Vijayawada, India
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Khelen A.C.,CSIR - Central Electrochemical Research Institute | Manikyamba C.,CSIR - Central Electrochemical Research Institute | Ganguly S.,Goa University | Singh T.D.,CSIR - Central Electrochemical Research Institute | And 3 more authors.
Precambrian Research | Year: 2017

Spectacular stromatolitic dolomites with varied morphological features are preserved in the Vempalle and Tadpatri Formations of the Proterozoic Cuddapah basin, eastern Dharwar Craton. They exhibit stratifera, columnar, conical, domal and spheroidal/lobate morphologies in which columns are branched at some places (in Tadpatri Formation). Based on their trace elements such as REY and stable isotope compositions (carbon and oxygen) the Vempalle stromatolites have been classified as three types. Vempalle I stromatolites exhibit pronounced positive Eu anomalies with small scale positive Ce anomalies whereas Vempalle II counterparts have slight negative to positive Eu, feeble positive Ce and positive Gd anomalies. Vemaplle III stromatolites display positive Ce, Eu and Gd anomalies. The Tadpatri Formation stromatolites have pronounced Gd anomalies with low order positive Ce and Eu anomalies. Significant depletion in δ18O is observed in Vempalle ranging from – 10.70‰ to −7.07‰ and 20.73‰ to −11.87‰ in Tadpatri Formations. The Tadpatri stromatolites display negative δ13C varying from −4. 56‰ to −1.26‰. Contrarily, the Vempalle stromatolites recorded both positive and negative δ13C ranging from −0.24‰ to 2.00‰ thereby reflecting their deviation from the popular belief of the boring billion concept of displaying Midproterozoic δ13C stasis. The flat REE patterns along with Ce, Eu and Gd anomalies, chondritic to superchondritic Y/Ho ratios collectively reflect on marine water conditions for their deposition with variable inputs of siliciclastic/terrigenous materials and hydrothermal signatures. These cherty dolomitic stromatolites were deposited in subtidal-intertidal-supratidal zones of a shallow shelf of Proterozoic open ocean under warm, alkaline and anoxic conditions. © 2017 Elsevier B.V.


Bala Karuna Kumar D.,Acharya Nagarjuna University | Rayapa Reddy K.,Acharya Nagarjuna University | Srinivasa Rao G.,Andhra Loyala College | Rama Rao G.V.,DAR College | Rambabu C.,Acharya Nagarjuna University
Journal of Chemical and Pharmaceutical Research | Year: 2011

The densities, viscosities and speeds of sound for the binary mixtures of N-methyl-2-pyrrolidone (NMP) with aniline (AB), bromobenzene (BB), and chlorobenzene (CB), over the entire composition range have been measured at T = (308.15, 318.15) K and atmospheric pressure. From these experimental values, excess free volume, excess internal pressure and deviations in acoustic impedance are computed and fitted to a Redlich-Kister type polynomial. The results are interpreted in terms of molecular interactions between the component molecules. Thermodynamic parameters under study suggest the existence of strong interactions between NMP and AB, or BB, or CB.


Govardhana Rao S.,St Marys Group Of Institutions Guntur | Madhu Mohan T.,Vasireddy Venkatadri Institute of Technology | Vijaya Krishna T.,Vasireddy Venkatadri Institute of Technology | Raju K.T.S.S.,Andhra Loyala College | Subba Rao B.,VSR & NVR College
Journal of Chemical Thermodynamics | Year: 2015

Density (ρ), refractive index (nD) and speed of sound (u) values are measured for the binary mixture of 1-butyl-3-methylimidazolium tetrafluoroborate and N-octyl-2-pyrrolidone over the entire range of mole fraction at temperatures from T = (298.15 to 323.15) K under atmospheric pressure. Using the basic experimental data, various acoustic and excess thermodynamic parameters are calculated and are discussed in terms of molecular interactions between the present investigated binary system. The excess values are fitted to Redlich–Kister polynomial equation to estimate the binary coefficients and standard deviation between the experimental and calculated values. Further, the molecular interactions in the binary mixture system are analysed using the experimental FT-IR spectrum recorded at room temperature. © 2015 Elsevier Ltd


