Journal Articles

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    The direct conversion of benzene to phenol by hydroxylation with hydrogen peroxide was carried out over various transition metals impregnated on MCM-41 and activated carbon. Copper-, iron-, and vanadium-impregnated on activated carbon gave better yields of phenol when compared to the corresponding reactions using cobalt-, nickel-, manganese-, and titanium-impregnated catalysts. Comparison of the MCM-41 and activated carbon-supported catalysts showed that activated carbon-supported catalysts gave a higher yield of phenol than did the MCM-41-supported catalysts. The activity of the transition metals supported on activated carbon in the production of phenol was V > Fe > Cu; the corresponding activity of the transition metals supported on MCM-41 was Cu > Fe > V. In addition to the role of transition metals in catalyzing the hydroxylation reaction, the hydrophobic nature of the activated carbon surface seems to enhance the performance of these catalysts relative to the MCM-41-supported catalysts.
    (Benzene hydroxylation to phenol catalyzed by transition metals supported on MCM-41 and activated carbon) Choi, J.-S.; Kim, T.-H.; Saidutta, M.B.; Sung, J.-S.; Kim, K.-I.; Jasra, R.V.; Song, S.-D.; Rhee, Y.-W.
    2004
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    Corrosion behavior of composition modulated multilayer Zn-Co electrodeposits produced using a single-bath technique
    (2009) Thangaraj, V.; Eliaz, N.; Hegde, A.
    Composition modulated alloy (CMA) electrodeposits of Zn-Co were produced from acid chloride baths by the single-bath technique. Their corrosion behavior was evaluated as a function of the switched cathode current densities and the number of layers. The process was optimized with respect to the highest corrosion resistance. Enhanced corrosion resistance was obtained when the outer layer was slightly richer with cobalt. At the optimum switched current densities 40/55 mA cm-2, a coating with 600 layers showed ~6 times higher corrosion resistance than monolithic Zn-Co electrodeposit having the same thickness. The CMA coating exhibited red rust only after 1,130 h in a salt-spray test. The increased corrosion resistance of the multilayer alloys was related to their inherent barrier properties, as revealed by Electrochemical Impedance Spectroscopy. The corrosion resistance was explained in terms of n-type semiconductor films at the interface as supported by Mott-Schottky plots. © 2008 Springer Science+Business Media B.V.
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    Electrodeposition and characterization Zn-Co alloy
    (2009) Hegde, A.; Thangaraj, V.
    The present work details optimization of a stable acid chloride bath for electroplating of bright Zn-Co alloy on mild steel using gelatin and glycine as additives. It was found that the addition of gelatin along with glycine changed the deposition pattern markedly. A suitable bath has been formulated using conventional Hull cell experiments. The bath under plating conditions were found to exhibit anomalous codeposition with preferential deposition of less noble (zinc) over more noble (cobalt) as characterized by Zn-Fe group metal alloys. Investigation revealed that the current density (c.d.), temperature, and pH of the bath have strong effect on the composition of the deposit. Influence of bath constituents and operating parameters on appearance and composition of deposits were studied as measure of their performance against corrosion. A variety of deposits were obtained and their corrosion resistances were measured by Tafel method with/without chrome passivation. Experimental results demonstrated the fact that the corrosion resistances of Zn-Co alloys increased with percent of Co in the deposit except at very high c.d. This is due to the fact at very high c.d. the deposit becomes very porous and thick as evidenced by SEM image. The formation of Zn-Co alloy is confirmed by EDAX analysis. A stable chloride bath for Zn-Co alloy deposition has been proposed and discussed. The formation of passive film on chromatization is indicated by almost same E corr value of all Zn-Co electroplates irrespective of the current densities at which they have been deposited. © 2009 Pleiades Publishing, Ltd.
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    Third-order optical nonlinear studies of Cobalt (II) Schiff base complex bearing triphenylphosphine using Differential Optical Kerr Gate and Z-scan studies
    (2010) Rudresha, B.J.; Badekai Ramachandra, B.; Ramakrishna, D.; Anthony, J.K.; Rotermund, F.
