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In order to achieve high current density in PEFCs, it is necessary to suppress the increase in concentration overvoltage caused by the liquid water in the gas diffusion layer (GDL), especially in substrate layer. This study aims to reduce the liquid water by removing the substrate layer to form by thin self-standing MPL which is made by specially arranged carbon mesh filled with carbon particles. Thickness of MPL is 50 mm to reduce oxygen transport resistance. Performance of the self-standing MPL was shown in the Fig.1. In-situ liquid water measurements using soft-Xray of self-standing MPL (Fig. (a)) and SGL-25BC (Fig. (b)) are compared. Self-standing MPL shows a drastic suppression of liquid compared with that of SGL-25BC. Figure 1

Cellulose nanofibers (CNFs) have been widely used as functional fillers in polymer composites. In the present study, polymer composite nanofibrous nonwoven air filters containing CNFs were prepared...

The development of oil and gas industries has resulted in environmental issues, such as oil pollution. Oil pollution in a marine environment, poses significant threats to not only coastal marine life, but also to the social economic activities of community living in the nearby areas. The spreading of the oil could be controlled efficiently using sorbents such as nanofiber, due to its high specific surface area, high porosity, small diameter, and small pore sizes properties. Common approach to produce nanofiber is by using electrospinning technique however, this technique has low productivity and requires a post treatment for solvent removal. However, a melt blowing technique is an alternative to electrospinning as it is highly productive and does not require any solvent. The mass production of nanofiber fulfils the demand of the material during an oil spill clean-up operation. Therefore, this review discusses the influence of melt blowing process conditions such as die, polymer, air and collector, on the properties of nanofiber targeted for oil-water separation for the application of oil spill clean-up.

The development of renewable energy technologies is of global importance. To realize a sustainable society, fossil-resource-independent technologies, such as solar- and wind-power generation, should be widely adopted. Pressure retarded osmosis (PRO) is one such potential renewable energy technology. PRO requires salt water and fresh water, both of which can be found at seawater desalination plants. The total power generation capacity of PRO, using concentrated seawater and fresh water, is 3 GW. A large amount of energy is required for seawater desalination, therefore, the introduction of renewable energy should be prioritized. Kyowakiden Industry Co., Ltd., has been working on introducing PRO to seawater desalination plants since 2001 and is attracting attention for its ongoing PRO pilot plant with a scale of 460 m3/d, using concentrated seawater and treated sewage water. In this study, we evaluated the feasibility of introducing PRO in existing desalination plants. The feasibility was examined based on technology, operation, and economy. Based on the number of seawater desalination plants in each country and the electricity charges, it was determined whether the introduction of PRO would be viable.

Nanofibers have unique functionalities based on their nanoscaled cross‐section, high specific surface area, and high molecular orientation inside the fibers. These functionalities can be improved by controlling their diameter, surface and internal structures. The introduction of ion‐exchange sites on the surface and/or inside the nanofibers provides novel high‐functional ion‐exchangers with high surface areas, high ion‐exchange and adsorption capacities, and high ionic conductivities. The present review highlights the fundamental aspects of ion‐exchange nanofibers (i.e. their size‐dependent unique properties and production methods) and their recent advances in the environment and energy applications (i.e. separation/purification processes and fuel cells). © 2018 Society of Chemical Industry

Steady-state pressure-retarded osmosis (PRO) performance of a pilot-scale (72 m2) cellulose triacetate (CTA) hollow fiber (HF) module using 0.5 M NaCl and tap water as the draw solution (DS) and feed solution (FS), respectively, was evaluated by a PRO test system with a DS regeneration unit under a wide range of operational conditions. We investigated the effects of varying operational parameters, such as DS and FS inlet flow rates and hydraulic pressure difference, on PRO performance (water flux, pressure drops on the FS and DS sides, and power density). To estimate the module performance, we used conventional membrane area-based power density (Warea), as well as proposed and used a novel estimable parameter, power output per module volume (Wvol.), which promises to be useful when designing full-scale PRO plants. The obtained Warea of the CTA HF module was 0.14 W/m2 and was approximately one sixth of the Warea reported for a thin-film composite (TFC) polyamide spiral wound (SW) module [Y. C. Kim et al., Environ. Sci. Technol, 2966–2973]. However, the Wvol. of the CTA HF module was 1.11 kW/m3-module and was at least 45% higher than those of the SW modules (0.75 kW/m3-module).

