Showing papers on "Supporting electrolyte published in 1989"

The Role of Inclusions on Initiation of Crevice Corrosion of Stainless Steel I . Experimental Studies

Abstract: A mathematical model for the initiation of crevice corrosion on 304 stainless steel in 01N NaCL was developed The central concept is that thiosulfate ions, formed by dissolution of MnS inclusions and trapped within the crevice, act in concert with chloride ions to cause passivity breakdown when their concentrations exceed critical values The model includes consideration of migration and diffustion of the supporting electrolyte, as well as ions produced by dissolution of metal and MnS inclusions Experimental data reported sperately in part I were compared with theoretical predictions

Self-diffusion in electrolyte solutions : a critical examination of data compiled from the literature

Abstract: 1. Introduction. 2. Explanatory Notes. 3. Tables of Self-Diffusion Data. For binary aqueous electrolyte solutions. For ternary aqueous electrolyte solutions. For mixed solvent electrolyte solutions. For non-electrolyte species in electrolyte solutions. Appendix I. Tables of limiting self-diffusion coefficients of ions. Appendix II. List of references to self-diffusion data which have not been included in the compilation. Index of Supporting Electrolyte Solutions. Index of Diffusing Species.

Voltammetric reduction and determination of hydrogen peroxide at an electrode modified with a film containing palladium and iridium

Abstract: Cyclic voltammetry of a mixture containing 0.2 mM Na2IrCl6, 0.1 mM PdCl2, 0.2 M K2SO4, and 0.1 M HCl between 1.2 and -0.3 V vs Ag/AgCl for five cycles at 50 mV s-1 yields a stable film on a glassy carbon electrode. The reduction of hydrogen peroxide in 0.1 M KCl is diffusion controlled at that modified electrode. Calibration curves obtained at a 100 mV s-1 scan rate are linear in the range 0.2-1.8 mM H2O2. The slope, 28 microA L mmol-1, is independent of film thickness. Since dissolved oxygen is reduced at about the same potential as H2O2, -0.3 V, at the modified electrode, it will act as an interferent in solutions that are not deaerated; however, the currents are additive. A second limitation of the described procedure is that with the KCl electrolyte the immobilized film must be reoxidized prior to each measurement. Preliminary data are described which suggest that this problem is alleviated by switching to a basic supporting electrolyte.

Luminescent and redox probes of structure and dynamics in quaternized poly(4-vinylpyridine) films on electrodes

Abstract: The properties of partially quaternized poly(4-vinylpyridine) films have been studied by coordinatively attaching luminescent and redox probes to free pyridine units within the polymer. Samples were examined as thin films spin coated onto glass or electrodes. The luminescent moiety was Re(CO){sub 3}(phen) (phen = 1,10-phenanthroline). It showed properties that depended strongly on the identity of the anion in the supporting electrolyte adjacent to the film. The emission maximum shifted to the red, and the quantum yield decreased in the order dry film > 0.1 M NaClO{sub 4} > 0.1 M potassium p-toluenesulfonate > 0.1 M KNO{sub 3}. The isotope effect caused by changing the solvent from H{sub 2}O to D{sub 2}O fell in the reverse order. The results show that the anion has a large impact on film structure. In nitrate the films are strongly hydrated, but in perchlorate they are dry and compact. The redox moiety was Ru(bpy){sub 2}Cl{sup 2+/1+}. The activation energies for electron diffusion in the network of redox centers were assessed by temperature-resolved chronocoulometry. The activation energies were independent of the concentration of redox centers in the film but were ordered according to electrolyte as given above. They were roughly linearly dependent on the degree ofmore » chemical cross-linking. The permeabilities of the films to redox-active ions in solution were larger than the electron diffusion coefficients by an order of magnitude but were strongly dependent on the anion of the supporting electrolyte, inversely in the order given above. The results suggest that electron diffusion is controlled by segmental motions within the polymer and that the anion dependence is a structural effect.« less

Morphological Evolution in Zinc Electrodeposition

Abstract: We present an experimental study of the electrodeposition of zinc in a thin layer, three‐electrode electrochemical cell. We show that as the steady‐state current‐potential behavior approaches mass transfer limited kinetics, the fractal dimension of the morphology of the deposit converges to the DLA value of . We also compare the evolution of the growth patterns with and without supporting electrolyte.

