Synthesis and characterization of conducting polymer composites based on polyaniline–polyethylene glycol–zinc sulfide system

Hybrid semiconducting polymer composites containing polyaniline, polyethylene glycol and zinc sulfide have been prepared in various combinations by in-situ polymerization of aniline using ammonium per disulfate in acidic medium. A biomimetic approach of controlled precipitation has been used. A mechanism of formation of these hybrid materials has been suggested in which polyethylene glycol works as a medium for diffusion-limited growth of various components during their precipitation. These materials have been characterized by a variety of spectroscopic techniques, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and alternating current impedance spectroscopy. Equivalent circuits for different contributions from grain, grain boundary and electrode for different systems have been determined with the help of complex non-linear least square analysis software. The microstructure-property correlation have been discussed along with the possible conduction mechanisms from the temperature dependence of conductivity as variable-dimension variable-range hopping for different compositions of single, double and triple composite materials.     

Intrinsic Seebeck Coefficient of Quantum Dots

The Seebeck coefficient S is an important performance characteristic of thermoelectric materials. In this paper we establish the fact that quantum dots and single-electron tunneling devices with narrow, well-spaced energy levels and sharp transmission resonances have a Seebeck coefficient independent of material parameters. By employing a delta function for the transmission resonances we arrive at an intrinsic expression for S in terms of the fundamental electronic charge e. We further confirm the validity of our result in the case of a transmission resonance with finite width.     

Multifunctional plasmonic Ag-hematite nano-dendrite electro-catalysts for methanol assisted water splitting: Synergism between silver nanoparticles and hematite dendrites

Hydrogen is the most environment friendly fuel and has the largest energy density but still much away from being a viable technology due to the cost associated with its production on-site on-demand. However, hydrogen production via water splitting could become potential commercial technology by designing new catalyst materials with low cost, desired surface structures and properties that govern hydrogen evolution reaction (HER) activity and stability. Here, we report the methanol assisted electrochemical water splitting using silver nanoparticles decorated hematite (Ag-hematite) dendrite nanostructures. Ag-hematite nano-dendrites prepared via two different methods viz. chemical co-precipitation and hydrothermal treatment are analysed and compared for their potential applications towards methanol assisted water splitting. It is found that Ag-hematite nano-dendrites prepared by chemical precipitation method shows much better activity as compared to both the parent materials (i.e. Ag NPs and hematite nano-dendrites) as well as Ag-hematite nano-dendrites synthesized by hydrothermal treatment. A baseline study showing the influence of methanol concentration, catalyst, catalyst support, and operating mode has been established. The analysis of the system was carried out as a function of onset potentials and kinetic parameters, including the Tafel slopes and exchange current densities. The effect of electrochemical promotion was investigated to see if it can increase the efficiency and performance of H₂ production through electrochemical processes. The observed electro-catalytic enhancement could be attributed to the synergistic effect of hematite dendrites, larger surface area of dendrite structure leading to higher loading of Ag NPs on the surface of HDs. Moreover, the endurance study was performed to check the stability of the presented electrocatalyst in acidic medium under both dark and light illumination conditions which shows that the presented composite catalyst is stable for minimum 100 scans even under light illumination with no signs of photo-corrosion.     

Preparation and characterization of crosslinked chitosan microspheres for the colonic delivery of 5-fluorouracil

In this work, we attempted to develop a simple and inexpensive colon specific pulsatile drug-delivery system using chitosan microspheres loaded with 5-fluorouracil (5-FU) using an enteric-coated soft gelatin capsule. Chemical crosslinking by glutaraldehyde and interactions between the polymer and the drug were determined by Fourier transform infrared spectral study. Scanning electron microscopy of the microspheres revealed spherical shapes with smooth surfaces. Differential scanning calorimetry studies confirmed the molecular dispersion of the drug in the polymer matrix. Three different formulations (i.e., F1, F2, and F3) were prepared by the variation of the amount of 5-FU. Encapsulation efficiencies of 5.5, 10.8, and 17.9% for drug loadings of 10, 20, and 50%, respectively, were obtained. In vitro release studies were conducted at pH 1.2 and pH 7.4 (to simulate actual gastrointestinal fluid and gastrointestinal tract conditions, respectively). The results indicate that chitosan microspheres released 5-FU in both acidic (60%) and basic pH (40%) conditions, whereas the capsule (filled with chitosan microspheres) showed only 8–10% release in acidic media and nearly 90% in basic media within 12 h. The newly designed pulsatile capsule device could be used for targeting 5-FU to the colon. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

