Post-spinning modification of electrospun nanofiber nanocomposite from Bombyx mori silk and carbon nanotubes

Electrospinning is an effective procedure for fabricating submicron to nanoscale fibers from synthetic polymer as well as natural proteins. We successfully electrospun regenerated silk protein from cocoons of Bombyx mori to produce random as well as aligned fibers with diameter less than 100 nm. The fibers were characterized using field emission environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and wide angle X-ray diffraction (WAXD) studies. Post-spinning treatment with methanol and/or stretching and co-electrospinning with single walled carbon nanotubes (CNT) were carried out to alter the strength, toughness, crystallinity and conductivity of silk nanofibers. Addition of just 1% CNT along with post-spinning treatments resulted in 7-fold increase in the strength and 35-fold increase in the modulus of silk nanofibers. Raman spectroscopy confirmed that CNTs were incorporated in the silk fibers. FT-IR spectroscopy and WAXD studies proved that silk-CNT nanofibers had more crystallinity compared to silk nanofibers without CNT. Four-probe method demonstrated that silk-CNT nanofibers had 4 times higher electrical conductivity compared to silk nanofibers without CNT.     

Bacterial synthesis of copper/copper oxide nanoparticles

A bacterial mediated synthesis of copper/copper oxide nanoparticle composite is reported. A Gram-negative bacterium belonging to the genus Serratia was isolated from the midgut of Stibara sp., an insect of the Cerambycidae family of beetles found in the Northwestern Ghats of India. This is a unique bacterium that is quite specific for the synthesis of copper oxide nanoparticles as several other strains isolated from the same insect and common Indian mosquitoes did not result in nanoparticle formation. By following the reaction systematically, we could delineate that the nanoparticle formation occurs intracellularly. However, the process results in the killing of bacterial cells. Subsequently the nanoparticles leak out as the cell wall disintegrates. The nanoparticles formed are thoroughly characterized by UV-Vis, TEM, XRD, XPS and FTIR studies.     

Effects of nano size mischmetal and its oxide on improving the hydrogen sorption behaviour of MgH2

This paper reports the catalytic effects of mischmetal (Mm) and mischmetal oxide (Mm-oxide) on improving the dehydrogenation and rehydrogenation behaviour of magnesium hydride (MgH₂). It has been found that 5 wt.% is the optimum catalyst (Mm/Mm-oxide) concentration for MgH₂. The Mm and Mm-oxide catalyzed MgH₂ exhibits hydrogen desorption at significantly lower temperature and also fast rehydrogenation kinetics compared to ball-milled MgH₂ under identical conditions of temperature and pressure. The onset desorption temperature for MgH₂ catalyzed with Mm and Mm-oxide are 323 °C and 305 °C, respectively. Whereas the onset desorption temperature for the ball-milled MgH₂ is 381 °C. Thus, there is a lowering of onset desorption temperature by 58 °C for Mm and by 76 °C for Mm-oxide. The dehydrogenation activation energy of Mm-oxide catalyzed MgH₂ is 66 kJ/mol. It is 35 kJ/mol lower than ball-milled MgH₂. Additionally, the Mm-oxide catalyzed dehydrogenated Mg exhibits faster rehydrogenation kinetics. It has been noticed that in the first 10 min, the Mm-oxide catalyzed Mg (dehydrogenated MgH₂) has absorbed up to 4.75 wt.% H₂ at 315 °C under 15 atmosphere hydrogen pressure. The activation energy determined for the rehydrogenation of Mm-oxide catalyzed Mg is ∼62 kJ/mol, whereas that for the ball-milled Mg alone is ∼91 kJ/mol. Thus, there is a decrease in absorption activation energy by ∼29 kJ/mol for the Mm-oxide catalyzed Mg. In addition, Mm-oxide is the native mixture of CeO₂ and La₂O₃ which makes the duo a better catalyst than CeO₂, which is known to be an effective catalyst for MgH₂. This takes place due to the synergistic effect of CeO₂ and La₂O₃. It can thus be said that Mm-oxide is an effective catalyst for improving the hydrogen sorption behaviour of MgH₂.     

