Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
83 results
Search Results
Item Simulation study of Borda's profile & parallel plane electrode to assess electric field uniformity(Institute of Electrical and Electronics Engineers Inc., 2003) Punekar, G.S.; Thejovathi, G.; Kishor, N.K.The electrode gaps which results in to uniform electric fields are the most widely used gap configurations in assessing dielectric strength. In the present study simulation results of two electrode gap configurations namely, parallel plane profile and Borda's profile are reported. The charge simulation method (CSM) is used to compute electric fields with errors in simulation being less than 0.04% (in potential). In order to assess the uniformity in electric field in the gap, numerical experiments are conducted by varying parameters like gap spacing, overall radius. Computed electric fields on the surface of the electrode help in comparing non-uniformity in electric fields for the two electrode configurations. Simulation results indicate that for the same overall dimension of the electrode and the gap spacing, parallel plane electrode gives lower non-uniformity factor when compared to the Borda's profile is that the maximum field on the electrode occurs at the edge of the electrode, which is away from the region of interest. Where as the maximum field in case of a plane electrode occurs at the edge of the linear portion of plane profile. Also looking at the field distribution along the gap axis indicates that Borda's profile yields more uniform fields. © 2003 Society of EMC Engineers.Item Activated carbon-polyethylenedioxythiophene composite electrodes for symmetrical supercapacitors(2008) Muthu, M.S.; Bhat, D.K.A symmetrical (p/p) supercapacitor has been fabricated by making use of activated carbon (AC)-poly-ethylenedioxythiophene (PEDPT)-composite electrodes for the first time. The composite electrodes have been prepared via electrochemical deposition of ?-napthalenesulphonate doped PEDPT onto AC electrodes. The characteristics of the electrodes and the fabricated supercapacitor have been investigated using cyclic voltammetry (CV) and AC impedance spectroscopy. The electrodes show a maximum specific capacitance of 158 Fg-1 at a scan rate of 10 mV s_1. This indicates that the in situ electro-polymerization of ethylenedioxythiophene (EDPT) onto AC could improve the performance of carbon electrodes for use in supercapacitors. © 2007 Wiley Periodicals, Inc.Item An analytical method to determine the response of a micro capacitive pressure sensor(2011) Simha, A.; Kulkarni, S.M.; Meenatchi Sundaram, S.The response of a capacitive pressure sensor is generally represented by a fourth order partial differential equation which is complex to solve and does not possess an exact solution. Several attempts have been made earlier through various techniques such as the Galerkin method, Finite Difference Method etc. In this paper an attempt has been made to develop a simple approximate analytical approach to determine the response of a capacitive pressure sensor whose diaphragm is designed to undergo very small deflections (typically less than 25 % of the thickness). The nonuniform gap between the electrodes is mathematically expressed as a combination of the initial gap between the electrodes (in the undeformed state) and a displacement function in (x, y). The proposed displacement function is then utilized in evaluating the capacitance as a function of the applied pressure. The results obtained from the analytical approach are benchmarked against those obtained from COMSOL Multiphysics®, a popular Finite Element Analysis tool in the MEMS industry. It is observed that the results obtained from COMSOL Multiphysics® and those from the analytical approach are in good agreement with a maximum deviation of about 3.38 %. © 2011 IFSA.Item Magnetically induced electrodeposition of Zn-Ni alloy coatings and their corrosion behaviors(Elsevier B.V., 2013) Rao, V.R.; Bangera, K.V.; Hegde, A.C.The less magnetic features of Zn-Ni alloy compared to Fe-Ni and Fe-Co alloys made it interesting to develop them under the influence of applied magnetic field. In this regard, the effects of a magnetic field (B) applied in a direction parallel and perpendicular to the nominal current, during electrodeposition process of Zn-Ni alloy have been investigated by means of X-ray diffraction and EDX analysis. The modification of crystal orientation by superimposition of a varying magnetic field is studied for alloys of constant nickel content (8 a %.), deposited at optimal current density (j) of 3.0 A dm-2. The effect of magnetic field on crystallographic orientation and hence the corrosion behaviors of the coatings were studied. The preferential orientations (101) and (002) of the zinc phase and (330) ?-Ni 5Zn21 phase are always favored to exist with parallel and perpendicular magnetic field. The preferential (321) ?