Broadband dielectric spectroscopy of Nafion‐117, sulfonated polysulfone (sPSF) and sulfonated polyether ketone (sPEK) membranes

Nafion^®‐117, sulfonated polysulfone (sPSF) and sulfonated polyetherketone (sPEK) are characterized using broadband dielectric spectroscopy in the frequency range of 10 MHz–100 mHz. Overall, there are 4–5 relaxation processes in these sulfonated membranes and a comparison of their spectral features allows assigning the relaxation processes. At an optimum amplitude of ～100 mV_rms, all the relaxations are clearly defined as the electrode polarization is minimized. At low temperatures (?130 °C), these membranes show a broad relaxation peak in the mid‐frequency region, which quickly shifts towards the high‐frequency region as the temperature is increased to ?90 °C. This peak is observed in proton exchange membranes for the first time due to the use of low ac amplitude, and it is assigned to the relaxation of the confined water in the micro‐pores. With all the membranes, the peak associated with ? SO₃H group relaxation is observed in the same frequency range at a temperature of ～?80 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44790.     

Semi-transparent thin film solar cells by a solution process

Easily processed, low cost, and highly efficient solar cells are desirable for photovoltaic conversion of solar energy to electricity. We present the fabrication of precursor solution processed CuInGaS2 (CIGS) thin film solar cells on transparent indium tin oxide (ITO) substrates. The CIGS absorber film was prepared by a spin-coating method, followed by two successive heat treatment processes. The first annealing process was on a hot plate at 300 °C for 30 min in air to remove carbon impurities in the film; this was followed by a sulfurization process at 500 °C in an H₂S(1%)/Ar environment to form a polycrystalline CIGS film. The absorber film with an optical band-gap of 1.52 eV and a thickness of about 1.1 µm was successfully synthesized. Because of the usage of a transparent glass substrate, a bifacial CIGS thin film device could be achieved; its power conversion efficiency was measured to be 6.64% and 0.96% for front and rear illumination, respectively, under standard irradiation conditions.     

Dynamic behavior of thin film sea water evaporators

This paper presents the results of analytic and experimental research on the dynamic and part-load behavior of horizontal aluminium-tube multieffect evaporators (ATME) of Israel Desalination Engineering (IDE) Ltd's make. The analytic investigation comprises the development of a computer program which describes the slow transients of the response of the evaporator to step changes in heating steam temperature. By reaching steady state at different steam temperatures it also calculates part-load behavior.The experiments were conducted on a 150 m³/day pilot plant at the IDE Tel-Baruch Test Station near Tel Aviv; they comprised startup tests and performance tests with variable heating steam temperatures, cooling water flow and vacuum system capacities. Comparison of the analytic and experimental results shows fair agreement.     

复合膜电极对溶液中碘离子电化学离子分离性能

在多孔碳纤维毡基体上通过化学沉积法制备了具有电活性的聚吡咯复合膜电极,在两电极体系下对溶液中的碘离子进行电化学离子吸附分离操作,其中氧化状态下具有阴离子交换功能的聚吡咯复合膜电极作阳极。考察了不同操作电压、溶液pH值对膜电极分离性能的影响,并在混合溶液中考察了膜电极对碘离子选择性。结果表明,电压的适当升高与溶液pH值的降低有利于提高膜电极对碘离子的吸附速率和容量增高。复合膜电极表现出对碘离子优良的选择性吸附特性和可多次重复使用性。     

复合膜电极对溶液中碘离子电化学离子分离性能

在多孔碳纤维毡基体上通过化学沉积法制备了具有电活性的聚吡咯复合膜电极,在两电极体系下对溶液中的碘离子进行电化学离子吸附分离操作,其中氧化状态下具有阴离子交换功能的聚吡咯复合膜电极作阳极。考察了不同操作电压、溶液pH值对膜电极分离性能的影响,并在混合溶液中考察了膜电极对碘离子选择性。结果表明,电压的适当升高与溶液pH值的降低有利于提高膜电极对碘离子的吸附速率和容量增高。复合膜电极表现出对碘离子优良的选择性吸附特性和可多次重复使用性。     

Mechanical properties and water vapor permeability of thin film from corn hull arabinoxylan

Isolated corn hull arabinoxylan was dissolved in water and provided a clear solution. Plasticizer (glycerol, propylene glycol, or sorbitol) was added to the arabinoxylan solution at 0–20 wt % (film dry weight), which was cast into stable films. Film thickness ranged from 22 to 32 μm. Mechanical properties, moisture content, and water vapor permeability (WVP) were studied for the arabinoxylan‐based films as a function of plasticizer concentration. Measured data for the corn hull arabinoxylan–based films were 13–18 wt % moisture content, 10–61 MPa tensile strength, 365–1320 MPa modulus, 6–12% elongation, and 0.23–0.43 × 10^?10 g m^?1 Pa^?1 s^?1 water vapor permeability. Plasticized arabinoxylan films produced in this study had lower WVPs than those of unplasticized films, which is likely attributable to the phenomenon known as antiplasticization. Scanning electron micrographs showed a homogeneous structure on film surfaces. Films containing sorbitol had the best moisture barrier properties. When grapes were coated with arabinoxylan and arabinoxylan/sorbitol films, weight loss rates of the fruit decreased by 18 and 41%, respectively, after 7 days. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2896–2902, 2004     