    The third-order optical nonlinearity of the composite film of coordination complex [CoLPPh3Cl] (L = N-(2-pyridyl)-N?-(salicylidene)hydrazine) and PMMA has been investigated by using Differential Optical Kerr Gate (DOKG) and Z-scan measurements. Large value of the third-order nonlinear optical susceptibility (?(3)) of the order of 10-10 esu was measured and its nonlinear response time was found to be faster than or comparable to the laser pulse width (90 fs) used. The single beam Z-scan technique was used to investigate the nonlinear absorption property of the composite near 800 nm. The sample exhibit saturable absorption. The nonlinear absorption coefficient of sample is found to be -32 cm/GW. © 2010 Elsevier B.V. All rights reserved.
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    Electroplating and characterization of Zn-Ni, Zn-Co and Zn-Ni-Co alloys
    (2010) Eliaz, N.; Venkatakrishna, K.; Hegde, A.C.
    Zn-Ni, Zn-Co and Zn-Ni-Co coatings were electrodeposited on mild steel from an acidic chloride bath containing p-aminobenzenesulphonic acid (SA) and gelatin. These additives changed the phase content in the coatings, most likely as a result of their adsorption at the surface of the cathode. The effect of gelatin was more pronounced than that of SA. The Faradaic efficiency was higher than 90%. As the current density was increased or the bath temperature was decreased, the concentration of the nobler metal in the coating increased. Both concentrations of Ni and Co in the ternary alloy increased as the applied current density was increased. Nickel and cobalt were found to have a synergistic catalytic effect. The thickness of all coatings increased as the applied current density was increased. The hardness increased with current density to a peak value, and then decreased. The rate of Zn deposition was heavily influenced by mass-transport limitation at high applied current densities, while the rates of Ni and Co deposition were not. The anomalous codeposition was explained by the great difference between the exchange current densities of Zn and the iron-group metal. Potentiodynamic polarization scans and electrochemical impedance spectroscopy showed that the corrosion resistance of the ternary Zn-Ni-Co alloy coatings was approximately 10 times higher than that of Zn-Ni and 7 times higher than that of Zn-Co. The improved corrosion resistance of the ternary alloy was attributed to its surface chemistry, phase content, texture, and surface morphology. The ternary Zn-Ni-Co coating may thus replace the conventional Zn-Ni and Zn-Co coatings in a variety of applications. © 2010 Elsevier B.V.
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    Microwave-assisted synthesis and magnetic studies of cobalt oxide nanoparticles
    (2011) Bhatt, A.S.; Bhat, D.K.; Tai, C.-W.; Santosh, M.S.
    An efficient microwave-assisted route has been used to synthesize nanoparticles of cobalt oxide. The particles were well characterized by transmission electron microscopy (TEM) which showed that the average diameter of the particles is around 6 nm. X-ray diffraction (XRD) studies further confirmed the formation of the spinel Co3O4. Purity of the products was detected by Fourier transform infrared spectroscopy (FTIR) combined with thermal gravimetric analysis (TG/DTG). The magnetic measurements revealed a small hysteresis loop at room temperature indicating a weak ferromagnetic nature of the synthesized Co3O4 nanoparticles. The magnetic moment of the particles was measured to be 4.27 ?eff. © 2010 Elsevier B.V. All rights reserved.
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    Electrochemical properties of chitosan-Co3O4 nanocomposite films
    (Elsevier B.V., 2011) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.
    Chitosan-Co3O4 composite films have been prepared by solution casting method. The obtained films have been characterised by XRD and FESEM. The electrical properties of the films are examined by impedance spectroscopy in the temperature range 303-343 K. The impedance plot of the films pronounces the role of temperature in charge-transfer resistance of the composite. Frequency as well as temperature dependencies of dielectric constant and dielectric loss exhibit the general trend followed by carrier dominated dielectrics. Electric modulus parameters give an insight on the ionic conductivity and relaxation phenomena of the composite films. The dielectric parameters along with modulus data have been exploited to discuss the conduction mechanism in the material. The minimum activation energy of 3.9 kJ mol -1 and maximum room temperature conductivity of 1.94 × 10 -2 S cm-1 were found for composite film with 8% Co 3O4 content. © 2011 Elsevier B.V. All rights reserved.
