Technical Physics and Prototype Engineering Division

Mumbai, India

Technical Physics and Prototype Engineering Division

Mumbai, India
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Sawant S.N.,Chemistry Division | Kulshreshtha S.K.,Chemistry Division | Yakhmi J.V.,Technical Physics and Prototype Engineering Division | Doble M.,Indian Institute of Technology Madras | And 2 more authors.
Thin Solid Films | Year: 2010

Langmuir-Blodgett (LB) films of an ethylenedithiotetrathiafulvalene (EDT-TTF) derivative containing hydroxyl groups, 4, 5-bis(11-hydroxyundecylthio) -4′, 5′-ethylenedithiotetrathiafulvalene were deposited without using stabilizer molecules. Doping of the film with iodine leads to oxidation of EDT-TTF moiety as evidenced by UV-vis and IR spectroscopy. X-ray diffraction studies reveal the presence of layered arrangement of the EDT-TTF derivative molecules in the LB film. Cyclic voltammetry studies indicate that the electrochemical oxidation of the EDT-TTF derivative in its LB film is irreversible. Due to the insulating nature of the alkyl chains, only the first layer of the LB film was found to be redox-active. The electrical conductivity of the 25 layer LB film was found to increase by two orders of magnitude on doping with iodine. On equilibrating the doped film in air, the conductivity gradually reduced with time and finally reached the conductivity of undoped film. This reversibility could be because of the steric hindrance induced by the two long alkyl groups. The alkyl chains help in rendering the EDT-TTF molecule amiable to LB film formation but are found to reduce the electrical conductivity of the films and also cause instability of the doped state. The hydroxyl groups at the end of the alky chain impart amphiphilic nature to the molecules and help in stabilizing the film at the air-water interface. © 2010 Elsevier B.V. All rights reserved.

Goutam U.K.,Technical Physics and Prototype Engineering Division | Sen S.,Technical Physics and Prototype Engineering Division | Jagannath,Technical Physics and Prototype Engineering Division | Singh A.K.,Technical Physics and Prototype Engineering Division | And 4 more authors.
International Journal of Nanoscience | Year: 2011

Co-doped SnO2 nanowires were grown by thermal evaporation of a mixture of Tin metal powder and CoCl2 · 6H2O in a tubular furnace. The growth occurs by vaporsolid growth mechanism. Nanowires grew along the sidewall of the alumina boat placed in the tubular furnace and the diameter of these nanowires (as was evident from scanning electron microscopy), was found to be in the range of 50 nm to 200 nm. Co was successfully doped in SnO2 lattice as revealed by X-ray diffraction data and was found to be in Co2+ state in the nanowires as detected by X-ray Photoelectron Spectroscopy measurements. Room temperature magnetic measurements, carried out using Vibrating Sample Magnetometer, indicated ferromagnetic behavior of the nanowires indicating their potential for spintronics applications. With increasing Co doping (upto 1%), the lattice parameters of SnO2 decreased and the saturation magnetization increased, suggesting a strong structure-magnetic property relationship. © 2011 World Scientific Publishing Company.

Mohan R.,Barkatullah University | Singh K.,Barkatullah University | Kaur N.,Barkatullah University | Kumar N.,Barkatullah University | And 5 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2010

The superconducting properties of RuSr 2GdCu 2O 8 (Ru-1212) superconductor strongly depend on the processing conditions. In this report we have made an investigation on the influence of processing method and heat treatments on the superconducting properties, as well as normal state resistivity of RuSr 2GdCu 2O 8 (Ru-1212) compound. The samples were prepared using solidstate reaction of high purity oxides and carbonates of constituents cations through direct method, precursor method, and standard method used for the synthesis of Ru-1212 compounds. These samples were then subjected to different annealing treatments in different atmosphere (oxygen and air) for 120 h. They have been investigated by X-ray diffraction, dc resistivity and scanning electron microscopy. The normal state resistivity has been studied on the basis of various conduction mechanisms. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patil S.S.,University of Pune | Koiry S.P.,Technical Physics and Prototype Engineering Division | Aswal D.K.,Technical Physics and Prototype Engineering Division | More M.A.,University of Pune
AIP Conference Proceedings | Year: 2010

