Faculty Publications
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Item [No abstract available](Springer Netherlands, Low cycle fatigue behavior of an (? + ?) titanium alloy) Nanjundaswamy, G.S.; Ramachandra, C.; Sengupta, P.K.; Chatterji, B.; Sudhakara Nayak, H.V.; Singh, A.K.1998Item Semiconducting thin films of cadmium telluride, both p-type and n-type, have been prepared by conventional thermal evaporation technique. The influence of various growth parameters such as the rate of deposition, deposition temperature, post-deposition heat treatment, and source material composition has been investigated. The films deposited at high deposition rates and low substrate temperatures exhibited an excess of tellurium and showed a p-type conductivity, whereas those deposited at high substrate temperature and low deposition rates contained excess cadmium and are n-type in nature. An intrinsic bandgap of 1.49 eV for stoichiometric films obtained by both electrical and optical characterization is reported.(Growth and characterization of vacuum deposited cadmium telluride thin films) Shreekanthan, K.N.; Kasturi, V.B.; Shivakumar, G.K.2003Item Electrical and magnetic properties of chitosan-magnetite nanocomposites(2010) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.Magnetite powders in nanometer size have been synthesized by the hydrothermal process. Various magnetic films of chitosan and the synthesized magnetite nanopowders containing different concentrations of the latter were prepared by ultrasonication route. The X-ray diffraction (XRD) studies and the transmission electron microscopy (TEM) images showed that the synthesized magnetite particles had 80 nm dimensions. The band gap of the composites was evaluated using the UV-visible Spectroscopy. The influence of magnetite content on the magnetic properties of the composite showed a decrease in the saturation magnetization with the decrease in the magnetic content. The effect of magnetite content on the dielectric properties of the polymer film at different frequencies from 0.01 to 105 Hz was studied using an electrochemical impedance spectroscopy. The possible mechanism for the observed electrical properties of the composite films was discussed. © 2010 Elsevier B.V. All rights reserved.Item 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.Item Chitosan/NiO nanocomposites: A potential new dielectric material(2011) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.; Tai, C.-W.The study of electrochemical behavior of organic-inorganic nanocomposite materials remains a major challenge for application in energy storage devices. Here, new composite materials of chitosan and NiO nanoparticles have been fabricated. The NiO nanoparticles are well characterized by infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The electrical properties of the films are studied by impedance spectroscopy at different temperatures; and thereby permittivity, electric modulus and conductivity data are obtained. By studying the variations in permittivity and electric modulus spectra with respect to applied frequency signal and temperature, the ionic conductivity of the material is investigated. The Correlated Barrier Hopping model is employed to understand the conduction mechanism. An admirable conductivity of 1.4 × 10-2 S cm -1 is obtained for a nanocomposite with 4 wt% NiO content. The activation energies of the composite films decrease with increase in NiO content, from 16.5 to 4.8 kJ mol-1. © 2011 The Royal Society of Chemistry.Item Characterization of poly(ethylene-co-vinyl acetate-co-carbon monoxide)/layered silicate clay hybrids obtained by melt mixing(2011) Anandhan, S.; Patil, H.G.; Babu, R.R.In recent times, polymer-layered silicate nanocomposites have drawn a great deal of attention because they often exhibit tremendous improvements in material properties compared with virgin polymers or conventional microor macro-composites. In the present study, nanocomposites were developed from organically modified clay and poly(ethylene-co-vinyl acetate-co-carbon monoxide) by melt mixing. FTIR spectroscopy reveals that the interaction between the organoclay and EVACO is thermodynamically favored. High resolution wide angle X-ray diffraction and transmission electron microscopy were used to study the morphology of the nanocomposites. Elemental mapping by scanning electron microscopy indicates good dispersion and distribution of the nanoclay in EVACO matrix. The mechanical properties of the nanocomposites are optimum at a clay loading of 3%. © Springer Science+Business Media, LLC 2011.Item Synthesis of worm-shaped carbon nanofibers over a sodium chloride support(2012) Ravindra, R.; Badekai Ramachandra, B.R.Worm-shaped carbon nanofibers (WCNFs) were synthesized in bulk by chemical vapour deposition at 680 °C using iron carboxylate as catalyst precursors and sodium chloride as catalyst support. The products were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction method. The purity of the purified products was determined by thermal analysis. TheWCNFyield was 6700% relative to catalyst. The simplicity, environmental friendliness and use of easily available low-cost precursors are the advantage of this synthesis technique. © Springer Science+Business Media B.V. 2012.Item 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.Item Synthesis of copper nanofluids using ascorbic acid reduction method via one step solution phase approach(2012) Shenoy, S.U.; Nityananda Shetty, A.N.A simple one step solution phase approach to synthesize copper nanofluids has been developed, involving simultaneous in situ synthesis of nanoparticles and their dispersion in the base fluid. Copper nitrate has been reduced using ascorbic acid in ethylene glycol under thermal as well as microwave conditions. Sodium lauryl sulfate has been used to control the size of the particle as well as to act as a stabilizing agent. The effect of ratio of the reactants, pH, power of microwave, reaction time, and dilution on the size of the particles has been studied using X-ray diffraction, transmission electron microscopy, and field-emission scanning electron microscopy. The characterization of the fluids has also been done using Fourier transform infrared spectrometry, ultraviolet-visible spectroscopy, selected area electron diffraction, and energy dispersive X-ray analysis. The thermal conductivity and viscosity of the fluid were also measured at various particle concentrations. The copper particles in the fluid were found to have size less than 50nm and were well dispersed in the fluid. Thus this method was found to preserve the advantages of the polyol process and aqueous chemical reduction method as well. The fluid was stable up to 5 weeks under stationary conditions at room temperature. This method employs fast, inexpensive, extendible process for the synthesis of copper nanofluids and also overcomes the drawbacks of two step process. Copyright © 2012 by ASTM International.Item Green approach to synthesize multi-walled carbon nanotubes by using metal formate as catalyst precursors(2013) Rajarao, R.; Badekai Ramachandra, B.The multi-walled nanotubes (MWNTs) have been synthesized in large scale by using metal formate as catalyst precursors. The calcium carbonate is used as catalyst support, it is chosen because of its non toxic and easily soluble nature. The synthesis was carried out by chemical vapor deposition method for 15 min under optimized conditions. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD) method. The purity of the as grown products and purified products were determined by thermal analysis. The obtained yield of MWNTs was about 8300 wt% relative to the nickel catalyst. This synthesis route avoids the lengthy process of calcination and reduction for the preparation of catalysts hence this method is more economical. This economical and environmental friendly synthesis route can be used for synthesizing MWNTs in large scale. Copyright © 2013 American Scientific Publishers All rights reserved.