bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydride storage
Authors: Sandrock G.
Published: December 2010

The principles and application of reversible metal hydrides for H
2
storage for fuel cells are reviewed. The practical use of fuel cell waste heat is important for supplying the required heat of desorption for the hydride. A tutorial overview of hydrides is given, starting with the definitions of H capacity, thermodynamic and other important hydride properties. Using the near‐ambient‐temperature PEM fuel cell as a reference application, a review of hydrides capable of supplying H
2
at pressures of 1–10 atm (absolute) and temperatures of 0–100 °C is given. Numerous such hydriding alloys and intermetallic compounds are available, but gravimetric H‐densities are no greater than about 2 wt%, a distinct shortcoming for vehicular fuel cell applications. Although near‐ambient‐temperature hydrides have volumetric, pressure and safety advantages over advanced compressed H
2
storage, they cannot compete on weight and, probably, cost bases. The potential for hydrides with greatly improved gravimetric capacities is discussed, especially relative to nanocrystalline Mg‐alloys and alkali metal alanates.
Methanol reformer design considerations
Authors: Hansen J. B.
Published: December 2010

The thermodynamic equilibrium gas compositions have been calculated for typical cases related to the use of methanol reformers in connection with fuel cells. Both steam reforming and partial oxidation with steam, air and methanol are considered. Using these basic considerations as guidelines, different reactor designs are discussed and examples given.

The reactor designs based on steam reforming alone mainly differ with respect to the method by which the heat is provided for the endothermal overall reaction. These reactor designs have the overall highest conversion energy efficiency, but reactors based on the simultaneous reactions with steam, air and methanol are faster to start up and more compact. The partial oxidation can either be of the catalytic types (flameless) or with a dedicated burner unit (autothermal) followed by a catalytic zone.

Finally the reformers can be integrated with a gas purification unit based on Pd membranes selective for hydrogen permeation.
Performance and durability of bipolar plate materials
Authors: Mepsted G. O. , Moore J. M.
Published: December 2010

The bipolar plate is a multifunctional component of the fuel cell; its primary roles are to evenly distribute reactant gases whilst removing water from the cell. It must also transfer the heat of reaction away from the cell, provide electrical conductivity between adjacent cells and prevent mixing of the fuel and oxidant. An optimized bipolar plate must satisfy a number of materials and construction requirements, have good electrical and thermal conductivity, gas impermeability and corrosion resistance. It should also have minimal volume and weight and be inexpensive. Historically, graphite has been chosen as a compromise between these requirements, it has good electronic conductivity, excellent corrosion resistance and a low density. However, it is expensive, porous in nature, lacks mechanical strength and is not viable for volume production. Two basic types of bipolar plates have emerged as probable replacements for graphite, including composites fabricated from graphite or carbon powder and a polymer resin and metallic. Composite plates are lower cost, lower weight and mechanically stronger than graphite, and they can be fabricated using cost‐effective moulding techniques. Composites are less conductive than graphite, but recent developments have seen conductivities improve to levels approaching that of graphite. Metals, such as stainless steels and titanium, have high mechanical strength and are gas impermeable. Thus, thin bipolar plates can be manufactured using techniques amenable to mass production. The bulk resistivities of most metals are at least an order of magnitude lower than graphite; however, this can be more than offset by contact resistance due to surface oxide layers or corrosion products. The successful utilization of metallic bipolar plates in proton exchange fuel cells depends upon either the identification of metals or alloys with low contact resistance but good corrosion resistance, or the development of low‐cost conductive and protective coatings.
Perfluorinated membranes
Authors: Doyle M. , Rajendran G.
Published: December 2010

Perfluorinated ionomer membranes have been the topic of a tremendous amount of research for over three decades due to their use as the predominant membrane system for proton exchange membrane fuel cell (PEMFC) applications. Their excellent physical properties, including high proton conductivity, oxidative and reductive stability, and mechanical properties, have enabled the PEMFC to reach the levels of performance achieved to date. However, the demands on the fuel cell system are increasing as new applications loom with their needs for lower cost, higher performance, and flexibility to accommodate new fuels. System demands are pushing operating temperatures higher, causing the water balance and humidification of the perfluorinated ionomer membrane to become important issues.