Thiol‐ene/clay nanocomposite thin film as novel transparent barrier

Thiol‐ene/clay (TE/clay) nanocomposite thin films were prepared by a simple photocuring process for use as transparent barrier films. In this work, tetrafunctional thiol and triene monomer were employed and organic clay surface modified with octadecylamine was mixed by sonication and a mechanical method as a reinforcing filler. The successful formation of the TE structure was confirmed by differential scanning calorimetry and X‐ray diffraction. The homogeneous dispersion (intercalation and exfoliation) of clay into the TE polymer matrix was observed with transmission electron microscopy. Atomic force microscopy images displayed the surface properties of the TE/clay nanocomposite thin films. The thermal expansion behavior of the resulting hybrid film was monitored by thermomechanical analysis. In addition, gas permeation properties as well as light transmittance of the TE/clay films were measured for potential applications in various fields as dimensionally stable films under heating and as a transparent barrier. Copyright © 2012 Society of Chemical Industry     

Recent Progress on Nafion‐Based Nanocomposite Membranes for Fuel Cell Applications

Proton exchange membrane fuel cells (PEMFCs) have attracted tremendous attention because of their high efficiency compared to other types of fuel cells. Nafion is the most commonly used polymer for membranes used in PEMFCs. A large variety of nanoparticles of different natures and sizes can be blended with a Nafion matrix, generating a new class of nanostructured electrolyte membrane with interesting physical properties. In this paper, we discuss the recent progress in the field of Nafion‐based nanocomposite membranes. They exhibit a significant improvement in thermo‐mechanical and thermal stability as well as proton conductivity at very low filler contents. The preparation, characterization, and properties of various types of Nafion‐based nanocomposite membranes are critically reviewed, and detailed examples are summarized.

     

Diamond film deposition from ethylene glycol/water solution using a dc-plasma jet method

A diamond film was deposited from a mixture of ethylene glycol and water using a dc−plasma jet method above liquid, in which the plasma was directly generated on a solution surface. Vaporized molecules from the surface were decomposed into radicals in the plasma. Optical emission spectroscopy revealed the presence of CO, OH, CH, C₂ and H. The relative intensities of C₂ to OH and CH increased with the ethylene glycol content. Diamond was deposited in the concentration range of ethylene glycol from 60 to 90 mol%. The 80 mol% concentration was the optimum value for diamond film deposition, whereas the lower concentration than 80 mol% resulted in an uncovered substrate at the center exposed to the jet. The typical growth rate of the diamond film was 10 μm/h. The crystalline film consisted of well faced particles less than 5 μm in size.     

A study of PVDF Langmuir‐Blodgett thin film using quartz crystal microbalance

Poly(vinylidene fluoride) (PVDF) was deposited onto a quartz crystal microbalance (QCM), using a standard Langmuir–Blodgett (LB) thin film deposition procedure. QCM technique was used to monitor the reproducibility of the LB film monolayer, and the fabricated QCM sensor was employed to detect the dimethyl methyl phosphonate (DMMP) vapor, a simulant of nerve agents. The results show that PVDF was successfully deposited from the water surface onto the quartz crystal substrate. The PVDF LB film is found to be highly sensitive to DMMP vapor, and frequency shifts are linear to the concentrations. The response of the sensor against DMMP is fast, large, and reversible. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Nanomechanical study of polymer‐polymer thin film interface under applied service conditions

Single layer and multilayer polymer thin film coating on polymer substrate are gaining significant importance in different industries. The quantitative and qualitative estimation of interface response for thin film coating under different service conditions is significantly important from the perspective of modeling and designing novel materials. However, to characterize an interface between the soft polymer layer and soft polymer substrate is challenging because of the confinement effect, surface roughness, the viscoelastic nature of the polymers involved, and most importantly, the comparable mechanical properties of soft polymeric film and polymer substrate. Nanoindentation technique was applied in this work to find out the mechanical response of thin film PMMA (100–200 nm) and Epoxy interfaces of different interfacial strengths. Interfaces of different strengths were obtained by exposing the film‐substrate system to different service conditions. It has been observed from this study that pile‐up plays a major role in finding out the mechanical response of the interfaces of different strengths. The hardness was observed to increase as the interfacial strength reduces. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43532.     

高效旋转薄膜蒸发器及其在糖液浓缩中的应用

介绍了高效旋转薄膜蒸发器的结构特点、性能特点及其用于物料浓缩的工艺流程 ,同时介绍了其在糖液浓缩中的应用 ,并与其它浓缩设备进行了对比     

Gas-tight yttria-doped barium zirconate thin film electrolyte via chemical solution deposition technique

A 500 nm thick yttria-doped barium zirconate (BZY) proton conducting electrolyte film, fabricated via a low-cost and high-throughput chemical solution deposition (CSD) technique, was sintered at a remarkably low temperature of 1000 °C, which is much lower than the typical solid state sintering temperature of minimum 1300 °C. Therefore, the detrimental issues, commonly encountered in solid state sintering, such as barium evaporation and phase separation, were not observed. Gas-tightness of the BZY film was confirmed by 8 h of stable open circuit voltage (OCV) at 1.08 V from a button fuel cell with NiO-BZY anode substrate and LSCF cathode. The application of the film is aimed at the electrolytes of intermediate to low temperature solid oxide fuel cells (SOFCs).     

