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Conducting Membranes (conducting + membrane)
Kinds of Conducting Membranes Selected AbstractsHybrid Polymer Electrolyte Fuel Cells: Alkaline Electrodes with Proton Conducting MembraneANGEWANDTE CHEMIE, Issue 7 2010Murat Ünlü Dr. Kluges Management: Eine neuartige Brennstoffzellenarchitektur vereint die Stabilität und hohe Ionenleitfähigkeit von Protonenaustauschmaterialien (PEM) mit dem überlegenen elektrochemischen Verhalten von Anionenaustauschmembran(AEM)-Elektroden. Das Wassermanagement ist gegenüber klassischen Polymerelektrolytmembran-Brennstoffzellen deutlich verbessert, wobei eine Selbstbefeuchtung der Zelle erreicht wird. [source] The Effects of Moisture in Low-Voltage Organic Field-Effect Transistors Gated with a Hydrous Solid ElectrolyteADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Nikolai Kaihovirta Abstract The concept of using ion conducting membranes (50,150 ,m thick) for gating low-voltage (1 V) organic field-effect transistors (OFETs) is attractive due to its low-cost and large-area manufacturing capabilities. Furthermore, the membranes can be tailor-made to be ion conducting in any desired way or pattern. For the electrolyte gated OFETs in general, the key to low-voltage operation is the electrolyte "insulator" (the membrane) that provides a high effective capacitance due to ionic polarization within the insulator. Hydrous ion conducting membranes are easy to process and readily available. However, the role of the water in combination with the polymeric semiconductor has not yet been fully clarified. In this work electrical and optical techniques are utilized to carefully monitor the electrolyte/semiconductor interface in an ion conducting membrane based OFET. The main findings are that 1) moisture plays a major part in the transistor operation and careful control of both the ambient atmosphere and the potential differences between the electrodes are required for stable and consistent device behavior, 2) the obtained maximum effective capacitance (5 ,F cm,2) of the membrane suggests that the electric double layer is distributed over a broad region within the polyelectrolyte, and 3) electromodulation spectroscopy combined with current,voltage characteristics provide a method to determine the threshold gate voltage from an electrostatic field-effect doping to a region of (irreversible) electrochemical perturbation of the polymeric semiconductor. [source] Highly Fluorinated Comb-Shaped Copolymers as Proton Exchange Membranes (PEMs): Improving PEM Properties Through Rational Design,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2006B. Norsten Abstract A new class of comb-shaped polymers for use as a proton conducting membrane is presented. The polymer is designed to combine the beneficial physical, chemical, and structural attributes of fluorinated Nafion-like materials with higher-temperature, polyaromatic-based polymer backbones. The comb-shaped polymer unites a rigid, polyaromatic, hydrophobic backbone with lengthy hydrophilic polymer side chains; this combination affords direct control over the polymer nanostructure within the membrane and results in distinct microphase separation between the opposing domains. The microphase separation serves to compartmentalize water into the hydrophilic polymer side chain domains, resulting in effective membrane water management and excellent proton conductivities. [source] Evaluation of mixed-conducting lanthanum-strontium-cobaltite ceramic membrane for oxygen separationAICHE JOURNAL, Issue 10 2009Lei Ge Abstract In this study, La0.4Sr0.6CoO3-, (LSC) oxide was synthesized via an EDTA-citrate complexing process and its application as a mixed-conducting ceramic membrane for oxygen separation was systematically investigated. The phase structure of the powder and microstructure of the membrane were characterized by XRD and SEM, respectively. The optimum condition for membrane sintering was developed based on SEM and four-probe DC electrical conductivity characterizations. The oxygen permeation fluxes at various temperatures and oxygen partial pressure gradients were measured by gas chromatography method. Fundamental equations of oxygen permeation and transport resistance through mixed conducting membrane were developed. The oxygen bulk diffusion coefficient (Dv) and surface exchange coefficient (Kex) for LSC membrane were derived by model regression. The importance of surface exchange kinetics at each side of the membrane on oxygen permeation flux under different oxygen partial pressure gradients and temperatures were quantitatively distinguished from the oxygen bulk diffusion. The maximum oxygen flux achieved based on 1.6-mm-thick La0.4Sr0.6CoO3-, membrane was ,4.0 × 10,7 mol cm,2 s,1at 950°C. However, calculation results