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    Large scale synthesis of carbon nanofibres on sodium chloride support
    (InTech Europe info@sagepub.co.uk, 2012) Rajarao, R.; Badekai Ramachandra, B.R.
    Large scale synthesis of carbon nanofibres (CNFs) on a sodium chloride support has been achieved. CNFs have been synthesized using metal oxalate (Ni, Co and Fe) as catalyst precursors at 680 °C by chemical vapour deposition method. Upon pyrolysis, this catalyst precursors yield catalyst nanoparticles directly. The sodium chloride was used as a catalyst support, it was chosen because of its non-toxic and water soluble nature. Problems, such as the detrimental effect of CNFs, the detrimental effects on the environment and even cost, have been avoided by using a water soluble support. The structure of products was characterized by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The purity of the grown products and purified products were determined by the thermal analysis and X-ray diffraction method. Here we report the 7600, 7000 and 6500 wt% yield of CNFs synthesized over nickel, cobalt and iron oxalate. The long, curved and worm shaped CNFs were obtained on Ni, Co and Fe catalysts respectively. The lengthy process of calcination and reduction for the preparation of catalysts is avoided in this method. This synthesis route is simple and economical, hence, it can be used for CNF synthesis in industries. © 2012 Rajarao and Bhat.
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    Magnetic domain studies of cobalt nanostructures
    (2012) Nagaraja, H.S.; Nagaraja, K.K.; Rossignol, F.; Dumas-Bouchiat, F.; Champeaux, C.; Catherinot, A.
    The pulsed laser deposition technique associated with a low energy cluster beam is used to deposit cobalt thin films with a thickness 100-200 nm and cobalt dots of a diameter 100-200 nm on silicon substrates. The deposited thin films of Co are composed of clusters of a size 10- 50 nm, with very few large grains as revealed by atomic force microscopy. The observations performed by magnetic force microscopy on as-grown thin films reveal randomly distributed out-of-plane magnetic domain structures. These magnetic domains are aligned linearly by applying an external magnetic field either perpendicular or parallel to the substrate during the deposition. In addition, the effect of film thickness and roughness on multidomains is reported. The increase of roughness resulted in the decrease of magnetic domain width from 200 to 100 nm. This decrease is accompanied by the appearance of instability in the stripe domain pattern. Well separated cobalt dots of diameter in the range of 100-200 nm are also deposited on silicon substrates, which show arc-like multidomains. The domains seem to be oriented along the long axis of the dots. The domain structure of Co nanodots is similar to that of Co thin films indicating strong magnetic coupling of clusters. © Springer Science+Business Media, LLC 2012.
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    Rapid removal of cobalt (II) from aqueous solution using cuttlefish bones; Equilibrium, kinetics, and thermodynamic study
    (2013) Sandesh, K.; Suresh Kumar, R.; JagadeeshBabu, P.E.
    The objective of this study is to assess the adsorption potential of cobalt (II) using cuttlefish bones. The bones were treated with 0.01 N HCl to enhance the heavy metal uptake. The adsorbent was characterized using scanning electron microscope and energy dispersive X-ray spectrometer. An adsorption study was conducted in a batch system to optimize process variables such as initial concentration of cobalt (II), pH, sorbent loading, particle size, process temperature, and contact time. The optimal pH was found to be 9. The kinetic data followed the pseudosecond-order kinetic model, and the equilibrium time was found to be 20 min. In the first minute of the adsorption process, 50% of the cobalt (II) was adsorbed by the cuttle bones. Adsorption isotherms were expressed by the Langmuir and Freundlich adsorption models. The Langmuir adsorption model fits the experimental data reasonably well compared with the Freundlich model. The maximum adsorption capacity of this new sorbent was found to be 76.6 mg g-1 at 40 °C. Thermodynamic parameters, including the Gibbs free energy (?Go), enthalpy (?Ho), and entropy (?So), indicated that the adsorption of cobalt (II) by cuttlefish bones was feasible and endothermic at a temperature range of 20-40 °C. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.