A review on electrically conductive polypropylene and polyethylene

Conductive plastics are new generation functional materials with potential application in electronics, space and aviation industries. Polypropylene (PP) and polyethylene (PE) being most common, widely available and cheapest thermoplastic, if made conductive, can be revolutionary in the field of engineering thermoplastics. The article deals with the fabrication of electrically conductive PP and PE for electromagnetic interference/radio frequency (EMI/RF) shielding applications and protection against electrostatic discharge (ESD). It reviews different fillers used by researchers to fabricate conductive PP and PE, several factors that affect the electrical conductivity of thermoplastic composites and various processing methods that can be adopted to prepare such composites. It exhaustively covers the preparation of such conductive composites, the processing methods involved therein, and the electrical properties of the end material. Emphasis has been given to comprehend the percolation threshold and means to reduce the latter in order to achieve high electrical conductivity in PP‐ and PE‐based composites at relatively low filler loading. POLYM. COMPOS., 35:900–914, 2014. © 2013 Society of Plastics Engineers     

Mechanics and dynamics of the strain-induced M1-M2 structural phase transition in individual VO₂ nanowires

The elastic properties and structural phase transitions of individual VO(2) nanowires were studied using an in situ push-to-pull microelectromechanical device to realize quantitative tensile analysis in a transmission electron microscope and a synchrotron X-ray microdiffraction beamline. A plateau was detected in the stress-strain curve, signifying superelasticity of the nanowire arising from the M1-M2 structural phase transition. The transition was induced and controlled by uniaxial tension. The transition dynamics were characterized by a one-dimensionally aligned domain structure with pinning and depinning of the domain walls along the nanowire. From the stress-strain dependence the Young's moduli of the VO(2) M1 and M2 phases were estimated to be 128 ± 10 and 156 ± 10 GPa, respectively. Single pinning and depinning events of M1-M2 domain wall were observed in the superelastic regime, allowing for evaluation of the domain wall pinning potential energy. This study demonstrates a new way to investigate nanoscale mechanics and dynamics of structural phase transitions in general.     

Plasmonic photosensitization of a wide band gap semiconductor: converting plasmons to charge carriers

A fruitful paradigm in the development of low-cost and efficient photovoltaics is to dope or otherwise photosensitize wide band gap semiconductors in order to improve their light harvesting ability for light with sub-band-gap photon energies.(1-8) Here, we report significant photosensitization of TiO2 due to the direct injection by quantum tunneling of hot electrons produced in the decay of localized surface-plasmon polaritons excited in gold nanoparticles (AuNPs) embedded in the semiconductor (TiO2). Surface plasmon decay produces electron-hole pairs in the gold.(9-15) We propose that a significant fraction of these electrons tunnel into the semiconductor's conduction band resulting in a significant electron current in the TiO2 even when the device is illuminated with light with photon energies well below the semiconductor's band gap. Devices fabricated with (nonpercolating) multilayers of AuNPs in a TiO2 film produced over 1000-fold increase in photoconductance when illuminated at 600 nm over what TiO2 films devoid of AuNPs produced. The overall current resulting from illumination with visible light is ～50% of the device current measured with UV (?ω>Eg band gap) illumination. The above observations suggest that plasmonic nanostructures (which can be fabricated with absorption properties that cover the full solar spectrum) can function as a viable alternative to organic photosensitizers for photovoltaic and photodetection applications.     

Development of Environment Friendly Bio Cross-Linker Finishing of Silk Fabric

Silk fabric easy care performance was assessed by using carboxylic acids. Cross-linker used in this study was citric acid, while sodium hypophosphite (SHP) was incorporated as a catalyst for cross-linking with silk. Enhancement in the easy care performance and shrinkage was obtained after treatment with citric acid. In addition, formic acid was used as swelling agent and treated fabric exhibited superior performance when it was incorporated in the recipe of citric acid. Antimicrobial performance of the silk fabric was also enhanced by using the above mentioned formulation.     

