Electrospinning preparation of a graphene oxide nanohybrid proton‐exchange membrane for fuel cells

Proton‐exchange membrane (PEM) is a core component of fuel cells that provides a channel for proton migration and transport. Prevailing PEMs fabricated using well‐established casting techniques have several limitations such as low proton conductivity, high fuel permeability, and poor stability. To overcome these shortcomings, this article introduces a graphene oxide (GO)‐based nanohybrid Nafion nanofiber membrane prepared using a facile electrospinning technique. On the one hand, electrospinning nanofibers provide efficient transport paths for protons, which tremendously enhance the proton conductivity. On the other hand, GO doping in PEM improves the self‐humidification, stabilities (mechanical, thermal, and chemical), and proton conductivity and reduces the fuel permeability. In this research, nanofiber membranes were obtained from Nafion solutions containing 0, 0.1, and 0.2 wt % GO via electrospinning. The morphology, structure, mechanical properties, proton conductivity, water uptake, and swelling properties of the membranes were studied. The results demonstrated that the comprehensive performance of PEM was significantly improved. The new findings may promote the wide application of PEM fuel cells. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46443.     

Polymeric gadolinium chelate–containing magnetic resonance signal‐enhancing coating materials: Synthesis,characterization, and properties

The present investigation deals with studies on novel magnetic resonance signal‐enhancing coating materials. The polyaminocarboxylate complexes of Gd³⁺ as side chains were prepared by the conjugation of N‐(2‐hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) with poly(styrene‐maleic acid) copolymer (SMA). The complexation of the Gd³⁺ ion to the conjugates was carried out by adding GdCl₃ to the solution of the polymer ligands. The resulting Gd³⁺‐containing polymer complexes were characterized by GPC, FTIR, NMR, and inductively coupled plasma–Auger electron spectroscopy, which confirmed that HEDTA was covalently attached to SMA and Gd³⁺‐containing polymer complexes were formed. The PP catheters were coated with the Gd³⁺‐containing polymer complexes and characterized by XPS. The result confirms that the Gd³⁺ complexes were coated on the surface of PP catheters. In the relaxation test, the relaxation rates of the water proton in the vicinity of the coated PP catheter surface increase significantly, suggesting that Gd³⁺‐containing polymer complex coating materials show great MR enhancement of water proton, and potentialities in making catheters used for endovascular interventions or therapy, visible by MRI. The influence of protein on the relaxation rates of coated PP catheter shows that the protein adsorption on the catheter surface influences the enhancement of the MR signal for the coating materials of Gd³⁺‐containing polymer complex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1358–1364, 2003     

Surface properties of emulsan‐analogs

The colloidal properties of emulsans formed by incubations of Acinetobacter calcoaceticus RAG‐1 on different carbon sources were studied. The apparent critical micelle concentrations (CMC) of the emulsans tested ranged from 25 to 58 mg/dm⁻¹. Surface and interfacial tensions of the solutions showed little dependence on pH between 2 and 10. In contrast, increasing the pH from 2 to 6.5 resulted in a substantial increase in their ability to effectively emulsify aliphatic hydrocarbons. Hexadecane‐in‐water emulsions were prepared having droplet sizes between 6 and 19 µm. Many of the emulsions thus formed were found to be stable with respect to coalescence for several months. Certain structural features such as the total content of fatty acids and hydroxy fatty acids were found to have a significant effect on emulsifying activity. The maximum emulsifying activity occurred for emulsans containing about 460 nmol of total fatty acid per mg of emulsan (nmol mg⁻¹). Emulsifying activity also showed a maximum at about 170 nmol mg⁻¹‐emulsan of 2‐ and 3‐ hydroxy dodecanoic acids. For substituents having chain lengths ≥15 carbonatoms, the emulsifying activity on hexadecane increased with their content up to 190 nmol mg⁻¹. On the other hand, for substituents having chain lengths of <15 carbonatoms, the emulsifying activity on hexadecane showed no obvious effect with their content up to 220 nmol mg⁻¹. A further increase in the shorter chain length fatty acids resulted in a decrease in emulsifying activity. Hence, a substrate‐specific interaction between emulsans and the dispersed phase was observed. © 1999 Society of Chemical Industry     

Effect of PES on the morphology and properties of proton conducting blends with sulfonated poly(ether ether ketone)

