Portugaliae
Electrochimica Acta

The electropolymerization of acrylamide in the presence of NaN03 in aqueous solution has been investigated on platinum electrodes. The polymer (polyacrylamide) is obtained in the bosom of the solution. The dependence of yields and molecular weights on parameters such as current density, monomer concentration, electrolyte concentration and temperature was determined.

Conducting polymer composite, polypyrrole/polyvinylsulphonate film prepared on a Pt electrode was degradated by applying anodic potentials at which the irreversible oxidation occurs. The effect of the "overoxidation" potential and polarization time on the electroactivity degradation was determined through the percentage of loss of stored charge. The degradation kinetic promoted by anodic polarization was obtained.

Swelling process related to electrochemical switching of conducting polymers between their reduced and oxidized states has been modelled, by using a thermodynamic treatment based on polymer gels swelling theories. A free energy function is assigned to both reduced and oxidized states, depending upon chemical and physical features of the polymer. The model is able to explain the changes in polymer volume observed when oxidation charge or electrolyte concentration are varied.

A sulphate-reducing bacteria (SRB) that is able to use nitrate as a final electron acceptor (Desulfovibrio desulfuricans ATCC 27774) was grown in lactate-nitrate medium. Weight loss and open circuit potential measurements, cyclic voltammetry and unidirectional polarisation were performed, both in sterile media as well as in the culture, using a mild steel electrode. These results were compared with previous ones obtained with the same bacteria grown in lactate-sulphate medium, thus allowing testing biocorrosion mechanism where either sulphide acumulates and cathodic depolarisation occurs or when only the last mechanism occurs.

The present work is a study on the electrodeposition of Copper on Zamak 5 from alkaline copper solution. The effects of time and current density on thick and cathodic current efficiency have been studied by gravimetric methods.

The corrosion of M2 high speed steel in aqueous media containing chloride, bromide, iodide, nitrate, sulphate and perchlorate salts of sodium and potassium of varying concentration has been studied using corrosion potential measurements, voltammetric and electrochemical impedance techniques. The influence of the cation was found to be small and an order of anion aggressiveness was established as: sulphate > chloride > bromide > perchlorate > iodide > nitrate.

Influence of the composition of molten mixtures Me2R04-Me2R207- U02R04 (Me = Li, Na, K, Cs; R = S, Mo, W) and of the main potentiostatic electrolysis parameters on the chemical, phase composition of cathode deposits and on their current efficiencies have been studied. Experiments were carried out at temperatures of up to 900°C in the air. It has been showed that uranyl-containing oxide salt melts with various cationic and anionic composition can be used for electrochemical obtaining of granular uranium oxides with the 0 / U atomic ratio ranging from 2.014 to 2.667.

Potentiometric measurements have been performed, at 25 °C, in cells of the type: Reference electrode 10mol/dm-3 KCl x g d m albumin (20

The functioning of a DNA-modified glassy carbon electrode was evaluated using the electrochemical system ferricyanide/ferricyanide, after different electrode conditioning in the absence or presence of the free bases adenine and guanine, and at different applied potentials. The results were compared with those obtained at the bare glassy carbon electrode

Square wave voltammetry at microdisk gold electrodes modified with a mercury film was used to quantify nickel levels in kidney samples of mice previously treated with a solution containing those species. Comparison of the results obtained by electrochemical techniques and atomic absorption spectrometry indicates that microelectrodes are a reliable quantitative technique and greatly enhances the working conditions.

Conventional gold electrode, gold, and mercury coated microelectrodes were used to study the electrochemical behaviour of iron species in osteoblast-like cell cultures medium. Gold microelectrodes, with or without surface modification, have shown to be useful tools for in vitro qualitative and quantitative analysis of iron ions released from stainless steel in biological systems.

The influence of the temperature and the electrolyte concentration on an alkaline Fuel Cell has been studied through the variation of the current density and the potential of the cell. As anode has been utilized a palladium membrane and as cathode, a carbon-tetrafluoroethylene-perovskit porous electrode. The electrolyte used is aqueous KOH.

In this work, an UV-vis spectrophotometer technique adapted to "in-situ" absorption-reflection experiments is presented. Visible spectra at different oxidation potentials for Polypyrrole/Polyvinylsulphonate composite controlled in 0.1 M LÍCIO4 water solution were performed. The evolution of the visible-absorption spectra in the oxidized and reduced states as a function of the number of cycles of the coloration/decoloration was followed.

A bilayer structure polypyrrole-flexible and inactive polymer has been constructed to transform molecular strain in macroscopic movement during electrochemical oxidation/reduction process of polypyrrole film. With the aim of optimizing bilayer movement, the rate (rad.s-1) of those electrochemomechanical movements for a same described angle (90°), the consumed electrical charge (mC) and electrical energy (mJ) under different electrical conditions and with different bilayer dimensions has been studied. The obtained results shown an increasing of both movement rate and consumed electrical energy per mass unit at increasing applied current per mass unit (mA.mg-1). Hower the electrical charge consumed remain constant. Also the bilayer dimensions have not influence on movement rate and on consumed electrical charge or energy per mass unit. However, for a constant consumed electrical charge per mass unit the angle traveled remains constant varying bilayer dimensions.