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Panja S.K.,Banaras Hindu University | Dwivedi N.,Banaras Hindu University | Noothalapati H.,National Chiao Tung University | Shigeto S.,National Chiao Tung University | And 4 more authors.
Physical Chemistry Chemical Physics | Year: 2015

The effects of interionic hydrogen bonding and π-π stacking interactions on the physical properties of a new series of picrate anion based ionic liquids (ILs) have been investigated experimentally and theoretically. The existence of aromatic (C2-H⋯O) and aliphatic (C7-H⋯O-N22 and C6-H⋯O-N20) hydrogen bonding and π-π stacking interactions in these ILs has been observed using various spectroscopic techniques. The aromatic and aliphatic C-H⋯O hydrogen bonding interactions are found to have a crucial role in binding the imidazolium cation and picrate anion together. However, the π-π stacking interactions between two successive layers are found to play a decisive role in tight packing in ILs leading to differences in physical properties. The drastic difference in the melting points of the methyl and propyl derivatives (mmimPic and pmimPic respectively) have been found to be primarily due to the difference in the strength and varieties of π-π stacking interactions. While in mmimPic, several different types of π-π stacking interactions between the aromatic rings (such as picrate-picrate, picrate-imidazole and imidazolium-imidazolium cation rings) are observed, only one type of π-π stacking interaction (picrate-picrate rings) is found to exist in the pmimPic IL. NMR spectroscopic studies reveal that the interaction of these ILs with solvent molecules is different and depends on the dielectric constant of the solvent. While an ion solvation model explains the solvation in high dielectric solvents, an ion-pair solvation model is found to be more appropriate for low dielectric constant solvents. The enhanced stability of these investigated picrate ILs compared with that of inorganic picrate salts under high doses of γ radiation clearly indicates the importance of weak interionic interactions in ILs, and also opens up the possibility of the application of picrate ILs as prospective diluents in nuclear separation for advanced fuel cycling process. © the Owner Societies 2015. Source

Pal D.B.,Indian Institute of Technology BHU Varanasi | Kumar H.,Defense Research and Development Organization DRDO | Giri D.D.,Indian Institute of Technology BHU Varanasi | Singh P.,Indian Institute of Technology BHU Varanasi | Mishra P.K.,Indian Institute of Technology BHU Varanasi
Advanced Science Letters | Year: 2014

Composite nanofibers of Cu/CeO2 were electrospunned using Cu(CH3COO–)2H2O and Ce(NO3)3 ·6H2O precursors, polyvinyl pyrrolidone fiber template and co-solvent mixture by volume 2:1 of C2H5OH/H2O followed by thermal treatment (500 °C, 3 h). The fabricated nanofibers were characterized by SEM, XRD, BET and FTIR for morphologies, structures, surface area and functional group, respectively. We observed continuous line feature in calcined composite nanofibers with an average diameter of 127 nm and CeO2 peaks were observed at 28.74°. © 2014 American Scientific Publishers All rights reserved. Source

Krushnamurty K.,Indian Institute of Technology Hyderabad | Srikanth I.,Indian Institute of Technology Hyderabad | Srikanth I.,Defense Research and Development Organization DRDO | Subrahmanyam Ch.,Indian Institute of Technology Hyderabad
Materials and Manufacturing Processes | Year: 2015

Carbon nanofibers (CNFs) are plasma etched by using cold plasma of air and helium for different time durations. Changes in surface functional groups of CNFs due to plasma treatment were estimated by using elemental analysis and temperature programmed decomposition in helium atmosphere. The influence of plasma etched CNFs on the toughness of epoxy and tensile and flexural strength of carbon-epoxy composites have been studied. Results indicate that, air plasma etched CNFs can improve the toughness of epoxy, while helium plasma etched CNFs could not impart improved toughness to epoxy composites. On the other hand, mechanical properties of carbon-epoxy made with air plasma etched CNFs improved significantly as compared to helium plasma etched CNFs as well as untreated CNFs. © 2015 Copyright © Taylor & Francis Group, LLC. Source

Krushnamurty K.,Indian Institute of Technology Hyderabad | Srikanth I.,Defense Research and Development Organization DRDO | Rangababu B.,Defense Research and Development Organization DRDO | Majee S.K.,Defense Research and Development Organization DRDO | And 2 more authors.
Advanced Materials Letters | Year: 2015

Organically modified montimorillonite nanoclay was added to the epoxy and E-glass-epoxy composites. The influence of nanoclay content (varied between 0 to 5wt %) on the relative crosslink density and the fracture toughness of the epoxy matrix was studied. Differential scanning calorimetry (DSC) indicated that the amino functional groups present on the nanoclay react with the epoxy matrix to increase the crosslink density of about 13 and 18% at 3 and 5wt% addition, respectively. The toughness of the epoxy composites increased by 25% at 3wt% addition of nanoclay, whereas, it decreases at 5wt%. Flexural strength and tensile strength of the E-glass-epoxy composites were found to increase by 12% and 11% respectively at 3wt% addition of nanoclay, while at 5wt% addition these properties decreased due to the matrix embrittlement. Interestingly matrix embrittlement is found to be beneficial in increasing the impact resistance due to spallation of embrittled matrix that ensures the dissipation of the impact energy. 5wt% nanoclay addition increases the impact strength by 29% and reduces the back face bulge of composite by 31%. These results may lead to the design and realization of glass-epoxy composites with better impact strength. © 2015 VBRI Press. Source

Prabu H.G.,Alagappa University | Talawar M.B.,Defense Research and Development Organization DRDO | Mukundan T.,Defense Research and Development Organization DRDO | Asthana S.N.,Defense Research and Development Organization DRDO
Combustion, Explosion and Shock Waves | Year: 2011

Research and development activities are on in many laboratories to develop methods for detecting energetic materials at the trace level. Production or application of high-energy materials may also contaminate the natural environmental systems. Therefore, development of a simple, portable, and inexpensive device for determining explosives at the trace levels is highly desirable. In this study, a stripping voltammetry technique is used for their analytical determination. The study is conducted in an acetonitrile medium. Optimum conditions are obtained in stripping voltammetry for individual analytes. The stripping voltammetric method is compound-selective and can be used for determining a particular high-energy material in a mixture. In this paper, we report the development of an electro-analytical procedure for detecting conventional energetic materials such as Tetryl, TNT, PETN, RDX, and HMX, using the stripping voltammetric method. © 2011 Pleiades Publishing, Ltd. Source

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