Development of alternate materials to Nafion, based on ionically conducting polymers and their blends is important for the wider applications of proton exchange membrane fuel cells. In this work, blends of sulfonated poly(ether ether ketone) (SPEEK) with poly(ether sulfone) (PES) are investigated. SPEEK with various ion exchange capacity (IEC) was prepared and blended with PES, which is nonionic and hydrophobic in nature. A comparative study of the water uptake, proton conductivity, and thermo‐mechanical characteristics of SPEEK and the blend membranes as a function of the IEC is presented. Addition of PES decreases the water uptake and conductivity of SPEEK. Chemical and thermal stability and mechanical properties of the membrane improve with the addition of PES. The effect of water content on the thermo‐mechanical properties of membranes was also studied. The morphology of blend membranes was studied using SEM to understand the microstructure and miscibility of the components. On the basis of the results, a plausible microstructure of the blends is presented, and is shown to be useful in understanding the variation of different properties with blending. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of lipid oxidation on fish lipids — amylopectin interactions

The results of studies on fish lipid oxidation effects on lipid‐amylopectin starch interactions are presented. Particular attention is paid to fish lipid availability (extractability from the system) and fatty acid contributions to individual lipid groups after mixing‐provoked interaction and after a 30‐day storage at —18 °C. The study involved model systems containing fish lipids at different levels of oxidation, lipids containing an antioxidant (BHA), and gelatinised amylopectin starch in a 10% aqueous solution. The lipid to starch ratio was 1:1. The test systems were subjected to selective extraction. The extracts were assayed for lipid content, peroxide value, anisidine value, fluorescence, and fatty acid composition. Compared to fresh fish lipids, those lipids, which were oxidised to a higher extent were shown to be more amenable to complexing with amylopectin, but they were also more readily released during frozen storage. On the other hand, addition of BHA stabilised the lipid‐amylopectin starch interaction during storage at —18 °C. In the entire systems tested, polyunsaturated fatty acids, eicosapentaenoic and docosahexaenoic acids in particular, proved to be most susceptible to binding, up to 90% of the latter being complexed.     

Effect of natural rubber on wood‐reinforced tannin composites

Natural rubber latex was added to composite materials formulated from a quebracho tannin adhesive crosslinked with hexamethylenetetramine and wood flour as a reinforcing filler. The final microstructure of the thermoset modified by the addition of different concentrations of latex was observed by scanning electron microscopy. The flexural and impact behavior of the modified materials was analyzed and related to the final microstructure of the composites. The effect of exposing the materials to humid environments was also evaluated. The measurements indicated that the addition of latex did not significantly reduce water absorption. However, it facilitated the preparation process of samples with low filler contents because of the increased viscosity of the mixture, which inhibited particle settling. On the other hand, the flexural properties increased with the addition of latex‐containing proteins through a reaction similar to tanning in leathers. The impact properties presented a similar trend, with the largest change occurring between 0 and 5% natural rubber in the matrix formulation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Intermediate Temperature Anode‐Supported Fuel Cell Based on BaCe0.9Y0.1O3 Electrolyte with Novel Pr2NiO4 Cathode

A proton conducting ceramic fuel cell (PCFC) operating at intermediate temperature has been developed that incorporates electrolyte and electrode materials prepared by flash combustion (yttrium‐doped barium cerate) and auto‐ignition (praseodymium nickelate) methods. The fuel cell components were assembled using an anode‐support approach, with the anode and proton ceramic layers prepared by co‐pressing and co‐firing, and subsequent deposition of the cathode by screen‐printing onto the proton ceramic surface. When the fuel cell was fed with moist hydrogen and air, a high Open Circuit Voltage (OCV > 1.1 V) was observed at T > 550 °C, which was stable for 300 h (end of test), indicating excellent gas‐tightness of the proton ceramic layer. The power density of the fuel cell increased with temperature of operation, providing more than 130 mW cm^–2 at 650 °C. Symmetric cells incorporating Ni‐BCY10 cermet and BCY10 electrolyte on the one hand, and Pr₂NiO_{4 + δ} and BCY10 electrolyte on the other hand, were also characterised and area specific resistances of 0.06 Ω cm² for the anode material and 1–2 Ω cm² for the cathode material were obtained at 600 °C.     