show theoretical oxygen fluxes as high as 2.98 × 10,5 mol cm,2 s,1 through a 5-,m-thick LSC membrane with ideal surface modification when operating at 950°C for air separation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The Effects of Moisture in Low-Voltage Organic Field-Effect Transistors Gated with a Hydrous Solid ElectrolyteADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Nikolai Kaihovirta Abstract The concept of using ion conducting membranes (50,150 ,m thick) for gating low-voltage (1 V) organic field-effect transistors (OFETs) is attractive due to its low-cost and large-area manufacturing capabilities. Furthermore, the membranes can be tailor-made to be ion conducting in any desired way or pattern. For the electrolyte gated OFETs in general, the key to low-voltage operation is the electrolyte "insulator" (the membrane) that provides a high effective capacitance due to ionic polarization within the insulator. Hydrous ion conducting membranes are easy to process and readily available. However, the role of the water in combination with the polymeric semiconductor has not yet been fully clarified. In this work electrical and optical techniques are utilized to carefully monitor the electrolyte/semiconductor interface in an ion conducting membrane based OFET. The main findings are that 1) moisture plays a major part in the transistor operation and careful control of both the ambient atmosphere and the potential differences between the electrodes are required for stable and consistent device behavior, 2) the obtained maximum effective capacitance (5 ,F cm,2) of the membrane suggests that the electric double layer is distributed over a broad region within the polyelectrolyte, and 3) electromodulation spectroscopy combined with current,voltage characteristics provide a method to determine the threshold gate voltage from an electrostatic field-effect doping to a region of (irreversible) electrochemical perturbation of the polymeric semiconductor. [source] Evolution of Permanent Deformations (or Memory) in Nafion 117 Membranes with Changes in Temperature, Relative Humidity and Time, and Its Importance in the Development of Medium Temperature PEMFCs,FUEL CELLS, Issue 4 2009G. Alberti Abstract An important problem for medium temperature polymer electrolyte fuel cells (MT PEMFCs) operating in the temperature range 90,140,°C is the short time-life of proton conducting membranes. To shed some light on the empirical annealing treatments used for increasing the membrane durability, a systematic research on the effects of thermal treatments of Nafion 117 membranes was undertaken with the hope that the information obtained could be useful for a better understanding of the real limits for MT PEMFCs. Kinetic experiments showed that, for each couple of T,RH values, the water taken up from the membrane reaches a constant value only after long times of equilibration (,200,h). Taking into account that the enlargements provoked by the water-uptake remain as permanent deformations when the samples are cooled, it was found that the evolution of the deformations provoked by changes in temperature and RH can be conveniently estimated at 20,°C by determining the water taken up after equilibration in liquid water. By relating the counter-elastic index of the matrix (nc(m)) to the extent of these deformations, a set of equations were obtained which allowed us to predict their evolution with changes of temperature and relative humidity. A good agreement with experimental values was found. The importance of this discovery for the development of MT PEMFCs is discussed. [source] Single Radiation-Induced Grafting Method for the Preparation of Two Proton- and Lithium Ion-Conducting MembranesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2006Mohamed Mahmoud Nasef Abstract Summary: Two distinct types of polymer electrolyte membranes for conducting protons and lithium ions have been prepared by a radiation-induced grafting method. The polymer electrolyte precursor (PVDF- g -PS) is obtained by the simultaneous grafting of styrene onto poly(vinylidene fluoride) (PVDF) followed by one of two specific treatments. This includes sulfonation with a chlorosulfonic acid/dichloromethane mixture to obtain proton (H+)-conducting membranes, or activation with LiPF6/EC/DC liquid electrolyte to obtain lithium ion (Li+)-conducting membranes. The chemical structure of the obtained electrolyte membranes is verified by FT-IR spectroscopy. Differential scanning calorimetry is used to examine the changes in the crystallinity and the thermal properties of both electrolyte membranes during the preparation process. The thermal stability of both electrolyte membranes is also evaluated using thermal gravimetrical analysis. The obtained polymer electrolyte membranes achieve