This section reviews the status of research and development activities around the Nafion®perfluorinated ionomer membrane and Nafion®solutions. The focus of the review is on the measurement of physical property data and new insights into the mechanisms of conduction in these systems. An attempt is made to summarize recent structural studies and characterization techniques that are bringing new insights into the conduction process, as well as recent efforts in mathematical modeling and computer simulations of the conduction process. Finally, membrane‐related issues that arise in the direct methanol PEMFC are reviewed and data on methanol transport in Nafion®membranes are summarized.
Inorganic/organic composite membranes
Authors: Jones D. J. , Rozière J.
Published: December 2010

This chapter briefly reviews the state of the art in the preparation and characterization of hybrid inorganic/organic membranes for fuel cells. Examples are drawn from the recent literature to demonstrate the advantages of inorganic/organic membranes compared with polymer‐only systems. Emphasis is placed on the different routes developed over recent years to hybrid fuel cell membranes leading to a high degree of dispersion of inorganic particles or proton‐conductors in a polymer matrix, including dispersion of exfoliated layered proton‐conductors in a polymer solution, in situ local growth of inorganic proton‐conductors in a pre‐formed polymer membrane, polymer in situ sol gel reactions of inorganic alkoxides and alkyl‐ or arylalkoxysilanes, and solvent transfer (aqueous to organic phase) of colloidal inorganic oxides.
Development ofCO‐tolerant catalysts
Authors: Ruth K. , Vogt M. , Zuber R.
Published: December 2010

Highly dispersed platinum/ruthenium, supported on carbon black, is today's standard anode catalyst material for polymer electrolyte fuel cells operated by reformate gas (hydrogen containing gases with traces of CO). In order to generate a high rate of hydrogen oxidation in the presence of CO, the catalyst has to be specifically designed for the system operation conditions. This includes the total precious metal loading of the catalyst, the ratio of platinum to ruthenium, the distribution of platinum and ruthenium on a nanoscopic scale as well as the oxidation state of the metal surface.

The current level of CO tolerance is in the range of a few hundred ppm dependent on the airbleed level used. Investigations on lifetime of Pt/Ru electrocatalysts demonstrate that these catalyst systems are principally suited to achieve the desired lifetime targets of polymer electrolyte fuel cells systems for mobile and residential application.

Besides the principal technical suitability of Pt/Ru catalysts, further requirements regarding to production and catalyst costs have to be fulfilled. The cost of precious metal precursor formation and catalyst production are important factors for the total production costs. However, enhancement of precious metal utilization and simplification of fuel cell systems are a must for the future mass application of fuel cells. These will generate further progress in catalyst development.
Precious metal supply requirements
Authors: Jaffray C. , Hards G.
Published: December 2010

Two scenarios for the growth of the transportation market for proton exchange membrane (PEM) fuel cell engines have been developed. A continuing growth in the global vehicle population and a continuing technological development to reduce platinum loadings employed in the fuel cells form the basis of this study. At current projected levels for fuel cell vehicles in 2010, the precious metal requirements will have a minor impact on precious metal supply and demand forecasts. Wholesale introduction of fuel cell vehicles to over 50% of the total market from beyond 2025, will require a significant increase in platinum supply. However, there are proven resources of platinum at current economical extraction depths to support a major fuel cell market such as this, provided the precious metal producers have sufficient demand visibility.
Diffusion media materials and characterisation
Authors: Mathias M. F. , Roth J. , Fleming J. , Lehnert W.
Published: December 2010

Gas‐diffusion media (also known as gas diffusers and gas‐diffusion backings) are required in most polymer electrolyte fuel cell (PEFC) designs. Their function is to provide uniform reactant (H2, O2, and electrons) access to and product (H2O) removal from the electrodes, efficient heat removal from the membrane electrode assembly (MEA), and mechanical support to the MEA. The vast majority of gas‐diffusion media are based on carbon‐fiber materials; a variety of forms are used, with carbon‐fiber paper and carbon cloth receiving widest application. This chapter describes the production and properties of currently available and emerging materials. Commonly employed treatments and coatings used to tailor the wicking and hydrophobic properties of diffusion media for efficient water removal are discussed. Finally, ex‐situ and in‐situ methods for characterizing diffusion media are described.
Catalyst coated composite membranes
Authors: Cleghorn S. , Kolde J. , Liu W.
Published: December 2010

The introduction of expanding polytetrafluoroethylene (ePTFE) micro‐reinforced composite perfluorosulfonic acid membranes by Gore (Gore‐Select
®
membrane) provides numerous benefits for polymer electrolyte membrane fuel cells (PEMFCs). This chapter reviews some of the important physical properties of the membranes such as tear strength, dimensional stability, hydrogen permeability, and resistance as a function of RH, comparing a commercially available nonreinforced membrane and the Gore‐Select
®
membrane.