Rao M.C.,Andhra Loyala College
Journal of Crystal Growth | Year: 2010

Thin films of LiCoO2 were prepared by pulsed laser deposition technique and the properties were studied in relation to the deposition parameters. The films deposited from a sintered composite target (LiCoO 2Li2O) in an oxygen partial pressure of 100 mTorr and at a substrate temperature of 300 °C exhibited preferred c-axis (0 0 3) orientation perpendicular to the substrate surface. The AFM data demonstrated that the films are composed of uniform distribution of fine grains with an average grain size of 80 nm. The grain size increased with an increase in substrate temperature. The (0 0 3) orientation decreased with increase in (1 0 4) orientation for the films deposited at higher substrate temperatures (>500 °C) indicating that the films' growth is parallel to the substrate surface. The composition of the experimental films was analyzed using X-ray photoelectron spectroscopy (XPS). The binding energy peaks of Co(2p 3/2) and Co(2p1/2) are, respectively, observed at 779.3 and 794.4 eV, which can be attributed to the Co3 bonding state of LiCoO2. The electrochemical measurements were carried out on Li//LiCoO2 cells with a lithium metal foil as anode and LiCoO 2 film as cathode of 1.5 cm2 active area using a Teflon home-made cell hardware. The Li//LiCoO2 cells were tested in the potential range 2.64.2 V. Specific capacity as high as 205 mC/cm2 μm was measured for the film grown at 700 °C. The growth of LiCoO 2 films were studied in relation to the deposition parameters for their effective utilization as cathode materials in solid-state microbattery application. © 2010 Elsevier B.V. All rights reserved.


Narendra K.,Vrsiddhartha Enggcollege | Narayanamurthy P.,Acharya Nagarjuna University | Srinivasu C.H.,Andhra Loyala College
E-Journal of Chemistry | Year: 2010

The ultrasonic velocity, density and viscosity in binary liquid mixture cyclohexane with o-xylene have been determined at different temperatures from 303.15 to 318.15 K over the whole composition range. The data have been utilized to estimate the excess adiabatic compressibility (βE), excess volumes (VE), excess intermolecular free length (LE f), excess internal pressure (πE) and excess enthalpy (HE) at the above temperatures. The excess values have been found to be useful in estimating the strength of the interactions in the liquid mixtures. Analysis of these parameters indicates that there are weak interactions among the components of the binary mixtures.


Reddy K.R.,Acharya Nagarjuna University | Kumar D.B.K.,Acharya Nagarjuna University | Rao G.S.,Andhra Loyala College | Sri P.B.S.,Dar College | Rambabu C.,Acharya Nagarjuna University
Fluid Phase Equilibria | Year: 2012

Consistent vapor-liquid equilibria (VLE) data at 95.3. kPa have been determined for the binary mixtures of N-methyl-2-pyrrolidone (NMP) +2-methoxyethanol (2-ME), +2-ethoxyethanol (2-EE), +2-butoxyethanol (2-BE) over the entire composition range using a Swietoslawski ebulliometer. The VLE data have been correlated by the Wilson model. The investigated binary systems show negative deviation from Raoult's law. None of the binary systems form maximum or minimum boiling point azeotropic mixtures. Also, densities of all three binary liquid mixtures over the entire mole fraction range are measured at 303.15, 308.15, 313.15, and 318.15. K using densimeter. Excess molar volumes are computed with variation in composition and temperature, and are correlated by the Redlich-Kister polynomial equation. The results of activity coefficients, excess Gibb's energies and excess molar volumes are correlated, and are discussed in terms of molecular interactions. Also, the effects of temperature and chain length of alkoxyethanols are studied and are discussed in terms of molecular interactions. © 2012 Elsevier B.V.