superior conductivity values: 1.61,×,10,3 S,·,cm,1 for Li+ and 5.95,×,10,2 S,·,cm,1 for H+ at room temperature at a polystyrene content of 50%. The results of this work suggest that high quality H+ - and Li+ -conducting membranes can be obtained using a single radiation-induced grafting method. Schematic representation of the single root for preparation of Li+ - and H+ -conducting membranes started by radiation-induced grafting of styrene onto a PVDF film followed by chemical treatment. [source] Polymer electrolyte membranes for high-temperature fuel cells based on aromatic polyethers bearing pyridine unitsPOLYMER INTERNATIONAL, Issue 11 2009Joannis K Kallitsis Abstract This review is focused on the design and synthesis of new high-temperature polymer electrolytes based on aromatic polyethers bearing polar pyridine moieties in the main chain. Such materials are designed to be used in polymer electrolyte fuel cells operating at temperatures higher than 100 °C. New monomers and polymers have been synthesized and characterized within this field in respect of their suitability for this specific application. Copolymers with optimized structures in order to combine excellent film-forming properties with high mechanical, thermal and oxidative stability and controlled acid uptake have been synthesized which, after doping with phosphoric acid, result in ionically conducting membranes. Such materials have been studied in respect of their conductivity under various conditions and used for the construction of membrane-electrode assemblies (MEAs) which are used for fuel cells operating at temperatures up to 180 °C. New and improved, in terms of oxidative stability and mechanical properties in the doped state, polymeric membranes have been synthesized and used effectively for MEA construction and single-cell testing. Copyright © 2009 Society of Chemical Industry [source] Proton conducting membranes based on poly(vinyl chloride) graft copolymer electrolytesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2008Jin Kyu Choi Abstract The direct preparation of proton conducting poly(vinyl chloride) (PVC) graft copolymer electrolyte membranes using atom transfer radical polymerization (ATRP) is demonstrated. Here, direct initiation of the secondary chlorines of PVC facilitates grafting of a sulfonated monomer. A series of proton conducting graft copolymer electrolyte membranes, i.e. poly(vinyl chloride)- g -poly(styrene sulfonic acid) (PVC- g -PSSA) were prepared by ATRP using direct initiation of the secondary chlorines of PVC. The successful syntheses of graft copolymers were confirmed by 1H-NMR and FT-IR spectroscopy. The images of transmission electron microscopy (TEM) presented the well-defined microphase-separated structure of the graft copolymer electrolyte membranes. All the properties of ion exchange capacity (IEC), water uptake, and proton conductivity for the membranes continuously increased with increasing PSSA contents. The characterization of the membranes by thermal gravimetric analysis (TGA) also demonstrated their high thermal stability up to 200°C. The membranes were further crosslinked using UV irradiation after converting chlorine atoms to azide groups, as revealed by FT-IR spectroscopy. After crosslinking, water uptake significantly decreased from 207% to 84% and the tensile strength increased from 45.2 to 71.5,MPa with a marginal change of proton conductivity from 0.093 to 0.083,S,cm,1, which indicates that the crosslinked PVC- g -PSSA membranes are promising candidates for proton conducting materials for fuel cell applications. Copyright © 2008 John Wiley & Sons, Ltd. [source] Physicochemical and electrochemical characterizations of organic montmorillonite (OMMT)/sulfonated poly(ether ether ketone) (SPEEK) composite membranesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010R. Gosalawit Abstract Physicochemical and electrochemical properties of the organic montmorillonite (OMMT)/sulfonated poly(ether ether ketone) (SPEEK) composite membranes are considered for their use as proton conducting membranes. The paper presents the preparation and characterization of SPEEK and its composite membranes with OMMT as well as their comparison to the reference Nafion® 117 membrane. Water uptake and thermal property (Td1) are improved when the OMMT loading content increases. Methanol permeability decreases as OMMT loading content increases up to as high as 53% (5 wt% OMMT/SPEEK composite membrane). For proton conductivity, all membranes show improvement when the operating temperature increases from 25 to 90 °C. The proton conductivity at 100 °C of 3 wt% OMMT/SPEEK composite membrane (5.6 × 10,2 S/cm) is one order of magnitude higher than that of Nafion® 117 (2 × 10,3 S/cm). Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | |||||||||||||