Faculty Publications

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    Modelling for organics and nutrients release during Benthal sludge stabilisation : Part I -organics
    (2008) Bhargava, D.S.; Shrihari, S.
    Settleable solids in the untreated and partially treated domestic and industrial effluents discharged into a river system undergoes settling and decomposition in the form of benthal sludge deposits, Early models of biochemical oxygen demand (BOD) assimilation in rivers do not account for the BOD contribution by these benthal sludge deposits. In this paper, a model for computations of the BOD contribution by benthos (both from the top aerobic layers and the leached portion of BOD from the bottom anaerobic layers) was presented. Observations from three sets of experiments at the chosen overlying water flow rates (500 ml/min, 1000ml/ min and 1500 ml/min) show a higher BOD contribution by benthos at higher overlying water flow rates. The ratio of the BOD contributions by benthos to the volatile solids in the top aerobic layers was lower when compared to the similar ratio in respect of the bottom layer volatile solids showing that a higher contribution was made by the top layers.
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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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    Development of nano-structured cyclic multilayer Zn-Ni alloy coatings using triangular current pulses
    (2011) Bhat, R.S.; Hegde, A.C.
    Cyclic multilayer alloy (CMA) deposits of Zn-Ni were developed on mild steel from sulphate bath having thiamine hydrochloride (THC) and citric acid (CA) as additives. CMA coatings were developed galvanostatically using triangular current pulses, under different conditions of cyclic cathode current density (CCCD's) and number of layers. The corrosion behaviors of the coatings were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy methods, and were compared with that of monolayer Zn-Ni alloy of same thickness. At optimal configuration, CMA coating represented as, (Zn-Ni)2.0/5.0/300 was found to exhibit ?40 times better corrosion resistance compared to monolayer alloy, (Zn-Ni)3.0. Cyclic voltammetry study demonstrated that THC and CA have improved the appearance of the deposit by complexation with metal ions. The corrosion protection efficacy of CMA coatings was attributed to the difference in phase structure of the alloy in successive layers, evidenced by XRD analysis. The formation of multilayer and corrosion mechanism was analyzed by Scanning Electron Microscopy (SEM) study. © 2011 Allerton Press, Inc.
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    Corrosion stability of electrodeposited cyclic multilayer Zn-Ni alloy coatings
    (2011) Bhat, R.S.; Udupa, K.R.; Hegde, A.C.
    This paper reports on a study of electrodeposition and characterisation of cyclic multilayer coatings of Zn-Ni alloy from a sulphate bath. Cyclic multilayer alloy coatings were deposited on mild steel through the single bath technique by appropriate manipulation of cathode current densities. The thickness and composition of the individual layers of the CMA deposits were altered precisely and conveniently by cyclic modulation of the cathode current during electrodeposition. Multilayer deposits with sharp change in composition were developed using square current pulses, using thiamine hydrochloride and citric acid as additives. Laminar deposits with different configurations were produced and their corrosion behaviours were studied by AC and DC methods in 5%NaCl solution. It was observed that the corrosion resistance of the CMA coating increased progressively with the number of layers (up to certain optimal numbers) and then decreased. The decrease in corrosion resistance at high degree of layering was attributed to interlayer diffusion due to less relaxation time for redistribution of metal ions at cathode during deposition. The coating configurations have been optimised for peak performance of the coatings against corrosion. It was found that CMA coating developed at cyclic cathode current densities of 3.0/5.0 A dm-2 with 300 layers showed the lowest corrosion rate (0.112×10-2 mm/year) which is ?54 times better than that of monolithic Zn-Ni alloy, deposited from the same bath. The protection efficacy of CMA coatings is attributed to the difference in phase structure of the alloys in successive layers, deposited at different current densities, evidenced by X-ray diffraction analysis. The formation of multilayers and corrosion mechanism were examined by scanning electron microscopy. © 2011 Institute of Metal Finishing.
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    Effect of surfactant on high capacitance of galvanostatically deposited MnO2
    (Elsevier B.V., 2012) Suhasini; Hegde, A.
    Manganese dioxide has been galvanostatically deposited on stainless-steel substrate from an aqueous acidic solution of manganese sulphate (1 M) in presence of a surface active agent (surfactant), namely, sodium lauryl sulphate (SLS), for supercapacitor applications. The deposits have been developed under different conditions of SLS and their specific capacitance is measured by cyclic voltammetry (CV) and also by galvanostatic charge/discharge cycle. The oxide film (?0.1 mg cm-2) anodized from the manganese solution at 2.0 mA cm-2 has shown the highest specific capacitance of 255.8 F g -1, at scan rate of 10 mV s-1. It is observed that the capacitance increased by about 40% compared to the oxide prepared in the absence of SLS. Improved specific capacitance is due to the effect of the surfactant molecules in the deposit, causing high surface area of the deposit. The deposit is found to display good cycleability, even up to 1500 cycles. The structure and surface morphology of the deposits have been studied by means of X-ray diffraction (XRD) analysis and Scanning Electron Microscopy (SEM). XRD study reveals that crystallinity of the deposit with SLS remains unchanged, both are amorphous in nature. The surface area of the deposit is found to increase considerably due to the effect of SLS, as evident by SEM study.© 2012 Elsevier B.V. All rights reserved.