Rao M.C.,Andhra Loyala College
Journal of Optoelectronics and Advanced Materials | Year: 2011

Thin films of LiCoO2 were grown by pulsed laser deposition technique on silicon substrates. Microstructural properties were studied with respect to their deposition parameters i.e. substrate temperature (T s), oxygen partial pressure (pO2) and target composition in the deposition chamber. The atomic force microscopy (AFM) data demonstrated that the pulsed laser deposited LiCoO2 thin films are homogeneous and uniform with regard to the surface topography. For the film deposited at 300 °C in oxygen partial pressure of 100 mTorr (prepared from target with 15% Li2O) is composed of roughly spherical grains of varying sizes and the average grain size is estimated to be around 80 nm. The grain size increased with the increase of substrate temperature. SEM results supported the AFM data. The growth of LiCoO2 films were studied in relation to the deposition parameters for their effective utilization as cathode materials in solid state microbattery application.


Rao G.S.,Andhra Loyala College | Sudhakar B.K.,Andhra Loyala College | Prasanna H.N.L.,Andhra Loyala College | Devasahayam V.,Andhra Loyala College | Chand N.R.K.,Andhra Loyala College
Materials Letters | Year: 2011

Glasses in the system (40-x) CaF2-x ZnO-60 B2O 3with x=5, 10, 15, 20, 25, 30, 35 mol% are prepared by the melt quenching method. The structural changes in the glasses with the variation of ZnO content are studied by FTIR spectroscopy with special reference to structural units of borates. From the analysis of the deconvoluted IR spectra of the glasses the mechanism of the conversion and reconversion of BO 3↔BO4 units is explained using the concept of the borate structural units i.e., di-, tri-, tetra-, penta-, ortho-, pyro-and metaborates. © 2010 Elsevier B.V. All rights reserved.


Reddy K.R.,Acharya Nagarjuna University | Kumar D.B.K.,Acharya Nagarjuna University | Rao G.S.,Andhra Loyala College | Sairam P.V.S.,Andhra Loyala College | And 2 more authors.
Journal of Chemical and Engineering Data | Year: 2012

Isobaric vapor-liquid equilibrium (VLE) data is determined for the binary mixtures of N-methyl-2-pyrrolidone + aminoethanol, N-methyl-2-pyrrolidone + chloroethanol, and N-methyl-2-pyrrolidone + phenylethanol at 95.3 kPa over the entire composition range using a Swietoslawski type ebulliometer. All three systems investigated show negative deviations from Raoult's law, and none of the binary systems formed azeotropic mixtures. The experimental VLE data of the three binary mixtures are correlated using the Wilson model. The computed vapor phase mole fractions, activity coefficients, and Gibbs energy along with optimum Wilson parameters are presented. The studies indicate that all three binary systems are nonideal liquid mixtures deviating from Raoult's law exhibiting negative values of excess Gibbs energies due to strong intermolecular hydrogen bonding between unlike molecules. © 2012 American Chemical Society.


Karuna Kumar D.B.,Acharya Nagarjuna University | Reddy K.R.,Acharya Nagarjuna University | Rao G.S.,Andhra Loyala College | Rao G.V.R.,DAR College | Rambabu C.,Acharya Nagarjuna University
Journal of Molecular Liquids | Year: 2012

The densities and viscosities for pure liquids N-methyl-2-pyrrolidone (NMP), aniline (AB), bromobenzene (BB), chlorobenzene (CB) and their binary mixtures containing NMP as a common component have been measured at 303.15, 308.15, 313.15 and 318.15 K as a function of composition of NMP. From these results, excess molar volumes, excess Gibb's free energy of activation of viscous flow and deviations in viscosity are computed. Excess properties are fitted to a Redlich-Kister type equation and the corresponding standard deviations are calculated. The experimental data of viscosity is used to test the applicability of empirical relations of Grunberg-Nissan, Katti-Chaudhri, Heric-Brewer and Hind et al. for the systems studied. The excess molar volumes are found to be negative whereas the deviations in viscosity and excess Gibb's free energy of activation of viscous flow values are found to be positive for all the mixtures, over the entire composition range. Partial molar volumes and apparent molar volumes at infinite dilution have been calculated. The variation of these properties with composition of NMP and temperature is discussed in terms of molecular interactions between component molecules. The strength of interaction of AB, BB, CB with NMP is found to obey the order AB > CB > BB. The IR, spectral studies of these binary mixtures also suggest specific interaction between the unlike molecules of the components and supported thermodynamic findings. © 2012 Elsevier B.V.

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