The performance of the Primea
®
membrane electrode assembly (MEA) Series based on the Gore‐Select
®
membrane is discussed and compared to thicker nonreinforced membranes. The reduced thickness of the electrolyte results in an obvious reduction in membrane resistance in the cell, but also provides increased membrane hydration uniformity as a result of the rapid water back diffusion. The combination of these factors provides improved power density, as well as the ability to operate fuel cell systems with sub‐saturated reactant streams and at higher temperatures.

Fuel cell test results for a series of reinforced and nonreinforced membranes, along with ex‐situ analysis, provides insight into predominant membrane failure mechanisms in PEMFCs. Thin reinforced membranes have been found to have significantly longer life than much thicker nonreinforced membranes, supporting the conclusion that mechanical properties of membranes maybe more important than their intrinsic chemical properties in dictating membrane life.

This chapter discusses the economic aspects of Gore‐Select
®
composite membranes compared to commercially available pure‐film membranes, including the combined benefits of increased performance and decreased ionomer content.
Durability
Authors: Wilkinson D. P. , St‐Pierre J.
Published: December 2010

Durability and reliability are necessary requirements for fuel cells to be introduced into the market place. However, activities necessary to meet these requirements are costly and time‐consuming. As a result, past experience and information is valuable and emphasis should be placed on ex situ and accelerated testing to minimize resource investment. In this contribution, gaps in knowledge are identified which could form the basis of further studies. The key components of performance degradation (kinetic, ohmic, mass transport) are briefly defined and provide a basis for the discussion on the sources of degradation (water management, impurities, reformate, materials, operating conditions, uniformity). Understanding of the factors affecting degradation leads to a discussion of possible mitigation strategies. Since the current state of the art is fragmentary and far from being comprehensive, further research efforts are required to clearly understand root causes, secondary effects and interactions in order to develop appropriate mitigation strategies for performance degradation.
System design for stationary power generation
Authors: Barbir F.
Published: December 2010

The stationary fuel cell system components, function and various design options with respect to application, grid connection, nominal power output, load following, choice of fuel, installation and cogeneration capabilities are discussed. Fuel processor, fuel cell stack design and operation requirements are treated only to an extent they that affect the system design and operation. Efficiency and economics of stationary fuel cell systems are also addressed.
System design for vehicle applications: Daimler Chrysler
Authors: Konrad G. , Sommer M. , Loschko B. , Schell A. , Docter A.
Published: December 2010

This article describes the fundamental procedure for designing fuel cell systems for vehicle applications, especially propulsion systems. It starts with the definition of the target specifications concerning vehicle performance, derived from the driving requirements of the customer. The design process of a fuel cell vehicle is repetitive and starts with a first vehicle concept, followed by the layout of drive train, where the requirements concerning fuel consumption, emissions, acceleration, top speed and climbing ability must be considered. The design procedure of the fuel cell system consists of the concept phase, the modeling phase as well as the simulation phase. The results, which include efficiency, emissions, turn‐down ratio, weight, volume, costs, cold start‐up time and heat rejection, are then compared with the original specifications. For a detailed simulation, input data and boundary conditions are necessary at the start, which can only result from the total design process — so these data have to be estimated before starting the layout process. The data found in the simulation of the fuel cell system are re‐used within the vehicle simulation. Analysis shows the sensitivity of the system concerning changes of a given technology and leads to the final definition of the design of all components of the drive system.
System design for transport applications
Authors: Lamm A. , Müller J.
Published: December 2010

