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Vijayawada, India

Kumar D.B.K.,Acharya Nagarjuna University | Reddy K.R.,Acharya Nagarjuna University | Rao G.S.,Andhra Loyala College | Sandhyasri P.B.,DAR College | And 2 more authors.
Journal of Molecular Liquids | Year: 2013

The ultrasonic speed (U) studies are carried out using single crystal variable path fixed frequency (2 MHz) ultrasonic interferometer on some aliphatic esters in N-methyl-2-pyrrolidone (NMP) at temperatures of 303.15, 308.15, 313.15 and 318.15 K. Excess molar volume, excess isobaric thermal expansion coefficient, excess isentropic compressibility and excess ultrasonic speed are computed from the experimentally measured ultrasonic speeds and densities of pure liquids NMP, methyl acetate (MA), ethyl acetate (EA), butyl acetate (BA) and their binary mixtures over the entire range of composition of NMP. The variation of these properties with composition and temperature of the binary mixtures is discussed in terms of molecular interactions of component molecules. The excess parameters are fitted to a Redlich-Kister type polynomial and the corresponding standard deviations are calculated. Thermodynamic parameters under study suggest the existence of strong interactions between NMP and aliphatic esters. The experimental data of viscosity is used to test the applicability of empirical relations of Grunberg-Nissan, Katti-Chaudhri, Heric-Brewer and McAllister for the systems studied. Also, ultrasonic speeds are theoretically evaluated based on scaled particle theory and compared with the experimentally measured values. The study reveals a close agreement between experimental and theoretical values of ultrasonic speed of these mixtures at all the temperatures under study. An attempt is made to study the temperature effect on the shapes of the interacting molecules in the binary liquid mixture using scaled particle theory in the temperature range 303.15-318.15 K. © 2013 Elsevier B.V. Source


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. Source


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. Source


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. Source


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. Source

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