This study evaluates the feasibility of a power generation system adopting pressure retarded osmosis (PRO) using seawater and fresh water. The authors measured the membrane power density of a commercially available hollow fiber membrane module. The power density of the current membrane module is 3.1 W/m2, but 6.5 W/m2 is required to realize a commercially feasible power plant adopting PRO. In this case of the net output power is 2.8 W/m2 when the DS pressure was 1.5 MPa and the FS pressure was 0.1 MPa, respectively. The cost of power generation is 0.20 $/kWh assuming a commercial plant that uses 1 million m3 of seawater per day and has the calculated membrane power density. It is necessary to improve the A and B values per membrane module to realize this system. Here, the A and B values are coefficients representing water permeability and salt permeability, respectively. The target membrane power density can be achieved using A and B values per membrane module of 2.05 × 10−6 m/s/MPa and 5.5 × 10−9 m/s, respectively. This evaluation is based on theoretical calculations using the solution-diffusion model of membrane permeation in PRO.

Sea water reverse osmosis (SWRO) would face some problems like energy saving and management of concentrated brine. To solve these problems at the same time, the energy recovery by Pressure Retarded Osmosis (PRO) was proposed in the Mega-ton Water System project. Prototype plant test was conducted using concentrated brine from SWRO plant and fresh water from regional waste water treatment facility. Hollow-fiber membrane module were examined in the prototype plant and the test operation was carried out for more than one year. We have reached the maximum membrane power density, 13.5 W/m2, using 10-in. module. Followings were still existing obstacles for further effective PRO. It was also challenging how to get clean fresh water from waste or river water without additional cost. Innovative new technologies were also required to address these concerns. We have also estimated plant cost and surveyed financial impacts on the energy saving of SWRO operation, based on the situation of currently operated SWRO plants worldwide, especially about the Mega-ton scale ones. Those studies indicated that potential market of PRO was 1–2 GW, and 10% energy saving was possible on the Megaton scale SWRO plants. Those results indicate that the commercialization plant would be available very near future.

Reverse osmosis (RO) membranes have been widely applied to seawater desalination and wastewater reclamation, and many large RO plants (>100,000 m3/d) have been constructed since 2000. Energy efficiency is indispensable for large plants, especially for future mega-ton scale seawater reverse osmosis (SWRO) plant (1,000,000 m3/d). In order to reduce energy demand in RO operation, high-efficient low-pressure RO membrane, energy recovery device (ERD), and pressure-retarded osmosis (PRO) which would recover power from salinity gradient between freshwater and concentrated brine were studied in the “Mega-ton Water System” project. A PRO hollow fiber membrane module was newly developed, and a practical continuous operation has been examined at a prototype plant for one year. The maximum 13.5 W/m2 of membrane power density using 10-inch module was established at our prototype PRO plant. As the results of the plant cost estimation and the financial impacts on the energy saving operation at the mega-ton scale...

Efficient water desalination constitutes a major challenge for the next years and reverse osmosis membranes will play a key role to achieve this target. In this work, a high-performance reverse osmosis nanocomposite membrane was prepared by interfacial polymerization in presence of multiwalled carbon nanotubes. The effect of carbon nanotubes on the chlorine resistance, antifouling and desalination performance of the nanocomposite membranes was studied. We found that the addition of carbon nanotubes not only improved the membrane performance in terms of flow and antifouling, but also inhibited the chlorine degradation of these membranes. Several reports have acknowledged the benefits of adding carbon nanotubes to aromatic PA nanocomposite membranes, but little attention has been paid to the mechanisms related to the improvement of flow rate, selectivity and chlorine tolerance. We carried out a comprehensive study of the chemical and physical effects of carbon nanotubes on the fully crosslinked polyamide network. The chemical structure, chlorine resistance and membrane degradation was studied by several analytical techniques, permeation and fouling studies, whereas the microstructure of the nanocomposite was studied by small and wide angle X-ray scattering, high resolution transmission electron microscopy, and molecular dynamics. We found that the addition of the nanotube affects the interfacial polymerization, resulting in a polymer network with smaller pore size and higher sodium and chlorine rejection. We simulated the hydration of the membrane in seawater and found that the radial distribution function of water confined in the pores of the nanocomposite membrane exhibited smaller clusters of water molecules, thus suggesting a dense membrane structure. We analysed the network mobility and found that the nanotube provides mechanical stability to the polymer matrix. This study presents solid evidence towards more efficient and robust reverse osmosis membranes using carbon nanotubes as mechanical reinforcing and chlorine protection additive.