Voltammetry in supercritical carbon dioxide at platinum microdisk electrodes coated with perfluorinated ion-exchange membranes

Abstract: It has previously been shown that the resistance of supercritical CO 2 is too high for voltammetry, even with microelectrodes, unless electrolytes and/or polar modifiers are present in the fluid. In a supercritical fluid flow system, such as chromatography, the use of an added electrolyte is not desirable. As an alternative, a film of an ionically conducting polymer, Nafion, placed over an electrochemical probe consisting of both a microdisk working electrode and a quasi-reference electrode, has been used. Undistorted voltammograms of ferrocene, 4-methylcatechol and 3,4-dihydroxy-benzylamine dissolved in supercritical CO 2 in the presence of small quantities of H 2 O have been obtained without the use of added supporting electrolyte. Experiments carried out in a supercritical fluid flow stream demonstrate the potential utility of membrane coated microelectrodes as chromatographic detectors

Solid electrolytic capacitor and manufacture thereof

Abstract: PURPOSE: To enhance generation efficiency of a solid electrolyte within a fine hole and a void and improve the electrostatic capacitance and the leakage current by forming an anion interface activation agent or a non-ion interface activation agent on a dielectric oxide film which is formed on an anode surface previously and by forming a solid electrolyte consisting of a conductive polymer film CONSTITUTION: A lead is attached to an anode foil 1 where a dielectric oxide film 2 is formed and then is dipped into sodium di(2-ethylhexyl)sulfosuccinate solution after reformation, thus forming an anion interface activation agent layer 3 Then, after this anode foil 1 is dipped into an ethanolic solution of pyrrole, it is further dipped into ammonium persulfate solution, thus forming a polypyrrole film 4 by chemical oxidation polymerization on the surface Then, it is dipped into an acetonitrile solution containing pyrrole monomer and a supporting electrolyte and electrolytic oxidation polymerization is performed with the polypyrrole film 4 as an anode, thus forming a polypyrrole 5 After that, a cathode layer is formed and resin sheathing is provided for obtaining a solid electrolytic capacitor COPYRIGHT: (C)1991,JPO&Japio

Chemically modified carbon paste and carbon composite electrodes

Abstract: Carbon paste electrodes and composite carbon electrodes modified by 20% silica gel (30 μm) within the electrode material exhibit many properties typical of a strand of carbon fiber microelectrodes in voltammetric measurements. Charged and uncharged species were studied on these electrodes; phenol, ferricyanide, and potassium ethylxanthogenate yield sigmoidal voltammograms with limiting currents that are virtually independent of the supporting electrolyte concentration. Phenol can be determined in the absence of the electrolyte in water containing up to 30% acetonitrile. Modified carbon composite electrodes are suitable for the determination of potassium ethylxanthogenate for the purposes of controlling flotation processes.

An alternating current impedance study of polypyrrole/poly(vinyl chloride) composites

Abstract: A.c. impedance studies of poly(vinyl chloride)–polypyrrole composites deposited on platinum electrodes and in contact with an acetonitrile solution containing 0.1 mol dm–3 tetrabutylammonium tetrafluoroborate (as supporting electrolyte) are described. Data are presented for the frequency range 0.1 Hz–65 kHz, and in this way the conductivity of the composite is found. The latter is related to the potential applied via the platinum electrode to the composite, and to the amount of polypyrrole incorporated within the composite. In-situ electrochemical e.s.r. measurements on the composite are also described, and these, together with the a.c. data, indicate the electrical properties and behaviour of the composite material to be similar to polypyrrole itself.

Liquid junctions for characterization of electronic materials. I. The potential distribution at the Si/methanol interface

Abstract: Photoelectrochemical cells consisting of n‐type 〈100〉‐Si wafers in methanolic solutions of ferrocene derivatives with LiClO4 as the supporting electrolyte have been analyzed using a complementary set of impedance spectroscopy, electroreflectance, and current‐voltage measurements. The results were interpreted in terms of charge accumulation modes correlated with junction parameters such as space‐charge layer, surface states, Fermi‐level pinning, and the possible presence of an insulating layer at the interface. The impedance of these junctions is interpreted in terms of an equivalent circuit. The Fermi level is partially pinned at a potential about 0.2 eV below the conduction band and is completely pinned at potentials positive to midgap. The electroreflectance results agree well with the impedance. The effect of an HF etching on the properties of the cells will be discussed. We have also compared the results in the methanolic solution with an aqueous electrolyte. The potential distribution obtained in this case is very similar to the ferrocene solution.