Department of Physics

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IIT Jodhpur

Graphene Oxide (GO)/Polystyrene (PS) nanocomposites of thisckness (50 μm) have been synthesized by solution blending method with DMF as solvent. The composites have been coagulated by drop wise addition of DMF into a large volume of methanol. These composites filled almost completely with graphene oxide (GO) as a filler concentration (0.01–0.5 wt %) by volume. Hydrogen adsorption study on these composites has been performed by sievert’s type apparatus at room temperature. The storage capacity upto 5.02 wt% has been obtained by repetition of various cycles at constant pressure. Dynamic Mechanical Analysis (DMA) has been performed for testing of mechanical strength of these fabricated composites. Storage modulus has been found to be increased at low concentration of graphene oxide in polystyrene matrix. Scanning Electron Microscopy (SEM) has been used for surface morphology of fabricated composites, from SEM micrographs layered structure of graphene oxide has been obtained. The Dielectric constant (up to 5.4) has been found at higher graphene oxide concentration in polystyrene matrix due to interfacial effect and accumulation of charges. From Differential Scanning Calorimetry (DSC) the glass transition temperature (90 °C) at higher concentration of graphene oxide in PS matrix has been obtained. © 2016 American Scientific Publishers. All rights reserved.

World University root node

Advanced Science Letters

Study of hydrogen adsorption on GO/PS based flexible nanocomposites at room temperature

Parabolic dish solar energy concentrator with aperture diameter 1.4 m and focal length 0.32 m is designed and fabricated to charge and store solar thermal energy in phase change material (PCM) based heat packs. Overall heat loss factor, heat duty, over all thermal efficiency, and optical efficiency factor are calculated using water sensible heating and cooling tests and values are 16.11 W m-2 K-1, 546.9 W, 49.2% and 0.62 respectively. The performance characteristic curve is generated using these parameters to understand its performance at different ambient temperatures and solar insolation. The fabricated concentrator has been used to charge 16 PCM heat packs with 150 g PCM in each heat pack, which took about 35 minutes for complete charging of PCM heat packs at average ambient temperature 39 °C and solar radiation flux density 715 W m-2 K-1. The charged heat packs are subjected to discharge studies at average ambient temperature about - 7 °C and observed heat release in the temperature range of 48 to 40 °C for 50 minutes, suggesting its applications for comfort and therapeutic applications in high altitude areas. © 2016 Author(s).

AIP Conference Proceedings

Charging studies of heat packs using parabolic dish solar energy concentrator for extreme conditions

Phase Change Materials (PCMs) are being used in thermal energy storage systems because of their high energy storage density, and heat storage/release in small temperature range near melting temperature. Such requirements compel to design and develop materials with high latent heat of fusion for thermal energy storage applications. This will rely on characterization of materials to understand their thermal properties as a function of temperature. In this work, an experimental set-up is presented for measuring the thermodynamic properties of materials, such as, temperature-time response, latent heat of fusion, specific heat of solids and liquids, melting-solidification temperatures, degree of supercooling and enthalpy-temperature response of PCMs. The present experimental test set-up, including specific PCM container, is designed and fabricated for characterization of low temperature PCMs with melting temperature in the range of 0-100°C. © 2016 IEEE.

2016 IEEE 1st International Conference on Control, Measurement and Instrumentation, CMI 2016

An experimental set-up for measuring thermodynamic response of low temperature phase change materials

The interplay between the various measures of quantum correlations is well known in stable optical and electronic systems. Here we study such foundational issues in unstable quantum systems. Specifically we study meson-antimeson systems (Formula Presented), which are produced copiously in meson factories. In particular, the nonclassicality of quantum correlations which can be characterized in terms of nonlocality (which is the strongest condition), entanglement, teleportation fidelity or weaker nonclassicality measures like quantum discord are analyzed. We also study the impact of decoherence on these measures of quantum correlations, using the semigroup formalism. A comparison of these measures brings out the fact that the relations between them can be nontrivially different from those of their stable counterparts such as neutrinos. © Società Italiana di Fisica/Springer-Verlag 2016

Fulltext

European Physical Journal Plus

Quantum correlations in B and K meson systems

Understanding the mechanisms and optimizing ion transport in polymer membranes have been the subject of active research for more than three decades. We present an overview of the progress and challenges involved with the modeling and simulation aspects of the ion transport properties of polymer membranes. We are concerned mainly with atomistic and coarser level simulation studies and discuss some salient work in the context of pure binary and single ion conducting polymer electrolytes, polymer nanocomposites, block copolymers, and ionic liquid based hybrid electrolytes. We conclude with an outlook highlighting future directions. Copyright © 2016 by Annual Reviews. All rights reserved.