We have recently developed the Zs (Zetta spinning) system, which is composed of two high speed nanofiber manufacturing methods, and it is applicable for both polymer solutions and polymer melts. The Zs–solvent system can be used for a polymer solution, its flow rate from a nozzle is a maximum of 2 mL/min to produce nonwoven fabrics, the Zs–melt can be used for polymer melts, and the maximum production rate of the molten polymer is about 1–2 kg/h to produce nanofiber wadding, which was fabricated during the Zs–solvent development. The development of the Zs system to produce mass nanofibers has expanded their potential applications, which include filters for air pollution, water and oil treatment, battery separators, medical separation, desert greening, building materials, etc.

This paper reports the facile and high-throughput fabrication method of anisotropic Au nanoparticles with a highly sensitive local surface plasmon resonance (LPR) using cylindrical nanofibers as substrates. The substrates consisting of nanofibers were prepared by the electrospinning of poly(vinylidene fluoride) (PVDF). The Au nanoparticles were deposited on the surface of electrospun nanofibers by vacuum evaporation. Scanning electron microscopy revealed the formation of a curved Au island structure on the surface of cylindrical nanofibers. Polarized UV-visible extinction spectroscopy showed anisotropy in their LPR arising from the high surface curvature of the nanofiber. The LPR of the Au nanoparticles on the thinnest nanofiber with a diameter of ~100 nm showed maximum refractive index (RI) sensitivity over 500 nm/RI unit (RIU). The close correlation between the fiber diameter dependence of the RI sensitivity and polarization dependence of the LPR suggests that anisotropic Au nanoparticles improve RI sensitivity.

Salinity power generation using membrane modules was examined by the Pressure Retarded Osmosis (PRO) system between pure water and concentrated brine in the Mega-ton Water System Project under the Japanese national project of “Funding Program for World-Leading Innovative R&D on Science and Technology” (FIRST Program). Pure water and concentrated brine were supplied from sewage treatment center and sea water desalination plant, respectively. It was proved that PRO was available between concentrated brine and purified water from treated sewage so that it was possible to construct the commercial salinity power generation plan by PRO. The advanced works suggested that the novel PRO membranes, which had high water flux, should be developed if we completed the PRO between sea water and river water.

The small-angle X-ray scattering measurements during tensile deformation have been performed for studying the structure and mechanical property relationships of twisted carbon nanotube (CNT) yarns. The tensile strength distribution and the diameter changes during tensile deformation have also been measured. The orientation distribution of the CNTs in the yarn has been determined and its changes during tensile deformation have been related to the variation of the tensile modulus with the twist angle. The tensile modulus and Poisson’s ratio of the yarns decreased with increasing twist angle, whereas the tensile strength of the yarn showed a maximum at the twist angle of 25°. At this twist angle, the distribution width of the tensile strength was minimum indicating the higher uniformity of the yarn structure.

Microscaled non-woven fabrics with fiber diameters in the range 1.8–3.1 μm were prepared by electrospinning from a chloroform solution of a degradable multiblock copolymer (PDLCL) consisting of crystallizable poly(ω-pentadecalactone) hard segments (PPDL) and poly(e-caprolactone) switching segments (PCL). The surface morphology and microstructure of the non-woven fabrics were characterized by scanning electron microscopy, temperature-controlled scanning probe microscopy, wide angle X-ray diffraction (WAXD), and small angle X-ray scattering (SAXS). The microstructural analysis demonstrated that the rod-like domains of hard segment (PPDL) formed in the electrospun PDLCL fiber functioned as physical crosslinks. Cyclic, thermomechanical tensile tests showed that the electrospun PDLCL fabrics exhibited good shape-memory properties with strain recovery rates of Rr = 89–95% and strain fixity rates of Rf = 82–83% after the 2nd cycle, when small deformations were applied at clinically relevant temperatures.

Salinity power generation using hollow fiber modules was examined using the pressure-retarded osmosis (PRO) system between pure water and concentrated brine. Pure water and concentrated brine were supplied from a regional sewage treatment facility and sea water desalination (sea water reverse osmosis [SWRO]) plant. To minimize the effect of the concentration polarization near the membrane surface on the pure water side, the number of open ports in the module was increased from 3 to 4 and that modification was found to be effective because non-permeating pure water, which left the module through fourth port, flushed leaked salt from the brine side through the membrane. Our prototype PRO plant got the maximum output power density, 7.7 W/m2 at a 2.5 MPa hydraulic pressure difference and a 38% permeation of pure water into the brine. To remove the organic foulant in the pure water, a low pressure Reverse Osmosis (RO) membrane and coagulation–sedimentation method with ozonation showed good results. Ho...