-Ni 5Zn21 orientation is found to be the characteristic of perpendicular magnetic field. Further, Zn (100) orientation is found to be non-responsive to the effect of parallel magnetic field. The coatings developed using perpendicular magnetic field is more corrosion resistant compare to that for parallel magnetic field. This is attributed to the additional (321) ?-Ni5Zn21 orientations. The changes in the phase structure of the coatings deposited at different magnetic field are attributed to the effect caused by the magnetic convection induced in the electrolytic solution, called MHD effect (magneto-hydrodynamic effect). The chemical composition of the alloy was found to be same in both natural and magnetically induced deposition due to constant Ni content in the bath. The variation in the surface morphology of the coatings was studied by scanning electron microscopy (SEM). The Zn-Ni alloy coating deposited at 0.8 T perpendicular B showed the highest corrosion resistance (with corrosion rate=0.26 × 10-2 mm y-1) compared to the one with no B (corrosion rate = 14.46 × 10-2 mm y-1). The improved corrosion resistance of the coatings was discussed in the light of magnetic field effect on crystallographic orientation. © 2013 Elsevier B.V. All rights reserved.Item Defluoridation of fresh water using the process of Electrocoagulation combined with Adsorption(2013) Wali, A.; Saidutta, M.B.In India, fluoride is the major inorganic pollutant of natural origin found in groundwater. Fluoride pollution occurs due to natural and manmade reasons and high concentrations have a detrimental effect on health. Electrochemical techniques like Electrocoagulation(EC) appears to be one of the most effective approaches for treatment of water and wastewater because of its versatility, safety, selectivity, amenability to automation and environmental compatibility. Results show that the percentage removal of fluoride was around 94 to 96% for monopolar and bipolar electrodes. Adsorbents like tricalcium phosphate and activated alumina used along with electrocoagulation process also gave promising results. © 2013 CAFET-INNOVA TECHNICAL SOCIETY.Item Electrodeposition and electro-catalytic study of nanocrystalline Ni-Fe alloy(Elsevier Ltd, 2014) Ullal, Y.; Hegde, A.C.This paper presents the electrodeposition protocol for development of a stable, inexpensive and efficient electrode material for water splitting reaction. Nanocrystalline Ni-Fe alloy coatings were deposited on copper electrode from acidic bath, at different cathode current densities (c.d). Coatings were tested for their electro-catalytic behaviours, namely for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 6 M KOH by cyclic voltammetry and chrono-potentiometry techniques. Experimental results demonstrated that these coatings can be used as potential material for water electrolysis. The corrosion stability of these coatings has also been tested in their working conditions (6 M KOH) by DC polarization method. The deposition conditions of Ni-Fe alloy were optimized for peak performance for both electro-catalytic reactions and corrosion stability. Ni-Fe alloy coatings deposited towards low and high c.d limits were found to be the better materials for OER and HER, respectively from same electrolytic solution. Further, Ni-Fe coating deposited at 6.0 Ad m-2 was found to be the most corrosion resistant. The structure-property relationship of electrodeposited coatings has been discussed by exploring PXRD, EDX and FESEM study. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Item Novel Co-Ni-graphene composite electrodes for hydrogen production(Royal Society of Chemistry, 2015) Subramanya, B.; Ullal, Y.; Shenoy, S.U.; Bhat, D.; Hegde, A.C.Active, stable and cost-effective electrocatalysts are key to water splitting for hydrogen production through electrolysis. Herein, we report the facile preparation of highly porous Co-Ni-graphene (Co-Ni-G) composite electrodes by electrodeposition for electrocatalytic applications. The incorporation of graphene into the Co-Ni matrix enhances the catalyst's activity for the hydrogen evolution reaction (HER) in an alkaline solution. The best coating exhibits a maximum current density of -850 mA cm-2 at -1.6 V, which is approximately 4 times better than that of the binary Co-Ni alloy indicating higher activity for hydrogen production. The addition of graphene to an electrolyte bath results in a porous encapsulated bundle of alloy nano-particles within the graphene network which effectively increases the electrochemically active surface area. As indicated by XPS analysis results, on addition of graphene the Co(0) and Ni(0) content in the deposit increases and as a result both cobalt/cobalt oxide and nickel/nickel oxide sites are evenly distributed on the Co-Ni-G electrode surface which is responsible for increased HER activity. The Tafel slope analysis showed that the HER follows a Volmer-Tafel mechanism. The structure-property relationship of the Co-Ni-G