The following contribution concerns direct methanol fuel cells (DMFC) and their ability to use the new technology as an electrochemical device in an electric propulsion system in the future. First, a brief introduction is given regarding alternative fuels and the attractiveness of methanol as one alternative fuel in comparison with hydrogen (CHG) and synthetic fuels. In addition, the properties of the DMFC propulsion system are compared with those of systems based on CHG and synthetic fuels from a technical point of view. Second, the design of the liquid‐feed DMFC system is discussed on the basis of comparison between a gaseous and a liquid‐feed DMFC system. Third, the CO2separation process is simulated, and hardware presented. The thermal management of a DMFC stack is also modeled. A brief description of system management concludes the chapter.
Seawater aluminum/air cells
Authors: Iudice de Souza J. P. , Vielstich W.
Published: December 2010

Aluminum/air cells have a theoretical energy density of 8.1 kWh kg
−1
. Using an alkaline electrolyte and aluminum alloys as the anodes, discharge currents of 200 mA cm
2
are obtained with a power density of 0.6 W cm
2
. Saline systems show a much lower power, but with a reasonable energy density of more than 2 kWh kg
−1
and stationary discharge conditions. It has to be considered that closed battery systems need an exchange of electrolyte due to the formation of insoluble aluminum hydroxides. Practical applications for the saline electrolyte version are, therefore, suggested via the use of seawater as the electrolyte in battery systems open to the sea.
Hy.Power — a technology platform combining a fuel cell system and a supercapacitor
Authors: Dietrich P. , Büchi F. , Tsukada A. , Bärtschi M. , Kötz R. , Scherer G. G. , Rodatz P. , Garcia O. , Ruge M. , Wollenberg M. , Lück P. , Wiartalla A. , Schönfelder C. , Schneuwly A. , Barrade P.
Published: December 2010

In a joint project, the Paul Scherrer Institut PSI, ETH Zurich, FEV Motorentechnik and Volkswagen have developed the fuel cell hybrid vehicle “Hy.Power”. Hy.Power is a technology platform for the demonstration of a powertrain combining a hydrogen fuel cell system designed for 40 kW peak net power output and a double‐layer capacitor arrangement with a peak power of 60 kW net. The gaseous hydrogen is stored in pressurized tanks of up to 350 bar. The potential of innovative technologies, such as newly designed bipolar plates and double‐layer capacitors as well as new air supply and humidification concepts, are tested under real conditions. The fuel cell system consists of six fuel cell stacks into which the media are fed in parallel. The performance of the Hy.Power technology demonstrator was successfully tested under extreme boundary conditions by crossing the Simplon Pass in the wintry Alps in January 2002.
Automotive development
Authors: Hacker V. , Kordesch K.
Published: December 2010

Alkaline fuel cells were the best performers in the initial decades of fuel cell development. In the past two decades a rapid change has taken place and many groups have stopped developing alkaline fuel cell systems. From the few remaining groups ZeTek was the only one to produce small series of stacks and prototypes of hybrid vehicles. The prototypes demonstrated that, in practice the alkaline fuel cell is well developed, simple to operate and is inexpensive to manufacture. The uses of alkaline fuel cells are still uncertain. The article gives an overview of the system packaging and operation of alkaline fuel cells when installed as on‐board chargers for mobile applications. The main driving force for application of alkaline fuel cells for electric vehicles in future will be the cost issue.
Potential economic impact of fuel cell technologies
Authors: Jochem E. , Schirrmeister E.
Published: December 2010

This section analyses the possible impacts on regional economies and employment from the introduction of the fuel cell into cars and as stationary small co‐generation plants into buildings and homes. For this purpose, the components of the new propulsion system or co‐generation plant are analyzed and assumed to substitute the components of the traditional components by using input/output analysis. The results demonstrate that there are substantial changes within the car and boiler industries and also in the outfitter and supplier industries. Depending on the car manufacturer's decision of what, where and by whom production will take place, the technological change may substantially influence a regional economy. The effect on employment of an annual production of half a million fuel cell‐driven cars ranges from an additional 40 000 jobs to job losses of 10 000. The chances and risks of this new energy‐converting technology require a sensitive and forward‐looking attitude of many players in a country or region producing cars or boilers, power and co‐generation plants today.
Enzyme catalysis in biological fuel cells
Authors: Barton S. C.
Published: December 2010

