Department Of Physics

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Conflict and peace in Eurasia
(Taylor and Francis, 2012) Mahapatra, D.A.
Focusing on a range of Eurasian conflicts, including Nagorno-Karabakh, South Ossetia and Abkhazia, this book offers contemporary perspectives on the ongoing conflicts in the Eurasia, with an emphasis on the attempts towards peace.The book brings into focus how various factors such as ethnicity, religion, border disputes, resources, and animosities inherited from the past play crucial role in these conflicts. it questions whether developments in Eurasia affect other conflicts across the globe, and if differences between parties can be resolved without pulling the relations beyond adjustable limits. The book goes on to look at how tricky the path to peace would be, and furthers the development of a framework of study of Eurasian conflicts in the post-Soviet world, while taking into account both internal and external variables in analyzing these conflicts. it is a useful contribution to Central Asian and Caucasian Politics and Security Studies. ? 2013 Selection and editorial matter, Debidatta Aurobinda Mahapatra.
Zirconia nanoparticles/ferroelectric liquid crystal composites for ionic impurity-free memory applications
(2013) Chandran, A.; Prakash, J.; Ganguly, P.; Biradar, A.M.
We observed an ionic impurity-free memory effect using a zirconia nanoparticles (ZNPs)/ferroelectric liquid crystal (FLC) composite. The pure and ZNPs doped FLC cells have been analyzed by means of dielectric spectroscopy, polarizing optical microscopy and electrical resistance/conductivity measurements. The memory behavior in ZNPs/FLC composite was confirmed by dielectric dispersion, electrical, and optical studies, whereas dielectric loss spectra confirmed the disappearance of the low-frequency relaxation peak, which appears due to the presence of ionic impurities in FLC materials. The observed memory effect has been attributed to minimization of the depolarization field and ionic charges, whereas the reduction of ionic effects has been attributed to the strong adsorption of ionic impurities on the surface of ZNPs. The ZNPs dispersed in FLCs may play a role in trapping the impurity ions (minimize the depolarization fields) under applied voltage and cause a better memory effect in ZNPs doped FLC material. Moreover, the ion adsorption capability of ZNPs is found to be almost independent of temperature as the value of resistance did not change remarkably on increasing the temperature. The reduction of ionic impurities of FLCs by doping ZNPs did not show degradation over time, as we repeated the experiments on the same sample cells after many days and did not find ionic effects in the ZNPs doped FLC materials. These studies would be helpful to provide an idea for designing ionic impurity-free memory devices. ? 2013 The Royal Society of Chemistry.
Probing the effect of temperature and electric field on the low frequency dielectric relaxation in a ferroelectric liquid crystal mesogen
(Elsevier, 2014) Chandran, Achu; Prakash, Jai; Joshi, Tilak; Biradar, A. M.
We present the characterization and dielectric spectroscopic investigations of a ferroelectric liquid crystal (FLC) material, namely KCFLC 10S. We experimentally demonstrate the observation of a low frequency dielectric relaxation mode along with Goldstone mode in the smectic C* phase of the FLC material under investigation. The behavior of low frequency dielectric relaxation mode has been systematically studied with temperature and applied bias field. The relaxation frequency of the low frequency dielectric relaxation has been found to be shifted toward the higher frequency side with an increase in temperature and field strength. This shift has been attributed to the single particle diffusion of fast ions. Further investigations on electrical conductivity (σ) with frequency at different electric field strengths revealed a Schottky-type of charge injection at electrode even under a small DC bias. The studies carried out in the present paper would be helpful to provide ideas for designing and developing advanced liquid crystal materials.
Evaluation of aluminium doped lanthanum ferrite based electrodes for supercapacitor design
(Elsevier, 2014) Rai, Atma; Sharma, A. L.; Thakur, Awalendra K.; Thakur, A.K.