Solubility measurement of methyl anthranilate in supercritical carbon dioxide using dynamic and static equilibrium systems

The solubility of methyl anthranilate in supercritical carbon dioxide was determined using dynamic and static equilibrium systems. Three temperatures (40, 60 and 80 °C) and a pressure range between 160 and 340 atm were applied for the dynamic solubility measurements. The flow rate was maintained at 0.5 mL min^?1 in the dynamic solubility measurements, where the solute solubility was claimed to be independent of the flow‐rate factor. Two temperatures (40 and 60 °C) and the pressure range between 100 and 265 atm were used in the static equilibrium system. The crossover pressure region was observed between 220 and 240 atm in the static system, but was not seen in the dynamic system. The solubility of methyl anthranilate determined by the static system was consistently higher than the dynamic solubility measurement, indicating that the static technique provided more reliable solubility data for methyl anthranilate than the dynamic technique. The solubility data obtained with the static system were in good agreement with the predictive models based on the Chrastil equation and the Peng–Robinson equation of state with the Panagiotopoulos and Reid mixing rule. Copyright © 2006 Society of Chemical Industry     

Experimental study of fine center electrode spark plug in bi-fuel engines

In the present work, the erosion of platinum fine center electrode spark plugs and conventional nickel plugs are investigated in a gasoline and natural gas bi-fuel engine. The effect of electrode erosion is evaluated by comparing the required ignition voltage and cold start ability of the different plug designs. After durability tests, platinum fine center electrode plug had insignificant electrode erosion and negligible gap growth; whereas the nickel plug had notable erosion and gap growth. There was no detectable side sparking for fine center electrode plugs. In terms of performance, the required ignition voltage of fine center electrode plug was lower than conventional spark plug. Also, results of a cold start test demonstrated that the starting time of the engine with fine electrode plugs was lower than conventional spark plugs. The surface of electrodes was studied by the scanning electron microscope and the energy dispersive X-ray spectroscopy techniques. Cracking and peeling was observed on the surface of the nickel conventional electrodes, but not on the surface of the platinum fine electrodes. These tests show that platinum fine center electrodes could be suitable for gasoline/natural gas bi-fuel engines to meet long lifetime demand.     

Sporulation and Heat Resistance of Spores from a Clostridium sp. RKD

A Clostridium sp. RKD isolated from the intestine of decaying fish, showing 99% sequence identity with Clostridium tetani at a 16S rRNA level, produced a neurotoxin that was neutralized by botulinum antitoxin (A+B+E). It also showed an amplification of near‐expected size when polymerase chain reaction (PCR) was performed using group‐ and type‐specific primers for botulinum neurotoxin type B. The isolate exhibited differences with both C. tetani and Clostridium botulinum with respect to phenotypic characteristics and chemotaxo‐nomic markers. Spore production was optimized with respect to media composition and stage of growth. Time‐dependant examination of sporulation revealed 2.6% to 49.0% spores in the late stationary phase culture when grown in different broth media. A simpler method for spore production and isolation from culture grown in tryptose sulfite cycloserine (TSC)/anaerobic agar sandwich resulted in >95% sporulation, which could be purified to near homogeneity by a simple 2‐step procedure. Thermal resistance of spores revealed a biphasic inactivation at lower temperatures with D values for linear inactivation varying from 26.6, 8.0, and 4.3 min at 70 °C, 80 °C, and 90 °C, respectively. The z values of 7.86 °C and 10.47 °C were obtained in the linear and tail regions, respectively. The Weibull parameter b values at 70 °C, 80 °C, and 90 °C were 27.38, 3.55, and 0.99, respectively, with a z’ value of 13.869 °C. The shape parameter n at 70 °C, 80 °C, and 90 °C were 0.63, 0.55, 0.45, respectively. Spores produced on 2 different media (cooked meat medium [CMM] and trypticase peptone yeast‐extract glucose [TPYG] agar) exhibited differences in heat resistance. The addition of lysozyme (50 jj.g/mL) before heat treatment resulted in increased thermal resistance of spores.