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Shih-Wei Lee Zelalem Gudeta Abdi Jyh-Chien Chen Kuei-Hsien Chen 《Journal of polymer science. Part A, Polymer chemistry》2021,59(8):706-720
Sulfonated polyaryletherketones (SPAEK) bearing four sulfonic acid groups on the phenyl side groups were synthesized. The benzophenone moiety of polymer backbone was further reduced to benzydrol group with sodium borohydride. The membranes were crosslinked by acid-catalyzed Friedel-Crafts reaction without sacrifice of sulfonic acid groups and ion exchange capacity (IEC) values. Crosslinked membranes with the same IEC value but different water uptake could be prepared. The optimal crosslinking condition was investigated to achieve lower water uptake, better chemical stability (Fenton's test), and higher proton conductivity. In addition, the hydrophilic ionic channels from originally course and disordered could be modified to be narrow and continuous by this crosslinking method. The crosslinked membranes, CS4PH-40-PEKOH (IEC = 2.4 meq./g), reduced water uptake from 200 to 88% and the weight loss was reduced from 11 to 5% during the Fenton test compared to uncrosslinked one (S4PH-40-PEK). The membrane showed comparable proton conductivity (0.01–0.19 S/cm) to Nafion 212 at 80°C from low to high relative humidity (RH). Single H2/O2 fuel cell based on the crosslinked SPAEK with catalyst loading of 0.25 mg/cm2 (Pd/C) exhibited a peak power density of 220.3 mW/cm2, which was close to that of Nafion 212 (214.0 mW/cm2) at 80°C under 53% RH. These membranes provide a good option as proton exchange membrane with high ion exchange capacity for fuel cells. 相似文献
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The fluids containing nanoparticles have enhanced thermo-physical characteristics in comparison with conventional fluids without nanoparticles. Thermal conductivity and viscosity are thermo-physical properties that strongly determine heat transfer and momentum. In this study, the response surface method was firstly used to derive an equation for the thermal conductivity and another one for the viscosity of bioglycol/water mixture (20:80) containing silicon dioxide nanoparticles as a function of temperature as well as the volume fraction of silicon dioxide. Then, NSGA-II algorithm was used for the optimization and maximizing thermal conductivity and minimizing the nanofluid viscosity. Different fronts were implemented and 20th iteration number was selected as Pareto front. The highest thermal conductivity (0.576 W/m.K) and the lowest viscosity (0.61 mPa.s) were obtained at temperature on volume concentration of (80 °C and 2%) and (80 °C without nanoparticle) respectively. It was concluded that the optimum thermal conductivity and viscosity of nanofluid could be obtained at maximum temperature (80 °C) or a temperature close to this temperature. An increase in the volume fraction of silicon dioxide led to the enhancement of thermal conductivity but the solution viscosity was also increased. Therefore, the optimum point should be selected based on the system requirement. 相似文献
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Masoomeh Jafarinejad Maryam Ezoddin Navid Lamei Khosrou Abdi Nima Babhadi‐Ashar Nazanin Pirooznia Maryam Akhgari 《Journal of separation science》2020,43(16):3266-3274
A novel effervescent tablet‐assisted demulsified dispersive liquid–liquid microextraction based on the solidification of floating organic droplet was developed to determine methadone prior to gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. In this method, a tablet composed of citric acid, sodium carbonate, and 1‐undecanol was utilized. The resulting effervescent tablet generated carbon dioxide in situ to disperse 1‐undecanol in the sample. Thus, the dispersive and extraction processes were performed in one synchronous step. An aliquot of acetonitrile as the demulsifier solvent was used for the separation of two phases instead of centrifugation. Under optimal conditions, the developed method was linear up to 50 000 µg/L with correlation coefficients higher than 0.99. Moreover, limits of detection and limits of the quantification were in the range of 3‐10 and 7‐30 µg/L in water and biological samples, respectively. Intra‐ and interday precisions (n = 6) of the spiked methadone at a concentration level of 50 µg/L were over ranges of 5.1‐6.8% and 5.7‐7.1%, respectively. The preconcentration factors and recovery values were obtained in the range of 140‐145 and 98.1 to 101.6% in real samples, respectively. 相似文献
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Archiv der Mathematik - Let R denote a commutative Noetherian ring, $$\mathfrak {a}$$ an ideal of R, and M an $$\mathfrak {a}$$ -cofinite R-module. The purpose of this article is to show that for a... 相似文献
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Hoda Molavi Abbas Yousefpour Akbar Mirmostafa Ali Sabzi Sepideh Hamedi Milad Narimani Nazanin Abdi 《Chromatographia》2017,80(7):1129-1135
Methanol in insulating oil has been proposed as a new marker for condition assessment of the solid insulation system of power transformers. In the current work, as a first step of using the new marker, an analytical static headspace gas chromatography/mass spectrometry method has been developed, optimized, and validated to measure methanol and ethanol contents in the insulating mineral oil. The analyzing setup consists of a 6890 N gas chromatograph equipped with a 5973 network mass spectrometer (MS) in the absence of a costly headspace autosampler, and the chromatography separation was performed on a 60 m × 320 µm × 0.5 µm VF-WAXms GC column. Calibration curves have been provided using several concentrations of the alcohols, and also limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation percentage (RSD%) have been determined. 相似文献
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