We report Al doped ferrites La1 - xAlxFeO 3(x = 0, 0.3) as an electrode material for supercapacitor design. The La1 - xAlxFeO3 has been synthesized via chemical route. Structural and microstructural evolution has been carried out by X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) respectively. The electrode property of La 1 - xAlxFeO3 has been evaluated by using three electrode systems, glassy carbon (working), Pt (counter) and Ag/AgCl (reference electrode) with H2SO4 as the electrolyte. The Al doped ferrites show better cycle life (~ 250) and columbic efficiency (?) (~ 96%) in comparison to un-doped lanthanum ferrite sample. An increase in specific capacitance (~ 1.5 times) has also been observed in Al doped lanthanum ferrite in comparison to lanthanum ferrite. The maximum specific capacitance for Al doped lanthanum ferrite is ~ 260 F/g as compared to lanthanum ferrite ~ 200 F/g. The improved specific capacitance, columbic efficiency and cycle life of Al doped ferrites may be related to a relative decrease in equivalent series resistance (95 ? for LFO to 55 ? LAFO) and lower M.W. of Al doped lanthanum ferrite. ? 2013 Elsevier B.V.
Preparation and characterization of MgO nanoparticles/ferroelectric liquid crystal composites for faster display devices with improved contrast
(2014) Chandran, Achu; Prakash, Jai; Naik, Kush Kumar; Srivastava, Avanish; Dabrowski, Roma; Czerwinki, Michat; Biradar, A. M.; Chandran, A.; Prakash, J.; Naik, K.K.; Srivastava, A.K.; Da?browski, R.; Czerwi?ski, M.; Biradar, A.M.
In this article, we present the formulation and characterization of a ferroelectric liquid crystal (FLC) mixture W301 composed of pyrimidine compounds. We observed that upon doping magnesium oxide nanoparticles (MgO NPs) into the host FLC, the MgO NPs/FLC composite showed significantly faster response and improved optical tilt angle. The decreased response time in the MgO NPs/FLC composite has been attributed to the decrease in rotational viscosity and increase in surface anchoring energy. The decrease in rotational viscosity of the composite is due to the torque experienced by both MgO NPs and FLC in the presence of an electric field and perturbations of order parameters of FLC. Due to the enhanced surface interaction of MgO NPs having surface defects with mesogens, strong surface anchoring is experienced on the FLC molecules that not only increased the speed of the response but also improved the optical tilt angle of the MgO NPs/FLC composites, which ultimately resulted in improved contrast. A systematic approach has been followed to elucidate the idea of designing faster display devices with improved contrast based on MgO NPs/FLC composites. ? 2014 The Royal Society of Chemistry.
Study of the shell effect on nuclear dissipation via neutron multiplicity measurement
(2014) Singh, V.; Behera, B.R.; Sadhukhan, J.; Pal, S.
Experimental neutron multiplicity data has been fitted using the Kramers' fission width, in statistical model calculations with and without inclusion of shell corrections in nuclear level density, nuclear masses and fission barrier. It has been found that the magnitude of dissipation strength changes to a large extent with inclusion of shell corrections in different ingredients of the statistical model. These observations clearly demonstrate the importance of shell corrections in statistical model calculations. ? Owned by the authors, published by EDP Sciences, 2014.
Self assembled monolayer based liquid crystal biosensor for free cholesterol detection
(American Institute of Physics Inc., 2014) Tyagi, M.; Chandran, A.; Joshi, T.; Prakash, J.; Agrawal, V.V.; Biradar, A.M.
A unique cholesterol oxidase (ChOx) liquid crystal (LC) biosensor, based on the disruption of orientation in LCs, is developed for cholesterol detection. A self-assembled monolayer (SAM) of Dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP) and (3-Aminopropyl)trimethoxy-silane (APTMS) is prepared on a glass plate by adsorption. The enzyme (ChOx) is immobilized on SAM surface for 12 h before utilizing the film for biosensing purpose. LC based biosensing study is conducted on SAM/ChOx/LC (5CB) cells for cholesterol concentrations ranging from 10mg/dl to 250 mg/dl. The sensing mechanism has been verified through polarizing optical microscopy, scanning electron microscopy, and spectrometric techniques. ? 2014 AIP Publishing LLC.
Optimal way of selecting cities and conveyances for supplying coal in uncertain environment
(Springer India, 2014) Kumar, Amit; Kaur, Amarpreet
In this paper, the limitations and shortcomings of the existing methods for solving fuzzy solid transportation problem are pointed out and to overcome these shortcomings, a new method is proposed for solving fuzzy solid transportation problem. The advantages of the proposed method over the existing methods are discussed. To illustrate the proposed method, an existing fuzzy solid transportation problem is solved. Also, to show the application of the proposed method in real life problems an existing real life fuzzy solid transportation problem is solved by the proposed method. ? 2014 Indian Academy of Sciences.
