Study of a Surface Plasmon Resonance Optical Fiber Sensor Based on Periodically Grating and Graphene

Silicon - In this paper an optical fiber sensor based on plasmonic resonance of graphene and periodically grating is designed and investigated. The proposed sensor consists of an optical fiber core...     

A new method to determine monomer concentration in the polymer particles of emulsion polymerization systems by dynamic light scattering

In the published article cited above, by considering corrections made on the eq. (19) which will be discussed in the next section, Figure 6 should be replaced with a following new Figure 1. Hence, and values of 0.379 and 5.68 mol.dm^?3, respectively, on pages 1055, 1061, and 1062 should be changed to their accurate values of 0.426 and 5.29 mol.dm^?3, respectively.     

Experimental investigation of continuous conductivity measurements during emulsion polymerizations having unstable/high‐fouling reaction mixture

Conductimetry is one of the online monitoring techniques employed for emulsion polymerization reactions, which can give continuous information about nucleation and growth of particles. The most important factor affecting conductivity sensors performance especially contacting (resistance) types is fouling. To investigate the consequences of fouling, four monomers with different tendencies for fouling were selected: methyl methacrylate, butyl acrylate, styrene, and butadiene. Two types of conductivity sensors were also selected to continuously measure conductivity: a two‐electrode sensor and an inductive sensor, and the performance of these sensors were evaluated based on some criteria such as conductivity behavior, amount of fluctuation, change in cell constant, repeatability, and status of the minimum of conductivity. The results obtained from the contacting sensor showed that fouling significantly decreased the performance of this sensor in different ways even in reaction mixtures having moderate fouling rates. However, the inductive conductivity sensor provided the possibility of reliably measuring conductivity during very high‐fouling and highly unstable emulsion polymerizations with very good repeatability. The capabilities of this sensor also allowed an exact recognition of the important points in the conductivity curves particularly the minimum of conductivity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44446.     

A computational study of adsorption H2S gas on the surface of the pristine,Al&P-doped armchair and zigzag BNNTs

Density function theory is used to study the H₂S adsorption on the surface of pristine, Al-, P- and Al&P- doped (4, 4) armchair and (8, 0) zigzag BNNTs. All considered different models for H₂S adsorption on the exterior and interior surface of nanotube are optimized by using B3LYP/6-31G (d, P) level of theory. The adsorption energy values (E_ads) of the B-I, B-II,C-I, D-I, D-II, F-I, F-II and H-II models are negative, while the E_ads values for the A-III, B-III, C-III, D-III, E-III, F-III, G-III and H-III models are positive. On the other hand, Al, P and Al&P doped in all models increase significantly the adsorption energy of H₂S on the surface of BNNTs, and so the selectivity of nanotube for adsorbing and making a sensor of H₂S increase significantly from original state. The positive values of the charge transfer parameters (ΔN) and more values of the electronic chemical potentials of H₂S gas for all studied models demonstrate that H₂S gas in this system has a donor electron effect on the nanotube. The MEP results display that a low charge transfer occurs from H₂S gas toward nanotube, resulting in a weak ionic bonding in the BNNTs’ surface.     

Preparation and characterization of a novel gelatin–poly(vinyl alcohol) hydrogel film loaded with Zataria multiflora essential oil for antibacterial–antioxidant wound‐dressing applications

This study was performed to evaluate the properties of poly(vinyl alcohol) (PVA), gelatin, and PVA–gelatin dispersions and films enriched with Zataria multiflora essential oil (ZO). The results reveal that the ζ potential, particle size, and viscosity values and the antioxidant and antibacterial activities of the dispersions changed significantly with the addition of ZO to the polymer matrix. Changes in the properties of the dispersions suggested the presence of interactions between PVA or gelatin and ZO. Such interactions could affect the mechanical and water‐barrier properties of the films. ZO induced remarkable decreases in the tensile strength, elastic modulus, and swelling and increases in the elongation at break, solubility, and water‐vapor permeability of the films. Scanning electron microscopy analyses proved the impact of ZO on the film morphology, which affected the film properties, including the mechanical and water‐barrier properties. The addition of ZO to the polymer led to a coarse film microstructure because of the hydrophobic ZO aggregates, which produced discontinuities in the film matrix. ZO considerably increased the antioxidant and antibacterial activities of the dispersions. Pseudomonas aeruginosa was the most resistant bacteria. The improved antioxidant and antimicrobial activities of the PVA–ZO and gelatin–ZO indicated that such products could effectively be used as wound dressings. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45351.     