The gold-polyaniline nanocomposite was synthesized by electrochemical route in two steps. In the first step polyaniline film was deposited by cyclic voltammetry on the ITO coated glass substrate, and then synthesis of gold-polyaniline nanocomposite via chronoamperometry. The synthesized gold-polyaniline nanocomposite film was characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), Ultra-violet spectroscopy (UV-vis) and Fourier Transform Infrared Spectrometry (FTIR). The SEM analysis shows well adherent gold nanoparticles on the surface of polyaniline nanofibers. The XRD and UV-Vis spectra indicate formation of gold nanoparticles. From the field emission studies, the value of the turn on field, corresponding to 1 nA emission current, is found to be 0.65 V/μm and emission current density of 1 μA/cm 2 has been drawn at an applied field of 1.1 V/μm. These values are observed to be superior than the reported ones. The field emission current stability investigated at 1 μA over duration of more than four hours is found to be good. The observed field emission characteristics suggest the gold polyaniline nanocomposite as promising material for field emission based applications. © 2010 American Institute of Physics.

Goswami M.,Technical Physics and Prototype Engineering Division | Deshpande S.K.,UGC-DAE Consortium for Scientific Research | Kumar R.,Technical Physics and Prototype Engineering Division | Kothiyal G.P.,Technical Physics and Prototype Engineering Division
Journal of Physics and Chemistry of Solids | Year: 2010

Sealing quality lithium zinc silicate (LZS) glasses of compositions (wt.%) (a) LZSL- Li2O: 12.65, ZnO: 1.85, SiO2: 74.4, Al2O3: 3.8, K2O: 2.95, P2O5: 3.15, B2O3: 1.2 (low ZnO), and (b) LZSH- Li2O: 8.9, ZnO: 24.03, SiO2: 53.7, Na2O: 5.42, P2O5: 2.95, B2O3: 5 (high ZnO) were prepared by conventional melt-quench technique and converted to glass-ceramics by controlled crystallization process. The electrical properties of these samples were measured using ac impedance spectroscopy technique over a frequency range of 10 Hz-15 MHz at several temperatures in the range of 323-673 K. The ac conductivity, dc conductivity, dielectric constant and loss factor were obtained from these measurements. The dc conductivity (σdc) follows the Arrhenius behaviour with temperature. It is observed that σdc in LZSL glass is significantly higher than in the LSZH glass and the activation energies for σdc for LZSL and LZSH glasses are 0.59 and 1.08 eV, respectively. It further observed that the conductivity value decreases nearly one order of magnitude on conversion to glass-ceramics. The behaviour is explained on the basis of distributions and nature of alkali ions and network structures in these samples. © 2010 Elsevier Ltd. All rights reserved.

Patil P.B.,Indian Institute of Technology Bombay | Kumar M.S.,Indian Institute of Technology Bombay | Aswal D.K.,Technical Physics and Prototype Engineering Division | Gupta S.K.,Technical Physics and Prototype Engineering Division
AIP Conference Proceedings | Year: 2010

A series of [Cu(tCu)/Co(25Å)]25 multilayers at higher spacer layer thickness have been deposited by dc magnetron sputtering. Magnetoresistance (MR) measurements have been carried out at different temperatures. MR curves showed hysteresis by displaying peaks at magnetic field Hp. The field values exhibiting the maximum resistance in the magnetoresistance curve (Hp) were greater than the coercivity (H c). The correspondence between the shape of the MR curve and that of the magnetization curve has been established and observed peak splitting in MR curves is attributed to a hardening in the magnetization reversal of some magnetic grains. © 2010 American Institute of Physics.

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