composite coating has been discussed by interpreting field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis results. © The Royal Society of Chemistry 2015.Item Novel eco-friendly synthesis of graphene directly from graphite using 2,2,6,6-tetramethylpiperidine 1-oxyl and study of its electrochemical properties(Elsevier B.V., 2015) Subramanya, B.; Bhat, D.K.Herein we report a simple, low cost, highly efficient and environment friendly one-pot method for the high throughput synthesis of graphene directly from graphite using 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and H2O2 under microwave irradiation. The formation mechanism of graphene nanosheets (GNS) as investigated by Raman spectroscopy and electron microscopy techniques reveal surface defect generation, intercalation and exfoliation as the main steps. The rapid and local Joule heating of graphite by microwave radiation results in simultaneous deoxygenation and exfoliation forming GNS. The as-synthesized GNS are a few layer thick with a high surface area of 937.6 m2 g-1 and a high C/O ratio of 9.2. These results open the perspective of replacing toxic oxidizing and reducing agents by environment friendly chemicals of similar efficacy, thus facilitating the large-scale production of GNS by a greener method. Furthermore, GNS exhibits good electrochemical performance with a large specific capacitance (197 F g-1), excellent rate capability and a long cycle life (1000 cycles) in neat 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte. It also has a high energy density of 76.03 W h kg-1 while simultaneously possessing a high power density of 1.12 kW kg-1. © 2014 Elsevier B.V.Item Novel Fe-Ni-Graphene composite electrode for hydrogen production(Elsevier Ltd, 2015) Badrayyana, S.; Bhat, D.K.; Shenoy, U.S.; Ullal, Y.; Hegde, A.We have developed a novel, efficient and economical composite electrode for hydrogen production. The electrode has been formed by embedding graphene in the Fe-Ni matrix via room temperature electrodeposition. The obtained active coatings have been tested for their efficiency and performance as electrode surfaces for hydrogen evolution reaction (HER) in 6 M KOH by cyclic voltammetry and chronopotentiometry techniques. The coating obtained at 60 mA cm-2 exhibited approximately 3 times higher activity for hydrogen production than that of binary Fe-Ni alloy. Addition of graphene to electrolyte bath resulted in porous 3D projections of nano-sized spheres of Fe-Ni on the surface of graphene, which effectively increased the electrochemically active surface area. XPS analysis results showed the equal distribution of both Ni metal and NiO active sites on the composite. The addition of graphene favoured the deposition of metallic nickel, which accelerated the rate determining proton discharge reaction. All these factors remarkably enhanced the HER activity of Fe-Ni-Graphene (Fe-Ni-G) composite electrode. The Tafel slope analysis showed that the HER follows Volmer-Tafel mechanism. The structure-property relationship of Fe-Ni-G coating has been discussed by interpreting field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis results. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Item Electrolytic Synthesis and Characterization of Electrocatalytic Ni-W Alloy(Springer New York LLC barbara.b.bertram@gsk.com, 2015) Elias, L.; Scott, K.; Hegde, A.Inspired by the more positive (about 0.38 V nobler) discharge potential of hydrogen on Ni-W alloy compared to that on both Ni and W, a Ni-W alloy has been developed electrolytically as an efficient electrode material for water electrolysis. The deposition conditions, for peak performance of the electrodeposits for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH medium have been optimized. Electrocatalytic activity of the coatings, deposited at different current densities (c.d.’s) for water splitting reactions of HER and OER was tested by cyclic voltammetry and chronopotentiometry. It was found that Ni-W alloys deposited, at 4.0 A/dm2 (having about 12.49 wt.% W) and 1.0 A/dm2 (having about 0.95 wt.% W) are good electrode materials as cathode (for HER) and anode (for OER), respectively. A dependency of the electrocatalytic activity for HER and OER with relative amount of Ni and W, in the deposit was found. The variation of electrocatalytic activity with W content showed the existence of a synergism between high-catalytic property of W (due to low hydrogen overvoltage) and Ni (having increased adsorption of OH? ions), for hydrogen (as cathode) and oxygen (as anode) evolution, respectively. Electrocatalytic activities of the coatings, developed at different c.d.’s were explained in the light of their phase structure, surface morphology, and chemical composition, confirmed by XRD, FESEM, and EDX analysis. The effect of c.d. on thickness, hardness, composition, HER, and OER was analyzed, and results were discussed with possible mechanisms. © 2015, ASM International.