The Determination of Surface Development in Cement Pastes by Nuclear Magnetic Resonance

Pulsed proton NMR was used to determine the specific surface of hydrating cement pastes. The method is based on the fact that the measured proton spin-lattice relaxation rate (l/ T₁ ) of water in cement pastes is (in view of the fast exchange between water molecules in the adsorbed and bulk phase) proportional to the fraction of water molecules covering the solid surface and thus proportional to the NMR surface of the newly grown hydration products. In general, the method can be used for powders, fibrous and porous materials in contact with liquid water, or other fluids containing protons.     

Fatty Acid Deoxygenation in Supercritical Hexane over Catalysts Synthesized Hydrothermally for Biodiesel Production

Deposition of catalytically active metal‐containing compounds on solid porous supports by using superheated (subcritical) water is a promising way to produce materials with unique physicochemical and catalytic properties. The hydrothermal method has been found to give catalysts with high surface area, fine distribution of the active phase, and high catalytic activity. In the current work, the catalytic activities of 10 % Ni and 10 % Co deposited on hyper‐cross‐linked polystyrene (HPS) by the hydrothermal method in the supercritical deoxygenation of fatty acids were compared. 10 % Ni/HPS was found to be the most active catalyst in the deoxygenation of stearic acid in supercritical n‐hexane.     

Tuning the Interfacial Reaction Between Bismuth‐Containing Sealing Glasses and Cr‐Containing Interconnect: Effect of ZnO

The interfacial reaction between sealing glasses and Cr‐containing interconnect presents a challenge for the development of solid oxide fuel cell (SOFC). In this work, we report that the interfacial reaction between bismuth‐containing sealing glasses and Cr‐containing interconnect can be tailored by ZnO dopant. The addition of ZnO contributes to a more open glass structure, resulting in the facilitated diffusion of ions in glass and thus the increase in the interfacial reaction. On the other hand, the further increase in ZnO content enhances the Bi³⁺→Bi⁵⁺ transition in glasses and reduces the redox interfacial reaction by consuming the oxygen available at the glass/metal interface. In addition, good joining can be observed at the sealing interface between ZnO‐containing glass‐ceramics and Crofer 22 APU, held in air at 700°C for 1400 h. Moreover, the glass‐ceramics show considerable electrical stability in oxidizing and reducing atmospheres. The reported results support the suitability of prepared glass‐ceramics as sealing materials for SOFC applications.     

Comparison of the effects of polyethylenimine and maleated polypropylene coupling agents on the properties of cellulose‐reinforced polypropylene composites

The desire to improve the properties of cellulose‐reinforced composites while producing them by methods as similar as possible to those used on an industrial scale is one of the driving forces in this field of research. In this work, extensive research for determining the mechanical, thermal, rheological, and physical properties of novel cellulose‐reinforced polypropylene composites containing a polyethylenimine (PEI) coupling agent was conducted. A comparison of their properties with those of reference composites without any coupling agent or containing a maleated polypropylene (MAPP) coupling agent was also carried out. The presence of the PEI coupling agent mainly gave rise to a substantial increase in the tensile and flexural strengths and elongations as well as the impact strength, heat deflection temperature (HDT), melt volume flow index, and water absorption of PEI‐containing composites in comparison with composites without any coupling agent added. However, the increases achieved in the tensile and flexural composite strengths and HDT were lower than those achieved with the MAPP coupling agent mainly for composites containing 50 wt % cellulose fibers. On the other hand, PEI‐containing composites exhibited, in most cases, larger elongations and energies required to break in tensile tests as well as larger impact strengths, melt volume flow indices, and water absorption percentages than MAPP‐containing composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(vinylidene fluoride) hollow‐fiber membranes containing silver/graphene oxide dope with excellent filtration performance

In this study, an antifouling poly(vinylidene fluoride) (PVDF) hollow‐fiber membrane was fabricated by blending with silver‐loaded graphene oxide via phase inversion through a dry‐jet, wet‐spinning technique. The presence of graphene oxide endowed the blended membrane with a high antifouling ability for organic fouling. The permeation fluxes of the blended membrane was 3.3 and 2.9 times higher than those of a pristine PVDF membrane for filtering feed water containing protein and normal organic matter, respectively. On the other hand, the presence of silver improved the antibiofouling capability of the blended membrane. For the treatment of Escherichia coli suspension, the permeation flux of the blended membranes was 8.2 times as high as that of the pristine PVDF membrane. Additionally, the presented blended membrane improved the hydrophilicity and mechanical strength compared to those of the pristine PVDF membrane, with the water contact angle decreasing from 86.1 to 62.5° and the tensile strength increasing from 1.94 to 2.13 MPa. This study opens an avenue for the fabrication of membranes with high permeabilities and antifouling abilities through the blending of graphene‐based materials for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44713.     

