Portugaliae
Electrochimica Acta

Synthesis, characterization and polymeric battery studies of Na+ ion conducting Nano- Composite Polymer Electrolyte (NCPE) membranes: (1-x) [75PEO: 25NaPO3]: x SiO2, where x = 0 - 15 wt. (%), has been reported. NCPE membranes have been casted using a novel hot-press technique in place of the traditional solution cast method. The dispersal of SiO2 in SPE host: (75PEO: 25NaPO3), a conductivity enhancement of an order of magnitude achieved in NCPE film: [93 (75PEO: 25NaPO3): 7 SiO2]. This has been referred to as Optimum Conducting Composition (OCC). Material characterizations have been done with the help of XRD, SEM and DSC techniques. The ion transport behaviour in hot-pressed NCPEs has been discussed on the basis of experimental measurements on some basic ionic parameters viz. conductivity (σ), ionic mobility (μ), mobile ion concentration (n) and ionic transference number (tion). The temperature dependent conductivity studies have been done to compute the activation energy (Ea) values from the ‘log σ – 1/T’ Arrhenius plots. The ion conducting solid state polymeric battery was fabricated and cell-potential discharge characteristics have been studied at different load conditions.

The influence of benzothiazole derivatives on corrosion inhibition of mild steel in 1 M H2SO4 was studied by weight loss, potentiodynamic polarization and AC-impedance techniques. The synergistic effect by the addition of halide ions had been studied. The experimental results showed that the inhibition efficiency increases with increasing inhibitor concentration, but decreases with increasing temperature; potentiodynamic polarization curves showed that benzothiazole derivatives acted as cathodic inhibitors in 1 M H2SO4. This was supported by the impedance measurements which showed a change in the charge transfer resistance and double layer capacitance, indicating adsorption of Benzothiazole derivatives on the mild steel surface. Atomic absorption spectroscopy studies showed that the inhibition efficiency increases with increasing inhibitor concentration.

Pollution control measures have resulted in replacement of chlorine by peroxide as bleaching chemical. Change of chemical affects corrosion aspects, the suitability of existing plant metallurgy and materials of construction of bleach plants. Accordingly long term immersion and electrochemical corrosion tests were conducted on stainless steel 304L, 316L, 2205 and 6% Mo and mild steel in peroxide solutions of pH 10. The materials were tested for uniform corrosion, pitting and crevice corrosion and attack around the weld area. Corrosion attack estimated from long term immersion tests is found in agreement, by and large, with that analyzed from electrochemical test. E-pH diagrams drawn for water-peroxide system have been used to understand the corrosivity of the peroxide media. An attempt has been made to suggest a suitable material of construction for handling the test media on the basis of degree of corrosion attack on them and their cost and the mechanical properties.

Spontaneous deposition of tin (Sn) in polycrystalline platinum (Pt pc) from a sulfuric acid solution of tin salts, was evaluated by conventional electrochemical techniques, to determine its characteristics. Tin was deposited from a solution of SnCl2 or SnSO4 in sulfuric acid 1 M. The degree of surface coating by Sn was calculated by evaluating the region of hydrogen electrosorption through voltammograms performed using solutions containing only the supporting electrolyte, and the supporting electrolyte containing the Sn salt, respectively. The adsorption behavior of tin and oxidation have been studied by the results obtained with platinum electrodes and electrodes of platinum/tin, considering as comparative parameter the adsorption efficiency with respect to the area free of platinum.

The degradation of crystal violet (CV) and malachite green (MG) by potassium persulfate, was investigated by spectrophotometric methods. The behavior of degradation of crystal violet by persulfate was found to be similar to that of malachite green with only one important difference concerning the order with respect to the dye: the degradation is pseudo second order with respect to CV, but first order with respect to MG. The order with respect to persulfate is one in both cases. Degradation of CV by persulfate was effective at pH range of 2-8 and was found to increase with an increase in the initial concentrations of persulfate, temperature, and the presence of Ag+. The factors that were found to decrease the degradation rate of CV include: the initial concentration of CV, and the presence of halide salts and of the surfactant SDS. The rate of degradation remained the same after addition of Co(II), Ni(II) and Cu(II) salts. The activation parameters of the degradation reaction (Ea, ΔG#, ΔH# and ΔS#) were calculated. Finally, cytotoxic study revealed a decrease in the toxicity of the degradation products.

Silver nanoparticles (AgNP) were synthesized by electrochemical method using high purity metallic silver in the presence of the surfactant Pluronic® f127. The synthesized nanoparticles were characterized using UV-Vis spectroscopy, Dynamic Light Scattering (DLS), X-Ray Dispersion Spectroscopy (XDS) and Scanning Electron Microscopy (SEM). The antimicrobial activity of AgNP was evaluated against Escherichia Coli. In presence of surfactant, the prepared nanoparticles led to a monomodal distribution with an average size less than 100 nm. The minimal inhibitory concentration (MIC) of the resulting suspension was evaluated using micro dilution method and the MIC results are satisfactory.