Faculty Publications
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Item A simple, rapid and accurate complexometric method for the determination of palladium(II) is proposed, based on the selective masking property of thioacetamide towards palladium(II). In the presence of diverse metal ions, palladium(II) is complexed with excess of EDTA and the surplus EDTA is back titrated at pH 5-5.5(acetic acid-sodium acetate buffer) with standard lead nitrate solution using xylenol orange as indicator. An excess of a 0.5% aqueous solution of thioacetamide is then added to displace EDTA from Pd(II)-EDTA complex. The released EDTA is titrated with the same standard lead nitrate solution as before. Reproducible and accurate results are obtained in the concentration range 0.5mg-17.80mg of palladium with relative error of ±0.16% and coefficient of variation not exceeding 0.26%. The effect of diverse ions is studied. The method is used for the determination of palladium in its complexes, catalysts and synthetic alloy mixtures.(Complexometric determination of palladium(II) using thioacetamide as a selective masking agent) Parameshwara, P.; Karthikeyan, J.; Nityananda Shetty, A.N.; Shetty, P.2006Item 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 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.Item Investigation into creep behaviour of Sn-40%Pb alloy using impression creep method(2009) Udaya Prasanna, H.U.; Udupa, K.R.; Prabhu, K.N.The creep behaviour of Sn-40%Pb hypereutectic alloys cast in the molds made of different materials was investigated using impression creep technique in the temperature range from zero to 32 °C and under the punching stress of 50 MPa. The creep curves.ie, profiles of indentation depth against time are generated and steady state creep rates (SSCRs) are determined. Activation energy was calculated knowing creep rates at different temperature levels. Standard metallographic technique was used to determine the grain size of alloys which were poured into different molds. It was found that SSCR, at all the temperature levels of testing, is a function of grain size of the material. The activation energy being in the range of 10kJ/mol -12 kJ/mol, suggests that the probable creep mechanism is dislocation glide aided by vacancy diffusion. Results of the experiments are discussed.Item Finite element analysis of open die extrusion of al-5zn-1mg alloy; Analiza izguravanja legure al-5zn-1mg kroz otvoreni kalup pomo]u kon?nih elemenata(2009) Geethalakshmi, K.; Srinivasan, K.In this work, an effort has been made to study the open die extrusion of Al-5Zn-1Mg alloy using finite element analysis. The two basic parameters of open die extrusion, i.e., die included angle and the extrusion strain are varied to find the corresponding limiting strain values. Effect of main parameters on the open die extrusion is analyzed, and the limiting range of deformation is obtained. The results obtained are verified by means of contrasting with the experimental data. Pure open die extrusion is found to be possible for extrusion strain (relative strain during extrusion) up to 0.28. However, as the extrusion strain increases from 0.09 to 0.28, upsetting dominates over pure extrusion on varying the die angle from 12° to 40°.Item Electrolytic preparation of cyclic multilayer Zn-Ni alloy coating using switching cathode current densities(2010) Venkatakrishna, K.; Hegde, A.C.Cyclic multilayer alloy (CMA) coating of Zn-Ni was developed on mild steel using single bath technique, by proper manipulation of cathode current densities. The thickness and composition of the individual layers were altered precisely and conveniently by cyclic modulation of cathode current densities. Multilayer coatings, having sharp change in compositions were developed using square current pulses. Gelatin and sulphanilic acid (SA) acid were used as additives. Laminar deposits with different configurations were produced, and their corrosion behaviors were studied, in 5% NaCl solution by electrochemical methods. It was observed that the corrosion resistance of CMA coating increased progressively with number of layers (up to certain optimal numbers) and then decreased. Cyclic voltammetry study demonstrated the role of gelatin and SA in multilayer coating. The coating configuration has been optimized for the peak performance against corrosion. The substantial decrease of corrosion rate, in the case of multilayer coatings was attributed to the changed intrinsic electric properties, evidenced by Electrochemical Impedance Spectroscopy (EIS) study. The surface morphology and its roughness were examined by Atomic Force Microscopy (AFM). The surface and cross-sectional view of coatings were examined, using Scanning Electron Microscopy (SEM). X-ray photoelectron spectrum (XPS) study was carried out for surface analysis. The relative performance of pure Zn, monolithic and CMA coatings were compared and discussed. © 2010 Springer Science+Business Media B.V.Item Electrodeposition of high performance multilayer coatings of Zn-Co using triangular current pulses(2010) Yogesha, S.; Hegde, A.C.Compositionally modulated alloy (CMA) coatings of Zn-Co were electrodeposited on to mild steel from an acid chloride bath containing thiamine hydrochloride, as an additive. Electroplating was carried out galvanostatically from a single bath containing Zn2+ and Co2+ ions. Gradual change in composition in each