Role of cell thickness in tailoring the dielectric and electro-optical parameters of ferroelectric liquid crystals
(Taylor and Francis Ltd., 2015) Prakash, J.; Chandran, A.; Malik, A.; Biradar, A.M.
Here, we report thickness dependence of dielectric and electro-optical parameters in ferroelectric liquid crystals (FLCs) without surface stabilisation. The dependence of dielectric and electro-optical parameters on cell thickness is observed by dielectric spectroscopy and electro-optical measurements. The dielectric permittivity (Formula presented.) measured by varying the cell thickness showed increase of (Formula presented.) with increase of cell thickness which is attributed to the presence of more ions and larger contributions of Goldstone mode in thick cells. The spontaneous polarisation also shows increment with increase of cell gap up to certain thickness range. The rotational viscosity decreases with increase in the cell thickness whereas the response time is more for thicker cells. The decrease in the rotational viscosity is attributed to lowering of elastic deformation with increase in cell thickness and the response time is directly proportional to cell gap. These studies would be utilised to understand the effect of cell thickness on dielectric and electro-optical properties of FLC materials and optimising the material parameters with cell thickness for better and efficient liquid-crystal-based devices. ? 2015 Taylor & Francis.
Relaxation behavior in clay-reinforced polymer nanocomposites
(Institute for Ionics, 2015) Sharma, A.L.; Thakur, A.K.; Sharma, A. L.
The effect of clay reinforcement on dielectric, conductivity, and mechanical relaxation behavior of a polymer clay nanocomposite film is reported. Polymer nanocomposite is composed of three component polymers (polyacrylonitrile) as a host matrix, salt (LiPF6) as conducting species, and clay (sodium montmorillonite) as intercalant. The macroscopic parameters like polymer glass transition temperature and available free mobile charge carriers have been analyzed properly using dynamic mechanical analysis and dielectric analysis. Dielectric analysis indicated distribution of relaxation time as a function of clay concentration, whereas conductivity spectrum exhibited dispersion at lower frequency followed by saturation region at intermediate frequency. The dispersion behavior is related to the electrode polarization attributed to faster ion dynamics. The dielectric and conductivity relaxation are in excellent correlation with mechanical relaxation owing to the changes in glass transition temperature due to polymer-ion-clay interaction. The proposed mechanism is a sequel to the experimental results. ? 2014, Springer-Verlag Berlin Heidelberg.
Study of optical properties of BaMn1-xCrxO3 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) manganites using microwave synthesis method
(American Institute of Physics Inc., 2015) Rani R.; Yadav K.
Barium manganite (BaMnO3), a perovskite based material, has been studied extensively. BaMnO3 properties can be changed by doping different elements at manganese (Mn) lattice site. We have prepared BaMnO3 and BaMn1-xCrxO3 (x=0.1, 0.2, 0.3, 0.4, 0.5) by Microwave Synthesizer. Data obtained from Fourier Transform Infrared Spectroscopy (FTIR) that the band gap of pure BaMnO3 is less as compare to the Cr doped BaMnO3. It is also clear from the FTIR that the band gap decreased with increasing the concentration of chromium. Broaden peak at 3201 cm-1 correspond to the stretching vibration of hydroxyl group (OH or H2O). The peaks appear on 724, 863 and 974 cm-1 is corresponding to the stretching vibration of metal oxide (M-O) bonds in the BaMnO3. BaMnO3 have applications in memory storage devices. - 2015 AIP Publishing LLC.
Role of salt concentration in blend polymer for energy storage conversion devices
(American Institute of Physics Inc., 2016) Arya, A.; Sadiq, M.; Sharma, A. L.
Solid Polymer Electrolytes (SPE) are materials of considerable interest worldwide, which serves dual purpose of electrolyte and separator between electrode compartments in renewable energy conversion/storage devices such as; high energy density batteries, electrochromic display devices, and supercapacitors. Polymer blend electrolytes are prepared for various concentration of salt (?/Li) with the constant ratio (0.5 gm) of each PEO and PAN polymers (blend polymer) using solution casting technique. Solid polymeric ionic conductor as a separator is the ultimate substitute to eliminate the drawback related to liquid and gel polymer ionic conductors. In the present work, solid polymer electrolyte film consisting of PEO, PAN and LiPF6 are examined for various concentration of lithium salt by keeping PEO/PAN blend ratio as a constant with a view to optimize the dominant salt concentration which could give the maximum conductivity at ambient temperature. ? 2016 Author(s).
