Physics - Research Publications
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Item Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte(Institute of Physics Publishing, 2018) Arya, A.; Sharma, A.L.In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO8-NaPF6+ x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times () have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation () was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole-Cole plot () in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed. ? 2018 IOP Publishing Ltd.Item Optimization of salt concentration and explanation of two peak percolation in blend solid polymer nanocomposite films(Springer New York LLC, 2018) Arya, A.; Sharma, A.L.The present paper is focused toward the preparation of the flexible and free-standing blend solid polymer electrolyte films based on PEO-PVP complexed with NaPF6 by the solution cast technique. The structural/morphological features of the synthesized polymer nanocomposite films have been investigated in detail using X-ray diffraction, Fourier transform infra-red spectroscopy, Field emission scanning electron microscope, and Atomic force microscopy techniques. The film PEO-PVP + NaPF6 ((Formula presented.)8) exhibits highest ionic conductivity ~ 5.92 ? 10?6 S cm?1 at 40 ?C and ~ 2.46 ? 10?4 S cm?1 at 100 ?C. The temperature-dependent conductivity shows an Arrhenius type behavior and activation energy decreases with the addition of salt. The high temperature (100 ?C) conductivity monitoring is done for the optimized PEO-PVP + NaPF6 ((Formula presented.)8) highly conductive system and the conductivity is still maintained stable up to 160 h (approx. 7 days). The thermal transitions parameters were measured by the differential scanning calorimetry (DSC) measurements. The prepared polymer electrolyte film displays the smoother surface on addition of salt and a thermal stability up to 300 ?C. The ion transference number (tion) for the highest conducting sample is found to be 0.997 and evidence that the present system is ion dominating with negligible electron contribution. Both linear sweep voltammetry and cyclic voltammetry supports the use of prepared polymer electrolyte with long-term cycle stability and thermal stability for the solid-state sodium ion batteries. Finally, a two peak percolation mechanism has been proposed on the basis of experimental findings. [Figure not available: see fulltext.] ? 2018 Springer-Verlag GmbH Germany, part of Springer NatureItem 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.Item Development of novel cathode materials based on MWCNT for energy storage/conversion devices(Springer Science and Business Media, LLC, 2017) Agnihotri, Shruti; Rattan, Sangeeta; Sharma, A. L.In Chap. 1, already available technology for energy storage solutions like capacitors, lead acid batteries, compressed air energy storage, flywheels has been discussed in order to compare their energy and power densities. Emphasis has been laid on Rechargeable Lithium ion Battery (Li-ion). Various materials which are already explored and used as cathode of battery has also been discussed with their merits and demerits. Further introduction of prepared orthosilicate material with used conductive additive Multiwalled carbon nano tube (MWCNT) has also given. In Chap. 2, methodology used to prepare respective Li2MnFeSiO4 material and its composite with MWCNT has been discussed in detail. Further, in order to validate its electrochemical application, different steps of cell assembly of Lithium half cell fabrication has also been discussed. Chapter 3 comprises of results obtained using standard Field emission scanning electron microscope (FESEM). Effect of used MWCNT on its morphology has been discussed in this chapter. A.C Impedance spectroscopy has been used to study variation in conductivity with respect to bared material. Possible reasons for increased conductivity with morphology has also been discussed in discussion. Chapter 4 includes conclusions drawn from mentioned results. This chapter summarizes measured conductivity values with different concentrations of MWCNT. Improved conductivity with respect to bared orthosilicate material has been pointed in this chapter. ? Springer International Publishing Switzerland 2017.