Characterization of CdSe thin films deposited by chemical bath solutions containing triethanolamine

Cadmium selenide (CdSe) thin films were prepared by chemical bath deposition on glass substrates at different temperatures beginning at room temperature (25 °C) upto 80 °C from an aqueous alkaline medium using a precursor solution containing cadmium acetate, 2,2′,2′′-nitrilotriethanol (triethanolamine), ammonia and sodium selenosulphate. The pH of bath was kept constant around 10.50±0.10. Energy dispersive analysis of X-rays confirmed that the films are nearly stoichiometric in composition. The structural and surface morphological properties have been studied by X-ray diffraction, Scanning electron microscopy and Atomic force microscope techniques. X-ray diffraction study reveals a cubic structure with preferential orientation along (111) direction. The dependency of structural parameters such as crystallite size, strain and dislocation density with different bath temperatures for CdSe thin films are calculated. X-ray peak broadening was used to evaluate the crystallite size and lattice strain by the Williamson–Hall plots. Optical properties are studied by photoluminescence spectra which shows blue shift in peak position and reduction in luminescence intensity were observed for films deposited at different bath temperatures.     

Effect of electron beam irradiation on the dielectric properties of fluorocarbon rubber

Terpolymeric fluorocarbon rubber (68 wt.-% fluorine, 1.4 wt.-% hydrogen) was subjected to electron beam irradiation using 1,1,1-trimethylolpropane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA), and pentaerythritol tetracrylate as radiation sensitizers. Compared to the original sample both the dielectric constant and the dielectric loss factor decrease for samples treated to a certain dose level, beyond which there is an increase. Similar improvement in dielectric properties is observed at relatively higher levels of TMPTA, owing to the increased degree of crosslinking. Among the various polyfunctional monomers used as radiation sensitizers, both the dielectric constant and the dielectric loss factor are higher for systems based on TPGDA due to the reduced crosslink density.     

Fatigue damage in a unidirectional SiC/Al composite due to push-pull and zero-pull loading

Axial fatigue behaviour due to fully reversible and zero-tension cyclic loads on specimens cut from a 5 mm thick panel of a unidirectional SiC/A1 composite has been investigated at room temperature. The panel contained 40 vol.% SiC fibres (SCS-2), sandwiched between 32 layers of A1 6061 foils, which were bonded together by hot-pressing. The loading was always parallel to the fibres. Steady hysteresis loops were observed in the stress-strain plot after about 3 cycles of loading. A plot of S/N curves showed that at load ratio R = 0 the fatigue strength of the composite was about 3 times higher than that of the monolithic matrix metal. At R = −1, however, the fatigue strength of the composite was even lower than that of the matrix metal. At both R = 0 and R = −1, the composite suffered large modulus losses (about 15%) at cycles well before the final failure. At R = 0 the modulus loss involved fibre breakage and matrix cracks, which were transverse as well as parallel to the loading direction, while at R = −1 it involved delamination cracks and barrelling of outer layers. Fractography after the final failure at R = 0 showed secondary cracks and fibre pull-out.     

Automated assume-guarantee reasoning for omega-regular systems and specifications

We develop a learning-based automated assume-guarantee (AG) reasoning framework for verifying ω-regular properties of concurrent systems. We study the applicability of non-circular (AG-NC) and circular (AG-C) AG proof rules in the context of systems with infinite behaviors. In particular, we show that AG-NC is incomplete when assumptions are restricted to strictly infinite behaviors, while AG-C remains complete. We present a general formalization, called LAG, of the learning based automated AG paradigm. We show how existing approaches for automated AG reasoning are special instances of LAG. We develop two learning algorithms for a class of systems, called ∞-regular systems, that combine finite and infinite behaviors. We show that for ∞-regular systems, both AG-NC and AG-C are sound and complete. Finally, we show how to instantiate LAG to do automated AG reasoning for ∞-regular, and ω-regular, systems using both AG-NC and AG-C as proof rules.     