In situ synthesis of ammonia by catalytic hydrolysis of urea in the presence of aluminium oxide for safe use of ammonia in power plants for flue gas conditioning

BACKGROUND: Ammonia is applied to increase the efficiency of an electrostatic precipitator for fly ash removal from a flue gas stream from a boiler using fossil fuel. In the present work, the hydrolysis of urea to generate ammonia for flue gas conditioning, with the help of aluminium oxide catalyst, has been studied. RESULTS: The effect of temperature, catalyst and initial concentration on the conversion was studied. Conversion was found to increase exponentially with temperature. Addition of catalyst resulted in an increase in conversion. Experiments were conducted with different doses of catalyst, and the optimum dosage of catalyst for a particular feed concentration was determined. A decrease in conversion was observed when the initial concentration of ammonia was increased. CONCLUSION: A study of reaction kinetics showed the effect of reaction time on conversion of urea to ammonia. The catalytic hydrolysis of urea, using aluminium oxide behaved as a first‐order reaction; the rate constant at different temperatures was found, and the activation energy determined. Copyright © 2011 Society of Chemical Industry     

A warm standby redundant system with correlated failures and repairs

This paper presents the analysis of a two-unit warm standby system assuming a bivariate exponential density for the joint distribution of failure and repair times of the units. Investigations regarding the stochastic behaviour and important reliability characteristics of the system have been made and earlier results have been verified as particular cases. A few graphs have also been provided to support the theoretical results.     

Characterization of interfacial and mechanical properties of “green” composites with soy protein isolate and ramie fiber

Environment-friendly fiber-reinforced composites were fabricated using ramie fibers and soy protein isolate (SPI) and were characterized for their interfacial and mechanical properties. Ramie fibers were characterized for their tensile properties and the parameters for the Weibull distribution were estimated. Effect of glycerol content on the tensile properties of SPI was studied. Interfacial shear strength (IFSS) was determined using the microbond technique. Based on the IFSS results and fiber strength distribution, three different fiber lengths and fiber weight contents (FWC) were chosen to fabricate short fiber-reinforced composites. The results indicate that the fracture stress increases with increase in fiber length and fiber weight content. Glycerol was found to increase the fracture strain and reduce the resin fracture stress and modulus as a result of plasticization. For 10% (w/w) of 5 mm long fibers, no significant reinforcement effect was observed. In fact the short fibers acted as flaws and led to reduction in the tensile properties. On further increasing the fiber length and FWC, a significant increase in the Young's modulus and fracture stress and decrease in fracture strain was observed as the fibers started to control the tensile properties of the composites. The experimental data were compared to the theoretical predictions made using Zweben's model. The experimental results are lower than the predicted values for a variety of reasons. However, the two values get closer with increasing fiber length and FWC.     

A spiral shaped regenerative microfluidic fuel cell with Ni‐C based porous electrodes

Microchannel geometry, electrode surface area, and better fuel utilization are important aspects of the performance of a microfluidic fuel cell (MFC). In this communication, a membraneless spiral‐shaped MFC fabricated with Ni as anode and C as a cathode supported over a porous filter paper substrate is presented. Vanadium oxychloride and dilute sulfuric acid solutions are used as fuel and electrolyte, respectively, in this fuel cell system. The device generates a maximum open‐circuit voltage of ~1.2 V, while the maximum energy density and current density generated from the fuel cell are ~10 mW cm^?2 and ~51 mA cm^?2, respectively. The cumulative energy density generated from the device after five cycles are measured as ~200 mW after regeneration of the fuel by applying external voltage. The spiral design of the fuel cell enables improved fuel utilization, rapid diffusive transport of ions, and in‐situ regeneration of the fuel. The present self‐standing spiral‐shaped MFC will eliminate the challenges associated with two inlet membrane‐less fuel cells and has the potential to scale up for commercial application in portable energy generation.