Polybenzimidazole gel membrane for the use in fuel cell

Thermoreversible gelation of polybenzimidazole (PBI) in phosphoric acid (PA) is investigated by studying the gel morphology, thermodynamics of the gelation, and gelation kinetics utilizing test tube tilting and UV-Vis spectroscopy techniques. Gelation kinetics studies reveal that both the gelation rate and critical gelation concentration (C^∗_t=∞) are function of gelation temperature (T_gel) and the molecular weight of PBI. Highly dense fibrillar network morphology with large number of longer and thinner fibrils is obtained for higher gel concentration and higher molecular weight PBI. Both the gel melting (T_gm) and gelation (T_gel) temperature depend upon the gelation concentration and molecular weight of PBI. The presence of self-assembled chains of PA molecules, which help to produce the PBI crystallites, is observed from the thermodynamical study. I.R. and Raman studies prove the presence of strong hydrogen bonding interaction between the PBI and the PA molecules, and the free PA molecules in the gel network. The gelation occurs in two-step processes which include a slow rate determining conformational transition from coil to rod and followed by aggregation of rod via crystallization. The PA loading of PBI membrane obtained from the PBI-PA gel is significantly high compared to the conventional imbibing process membrane. The PBI gel membrane displays very high thermal and mechanical stabilities. The high acid loading and superb thermo-mechanical stability are due to the gel network structure of the membrane. The proton conductivity of the membrane at 160 °C and 0% relative humidity (RH) is ∼0.1 S cm⁻¹, which is higher than the reported values in the literature for the PBI. The activation energy of the proton conduction is 14-15 kJ/mol indicating faster proton transfer by hopping process inside the gel network.     

Control of cascaded transformer multilevel inverter based DSTATCOM

In this paper, the design of a distribution static compensator (DSTATCOM) based on cascaded transformer multilevel inverter is proposed. The topology requires controlling only a common dc storage capacitor. Two-level ramp-comparison current control method is extended for the multilevel inverter using phase-shifted multi-carrier PWM. The method provides equal switching stress and power handling for all the cascaded units. The net switching frequency increases while the ripple magnitude reduces using multilevel topology. These cause the feedforward gain to increase leading to a higher bandwidth of the control loop. An expression of the feedforward gain is derived for fixed switching frequency modulation of the inverter. It is shown that the use of proportional plus resonant controller with proposed multilevel modulation improves the tracking characteristics at fundamental frequency. A seven-level inverter based DSTATCOM is proposed for the application to the three-phase medium voltage distribution system and the results are shown through the PSCAD/EMTDC simulation. The proposed modulation and control scheme is validated through the experimental results that are obtained using the laboratory model of a single-phase, five-level inverter based DSTATCOM.     

Lipid distribution on textiles in relation to washing with lipases

Effectiveness of lipase in detergency was studied using three test soils (lard, artificial sebum, and olive oil) on a woven cotton fabric. Distribution of oily soil on fabrics was determined for three different treatments (unwashed, washed with detergent without lipase, and washed with detergent plus lipase). Osmium tetroxide was used to label lipid soil for analysis in the scanning electron microscope. Both longitudinal and cross-sectional backscattered electron images for unwashed samples showed that soil was present on surfaces of the cotton fibers and in interfiber spaces of the yarn bundle. Lard soiled samples had large deposits on the fabric surfaces, while artificial sebum and olive oil appeared more uniformly distributed throughout the textile. Oil was deposited in the interfiber capillaries of the yarn bundle and in the crenulation, secondary walls, and lumen of the fibers. Energy dispersive X-ray microanalysis was used to determine relative concentrations of oil at selected morphological locations within the fiber structure and at the fiber surface. Soil distributions within the fibrous structures differed with type of soil and laundry treatment. Backscattered electron images dramatically demonstrated the effect of lipase on cleaning. After washing with detergent plus lipase, yarn surfaces had much less residual soil; residual soil that remained was in the irregularities of the cotton fiber surfaces. Concentrations of oil in the secondary walls, crenulations, lumen, and the fiber surfaces were lower after lipase treatment for all three soils. While washing with detergent removed soil from the yarn and fiber surfaces and the crenulation of the cotton fiber, only the samples washed with detergent plus lipase had lower concentrations of soils within the secondary wall and lumen of the cotton fibers. Fabrics soiled with olive oil and washed with detergent plus lipase had the lowest concentrations of residual soil across the textile structure; the residual soil observed was mainly in the irregularities on the fiber surfaces.     

Human Serum Transferrin Fibrils: Nanomineralisation in Bacteria and Destruction of Red Blood Cells

Fibrils formed by human serum transferrin [(1–3 μM ) apo‐Tf, partially iron‐saturated (Fe_0.6‐Tf) and holo‐Tf (Fe₂‐Tf) forms], from dilute bicarbonate solutions, were deposited on formvar surfaces and studied by electron microscopy. We observed that possible bacterial contamination appears to give rise to long, pea‐pod‐like (PPL) structures for Fe₂‐Tf, attributable to the formation of polyhydroxybutyrate (PHB) storage granules, under the nutrient‐limiting conditions used. These PPL structures contained periodic nanomineralisation sites susceptible to uranyl stain. Extended incubation of transferrin solutions (about four days) gave rise to extensive transferrin fibril structures. Optical microscopy and AFM studies showed that red blood cells (RBCs) readily adhere to these fibrils. Moreover, the fibrils appear to penetrate RBC membranes and to induce rapid cell destruction (within about 5 h). It is speculated that in situations in vivo where transferrin fibrils can form, such interactions might have adverse physiological consequences, and further studies could aid the understanding of related pathological events.     

