Faculty Publications
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Item 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.Item Surface modification by multilayered Zn-Co alloy coatings(2012) Yogesha, S.; Udupa, K.R.; Hegde, A.Nanostructured multilayer alloy or composition modulated multilayer alloy coatings of Zn-Co have been developed, and their corrosion behaviours were studied by potentiodynamic polarization and electrochemical impedance spectroscopy methods. The coatings were developed galvanostatically using square, triangular and sawtooth current pulses through single bath technique. The cyclic cathode current density and the numbers of layers have been optimised for peak performance of the coatings against corrosion. Under optimal conditions, the coatings developed using square, triangular and sawtooth current pulses were found to be respectively y100, 80 and 90 times more corrosion resistant than monolithic alloy of same thickness. The better corrosion resistances of the composition modulated multilayer alloy coatings were attributed to the dielectric barrier at the interface, as evidenced by dielectric spectroscopy. Surface morphology, multilayer formation and surface after corrosion tests were examined by scanning electron microscopy. © 2012 Institute of Materials, Minerals and Mining.Item Hardness and electrochemical behavior of ceramic coatings on inconel(International Association of Physical Chemists, 2012) Sujaya, C.; Shashikala, H.D.; Umesh, G.; Hegde, A.Thin films of ceramic materials like alumina and silicon carbide are deposited on Inconel substrate by pulsed laser deposition technique using Q-switched Nd: YAG laser. Deposited films are characterized using UV-visible spectrophotometry and X-ray diffraction. Composite microhardness of ceramic coated Inconel system is measured using Knoop indenter and its film hardness is separated using a mathematical model based on area-law of mixture. It is then compared with values obtained using nanoindentation method. Film hardness of the ceramic coating is found to be high compared to the substrates. Corrosion behavior of substrates after ceramic coating is studied in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The Nyquist and the Bode plots obtained from the EIS data are fitted by appropriate equivalent circuits. The pore resistance, the charge transfer resistance, the coating capacitance and the double layer capacitance of the coatings are obtained from the equivalent circuit. Experimental results show an increase in corrosion resistance of Inconel after ceramic coating. Alumina coated Inconel showed higher corrosion resistance than silicon carbide coated Inconel. After the corrosion testing, the surface topography of the uncoated and the coated systems are examined by scanning electron microscopy. © 2012 by the authors; licensee IAPC, Zagreb, Croatia.Item Development of nanolaminated multilayer Ni-P alloy coatings for better corrosion protection(Royal Society of Chemistry, 2016) Elias, L.; Bhat, K.U.; Hegde, A.Nanolaminated multilayer Nickel-Phosphorous (Ni-P) alloy coatings were developed on mild steel from a citrate bath using glycerol as an additive. Multilayer Ni-P alloy coatings having nanolaminated layers of alloys of alternatively different compositions have been developed using pulsed direct current (DC) by cyclic modulation of the cathode current density. The composition and number (hence thickness) of the layers were tailored by periodic modulation of the current density (c.d.) and time using a programmable power source. The deposition conditions were optimized for both the composition and thickness of the individual layers for the best performance of the coatings against corrosion. Electrochemical corrosion study, evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that the multilayer Ni-P alloy coating with 300 nanolaminated layers, represented as (Ni-P)1.0/4.0/300 showed several fold better corrosion resistance compared to its monolayer counterpart (deposited using regular DC) from the same electrolytic bath. Drastic improvement in the corrosion protection efficacy of the nanolaminated multilayer Ni-P alloy coatings were attributed to an increase in number of interfaces, separating layers of alloys having different morphologies, compositions and phase structures, which was supported by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses, respectively. The corrosion rates of the multilayer Ni-P alloy coatings were decreased with increasing number of layers, only up to an optimal level and then increased. The increase in corrosion rates at a higher degree of layering were attributed to the diffusion of layers, due to the very short deposition time of each layer. © The Royal Society of Chemistry 2016.Item Impact of copper doping on the electrochemical response of MnSe2 as anode for lithium-ion battery(Springer, 2024) Mukesh, P.; Lakshmi Sagar, G.; Brijesh, K.; Kumawat, S.; Hegde, A.; Kumar, A.; Nagaraja, H.S.Transition Metal Chalcogenides (TMC), due to their unique physicochemical properties, are studied in various fields and have potent applications in energy storage applications. This work is based on the synthesis and characterization of copper-doped manganese di-selenide and the effect of its doping on electrochemical performance as anode material for lithium-ion battery applications using the solvothermal method. The characterization techniques used are X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, XPS, UV–visible absorption spectroscopy, and electrochemical analysis. The XRD data confirms the formation of MnSe2 exhibiting Cubic crystal geometry. The FESEM images show the micro-cube-like structure with agglomerated nanocluster nanostructures on the surface with a dimension of 100–200 nm. The doping of the copper has decreased the band gap of the MnSe2, as studied by the UV–visible absorption spectrum. The electrochemical performance is analyzed as anode material for lithium-ion batteries. The charge/discharge measurements show a specific capacity of 706 mAh g−1 as the initial discharge capacity and 336 mAh g−1 as the initial charge capacity at 0.1 A g−1 current density. Meanwhile, 3% Copper-doped MnSe2 showed a better specific capacity of 878 mAh g−1 as the initial discharge capacity and 461 mAh g−1 as the initial charge capacity at 0.1 A g−1 current density. Cyclic stability, rate capability, and electrochemical impedance spectroscopy were performed, and it shows that 3% copper-doped MnSe2 has good stability and better conductivity and charge kinetics, indicating copper doping has enhanced the electrochemical performance of pristine MnSe2. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.Item Synergistic boost in Fe3O4 anode performance for li-ion batteries via Zn and Cu double doping and multi-walled carbon nanotube composite integration(Elsevier B.V., 2024) Kumar, A.; Mukesh, P.; Lakshmi Sagar, G.; Hegde, A.; Nagaraja, H.S.In this study, a novel nanocomposite material comprising pure Fe3O4 (FO), doped Zn0.5Cu0.5Fe2O4-3 (ZCFO-3), and Zn0.5Cu0.5Fe2O4-3@ Multi-walled carbon nanotube (ZCFO-3@MWCNT) nanocomposite material is carefully prepared using a simple one-step hydrothermal process. Comprehensive surface and morphological analysis are conducted using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and High-resolution transmission electron microscopy (HRTEM), while compositional studies are investigated through Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The electrochemical performance is fully analyzed through Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), rate capability tests, discharge/charge capacity, and cyclic stability evaluations. Among these three nanomaterials, ZCFO-3@MWCNT nanocomposite at 100 mA g−1 current density reveals the best performance, with a discharge capacity of 1974 mAh g–1, ZCFO-3 and FO reveal 1340 mAh g–1 and 1317 mAh g–1 respectively. After 800 cycles at 500 mA g−1 current density, ZCFO-3@MWCNT stays strong with a discharge capacity of 646 mAh g–1, while ZCFO-3 manages only 362 mAh g–1 and FO only 111 mAh g–1. After 1200 cycles at 500 mA g−1, the nanocomposite still delivers 518 mAh g–1. This study suggests that ZCFO-3@MWCNT could be a promising anode material for lithium-ion batteries. © 2024 Elsevier B.V.