Dialkyl quarter- and quinquethiophenes end-capped with β-connected thiophenes are prepared, and the field-effect transistor (FET) properties are investigated. Molecular orbital calculation as well as the redox and optical measurements indicate that the β-isomers have low-lying HOMO levels and large energy gaps compared with the α-isomers. Molecular packing of the dihexylquaterthiophene with β-isomers consists of a typical herringbone motif analogous to the α-isomers. In the single crystal, the alkyl chains are extending in the tilted directions from the core molecular plane, but straightly extending in the thin films, resulting in even more perpendicular molecular arrangement to the substrate than the α-isomers. These β-isomers show p-type FET performance comparable to the corresponding α-isomers, whereas all new oligothiophenes show air stability better than the corresponding α-isomers. In particular, dihexylquinquethiophene with β-isomers has shown significantly improved air stability maintained over 270 days. This stabilization effect is ascribed to the low-lying HOMO level and the dense packing realized by perpendicular molecular arrangement.

Liquid crystal polymer (LCP) nanofibers were prepared by electrospinning from isotropic and biphasic poly(γ-benzyl-L-glutamate) (PBLG)/dichloromethane-pyridine solutions. The as-spun PBLG fiber from the isotropic solutions had an undulating orientation of closed packed α-helices like a serpentine trajectory. The as-spun fibers from the biphasic solutions containing the LC phase, on the other hand, had uniaxially oriented hexagonal lattices of α-helices along the fiber axis. These results indicated that the orientation of the ordered structure of the electrospun lyotropic LCP fibers can be controlled by the initial microstructure of the spinning solution.

In the present paper, we report a novel ion-exchange carbon nanomaterial, surface sulfonated carbon nanofiber (S-CNF) fabrics, with a high surface area and high ion-exchange and adsorption capacities. S-CNF fabrics bearing SO3H groups were prepared by electrospinning, successive carbonization and sulfonation. We observed a nanosize effect, in which the surface area, and ion-exchange and adsorption capacities significantly increase with a decrease in the fiber diameter. The prepared fabrics with a diameter of 80 nm had the maximum values for the total pore surface area of 32.2 m2 g−1, the ion-exchange capacity of 2.94 mmol g−1, and an adsorption capacity of 943.1 mg g−1 for methylene blue (MB). The MB adsorption capacity is two times higher than that of commercial activated carbons. These results highlight the fact that the surface functionalized CNF fabrics with ionic groups are promising materials for high-capacity ion-exchangers.

Carbon nanotubes/polyamide (PA) nanocomposite thin films have become very attractive as reverse osmosis (RO) membranes. In this work, we used molecular dynamics to simulate the influence of single walled carbon nanotubes (SWCNTs) in the polyamide molecular structure as a model case of a carbon nanotubes/polyamide nanocomposite RO membrane. It was found that the addition of SWCNTs decreases the pore size of the composite membrane and increases the Na and Cl ion rejection. Analysis of the radial distribution function of water confined in the pores of the membranes shows that SWCNT+PA nanocomposite membranes also exhibit smaller clusters of water molecules within the membrane, thus suggesting a dense membrane structure (SWCNT+PA composite membranes were 3.9% denser than bare PA). The results provide new insights into the fabrication of novel membranes reinforced with tubular structures for enhanced desalination performance.

This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50 °C )= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability.

In membrane separation, the incorporation of a given target molecule into a membrane is an important process to express permselectivity. Molecular imprinting method is an easy way to introduce molecular recognition sites into synthetic membranes. Applying an alternative molecular imprinting, various polymeric materials can be converted into membranes with molecular recognition sites toward a given target molecule. In membrane separation, flux values, and permselectivities, which often show a trade-off relationship, are important membrane performances. In a sense, the enhancement of flux is more important than that of permselectivity. Molecularly imprinted nanofiber membranes, which are fabricated by simultaneously applying an alternative molecular imprinting and an electrospray deposition, have potential that both flux and permselectivity can be simultaneously enhanced.

In this study, the effect of cationic surfactant (benzalkonium chloride) on the transport of KCl through a sulfonated styrene-divinyl benzene cation-exchange membrane was investigated. The presence of benzalkonium chloride as the cationic surfactant, which interacts with the sulfonic groups on membrane surface, has to disturb the transport of K+ ions and directly gives responses in its chronopotentiogram. The electrodialysis of the cationic surfactant solution showed an irreversible monotonous increase of the total system potential due to the fouling phenomena. However, a small amount of cationic surfactant in the membrane surface vicinity was observed to give a fluctuating chronopotentiogram at the high current density. This fluctuation is started by a steep increase and followed by the decrease of potential, which finally relaxed to reach a steady state. This potential fluctuation is proposed to be the response of a structural transformation of surfactant micelles on the membrane surface under perturbation of the externally applied electric field, which is discussed and examined qualitatively in this report.