The Enhancement Effect of Mesoporous Graphene on Actuation of Nafion‐Based IPMC

A facile method to fabricate ionic polymer‐metal composite (IPMC) actuators is proposed. A blend of mesoporous graphene (MG) and Nafion is used as the ionic matrix, which is sandwiched by two layers of blend of reduced graphene oxide (rGO) and Nafion as the electrodes. When subjected to an electrical field of 3 V, the IPMC actuator exhibits a blocking force of 10 gf g^?1 for 20 s, and the same behavior can be repeatedly played for hundreds of cycles. MG improves the mechanical properties of Nafion‐based IPMC, more importantly, the mesopores in graphene provide additional pathway for the diffusion of cationic clusters and thus enhance the actuation speed. In addition, the surface electrodes of rGO protect the interlamellar liquid from evaporation thus ensure the durability.

     

Aggregation properties of MEH-PPV/PMMA blends in solution and thin film

We conducted the first in-depth investigation into the (modified) aggregation state of poly-[2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylenevinylene] (MEH-PPV)/poly(methyl methacrylate) (PMMA)/toluene solution and solution-cast thin film to shed light on prior research reporting diverse, often ambiguous, trends regarding the efficacy of blending an optically inert polymer with conjugated polymer for optoelectronic applications. The major innovation consists in systematically correlating the characteristic ratio a ₁/a ₂ extracted from photoluminescence spectrum, which assesses the relative contribution of intrachain-exciton and interchain-aggregate species to light emission in thin film, with the ρ-ratio obtained from (index-matching) dynamic/static light scattering analyses, which reveals the structural compactness of aggregates in solution. We elucidated that this strategy led to an unambiguous revelation of the individual effects of MEH-PPV concentration, PMMA molecular weight, and the blending ratio—three essential factors not identified or discriminated previously—and shed light on the underlying MEH-PPV/PMMA interactions in solution that ultimately determine the optical performance of solution-cast thin film.     

Properties of syndiotactic-rich poly(vinyl alcohol) thin film in water. III. Contraction and extension of drawn and annealed thin film in water

Contraction and extension behaviors in water for drawn (four times original length) and annealed (at 60–215°C) thin films of poly(vinyl alcohol) (PVA_VTFA) derived from vinyl trifluoroacetate have been examined. At a constant temperature of 25°C, drawn films annealed at 60–190°C contracted after a certain standing time. Length of films annealed at 200°C did not change after standing of 20 min and film annealed at 215°C extended very little. As the temperature was raised, the drawn films annealed at 60–190°C contracted further until a certain temperature and then extended. The drawn film annealed at 200°C first started contraction at 70°C. The drawn film annealed at 215°C extended further very little until 75°C and then contracted very little until 99°C (in boiling water). In standing at 99°C, it contracted very little with standing and resisted without breaking for 300 min.     

Electrochemical oxidation of water on synthetic boron-doped diamond thin film anodes

Electrolysis in aqueous 1 M HClO₄ and 1 M H₂SO₄ solutions has been carried out under galvanostatic conditions using boron-doped diamond electrodes (BDD). Analyses of the oxidation products have shown that in 1 M HClO₄ the main reaction is oxygen evolution, while in H₂SO₄ the main reaction is the formation of H₂S₂O₈. In both electrolytes small amounts of O₃ and H₂O₂ are formed. Finally, a simplified mechanism involving hydroxyl radicals formed by water discharge has been proposed for water oxidation on boron-doped diamond anodes.     

Fabrication and properties of solution processed all polymer thin‐film ferroelectric device

A ferroelectric device, making use of a flexible plastic, polyethylenterephtalate (PET), as a substrate was fabricated by all solution processes. PET was globally coated by a conducting polymer, poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) acid (PEDOT/PSSH), which is used as bottom electrode. The ferroelectric copolymer, poly(vinylidenefluoride–trifluoroethylene) (PVDF–TrFE), thin film was deposited by spin‐coating process from solution. The top electrode, polyaniline, was coated by solution process as well. The ferroelectric properties were measured on this all solution processed all polymer ferroelectric thin‐film devices. A square and symmetric hysteresis loop was observed with high‐polarization level at 15‐V drive voltage on a all polymer device with 700 Å (PVDF–TrFE) film. The relatively inexpensive conducting polyaniline electrode is functional well and therefore is a good candidate as electrode material for ferroelectric polymer thin‐film device. The remnant polarization P_r was 8.5 μC/cm² before the fatigue. The ferroelectric degradation starts after 1 × 10³ times of switching and decreases to 4.9 μC/cm² after 1 × 10⁵ times of switching. The pulse polarization test shows switching take places as fast as a few micro seconds to reach 90% of the saturated polarization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011