Simultaneous effect of organoclay and controlled peroxide curing on dielectric properties and flammability of LLDPE/EMA blend

The effect of organoclay Cloisite^?20A and controlled peroxide curing on the dielectric properties and flammability of LLDPE/EMA blend is explored in this article. The organoclay Cloisite^?20A were melt blended with the LLDPE/EMA system at 1, 3, 5, and 7 wt% loading through the variation of the sequence of addition. The dielectric properties of the blend composites are evaluated at different temperature and frequency ranges. Results obtained reveal that the dielectric properties of LLDPE/EMA blend is influenced remarkably by extent of clay loading, variation of sequence of addition of organoclay, and controlled peroxide curing. Both the frequency and temperature dependency of dielectric constant is higher for filled samples than for control blend. On peroxide curing, dielectric constant decreases for all samples and is more significant in case of filled samples. The volume resistivity and breakdown voltage of the samples have also been evaluated. Limiting oxygen index of LLDPE/EMA blends is moderately improved on addition of organoclay.     

Thermal and thermo‐oxidative degradation study of a model LDPE/EVA based TPE system: Effect of nano silica and electron beam irradiation

The effect of nano‐silica on the thermal degradation behavior of Low density polyethylene‐poly(ethylene‐ co‐vinyl acetate) (LDPE‐EVA) based thermoplastic elastomeric (TPE) system was monitored using thermo gravimetric analysis (TGA) in nitrogen and oxygen atmospheres (air), respectively. The pristine nano silica was melt‐blended with the LDPE‐EVA system at different loadings by varying the sequence of addition. In one of the compositions, coupling agent (Si69) was used. In nitrogen, thermal stability of such systems remained unchanged. However, in oxygen atmosphere, the TGA thermograms reflected a dramatic change. A two staged degradation was observed for all the samples. The enhancement in thermal stability particularly upto the low conversion levels was interpreted in terms of the barrier effect of silica particles on the O₂ flow into the sample. The activation energies of degradation up to lower range of conversions were determined by nonisothermal and isothermal kinetic analyses. These were found to register a similar trend for various systems studied. Upon electron beam irradiation of such filled LDPE/EVA systems at controlled doses (20 and 40 kGy), the thermal stabilities were enhanced marginally. Overall, the thermal stabilities of the TPE nanocomposites are the function of sequence and extent of nano silica addition, presence of coupling agent and extent of irradiation. POLYM. COMPOS., 31:1387–1397, 2010. © 2009 Society of Plastics Engineers     

Dynamic and capillary rheology of LDPE‐EVA–based thermoplastic elastomer: Effect of silica nanofiller

The effect of pristine silica nanoparticles on the dynamic and capillary rheology of a model LDPE‐EVA thermoplastic elastomeric system is explored in this paper. The pristine silica nanoparticles were melt‐blended with the LDPE‐EVA system at 1.5, 3, and 5 wt% loadings, respectively, by varying the sequence of addition. In one of the compositions, coupling agent bis‐[3‐(triethoxysilyl)propyl] tetrasulphide (Si‐69) was used to improve the interaction of hydrophilic silica particles with polymer matrix. Results obtained reveal that the viscoelastic behavior of such composites is influenced remarkably by loadings of silica, variation of sequence, and addition of Si‐69. Upon addition of coupling agent, G′ value increases especially at higher strain levels due to increased polymer‐filler interactions. All systems with various loading of nanosilica represent an increase in elastic response with increasing frequency. Both the unfilled and filled blends exhibit rheological behavior of non‐Newtonian fluids. But interestingly, the viscoelastic response varies markedly with the temperature. The dynamic and steady shear rheological properties register a good correlation in regard to the viscous vs. elastic response of such systems. Finally, the rheological behavior is correlated with morphology of the present system processed at various shear rates. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Engineering properties of electron beam‐crosslinked ethylene methyl acrylate copolymer

Effect of electron beam on mechanical, thermal, and morphological properties of ethylene methyl acrylate copolymer, grade Elvaloy 1335 has been investigated. The copolymer was subjected to varying doses of electron beam radiation with different proportion of the sensitizer trimethylolpropane trimethacrylate (TMPTMA). It was observed that with increase in electron beam dose, the physicomechanical properties of the crosslinked copolymer improve, reaches an optimum level and subsequently deteriorates. The thermal properties as envisaged from thermogravimetric analysis and differential scanning calorimetric studies revealed stability of the crosslinked irradiated samples over that of the unirradiated ones. The thermal stability was also found to attain the maximum at the same level of radiation and sensitizer. The morphological studies showed consistency with the mechanical properties. Based on the overall study, it may be concluded that ethylene methyl acrylate copolymer with 1 phr TMPTMA at 60 kGy radiation dose is the optimum condition within the range studied in this investigation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010