Effects of Silicon and Organic Manure on Growth,Fruit Yield,and Quality of Grape Tomato Under Water-Deficit Stress

Silicon - Mitigation of deleterious effects of drought stress on the growth and productivity of agronomic and horticultural crops warrants urgent and sustainable actions. Soil application of...     

Physical,mechanical, and transdermal diltiazem release analysis of nanosilica tailored various poly(vinyl alcohol) membranes

Hybrid membranes based on poly(vinyl alcohol) (PVA) of widely different molecular weights and ex situ nanosilica were synthesized and characterized as transdermal delivery device for Diltiazem hydrochloride. Investigations showed that change in PVA molecular weight strongly influenced physico‐mechanicals of the hybrids especially at low nanosilica content than at higher levels. As for example at 1 wt %, low molecular weight PVA induced finer dispersion of silica nanoparticles resulting into higher dry state crystallinity and mechanical strength but slightly lower biocompatibility as compared to high molecular weight PVA. Those variations in physico‐mechanicals finally affected Diltiazem retention and its elution from those membranes under physiological conditions. Low molecular weight PVA produced highest drug retention as well as slowest yet steady release than both high molecular weight PVA and neat PVA membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2076–2086, 2013     

Study of PANI-MeSA conducting polymer dispersed in UV-curing polyester acrylate on galvanized steel as corrosion protection coating

Polyaniline (PANI) was synthesized by chemical oxidative polymerization using methane sulfonic acid (MeSA) as dopant and ammonium peroxodisulfate as oxidizer. Coatings of PANI-MeSA dispersed in polyester acrylate resin were applied on galvanized steel and UV-cured. The UV-curing resin base was studied to provide high performance and environmental friendly coating system. Morphology and mechanical properties of the coatings were investigated by scanning electron microscopy (SEM) and microindentation hardness tests. Long-term open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements were performed in 3 wt.% NaCl solution. SEM images show dispersion of the PANI particles in the coating, and electrochemical studies show long term active anodic ennoblement introduced to the protective system in the presence of PANI, shifting OCP value to nobler region. The changes in impedance value of the system during long-term exposure to the electrolyte give useful information about the PANI mechanism of action in corrosion protection and indicate the redox action (changing of states) of PANI under the defects healing process.     

Negative ion beam extraction in ROBIN

The RF based single driver ?ve ion source experiment test bed ROBIN (Replica Of BATMAN like source in INDIA) has been set up at Institute for Plasma Research (IPR), India in a technical collaboration with IPP, Garching, Germany. A hydrogen plasma of density 5 × 10¹² cm^?3 is expected in driver region of ROBIN by launching 100 kW RF power into the driver by 1 MHz RF generator. The cesiated source is expected to deliver a hydrogen negative ion beam of 10 A at 35 kV with a current density of 35 mA/cm² as observed in BATMAN.In first phase operation of the ROBIN ion source, a hydrogen plasma has been successfully generated (without extraction system) by coupling 80 kW RF input power through a matching network with high power factor (cos θ > 0.8) and different plasma parameters have been measured using Langmuir probes and emission spectroscopy. The plasma density of 2.5 × 10¹¹ cm^?3 has been measured in the extraction region of ROBIN. For negative hydrogen ion beam extraction in second phase operation, extraction system has been assembled and installed with ion source on the vacuum vessel. The source shall be first operated in volume mode for negative ion beam extraction. The commissioning of the source with high voltage power supply has been initiated.     

How the monomer concentration of polymerization influences various properties of polybenzimidazole: A case study with poly(4,4′‐diphenylether‐5,5′‐bibenzimidazole)

In this work, a series of poly(4,4′‐diphenylether‐5,5′‐bibenzimidazole)s (OPBIs) were synthesized from 4,4′‐oxybis(benzoic acid) and 3,3′,4,4′‐tetraaminobiphenyl through the variation of the initial monomer concentration with a solution polycondensation technique in a poly(phosphoric acid) medium. The resulting polymers were characterized by various techniques such as infrared (IR), nuclear magnetic resonance, dynamic mechanical analysis (DMA), and thermogravimetric analysis. The initial monomer concentration in the polymerization mixture played an important role in controlling the molecular weight of the resulting polymers. A temperature‐dependent IR study showed that the free movement of the ? NH group of the imidazole ring was blocked by the absorbed moisture. The DMA study showed that the glass‐transition temperature (T_g) varied with the molecular weight, and the presence of the ether linkage in the OPBI polymer backbone had a significant influence on T_g. A high‐molecular‐weight OPBI polymer tended to form a supramolecular organization, which influenced the thermal characteristic of the polymer. Photophysical studies demonstrated the fluorescent characteristics of the OPBI polymers in both solid and solution states. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009