actions by greenhouse emissions CO 2 . This article is a compilation of WAG application projects in the literature, as well as issue related to Brazilian initiatives that focuses on numerical simulations using reservoir models, since the carbonate rocks common to the pre-salt reservoirs are reactive the injected fluids . DOI: 10.5935/1984-6835.20160055

Electrochromic Behavior of Vanadium Oxide Nanostructures Synthesized by Melt Sonoquenching

This paper reports a new procedure for V2O5 synthesis using the combination of two traditional methods, melt quenching and sonochemistry, called melt sonoquenching. The resulting nanomaterial was characterized by several methods in order to verify physical and chemical characteristics, and its possible use as electrochromic electrode material. Scanning electron micrographs revealed V2O5 nanofibers with lengths varying from 140 to 160 nm, and diameters varying from 10 to 15 nm, X-ray diffraction experiments pointed to an amorphous structure with an interlamellar spacing of 13.3 Å. Chemical composition was estimated by TGA, suggesting that the composition for such xerogel oxide was V2O5.1.8H2O. Besides these, spectroelectrochemical characterization showed a transmittance variation of 45 % at 410 nm, with coloration persistence of 91.3 %, response times for the oxidation and reduction were, respectively, 1 s and 3.5 s, being such electrochomic efficiency of 55 cmC in throughout 100 cycles of color changes from blue-green-orange.

Influence of Cold Plastic Deformation in the Hardness and Corrosion Resistance of Superduplex Stainless Steels Aged at 475 °C

Superduplex stainless steels (SDSS) combine elevated mechanical properties with a high corrosion resistance in severe environments. This class of materials is employed in pipes, pressure vessels, heat exchangers, pumps and other components in industries that operate with highly corrosive fluids. However, in continuous service conditions, such as in reactors and heat exchangers, high temperatures can be achieved. Thus, the purpose of this work is the determination of the influence of prior cold plastic deformation, with true strain of 1.39, in hardness and corrosion resistance of SDSS UNS S32750 and UNS S32760 obtained after thermal aging at 475 °C. The motivation of this study is due to the fact that certain components of process equipment may be deformed at low or high temperatures, in hi h the delete ious α’ phase p e ipitatio ki eti s is o e i te se. The esults sho that old plastic deformation accelerates the precipitation kinetics of this phase in SDSS UNS S32750 and UNS S32760.

Electrochromic Windows: A New Age in Energy Efficiency

In this work an overview regarding smart electrochromic windows as a promising technology capable of providing significant energy savings in buildings is presented. Electrochromic windows are devices able to control of light and acclimatization of indoor spaces. Therefore, these technologies allow energy savings with lighting and HVAC systems of these spaces. These devices are already commercially available and research and development in such field is increasing, due to its technological and financial importance.

Estudo da Influência da precipitação de fases deletérias na resistência à corrosão por ensaio de polarização anódica cíclica em aços inoxidáveis superduplex

The influence of deleterious phases precipitation in corrosion resistance was investigated in two superduplex stainless steel (SDSS) UNS S32750 with different grain sizes. Isothermal treatments were performed in order to introduce various quantities of deleterious phases, such as chi, sigma, secondary austenite and chromium nitrides. Under these conditions corrosion tests were carried out by cyclic anodic polarization method. Studies by light optical microscopy (LOM) and scanning electron microscopy (SEM) were performed to characterize the precipitated phases and the precipitation kinetics. The results allow to correlate the values obtained by polarization tests with the percentage of deleterious phases precipitates to the different conditions of treatments of SDSS with similar compositions, but with different grain sizes. It was observed that the grain sizes and aging temperature influence the kinetics of precipitation, morphology and size of deleterious phases. These features affect the corrosion resistance of SDSS.

A new hybrid electrochromic material: vanadium oxide/ eriochrome black T

In this work, we describe the synthesis of a new hybrid material, which is consists of the eriochrome black T (sodium 1-[(1-hydroxynaphthcalen-2-yl-hydrazinylidene]-6-nitro-2- naphthol-4-sulfonate) and vanadium pentoxide xerogel using a melting sonoquenching technique. This hybrid material was apply in electrochromic electrodes. The hybrid material was characterized by X-ray difraction, FT-IR, AFM and spectroelectrochemically. The hybrid presented good reversibility and cyclability during 50 cycles studied, electrochromic efficiencies were about 50 cm2 C−1 (375 nm and 400 nm) and the ΔOD at 375 nm and 400 nm were 0.236 and 0.159 respectively wavelenghts. The response times were 0.7 to 3.3 s for 375 nm and 0.7 to 2.0 s for 400 nm. The hybrid is a potential material to be used in electrochromic applications.