layer was effected by triangular current pulses, cycling between two cathode current densities. Compositionally modulated alloy coatings were developed under different conditions of cyclic cathode current density and number of layers, and their corrosion resistances were evaluated by potentiodynamic polarisation and electrochemical impedance spectroscopy. The formation of multilayer and corrosion mechanism was analysed using scanning electron microscopy. The corrosion resistances of CMA and monolithic alloy coatings were compared with that of the base metal. Compositionally modulated alloy coating at optimal configuration, represented as (Zn-Co) 2•0/4•0/300, was found to exhibit ?80 times better corrosion resistance compared with monolithic (Zn-Co)3•0 alloy, deposited for the same length of time from the same bath. Improved corrosion resistance was attributed to the formation of n-type semiconductor film at the interface, supported by Mott-Schottky plots. Decrease in corrosion resistance at high degree of layering was found, and is due to lower relaxation time for redistribution of solutes in the diffusion double layer, during plating. © 2010 Maney Publishing.Item Spectrophotometric determination of platinum(IV) in alloys, complexes, environmental, and pharmaceutical samples using 4-[N,N-(diethyl)amino] benzaldehyde thiosemicarbazone(2010) Naik, P.P.; Karthikeyan, J.; Nityananda Shetty, A.N.4-[N,N-(Diethyl)amino] benzaldehyde thiosemicarbazone (DEABT) is proposed as an analytical reagent for the spectrophotometric determination of platinum(IV). The DEABT forms 1:2 yellow complex with Pt(IV), which is sparingly soluble in water and completely soluble in water-ethanol-DMF medium. The Pt(IV)-DEABT complex shows maximum absorbance at 405 nm. Beer's law is valid up to 7.80 ?g cm-3, and optimum concentration range for the determination of platinum(IV) is 0.48-7.02 ?g cm-3. The molar absorptivity and Sandell's sensitivity of the method are found to be 1.755 × 104 dm3 mol-1 cm-1 and 0.0012 ?g cm-2, respectively. The relative error and coefficient of variation (n=6) for the method does not exceed ±0.43% and 0.35%, respectively. Since the method tolerates a number of metal ions commonly associated with platinum, it can be employed for the determination of platinum in environmental samples, pharmaceutical samples, alloys, catalysts, and complexes. The method is rapid as the Pt(IV)-DEABT complex is soluble in water-ethanol-DMF medium and not requiring any time consuming extraction method for the complex. © 2010 Springer Science+Business Media B.V.Item Composition modulated multilayer Zn-Fe alloy coatings on mild steel for better corrosion resistance(2011) Venkatakrishna, K.; Hegde, A.C.Composition modulated alloy (CMA) of Zn-Fe coatings were developed on mild steel galvanostatically from chloride bath containing sulphanilic acid (SA) and ascorbic acid (AA) through single bath technique (SBT). The properties of CMA coatings were found to depend on the thickness of individual layers and switching cathode current densities (SCCDs). The CMA (Zn-Fe) coating, having 120 layers, deposited at 20 and 50mAcm-2, were found to show the least corrosion rate (1.545 × 10-2mmy-1) compared to monolithic alloy (32.5 × 10-2mmy-1) of the same thickness. The improved corrosion resistance of multilayered coatings was due to the fact that the defects and failures occurring in a single layer in the deposition process is covered by the successively deposited coating layers, and hence the corrosive agent path is extended or blocked. Further, the high corrosion resistance of CMA Zn-Fe coatings was attributed to the "dielectric barrier" of the coatings, evidenced by dielectric spectroscopy and Mott-Schottky's plot. The corrosion rate was found to increase at high degree of layering, and is attributed to less relaxation time for redistribution of metal ions in diffusion layer, during plating. In other words, at higher layer thickness, the CMA coating tends to become a monolithic. CMA coatings were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). © Taylor & Francis Group, LLC.Item Analytical properties of p-[N,N-bis(2-chloroethyl)amino]benzaldehyde thiosemicarbazone: Spectrophotometric determination of palladium(II) in alloys, catalysts, and complexes(2011) Karthikeyan, J.; Parameshwara, P.; Nityananda Shetty, A.N.p-[N,N-bis(2-chloroethyl)amino]benzaldehyde thiosemicarbazone (CEABT) is proposed as a new, sensitive, and selective analytical reagent for the spectrophotometric determination of palladium(II). The reagent reacts with palladium(II) in the pH range 1-2 to form a yellow-colored complex. Beer's law is obeyed in the concentration range up to 2.64 ?g cm-3. The optimum concentration range for minimum photometric error as determined by Ringbom's plot method is 0.48-2.40 ?g cm-3. The yellowish Pd(II)-reagent complex shows a maximum absorbance at 395 nm, with molar absorptivity of 4.05 × 104 dm3 mol-1 cm-1 and Sandell's sensitivity of the complex from Beer's data, for D= 0.001, is 0.0026 ?g cm-2. The composition of the Pd(II)-CEABT reagent complex is found to be 1:2 (M-L). The interference of various cations and anions in the method were studied. The proposed method was successfully used for the determination of Pd(II) in alloys, catalysts, complexes, water samples, and synthetic alloy mixtures with a fair degree of accuracy. © 2010 Springer Science+Business Media B.V.