Annual Review of Chemical and Biomolecular Engineering

Computer Simulations of Ion Transport in Polymer Electrolyte Membranes

Using atomistic molecular dynamics simulations, we study the ion diffusivities and conductivities of polyethylene oxide polymer electrolytes doped with LiBF4 salt and containing dispersed Al2O3 nanoparticles. We consider nanoparticles of two different surface chemistries: (a) containing acid rich surface sites (α-Al2O3); (b) containing roughly equal acidic and basic surface sites (γ-Al2O3). We compare the ionic diffusivities and conductivities of such systems with our earlier results [Mogurampelly et al. Macromolecules 2015, 48, 2773-2786] for systems containing basic surface sites on the nanoparticles (β-Al2O3). In the presence of α-Al2O3 and γ-Al2O3 nanoparticles, we observe a monotonic decrease of ionic conductivities and mobilities with particle loading. These results are consistent with our earlier findings in the context of β-Al2O3 nanoparticles. Our analysis identifies that the ionic mobilities and conductivities correlate with the combined effects of the changes in polymer segmental dynamics and the modifications in the local environment of ionic species arising from the introduction of nanoparticles. © 2015 Elsevier B.V. All rights reserved.

Solid State Ionics

Influence of nanoparticle surface chemistry on ion transport in polymer nanocomposite electrolytes

We use atomistic simulations to probe the ion conductivities and mechanical properties of polyethylene oxide electrolytes containing Al2O3 nanoparticles. We specifically study the influence of repulsive polymer-nanoparticle and ion-nanoparticle interactions and compare the results with those reported for electrolytes containing the polymorph β-Al2O3 nanoparticles. We observe that incorporating repulsive nanoparticle interactions generally results in increased ionic mobilities and decreased elastic moduli for the electrolyte. Our results indicate that both ion transport and mechanical properties are influenced by the polymer segmental dynamics in the interfacial zones of the nanoparticle in the ion-doped systems. Such effects were seen to be determined by an interplay between the nanoparticle-polymer, nanoparticle-ion, and ion-polymer interactions. In addition, such interactions were also observed to influence the number of dissociated ions and the resulting conductivities. Within the perspective of the influence of nanoparticles on the polymer relaxation times in ion-doped systems, our results in the context of viscoelastic properties were consistent with the ionic mobilities. Overall, our results serve to highlight some issues that confront the efforts to use nanoparticle dispersions to simultaneously enhance the conductivity and the mechanical strength of polymer electrolyte. © 2016 Author(s).

Journal of Chemical Physics

Influence of nanoparticle-ion and nanoparticle-polymer interactions on ion transport and viscoelastic properties of polymer electrolytes

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type. © 2016 AIP Publishing LLC.

Review of Scientific Instruments

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes

Starburst galaxies and star-forming regions in the Milkyway, with high rate of supernova activities, are candidate sources of high-energy neutrinos. Using a gamma-ray selected sample of these sources we perform statistical analysis of their angular correlation with the four-year sample of high-energy starting events (HESE), detected by the IceCube Neutrino Observatory. We find that the two samples (starburst galaxies and local star-forming regions) are correlated with cosmic neutrinos at ∼ (2-3)σ (pre-trial) significance level, when the full HESE sample with deposited energy 20 TeV is considered. However when we consider the HESE sample with deposited energy 60 TeV, which is almost free of atmospheric neutrino and muon backgrounds, the significance of correlation decreased drastically. We perform a similar study for Galactic sources in the 2nd Catalog of Hard Fermi-LAT Sources (2FHL, >50 GeV) catalog as well, obtaining ∼ (2-3)σ (pre-trial) correlation, however the significance of correlation increases with higher cutoff energy in the HESE sample for this case. We also fit available gamma-ray data from these sources using a pp interaction model and calculate expected neutrino fluxes. We find that the expected neutrino fluxes for most of the sources are at least an order of magnitude lower than the fluxes required to produce the HESE neutrinos from these sources. This puts the starburst sources being the origin of the IceCube HESE neutrinos in question. © 2016 IOP Publishing Ltd and Sissa Medialab srl.

Journal of Cosmology and Astroparticle Physics

Angular correlation between IceCube high-energy starting events and starburst sources

The thin-film structures of DC/FR magnetron-sputtered ZrOx/ZrC–ZrN/Zr tandem solar-selective coatings are investigated using X-ray diffraction and room-temperature Raman spectroscopic measurements. These studies suggest that the major contribution is coming from h-ZrN0.28, c-ZrC, h-Zr3C2 crystallographic phases in ZrN–ZrC absorber layer, in conjunction with mixed ZrOx crystallographic phases. The change in structure for thermally annealed samples has been examined and observed that cubic and hexagonal ZrOx phase converted partially into tetragonal and monoclinic ZrOx phases, whereas hexagonal and cubic ZrN phases, from absorber layer, have not been observed for these thermally treated samples in air. These studies suggest that thermal treatment may lead to the loss of ZrN phase in absorber, degrading the thermal response for the desired wavelength range in open ambient conditions in contrast to vacuum conditions. © 2016, Springer-Verlag Berlin Heidelberg.