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    Magnetron sputtered MoO3/carbon nanotube composite electrodes for electrochemical supercapacitor
    (Elsevier B.V., 2013) Aravinda, L.S.; Nagaraja, K.K.; Bhat, K.; Badekai Ramachandra, B.
    Molybdenum oxide (MoO3) has been deposited on multiwalled carbon nanotubes (MWCNTs) using DC reactive magnetron sputtering of molybdenum for supercapacitor applications. The deposits of MoO3 have been developed under different intervals of time. The structure and surface morphology of the deposits have been characterized by means of X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM). X-ray diffraction peaks of the composite films reveal the formation of crystalline structure of MoO3. The electrochemical performance of the composite films was studied using cyclic voltammetry (CV), galvanostatic charge discharge and electrochemical impedance spectroscopy measurements. The composite film exhibits maximum specific capacitance of 70 F g-1 at a scan rate of 10 mV s-1 in 1 M Na2SO4 electrolyte. The nanocomposite electrode material shows specific capacitance which is almost four fold increase with respect to that of bare MWCNTs. The effect of coating duration on specific capacitance has been studied. The nanocomposite film is found to display good cycleability, even up to 1000 cycles. © 2013 Elsevier Inc. All rights reserved.
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    Influence of substrate temperature and post deposition annealing on the properties of vacuum deposited ZnSe thin films
    (2013) Rao, K.; Bangera, K.V.; Shivakumar, G.K.
    The effects of substrate temperature and post deposition annealing on the structural, optical and electrical properties of vacuum deposited ZnSe thin films are presented here. The chemical composition of the films varied drastically with substrate temperature which in turn caused changes in various properties of the films. The grain size of the films increased with substrate temperature and also after annealing. The electrical properties of the films were found to be varying as a function of chemical composition and grain size. © 2012 Elsevier Ltd.
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    Electrofabrication of multilayer Fe-Ni alloy coatings for better corrosion protection
    (Springer Verlag service@springer.de, 2014) Ullal, Y.; Hegde, A.C.
    Electrofabrication of multilayer Fe-Ni alloy coatings were accomplished successfully on mild steel and their corrosion behaviors were studied. Multilayer comprised of alternatively formed 'nano-size' layers of Fe-Ni alloy of different composition have been produced from a single bath having Fe 2+and Ni2+ ions using modulated (i.e. periodic pulse control) current density (cd). The deposition conditions were optimized for both composition and thickness of individual layers for best performance of the coatings against corrosion. The deposits were analyzed using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Hardness Tester, electrochemical AC and DC methods respectively. The multi layered deposits showed better corrosion resistances compared to the monolayer Fe-Ni (CR = 3.77 mm year-1) coating deposited using DC from the same bath; the maximum corrosion resistance being shown by the coating having 300 layers, deposited at cyclic cathodic current densities of 2.0 and 4.0 A dm-2 (CR = 0.03 mm year-1). Drastic improvement in the corrosion performance of multilayer coatings were explained in the light of changed kinetics of mass transfer at cathode and increased surface area due to modulation and layering. © 2014 Springer-Verlag Berlin Heidelberg.
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    A geological and geotechnical investigation of some rocks in Trivandrum area, Kerala, India
    (CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2015) Anand, R.S.; Venkat Reddy, D.
    In the Indian stone industry, possessing huge reserves of about 1,690 million cum dimensional stone deposits, geological and geotechnical parameters of commercial rock deposit plays a significant role in the economic exploitation of quality commercial rock deposits. The success of the commercial stone industry solely depends upon the availability of large reserves of defect free raw materials. An attempt is made here to study the geological and geotechnical properties of different rocks from Trivandrum area, Kerala. A variety of rock samples from different parts of Trivandrum are subjected to study petrographic, physical and strength parameters. Geological studies reveals that inherent geological discontinuities in rock deposits like multiple joints, weathering, foliations and variations in color of the rocks etc. lead to huge wastage of resources, because such rocks are not suitable for any engineering purpose. The geotechnical studies conducted gives an idea about the physical and strength properties of the rocks. The result of the study gives the rock which has maximum favorable properties for use in construction engineering applications, out of the available ones in the study area. © 2015 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
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    An Alternative Method to Estimate Fundamental Period of Layered Soil Deposit
    (Springer India sanjiv.goswami@springer.co.in, 2015) Vijayendra, K.V.; Nayak, S.; Prasad, S.K.
    There are several approximate methods available for the estimation of fundamental period of layered soil deposits. Approximate methods based on weighted average of shear wave velocities of the layered soil profile are most widely employed in practice. On the other hand, methods which are more accurate are tedious and iterative in procedure; hence they are unpopular for quick estimation of fundamental period of soil deposits. A new method for computing the fundamental period of multilayered soil deposit is proposed in the present study. In this method, layered shear wave velocity profile is replaced with an equivalent linearly varying profile. Subsequently, based on analytical solution for fundamental period of the deposit with linearly varying shear wave velocity profile, an equation to estimate the fundamental period of the actual layered soil deposit is proposed. The efficiency of the proposed method and other available methods is relatively verified by comparing their results with values computed from recorded earthquake accelerograms of instrumented geotechnical downhole arrays. This comparative study, establishes accuracy and consistency of the proposed method vis-à-vis exact methods. © 2014, Indian Geotechnical Society.