• V Lakshminarayanan

      Articles written in Journal of Chemical Sciences

    • Applications of exponential relaxation methods for corrosion studies and corrosion rate measurement

      V Lakshminarayanan S R Rajagopalan

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      Investigations on the use of an exponential relaxation technique for studying corrosion systems are reported. It is shown that the polarisation resistance and the double layer capacitance of corrosion systems can be obtained by the small amplitude exponential relaxation technique (laert). It is demonstrated, that the rate of corrosion can be measured by the large amplitude exponential relaxation technique (laert). This technique yields ‘accelerated Tafel plot’ only when the charging current is negligible, which is seldom so. Methods for correcting for double layer charging are described. Double layer capacitance as a function of potential is obtained fromlaert. Therefore it can be used for studies on inhibitors. The utility oflaert for corrosion systems with only one of the conjugate reactions under activation control is established. The effect of series resistance (Re) is discussed and anin situ method for its determination is described. A procedure for correcting the experimental data for errors due toRe is given.

    • Electrochemical studies of redox probes in self-organized lyotropic liquid crystalline systems

      P Suresh Kumar V Lakshminarayanan

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      Lyotropic liquid crystalline phases formed by surfactants are of special importance due to their close resemblance to biological systems. The redox reactions in such ordered media are of fundamental interest in understanding several complex processes occurring in the biological media, where the former can act as model systems. In this work, we have carried out the redox reactions of benzoquinone| hydroquinone, methyl viologen and ferrocenemethanol probes in a lyotropic hexagonal columnar phase (H1 phase) using cyclic voltammetry and electrochemical impedance spectroscopic studies. The liquid crystalline phase we have studied is made up of the non-ionic surfactant, Triton X-100 and water. Polarizing optical microscopic examination confirmed that the columnar hexagonal phase is retained even after the addition of redox probe as well as the supporting electrolyte. Our studies show a significant shift in the half-peak potentials of the redox probes in the H1 phase as compared to the solvent phase. The diffusion coefficient values for different redox probes in the H1 phase were also found to be significantly reduced when compared to the corresponding solvent media.

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