1. Preparation and electrochemical characterization of aluminium liquid battery cells with two different electrolytes ($NaCl-BaCl_2-AlF_3-NaF$ and $LiF-AlF_3-BaF_2$)Viktor Napast, Jože Moškon, Marko Homšak, Aljana Petek, Miran Gaberšček, 2015, original scientific article Abstract: The possibility of preparation of operating rechargeable liquid battery cells based on aluminium and its alloys is systematically checked. In all cases we started from aluminium as the negative electrode whereas as the positive electrode three different metals were tested: $Pb$, $Bi$, and $Sn$. Two types of electrolytes were selected: $Na_3AlF_6-AlF_3-BaCl_2-NaCl$ and $Li_3AlF_3-BaF_2$. We show that some of these combinations allowed efficient separation of individual liquid layers. The cells exhibited expected voltages, relatively high current densities and could be charged and discharged several times. The capacities were relatively low (120 mAh in the case of $Al-Pb$ system), mostly due to unoptimised cell construction. Improvements in various directions are possible, especially by hermetically sealing the cells thus preventing salt evaporation. Similarly, solubility of aluminium in alloys can be increased by optimising the composition of positive electrode.
Keywords: liquid batteries, aluminium, alloy, electrochemistry
Published in DKUM: 24.08.2017; Views: 1390; Downloads: 339
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2. Influence of transient response of platinum electrode on neural signals during stimulation of isolated swinish left vagus nervePolona Pečlin, Franci Vode, Andraž Mehle, Igor Grešovnik, Janez Rozman, 2012, original scientific article Abstract: The main aim of the work was to measure transient response characteristics of interface between platinum stimulating electrodes and isolated swinish left cervical vagus nerve (segment), when electrical stimulating pulses are appliedto preselected locations along the segment and elicited neural signals,also described as compound action potentials (CAPs), are recorded fromparticular compartments of the nerve. The stimulating system was manufactured as a silicone self-coiling spiral cuff (cuff) with embedded matrix of ninety-nine rectangular electrodes (0.5 mm in width and 2mm in length), made of 45 microm thick annealed platinum ribbon (99.99 % purity), and a geometric surface of 1 mm2. For electrical stimulation, a current quasitrapezoidal, asymmetric and biphasic pulses with frequency of 1 Hz, were used. To test an influence of stimulating pulses having different parameters and waveforms on elicited CAPs, various degree of imbalance between an electric charge (charge) injected in cathodic phase as well as charge injectedin anodic phase of a biphasic stimulating pulse, were deployed and compared. To identify the differences in elicited CAPs however, an integral ofthe CAP cathodic phase as well as integral of the CAP anodic phase of stimulating pulse, were calculated and compared. Results showed a strong component superimposed in the CAPs, considered as an ensemble artefact which greatly obscured the components of the CAPs, and various components did overlap. Results also showed that stimulating pulses, having preset certain degree of imbalance between charge injected in cathodic and charge injected inanodic phase, elicited a slight change in a positive waveform deflection of CAP manifested under a cathodic phase as well as slight change in a negative waveform deflection of CAP manifested under an anodic phase. (Abstract truncated at 2000 characters)
Keywords: electrical stimulation, platinum electrodes, left vagus nerve, electrochemistry, electrical charge
Published in DKUM: 16.03.2017; Views: 1405; Downloads: 122
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3. An effect of sodium dodecylsulfate on the corrosion of copper in sulphuric acid mediaRegina Fuchs-Godec, Valter Doleček, 2004, original scientific article Abstract: The effect of sodium dodecylsulfate (SDS) on copper corrosion in a solution of 0.5 M H2SO4 + x M SDS was studied using electrochemical polarisation measurements. The critical micelle concentration (CMC) of SDS in 0.5 M H2SO4 is 8 * 10-4 M, and the experimental concentrations of SDS were in the range below and above the CMC. It was found that SDS is a good anodic inhibitor at lower anodic overpotentials, i.e. very close to the rest potential. Adsorptionof the inhibitor obeys the Langmuir isotherm. Plots of log [▫$theta$▫/(1-▫$theta$▫)] versus log ▫$c_{inh}$▫ yielded straight lines with a slope change at the CMC. Accordingly, the CMC could be determined from these electrochemical measurements. The values of ▫$Delta$▫▫$G_{ads}$▫ calculated from the Langmuir plots are negative, suggesting that the inhibitive action of SDS in 0.5 M H2SO4 results from the electrostatic adsorption of C12H25SO4- ions onto the positively charged copper surface.
Keywords: electrochemistry, corrosion inhibitors, surfactants, potentiodynamic polarisation, corrosion kinetic parameters, copper, Langmuir isotherm, critical micelle concentration, sulphuric acid
Published in DKUM: 01.06.2012; Views: 1905; Downloads: 109
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4. x-ray absorption study of CeO2 and Ce/V mixed oxide thin films obtained by sol-gel depositionJana Padežnik Gomilšek, Irena Kozjek-Škofic, Nataša Bukovec, Alojz Kodre, 2004, original scientific article Abstract: CeO2 and Ce/V mixed oxide thin films prepared by sol-gel deposition and annealed in an air or argon atmosphere have been studied by chronocoulometry and by XAFS (X-ray absorption fine structure). Multielectron photoexcitations (MPE), well known to pervade XAFS spectra of Ce making the analysis of structural parameters unreliable, are removed with the help of the atomic absorption background, determined on simple Ce compounds. Distinct MPE estimates for Ce3+ and Ce4+ ions are used. In the analysis of the recovered pure XAFS signal, the degree of disorder is found to depend on the Ce/V molar ratio and on the heating atmosphere. The disorder correlates with charge capacity of films, both increasing with vanadium content and V4+/V5+ molar ratio.