Electronic structure engineering of various structural phases of phosphorene
(Royal Society of Chemistry, 2016) Kaur, Sumandeep; Kumar, Ashok; Srivastava, Sunita; Tankeshwar, K.
We report the tailoring of the electronic structures of various structural phases of phosphorene (?-P, ?-P, ?-P and ?-P) based homo- and hetero-bilayers through in-plane mechanical strains, vertical pressure and transverse electric field by employing density functional theory. In-plane biaxial strains have considerably modified the electronic bandgap of both homo- and hetero-bilayers while vertical pressure induces metallization in the considered structures. The ?-P homo-bilayer structure showed the highest ultimate tensile strength (UTS ? 6.21 GPa) upon in-plane stretching. Upon application of a transverse electric field, the variation in the bandgap of hetero-bilayers was found to be strongly dependent on the polarity of the applied field which is attributed to the counterbalance between the external electric field and the internal field induced by different structural phases and heterogeneity in the arrangements of atoms of each surface of the hetero-bilayer system. Our results demonstrate that the electronic structures of the considered hetero- and homo-bilayers of phosphorene could be modified by biaxial strain, pressure and electric field to achieve the desired properties for future nano-electronic devices. ? the Owner Societies 2016.
Electronic Properties and Mechanical Strength of β- Phosphorene Nano-ribbons
(AIP Publishing, 2016) Swaroop, Ram; Bhatia, Pradeep; Kumar, Ashok
We have performed first principles calculations to find out the effect of mechanical strain on the electronic of zig-zag edged nano ribbons of β-phosphorene. It is found that electronic get opened-up to 2.61 eV by of the edges of ribbons. Similarly, the mechanical strength is found to be increase from 1.75 GPa to 2.65 GPa on going from unpassivated nano ribbons to passivated ones along with the 2% increase in ultimate tensile strain. The value of passivated ribbon gets decreased to 0.43 eV on applying strain up to which the ribbon does not break. These tunable of β-phospherene with with H-atom and applying mechanical strain offer its use in tunable nano electronics.
Tunable electronic and dielectric properties of b-phosphorene nanoflakes for optoelectronic applications
(Royal Society of Chemistry, 2016) Bhatia, Pradeep; Swaroop, Ram; Kumar, Ashok
Since the discovery of α-phosphorene, it has drawn considerable attention because of its possible exfoliation as single layers. We report electronic and dielectric properties of β-phosphorene nanoflakes in various configurations using density functional theory. Armchair edge nanoflakes with various shapes are magnetic semiconductors while hydrogen passivated edge structures are non-magnetic semiconductors with energy gap in the range of ∼2.3–2.7 eV which is suitable for solar cell applications. Dielectric functions are highly anisotropic in the low energy range and become isotropic above 10 eV energy. The calculated static dielectric constant shows strong dependence on the shape and edge structure of the considered nanoflakes. We found significantly large plasmonic energy differences for nanoflakes with a particular shape but having different edge configurations. Our results demonstrate that electron energy loss spectroscopy may be useful to determine the various shapes and edge configurations of β-phosphorene nanoflakes. The tunable energy gap and dielectric response make the considered nanoflakes potential candidates for optoelectronic device applications.
Optimization of Free standing Polymer Electrolytes films for Lithium ion batteries application
(Integrated Science, 2016) Sadiq, M.; Arya, Anil; Sharma, A. L.
The free standing polymer nancomposite films consisting of blend polymer based on Poly(acrylonitrile) (PAN) as host polymer–Poly(ethylene oxide)(PEO) as a copolymer, Dimethylformamide (DMF) as solvent and Lithium hexaflourophosphate (LIPF6) as a conducting speciesm were prepared. Keeping in view of characterization of solid state film such as, Fourier transform infrared (FTIR) spectroscopy is done for an understanding of the microscopic interaction among the different component present in the material system. The energy storage/conversion device applications have been analyzed by the impedances spectroscopy. The surface morphology or micro-structural of the polymer nanocomposite electrolytes film was analyzed by FESEM. The electrochemical stability window was about ~4V for the polymer electrolyte film at (/Li=6). The advantageous outcome of PAN combining with PEO based electrolytes is in comparable electrical conductivity and wider electrochemical stability window. Further optimization might lead to practical solid state polymer electrolytes for lithium ion batteries.
