Efficient three-component Gewald reactions under Et3N/H2O conditions

In a medium consisting of triethylamine and water, α-methylene ketones undergo room temperature Gewald reactions with elemental sulfur and ethyl cyanoacetate (or malononitrile) to yield 2-aminothiophene derivatives efficiently within short time periods. Because of the high polarity of the medium, products precipitate in the reaction mixtures spontaneously. This makes isolation of the products easy by simple filtration and avoids cumbersome chromatographic separations. Mechanistic studies suggest that the reactions proceed via a Knoevenagel condensation pathway.     

Prediction of hydrate formation conditions to separate carbon dioxide from fuel gas mixture in the presence of various promoters

In this study estimation of hydrate formation conditions to separate carbon dioxide (CO₂) from fuel gas mixture (CO₂+H₂) was investigated in the presence of promoters such as tetra-n-butylammonium bromide (TBAB), tetra-n-butylammonium fluoride (TBAF), and tetra-n-butyl ammonium nitrate (TBANO₃). The emission of CO₂ from the combustion of fuels has been considered as the dominant contributor to global warming and environmental problems. Separation of CO₂ from fuel gas can be an effective factor to prevent many of environmental impacts. Gas hydrate process is a novel method to separate and storage some gasses. In this communication, a feed-forward artificial neural network algorithm has been developed. To develop this algorithm, the experimental data reported in the literature for hydrate formation conditions in the fuel gas system with different concentrations of promoters in aqueous phase have been used. Finally, experimental data compared with estimated data and with calculation of efficiency coefficient, mean squared error, and mean absolute error show that the experimental data and predicted data are in acceptable agreement which demonstrate the reliability of this algorithm as a predictive tool.     

Porous calcium titanate and sorption and desorption of water under ambient conditions: a study by conventional and synchronous luminescence spectroscopy

We report chemical synthesis and characterization of micro/mesoporous CaTiO₃ by X-ray diffraction (XRD), nitrogen sorption/desorption, small angle XRD, diffuse reflectance optical spectroscopy, and luminescence spectroscopy under ambient conditions. We determined the energies of absorption and emission transitions through electronic midgap states in micro/mesoporous calcium titanate by optical spectroscopy, “conventional” photoluminescence (PL) spectroscopy and, for the first time, synchronous luminescence spectroscopy at 25?°C. Micro/mesoporous CaTiO₃ reversibly sorbs and desorbs water vapor in ambient air, with water sorption capacity being close to the total pore volume. The luminescence of micro/mesoporous CaTiO₃ in visible range at room temperature is repeatedly significantly increased upon desorption of water and decreased (quenched) upon sorption of water vapor in air, due to the interactions of the adsorbate with electronic surface midgap states.     

Investigation and characterization of the nanoscale precipitation sequence and their kinetics in Al–1.0% Mg2Si–0.4 wt% Si–0.5Cu (wt%) alloy

Nonisothermal differential scanning calorimetry technique has been applied on Al–0.63 mass% Mg–0.77 mass% Si–0.5 mass% Cu alloy. Seven reaction peaks have been observed from differential scanning calorimetry (DSC). High resolution transmission electron microscopic (HRTEM) investigation has also been carried out for specimens heated with the same heating rate to the peak temperatures of the corresponding processes in the differential scanning calorimetry scans in order to characterize the developed precipitates at these temperatures. As per our results obtained from DSC and HRTEM investigations, the precipitation sequence can be written as: α_sss → Si–Mg–vacancy clusters → GP zones → β″-phase and random precipitates → type C and/or Q′-phase → predominant Q′-phase + a few β(Mg₂Si)-phase and Si precipitates. In addition to that, the activation energies associated with the precipitation of β″ and Q′ were found close to the diffusion energies of Si and Mg in Al matrix. This result suggests that the diffusion of the solute atoms to form the precipitates is the appropriate mechanism of controlling both types of precipitates.     

A Study on Physical Properties of Melt Blended Acrylonitrile Butadiene Styrene/Ethylene Vinyl Acetate Modified with Linear Low Density Polyethylene and Montmorillonite

In this study, acrylonitrile butadiene styrene/ethylene vinyl acetate-based melt blends were prepared using linear low-density polyethylene as modifier. Commercially available sodium montmorillonite clay was organically modified and incorporated in blends. Fourier transformed infrared was used to confirm the structure of the blend and composites. Morphology of acrylonitrile butadiene styrene / ethylene vinyl acetate blend showed two-phase structure that formed a well-aligned pattern with fine nanoclay distribution. Addition of organo-modified clay depicted increase in tensile strength (43%) and modulus (89%) in damage-free range. XRD results of sodium montmorillonite, organically modified Na-montmorillonite, and PNCs were compared to investigate the degree of dispersion in matrix.     

Evaluation of thermal fire hazard of 10 polymeric building materials and proposing a classification method based on cone calorimeter results

The use of polymeric building materials has been grown in many countries of Middle East in recent years. However, there are only a few fire testing laboratories in this region. Therefore, development of a method for controlling the reaction to fire of materials with bench scale tests is necessary. Providing a framework for classification of thermal fire hazard of materials based on bench scale heat release rate results was attempted. The fire behavior of 10 polymeric building materials was tested with cone calorimeter. The relationship between reaction to fire variables and physical properties of tested samples was examined. The thermal fire hazards of materials were assessed using methods presented by different researchers and with Conetools software. The results revealed that time to ignition, peak rate of heat release, and total heat release are essential variables for determining the fire hazard of materials. A classification method is proposed, which can be used in building codes in countries where the full‐scale test facilities are not available. The method also can be used for quality control purpose and evaluation of fire behavior of materials in bench scale by manufacturers. An example of potential requirements for interior finishes for some occupancy types is also presented. Copyright © 2013 John Wiley & Sons, Ltd.     

Corrosion Behavior of Pure Copper Surrounded by Hank’s Physiological Electrolyte at 310 K (37 °C) as a Potential Biomaterial for Contraception: An Analogy Drawn Between Micro- and Nano-grained Copper

This work aims to evaluate the corrosion behavior of pure copper from the microstructural viewpoint for a biomedical application, namely intrauterine devices. For this purpose, Tafel polarization and electrochemical impedance spectroscopy (EIS) techniques were used to evaluate the corrosion behavior of annealed pure copper (with the average grain size of 45 ± 1 µm) and nano-grained microstructure in physiological electrolyte of Hank at 310 K (37 °C). Pure copper in nanoscale grain size, typically an average of 90 ± 5 nm, was successfully made by eight-cycle accumulative roll bonding process at room temperature. On the basis of Tafel polarization results, it was revealed that nano-grained sample had lower corrosion current density and more noble corrosion potential for prolonged exposure in Hank’s physiological solution at 310 K (37 °C). In addition, the EIS results showed that the nano-grained sample had more corrosion resistance compared to the coarse-grained one for long-time immersion.     

A fuzzy multi-objective programming model for supplier selection with volume discount and risk criteria

In contemporary supply chain management, the performance of potential suppliers is evaluated against multiple criteria. In this paper, a fuzzy multi-objective programming model is outlined to propose supplier selection taking quantitative, qualitative, and risk factors into consideration. Also quantity discount has been considered to determine the best suppliers and to place the optimal order quantities among them. The mixed integer derivative nonlinear programming is obtained from fuzzy multi-objective programming model by chance-constrained method. To solve this problem, an innovative method is proposed. In addition, several “what if” scenarios are facilitated. Finally, a real-life sample is used to validate the proposed model.