Electrospinning is a versatile method for forming continuous thin fibers based on an electrohydrodynamic process. This method has the following advantages: (i) the ability to produce thin fibers with diameters in the micrometer and nanometer ranges; (ii) one-step forming of the two- or three-dimensional nanofiber network assemblies (nanofibrous membranes); and (iii) applicability for a broad spectrum of molecules, such as synthetic and biological polymers and polymerless sol-gel systems. Electrospun nanofibrous membranes have received significant attention in terms of their practical applications. The major advantages of nanofibers or nanofibrous membranes are the functionalities based on their nanoscaled-size, highly specific surface area, and highly molecular orientation. These functionalities of the nanofibrous membranes can be controlled by their fiber diameter, surface chemistry and topology, and internal structure of the nanofibers. This report focuses on our studies and describes fundamental aspects and applications of electrospun nanofibrous membranes.

For a material for organic thin-film transistors, not only high mobility but also low threshold voltage and long-term stability are important requirements. In order to realize these properties, materials with relatively large oxidation potentials, namely weak donors, have been designed as p-channel organic semiconductors. Here we propose a different strategy; transistor properties of dibenzotetrathiafulvalene (DBTTF) are significantly improved by the introduction of tert-butyl groups. Although this chemical modification does not much change the ionization potential, small threshold voltage and stability over several months are attained together with the improved mobility, probably due to some kind of passivation effect of the bulky tert-butyl groups. In contrast, the systematic fluorine substitution rapidly diminishes the transistor performance. There are two kinds of herringbone structures with much different dihedral angles of about 50° and 130°, and the tert-butyl compound falls into the former category.

Multiwalled carbon nanotube (MWNT)/poly(vinyl butyral) (PVB) composite nanofibers were prepared by electrospinning, successive twisting and heat treatment. The MWNTs were highly oriented in an electrified thin jet during electrospinning. The heat treatment of the twisted electrospun nanofiber yarns produced the characteristics of the CNT in the composite nanofiber yarns and enhanced their electrical properties, mechanical properties, and thermal properties. The electrical conductivity of the heated yarn was significantly enhanced and showed the maximum value of 154 S cm(-1) for the yarn heated at 400 °C. It is an order of magnitude higher than other electrospun CNT composite materials. These results demonstrated that the novel top-down process based on electrospinning, twisting, and heat treatment provide a promising option for simple and large-scale manufacture of CNT assemblies.

A pressure-retarded osmosis (PRO) power generation system is a hydroelectric power system which utilizes permeation flow through a semipermeable membrane. Permeation flow is generated by the potential energy of the salinity difference between sea water and fresh water. Since the cost of the membrane is high, the permeation performance of the membrane must be improved in order to realize PRO systems. We have investigated reverse osmosis (RO) membrane products as semipermeable membranes and measured the permeation volume of a few products. The generation power per unit membrane area calculated from the permeation volume is about 0.62 W/m2. But as a result of our improvements (greater salt water volume, spacers for fresh water channel with the function of discharging concentrated salinity, extralow-pressure type of membrane, washing the support layer of membrane when the generation power falls by half) the generated power may be 2.43 W/m2. Then the power system cost would be about 4.1 million yen/kW. In addition, if the support layer of the membrane is made thinner and a PRO system is applied to equipment where pumping power for another purpose is available (wastewater treatment plants located at the seaside, thermal and nuclear power plants, sea water desalination plants), the generated power may be increased. These improvements may enable PRO systems to be realized at a cost close to that of photovoltaic power systems. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(2): 8–20, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.21000

A series of β-linked quaterthiophene and tetrathiafulvalene dimers 1–4 has been prepared. Their redox and optical properties are almost the same as the parent monomers indicative of very little interaction between the monomers. Crystal structures of 1, 2, and 4 are highly one-dimensional, in which molecular structure of 1 is planar whereas those of 2 and 4 are in a bent form.

Solid-state and flexible zinc carbon (or Leclanche) batteries are fabricated using a combination of functional nanostructured materials for optimum performance. Flexible carbon nanofiber mats obtained by electrospinning are used as a current collector and cathode support for the batteries. The cathode layer consists of manganese oxide particles combined with single-walled carbon nanotubes for improved conductivity. A polyethylene oxide layer containing titanium oxide nanoparticles forms the electrolyte layer, and a thin zinc foil is used as the anode. The battery is shown to retain its performance under mechanically stressed conditions. The results show that the above configuration can achieve solid-state mechanical flexibility and increased shelf life with little sacrifice in performance.