Characterization of the glycerolipid composition of a high‐palmitoleic acid sunflower mutant

The glycerolipid composition of a high‐palmitoleic acid sunflower (Helianthus annuus L.) mutant accumulating up to 20% of n‐7 fatty acids was studied. This line produces oil with a complex triacylglycerol (TAG) composition, containing species that have not been previously identified in sunflower. In this regard, palmitoleic acid was esterified in an unexpected way in the three positions of the TAG molecules. The polar glycerolipid composition of the mutant was also studied, in order to identify and quantify the changes in membrane lipids imposed by the sunflower enzymatic machinery during the accumulation of the unusual n‐7 fatty acids. The high‐palmitoleic mutant accumulated important quantities of n‐7 fatty acids in the polar lipid fraction, especially in the phosphatidylcholine lipid class. However, the total polar lipid content of these lines was not affected. On the other hand, the mutations responsible for the n‐7 lipid accumulation induced an important decrease in the oil yield of the new mutant.     

Effects of Lupin Oil on Carp Lipids during Chilling 2. Changes in Fatty Acid Composition

Rearing carp for 6 weeks on diets containing 5% lupin oil slightly affected the composition of the component fatty acids in various lipid classes of the fillets. On the other hand, the incorporation of lupin oil in the diet did not affect the trend in the changes occurring in the component fatty acids of the different lipid classes during chilling storage of the carp fillets. Thus, the percentage of saturated and monounsaturated fatty acids increased whereas the percentages of polyunsaturated fatty acids decreased during storage.     

Novel sodium alginate/polyethyleneimine polyion complex membranes for pervaporation dehydration at the azeotropic composition of various alcohols

Dense polyion complex membranes of anionic sodium alginate (NaAlg) and cationic polyethyleneimine (PEI) were prepareand crosslinked with glutaraldehyde for dehydration of alcohol–water mixtures by pervaporation (PV). The membranes were characterized by ion‐exchange capacity measurement, Fourier transform infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy to investigate the extent of cross‐linking, intermolecular interactions, thermal stability, and surface and cross‐sectional morphologies, respectively. Wide‐angle X‐ray diffraction was used to investigate the crystallinity of the membranes. PV dehydration characteristics of the membranes were determined as a function of PEI content, crosslinking time as well as feed water composition. Transport parameters such as sorption, diffusion and permeability of water and alcohols through the membranes were determined. Among the four different membrane compositions, the polyion complex containing 40% PEI was found to yield optimum separation data in terms of membrane stability, selectivity and permeability. On the other hand, 10% PEI‐containing membrane gave the highest selectivity with the lowest flux at ambient temperature, but the membranes were not sufficiently stable. Copyright © 2007 Society of Chemical Industry     

Stability and rheological study of sodium carboxymethyl cellulose and alginate suspensions as binders for lithium ion batteries

Currently, the most widely used binder in batteries is polyvinylidene fluoride with N‐methyl‐2‐pyrrolidone used as a solvent. This solvent is flammable and toxic. Here, we focus on the suitability of using water‐soluble sodium alginate (Na‐alginate) and sodium carboxymethyl cellulose (Na‐CMC) as alternative biobased binder materials for the anodes of lithium ion batteries. It reduces the environmental impact of current manufacturing processes. However, control of the rheological characteristics of the binder whilst containing active and conductive additives is key for optimized processing. Here, we perform stability and rheological measurements of Na‐alginate and Na‐CMC solutions containing varying amounts of graphite and carbon black used as active and conductive materials, respectively. Compared with the benchmark Na‐CMC, the degree of flocculation shows that for the same concentration of binder in water, Na‐alginate suspensions are more stable. The rheology measurements show that Na‐alginate slurries have a higher viscosity than Na‐CMC at a shear rate of 50 s^?1 with that for a 1.5% of Na‐alginate binder being 1.26 Pa s while for Na‐CMC it was for 0.20 Pa s. The loss factor was lower for Na‐Alginate, between 2 and 3 against between 2.9 and 3.3 for Na‐CMC, showing a more developed network structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46217.     