Biocatalysts represent a compelling alternative to precious metals as catalysts for low‐temperature fuel cell power systems. Enzymatic catalysts capable of reducing oxygen or oxidizing small organic molecules can be less expensive and manufacturable, and have favorable reaction selectivity as compared to precious metals. The key barriers to realization of practical biocatalyzed fuel cells are the insufficient current, power, and lifetime achievable with current devices. Recently, significant progress has been made in addressing these issues, from the standpoint of fundamental studies of electron transfer to enzymes, mediation of enzyme‐catalyzed reactions, and immobilization of enzymes in materials that confer stability and high surface area for heterogeneous reactions. In this article, we introduce concepts in enzyme catalysis for energy applications and describe important recent progress.
Catalysts for the electro‐oxidation of small molecules
Authors: Watanabe M. , Uchida H.
Published: December 2010

Direct oxidation‐type fuel cells (DOFCs) have attracted great interest as a primary power source for portable electronic devices, wheelchairs, vehicles, and robots because of their simple system (no additional equipment such as a fuel reformer) and ease of maintenance. The direct methanol fuel cell (DMFC) is a typical example of DOFC. Development of highly active anode catalysts for them is one of the most important issues in achieving high‐energy conversion efficiency in DOFCs. To design such new electrocatalysts, we discuss the mechanism of methanol oxidation reaction (MOR) as well as CO oxidation reaction at several electrodes, based onin situFTIR spectroscopy and X‐ray photoelectron spectroscopy combined with an electrochemical cell (EC‐XPS). We also show changes in the MOR activities at various Pt alloy electrodes over the wide temperature range from 20 to 120 °C, obtained by using a thin‐layer flow cell under pressurized operation. The electrooxidation of methoxy fuels is briefly discussed.
Density functional theory applied to electrocatalysis
Authors: Venkatachalam S. , Jacob T.
Published: December 2010

A combination of density functional theory (DFT) and thermodynamic considerations is used to evaluate the electrochemical (a,T, Δϕ) phase diagram for Pt(111) in contact with an aqueous electrolyte, which is then compared with experimental data. After specifying the electrode potential region at which no surface oxidation or oxide formation occurs, DFT calculations on the reaction of H2 + 1/2O2→ H2O over a Pt catalyst via direct oxygen reduction are discussed. Within these studies we first examine the binding characteristics and energetics for each likely intermediate chemisorbed on the Pt(111) surface, modeled by a 35‐atom cluster: O, H, O2, H2, OH, OOH, H2O2, and H2O. Then, the pathways for the dissociation processes of the various intermediates were calculated. Using binding energies and dissociation barriers, two main reaction mechanisms could be distinguished: O2dissociation and OOH/H2O2formation. While the latter one is the only mechanism to be expected when neglecting the surrounding water, both pathways have almost comparable reaction barriers when taking water into account.
Platinum dissolution models and voltage cycling effects: platinum dissolution in polymer electrolyte fuel cell (PEFC) and low‐temperature fuel cells
Authors: Ota K. , Koizumi Y.
Published: December 2010

All the metals except gold form a metal oxide on the surface in the presence of oxygen at room temperature. Once an oxide layer is formed on a metal surface, it dissolves into a solution to some extent. This is the dissolution. Even platinum makes an oxide layer and has solubility. Platinum islands in an electrolyte membrane in polymer electrolyte fuel cells (PEFCs) were reported in many papers. These islands are closely related to the dissolution of Pt from cathode. Platinum dissolves in an acidic media in the presence of oxygen although the solubility is very low. The solubility is proportional to pH of sulfuric acid solution and increases at higher temperatures. The dissolution reaction follows the acid dissolution mechanism. The dissolution reaction is enhanced by the potential cyclings. Considering the characteristics of fuel cell vehicles, there are voltage changes and the dissolution of Pt should be reduced.
Alkaline anion‐exchange membranes for low‐temperature fuel cell application
Authors: Varcoe J. R. , Poynton S. D. , Slade R. C. T.
Published: December 2010

This review introduces alkaline anion‐exchange membranes (AAEM), the alkaline equivalents to the better known proton‐exchange membranes (PEM), their chemistries, and their applications in hydrogen solid alkaline fuel cells (SAFC). There has been a recent increase in understanding of AAEM behaviour in SAFCs; however, the field is still in its infancy compared to proton‐exchange membranes fuel cells (PEMFCs). Current AAEMs only exhibit adequate properties for application in SAFCs at higher humidities. Thinner AAEMs perform best due to facilitated supply of reactant water to the cathode oxygen reduction sites and reduced internal resistances. Further developments in alkaline ionomers are urgently required for high performance SAFCs.
Conductivity, permeability, and ohmic shorting of ionomeric membranes
Authors: Mittelsteadt C. K. , Liu H.
Published: December 2010