Effect of support layer on gas permeation properties of composite polymeric membranes

PES/Pebax and PEI/Pebax composite membranes were prepared by coating the porous PES and PEI substrate membranes with Pebax-1657. The morphology and performance of the prepared membranes were investigated by SEM and CO₂ and CH₄ permeation tests. The CO₂ permeances of 28 and 52 GPU were achieved for PES/Pebax and PEI/Pebax composite membranes, respectively, with CO₂/CH₄ selectivities almost equal to that of Pebax (26). The experimental data were further subjected to a theoretical analysis using the resistance model. It was found that the porosity and the thickness of the dense section of PES substrate were an order of magnitude higher than those of PEI substitute. The porosity/thickness ratio of PEI substrate was, however, higher than PES, explaining the higher permeance of PEI/Pebax composite membrane. Substrates with porosities much higher than the Henis-Tripodi gas separation membrane were used in this work, aiming to achieve the selectivity of Pebax, rather than those of the substrate membrane materials.     

Simultaneously energy production and dairy wastewater treatment using bioelectrochemical cells: In different environmental and hydrodynamic modes

A successful design, previously adapted for treatment of complex wastewaters in a microbial fuel cell (MFC), was used to fabricate two MFCs, with a few changes for cost reduction and ease of construction. Performance and electrochemical characteristics of MFCs were evaluated in different environmental conditions (in complete darkness and presence of light), and different flow patterns of batch and continuous in four hydraulic retention times from 8 to 30 h. Changes in chemical oxygen demand, and nitrate and phosphate concentrations were evaluated. In contrast to the microbial fuel cell operated in darkness (D-MFC) with a stable open circuit voltage of 700 mV, presence of light led to growth of other species, and consecutively low and unsteady open circuit voltage. Although the performance of theMFC subjected to light (L-MFC)was quite lowand unsteady in dynamic state (internal resistance = 100 Ω, power density = 5.15 W·m^-3), it reached power density of 9.2 W·m^-3 which was close to performance of D-MFC (internal resistance = 50 Ω, power density = 10.3 W·m^-3). Evaluated only for D-MFC, the coulombic efficiency observed in batch mode (30%) was quite higher than the maximum acquired in continuous mode (9.6%) even at the highest hydraulic retention time. In this study, changes in phosphate and different types of nitrogen existing in dairy wastewater were investigated for the first time. At hydraulic retention time of 8 h, the orthophosphate concentration in effluent was 84% higher compared to influent. Total nitrogen and total Kjeldahl nitrogen were reduced 70% and 99% respectively at hydraulic retention time of 30 h, while nitrate and nitrite concentrations increased. The microbial electrolysis cell (MEC), revamped from D-MFC, showed the maximum gas production of 0.2 m³ H₂·m^-3·d^-1 at 700 mV applied voltage.     

Synthesis of polybutadiene nanoparticles by emulsion polymerization: The effect of electrolyte and initiator type on particle size and reaction kinetics

Emulsion polymerization of the butadiene (Bu) was performed in the presence of disproportionate potassium rosinate (DPR) as anionic emulsifier, potassium hydroxide (KOH), and potassium carbonate (K₂CO₃) as electrolytes, and three different initiators including potassium persulfate (KPS), 2,2^′-azobisisobutyronitrile (AIBN) or 4,4′-azobis(4-cyanovaleric acid) (ACVA, also known as VAZO) at 70 °C. Latexes were prepared with a solid content of about 30 wt%. The particle size and its distribution were measured by dynamic light scattering (DLS) analysis, while the polymerization conversion was determined gravimetrically at different time intervals. Results on the emulsion polymerization of Bu in the presence of KOH and K₂CO₃ co-electrolytes showed that adding KOH to the reaction media decreases the polymerization rate. Positive effect of co-electrolytes on the control over polybutadiene latex (PBL) particles size and its distribution was also confirmed, where K₂CO₃ played roles as electrolyte and pH buffer and KOH served double roles as electrolyte and alkaline supplier of the reaction media. Complete solubility of the AIBN in Bu resulted in higher rate of polymerization in the presence of AIBN in comparison to other initiators, i.e., VAZO or KPS. The results showed that initiator type plays a significant role on the formation of PBL nanoparticles and kinetics of the polymerization. The kinetic studies revealed that emulsion polymerization of Bu follows case 1 (i.e., \(\bar{n}\) ?0.5, where \(\bar{n}\) indicates average number of the propagating chains per particle) of the Smith-Ewart kinetics.     

真空感应熔炼炉真空度对Ni-Fe-Cr基合金力学性能的影响(英文)

为研究真空感应熔炼炉的真空度对Ni-Fe-Cr基合金力学性能的影响,在不同真空度条件下制备 4 个样品。化学分析结果表明:在氩气保护气氛下,Al和Ti的损耗较多,而在真空条件下其损耗较少。气体分析结果表明:样品中氧和氮的含量随真空度的增加而降低。而在更高的真空度下,样品中的氧和氮则没有损耗。热力学计算表明:由于平衡的氧含量值较低,TiO2和Al2O3生成的可能性高。高真空度使合金的拉伸强度和屈服强度降低,但是由于少量的杂质以及Al和Ti的损耗,合金的伸长率和断面收缩率增加。此外,提高真空度使合金由脆性断裂转变为韧性断裂。