Modelling of transport properties and state of water of polyelectrolytes containing various amounts of water

Atomistic molecular modelling is used to construct sulfonated PVF-based polyelectrolyte materials containing 0, 10 or 40 wt% of water. The systems contain hydronium ions, with which the classical diffusion of the hydronium ions can be simulated, and particles called protons, with which the proton hopping mechanism can be simulated. System containing 40 wt% of water is conducting. Both the proton hopping and the classical diffusion mechanisms occur in the system and neither of them is dominating. The interactions between ions are calculated and they are found to be relatively small. Diffusion coefficients of the protons, hydronium ions and the water molecules are reported and the movement of ions is studied. The location of the protons, the hydronium ions and the water molecules is studied at the atomistic level. In system containing 40 wt% of water, water clusters are seen. There are no remarkable differences between the results that are measured for similar materials or calculated in this study.     

Proton conducting PAMPS networks: From flexible to rigid materials

To elaborate tailor‐made proton conducting materials showing an interesting range of flexibility, a series of conetworks combining poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS) and poly(ethylene oxide) dimethacrylate (PEGDM) with various chain lengths was synthesized. The homogeneity of these conetworks was checked by differential scanning calorimetry and dynamic mechanical thermal analysis. The swelling behavior of these materials is strongly influenced by the amount of sulfonic acid groups and the endothermal peak temperature, characteristic of the presence of bound water in the conetwork, increases from 65 to 120°C when AMPS amount increases from 10 to 75 wt %. In addition, the proton conductivity of these materials varies from 10^?3 to 10^?1 S cm^?1, depending on the AMPS amount. The storage moduli were found to be affected by both the AMPS content in the conetwork and its crosslinking density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Liquid–Liquid Extraction of Isovaleric Acid Using Alamine 308/Diluent and Conventional Solvent Systems: Effect of Diluent and Acid Structure

Abstract

Distribution of isovaleric (3‐methyl butanoic) acid between water and Alamine 308 (triisooctylamine) dissolved in C₅ and C₆‐ring included diluents of proton‐donating and ‐accepting (cyclopentanol, cyclohexanone), polar (chlorobenzene) and inert (toluene) types, as well as a comparison with the extraction equilibria of pure diluent alone (chloroform) have been studied at 298 K. Among the tested C₆ ring‐containing and aliphatic diluents, cyclic alcohol/amine system yields the highest synergistic extraction efficiency. The strength of the complex solvation was found to be reasonably large for halogenated aromatics favoring mainly the formation of acid₁‐amine₂ structure. The influence of the acid structure over distribution has been interpreted through comparing the extractabilities of seven acids containing different functional groups, i.e., isovaleric, formic, levulinic, acetic, propanoic, pyruvic and nicotinic acids. The results were correlated using a modified linear solvation energy relation (METLER) and versions of the mass action law, i.e., a chemodel approach and a modified Langmuir equilibrium model comprising the formation of one or two acid‐multiple amines complex formation.     

Photopinking of white PVC products: A kind of magic

Short‐term photoeffects like photograying, photobluing, and photopinking are well‐known in the polyvinyl chloride (PVC) industry. While photobluing and photograying are well understood regarding their mechanisms of occurrences there are still some missing facts. Furthermore, there are three different types of pinking effects with three different mechanisms and consequently three different ways to avoid this discoloration of mainly white PVC products. The recent paper is focusing on one hand of the photopinking of PVC products, which are stabilized with nitrogen‐containing, organic stabilizer whose mechanism was not explained until today. In the past there was neither a method to analyze nor to simulate this type of photopinking. However, the discovery of a charge transfer complex between the nitrogen‐containing substance and nitric acid gave the basic idea to investigate this phenomenon by photo‐electromotive force investigations of titanium dioxide and the nitrogen‐containing substance and by cyclo voltammetry. On the other hand, the authors are attempting to supplement the findings regarding the mechanism of the photopinking of white window profiles which are lead stabilized and which were installed north‐facing in cooler areas with high humidity. Again, a simulation and the analysis of the color‐giving substance of the north‐faced photopinking were impossible in the past. The authors assumed that antioxidants might play an important rule for this type of discoloration. They supported their hypothesis by synthesis of quinoid structures based on antioxidants, spectroscopic investigations, artificial weathering, and electrochemical calculations. J. VINYL ADDIT. TECHNOL., 24:195–207, 2018. © 2016 Society of Plastics Engineers