Highly stable supercapacitive performance of one-dimensional (1D) brookite TiO2 nanoneedles
(Royal Society of Chemistry, 2016) Devan, R.S.; Ma, Y.-R.; Patil, R.A.; Lukas, S.-M.
We report the highly stable supercapacitive performance of one-dimensional (1D) nanoneedles of brookite (?) TiO2 synthesized on a conducting glass substrate. The 1D ?-TiO2 nanoneedles synthesized over a large area array utilizing hot-filament metal vapor deposition (HFMVD) were ?24-26 nm wide, ?650 nm long and tapered in a downward direction. X-ray photoemission spectroscopy (XPS) revealed their chemical properties and stoichiometric Ti and O composition. The 1D ?-TiO2 nanoneedles execute as parallel units for charge storage, yielding a specific capacitance of 34.1 mF g-1. Electrochemical impedance spectroscopy revealed that the large surface area and brookite crystalline nature of the 1D nanoneedles provided easy access to Na+ ions, and resulted in low diffusion resistance, playing a key role in their stable charging-discharging electrochemical mechanism. Moreover, the non-faradic mechanism of these nanoneedles delivered better durability and high stability up to 10000 cycles, and a columbic efficiency of 98%. Therefore, 1D ?-TiO2 nanoneedles hold potential as an electrode material for highly stable supercapacitive performance with long cycle lifetime. ? 2016 The Royal Society of Chemistry.
Electronic properties and mechanical strength of ?-phosphorene nano-ribbons
(American Institute of Physics Inc., 2016) Swaroop, Ram; Bhatia, Pradeep; Kumar, Ashok
We have performed first principles calculations to find out the effect of mechanical strain on the electronic properties of zig-zag edged nano ribbons of ?-phosphorene. It is found that electronic band-gap get opened-up to 2.61 eV by passivation of the edges of ribbons. Similarly, the mechanical strength is found to be increase from 1.75GPa to 2.65GPa on going from unpassivated nano ribbons to passivated ones along with the 2% increase in ultimate tensile strain. The band-gap value of passivated ribbon gets decreased to 0.43 eV on applying strain up to which the ribbon does not break. These tunable properties of ?-phospherene with passivation with H-Atom and applying mechanical strain offer its use in tunable nano electronics.
Interactions of Gas Molecules with Monolayer MoSe 2 : A First Principle Study
(AIP Publishing, 2016) Sharma, Munish; Jamdagni, Pooja; Kumar, Ashok; Ahluwalia, P. K.
We present a first principle study of interaction of toxic gas molecules (NO, NO2 and SO2) with MoSe2. The predicted order of sensitivity of gas molecule is NO2 > SO2 > NO. strongly influence the electronic behaviour of MoSe2 by inducing in the vicinity of Fermi energy. NO and SO2 is found to induce p-type effect while to metallic transitions occur on NO2 Our findings may guide the experimentalist for sensor based on MoSe2
Electron transport behavior and charge ordering phenomena in La0.5Ca0.5MnO3
(Elsevier Ltd, 2016) Kekade, S.S.; Devan, R.S.; Deshmukh, A.V.; Phase, D.M.; Choudhary, R.J.; Patil, S.I.
In this study, the polycrystalline sample of La0.5Ca0.5MnO3 (LCMO) with perovskite (Orthorhombic) crystalline structure was synthesized by citrate gel method. The temperature dependent magnetization studies exhibit both paramagnetic to ferromagnetic and ferromagnetic to antiferromagnetic transition of LCMO at ?230 K and ?150 K, respectively. The X-ray photoemission spectroscopy data revealed electronic structures, chemical properties, while the valence band photoemission spectra for LCMO measured at various photon energies ranging from 40 eV to 60 eV, showed Fano curve like resonance behavior for Mn 3p to 3d transition and also confirmed the change of DOS near Fermi level. ? 2016 Elsevier B.V.