Keywords: thin flms, cerium dioxide, cerium-vanadium mixed oxide, x-ray absorption, electrochemistry, sol-gel technology, XSAFS
Published in DKUM: 01.06.2012; Views: 2429; Downloads: 99
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5. Inhibitory effect of non-ionic surfactants of the TRITON-X series on the corrosion of carbon steel in sulphuric acidRegina Fuchs-Godec, 2007, original scientific article Abstract: The corrosion inhibition characteristics of non-ionic surfactants of the TRITON-X series, known as TRITON-X-100 and TRITON-X-405, on stainless steel (SS) type X4Cr13 in sulphuric acid were investigated by potentiodynamic polarisation measurements. It was found that these surfactants act as good inhibitors of the corrosion of stainless steel in 2 mol L-1 H2SO4 solution, but the inhibition efficiency strongly depends on the electrode potential. Thepolarisation data showed that the non-ionic surfactants used in this study acted as mixed-type inhibitors and adsorb on the stainless steel surface, in agreement with the Flory-Huggins adsorption isotherm. Calculated Gads values are -57.79 kJ mol-1 for TRITON-X-100, and -87.5 kJ mol-1 for TRITON-X-405. From the molecular structure it can be supposed that these surfactants adsorb on the metal surface through two lone pairs of electrons on the oxygen atoms of the hydrophilic head group, suggesting a chemisorption mechanism.
Keywords: electrochemistry, corrosion inhibitors, non-ionic surfactants, Flory-Huggins isotherm, critical micelle concentration, sulphuric acid
Published in DKUM: 01.06.2012; Views: 2160; Downloads: 107
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6. Ecological alternatives to the reduction and oxidation processes in dyeing with vat and sulphur dyesMojca Božič, Vanja Kokol, 2008, review article Abstract: This article gives a summary of the most commonly used ecologically unfriendly processes for the reduction and oxidation of vat and sulphur dyes. It also describes the new alternatives that are in the development stage and could be important in the near future. Sodium dithionite as the dominant reducing agent produces large amounts of sodium sulphate, and also toxic sulphite and thiosulphate as by-products. Consequently, high amounts of hydrogen peroxide and alkali are required for the treatment of effluents, which add to the cost of the process. Attempts have been made to use organic biodegradable reducing agents, enzymes, catalytic hydrogenation, and also indirect or direct, electrochemical reductive methods that employ a redox mediator (electron-carrier). The reduction has also been carried out via the dye radical molecule or, in the case of indigo, by direct electrochemical reduction using graphite as the electrode material. Physical techniques, for example using ultrasound, magnetic fields or UV have been shown to be effective only when used to accelerate methods using classical reduction and oxidation processes. However, although these methods offer some environmental benefits, there is still no satisfactory alternative reducing and/or oxidising agent available today.
Keywords: textile dyeing, vat dyes, sulphur dyes, reduction, oxidation, catalysis, ecology, organic agents, electrochemistry, ultrasound, magnetic field, UV application, biotechnology
Published in DKUM: 01.06.2012; Views: 3143; Downloads: 119
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7. The adsorption, CMC determination and corrosion inhibition of some N-alkyl quaternary ammonium salts on carbon steel surface in 2 M H2SO4Regina Fuchs-Godec, 2006, original scientific article Abstract: Electrochemical measurements were performed to investigate the effectiveness of cationic surfactants of the N-alkyl quaternary ammonium salt type, i.e. myristyltrimethylammonium chloride (MTACl), cetyldimethylbenzylammonium chloride (CDBACl), and trioctylmethylammonium chloride (TOMACl), as corrosion inhibitors for type X4Cr13 ferritic stainless steel in 2 M H2SO4 solution. Potentiodynamic polarization measurements showed that these surfactants hinder both anodic and cathodic processes, i.e. act as mixed-type inhibitors. It was found that the adsorption of the N-alkyl ammonium ion in 2 M H2SO4 solution follows the Langmuir adsorption isotherm. Plots of log ▫$[/theta$▫/(1-▫$/theta$▫)] versus log▫$c_{inh}$▫ yielded straight lines with a slope, which changed drasticallyat the critical micelle concentration (CMC) of the surfactants studied. Accordingly, the CMC could be accurately determined from these measurements. The calculated values of the free energy of adsorption ▫$/Delta$▫▫$G_{ads}$▫ are, in cases when the charge on the metal surface is negative with respect to the PZC, relatively high what is characteristically for the chemisorption. On the other hand, for positive metal surfaces it is assumed that ▫$SO_4^{2-}$▫ anions are adsorbed first, so the cationic species would be limited by the surface concentration of anions. Accordingly ▫$/Delta$▫▫$G_{ads}$▫ values were lower in this case and the adsorption is due to merely electrostatic attraction, which is characteristically of physisorption.
Keywords: electrochemistry, corrosion inhibitors, cationic surfactants, Langmuir isotherm, corrosion kinetic parameters, critical micelle concentration, sulphuric acid
Published in DKUM: 30.05.2012; Views: 2818; Downloads: 107
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