Nanocrystalline zinc indium vanadate: a novel photocatalyst for hydrogen generation

Hydrogen is a future fuel and hence production of cheap hydrogen is an important area of research. Recently, the photocatalysts were used to generate hydrogen from water and hydrogen sulfide splitting under solar light. Hence, we designed Zinc Indium Vanadate, a novel visible light active photocatalyst and used for the generation of hydrogen by using solar light. We have demonstrated the synthesis of ZnIn2V2O9 (ZIV) catalyst by sonochemical route using NH4VO3, In (NO3)3 and Zn(CH3COO)2 as a precursors and PVP as a capping agent. The obtained product was further characterized by XRD, UV-DRS and FESEM. The XRD pattern reveals the existence of monoclinic crystal structure and broader peaks indicating the nanocrystalline nature of the material. The particle size was observed in the range of 50-70 nm. The optical study showed the absorption edge cut off at 520 nm with estimated band gap about 2.3 eV. Considering the band gap in visible range, ZnIn2V2O9 was used as a photocatalyst for photodecomposition of H2S under visible light irradiation to produce hydrogen. We observed excellent photocatalytic activity for the hydrogen generation by using this photocatalyst.     

Yield behavior of gelled waxy oil in water-in-oil emulsion at temperatures below ice formation

Paraffinic waxes precipitate from bulk oil when oil temperatures are lower than the oil wax appearance temperature. The oil can form a gel if the temperature goes below the pour point, especially under quiescent conditions. The strength of the gelled waxy oil increases as temperature decreases further. Application of a mechanical shear deforms and fractures the gel. It is shown that this strength reduction in the gel is irreversible under isothermal conditions. In subsequent cooling, the prior fractured gel even showed much less yield stress than the gel from the shear-free condition at measured temperature. This study explored the gel strength behavior in water-in-oil (w/o) emulsion state. Three different model oils, water-free oil, 10 wt.% w/o and 30 wt.% w/o, were used to determine the yield stress using vane method. Both emulsified oils showed less yield stress values at temperatures between the pour points and ice temperature. Compared to water-free oil at temperatures below ice formation, the higher yield stresses were observed in 10 wt.% w/o oil; however, the lower yield stresses in 30 wt.% w/o oil. Subsequent cooling option after prior gel breakage was also examined.     

Reliable and Secure Cooperative Communication for Wireless Sensor Networks Making Use of Cooperative Jamming with Physical Layer Security

Interference is generally considered as the redundant and unwanted occurrence in wireless communication. This research work proposes a novel cooperative jamming mechanism for scalable networks like wireless sensor networks which makes use of friendly interference to confuse the eavesdropper and increase its uncertainty about the source message. The communication link is built with the help of Information theoretic source and channel coding mechanisms. The whole idea is to make use of normally inactive relay nodes in the selective Decode and Forward cooperative communication and let them work as cooperative jamming sources to increase the equivocation of the eavesdropper. In this work, eavesdropper’s equivocation is compared with the main channel in terms of mutual information and secrecy capacity.     

Improved Ultraviolet (UV) Radiation Stability of the Polypropylene (PP) Films of Woven Jumbo Bags for Outdoor Applications

Several formulations were developed with polypropylene (PP) in combination with antioxidants, calcium stearate, hindered amine light stabilizers (HALS) and ultraviolet light absorber (UVA) for making woven jumbo bags, which will be capable of carrying a load of two tons of materials in outdoor conditions. Thin films of these formulations were extruded followed by stretching to improve mechanical properties. Both stretched and un-stretched PP films were subjected to severe accelerated weathering by ultraviolet (UV) radiation for various periods and it was observed that un-stretched films reached 50% retention of tensile strength (TS) within 500 hours of exposure, while stretched films (tapes) did not reach 50% TS retention even after 10,500 hours of the exposure indicating an improved UV stability of the stretched films of PP.     

Investigation of effect of protonic acid media on the optical and thermal properties of chemically synthesized poly(o-toluidine)

Conducting polymer, Poly(o-toluidine) was synthesized by chemical oxidative polymerization method using different inorganic acids such as HCl, H₂SO₄, HClO₄, HNO₃, H₃PO₄ and H₃BO₃ as protonic acid media. Synthesized polymers were characterized by UV-Visible and FT-IR spectroscopy. Conducting emeraldine salt phase of the polymer has been confirmed with the help of spectroscopic analysis. Thermal stability of these polymers were investigated by thermogravimetric (TG/SDTA) analysis. Increase in conductivity with increase in temperature was observed in all the samples.