To minimize resistance losses, polymer electrolyte membranes are being fabricated thinner and with a higher acid content. This affects membrane resistance, gas permeability, and membrane durability. Models for the conductivity of perfluorinated sulfonic acid (PFSA) and sulfonated aromatic hydrocarbons are developed on the basis of the conductivity of small‐molecule analogues. These models are used to project an upper bound for conductivity of these systems. Gas permeability of PFSA membranes is modeled by separating transport into the hydrophobic and hydrophilic regions. Generally it is found that the gas permeability of PFSA materials is higher than that of hydrocarbon membranes. Two types of ohmic shorting tests are conducted on membranes of various thicknesses as well as membranes with an expanded poly(tetrafluoroethylene) support. Membranes with thickness above 90 μm do not short by these tests. For thinner membranes, both the addition of a catalyst layer and the poly(tetrafluoroethylene) support mitigates ohmic shorting.
Direct three‐dimensional visualization and morphological analysis of pt particles supported on carbon by transmission electron microtomography
Authors: Ito T. , Matsuwaki U. , Otsuka Y. , Katagiri G. , Kato M. , Matsubara K. , Aoyama Y. , Jinnai H.
Published: December 2010

The polymer fuel cell electrode (PFCE), consisting of platinum particles or platinum alloy particles supported on carbon particles and proton‐conducting ionomer binder, is one of the most important components in the fuel cell. The three‐dimensional (3‐D) imaging technique is important for the precise characterization of the carbon‐supported catalysts and the electrode. In this study, the Pt particles as the catalysts supported on different kinds of carbon particles were examined by transmission electron microtomography (TEMT) to obtain the first 3‐D structure of the carbon‐supported catalyst and to then evaluate the significant parameters that should allow characterization of the catalyst, i.e., the Pt nanoparticles supported on high‐surface area carbons. To obtain quantitative 3‐D images of the catalysts that contain extremely small Pt particles on the order of a few nanometers in diameter, a special sample preparation technique was developed for the TEMT experiments. As a result, the spatial resolution of ca 0.5 nm was achieved for the first time. On the basis of such very quantitative 3‐D images, a series of 3‐D image analysis algorithms were developed and used to evaluate significant structural parameters, e.g., the size and spatial distribution of the Pt particles on the carbon substrate, the “degree of embeddedness” of Pt into the carbon support, and the effective surface area of the catalyst per unit volume. These morphological parameters are useful in characterizing fuel cell catalysts and may be significant in studying the degradation mechanisms of catalysts during operation if they are examined before and after the operation.
Observation and modeling of thermal stresses in cells and cell stacks
Authors: Yakabe H.
Published: December 2010

Solid oxide fuel cells (SOFCs) are composed of ceramic components, and the mechanical reliability of cells is a serious subject in the development of SOFCs. In particular, the durability of the cell components against stresses during practical operations is an important problem. To evaluate the mechanical reliability of SOFCs, the magnitude of the stresses in cell components and the strength of the components against the stresses must be considered precisely. In this article, mechanical stresses in cells and cell stacks are evaluated experimentally and numerically.
Electrode degradation mechanisms studies by current distribution measurements
Authors: Carter R. N. , Gu W. , Brady B. , Yu P. T. , Subramanian K. , Gasteiger H. A.
Published: December 2010

A technique is described for determining the source and degree of electrodes degradation in membrane electrode assemblies (MEAs) from proton exchange membrane fuel cells. This technique is nondestructive and provides spatial resolution across the MEA's active area. The degradation modes that are considered are the oxygen reduction activity loss through either electrochemically active area or mass activity loss, increased gas transport resistance from corrosion of the catalyst's carbon support, and the increased protonic transport loss through chemical degradation of the electrode layer's ion‐conducting polymer. A current distribution tool is used with cyclic voltammetry and polarization curves to isolate each of the primary sources of voltage degradation. Results of new MEAs are presented first to demonstrate the approximate resolution of the test method. Then results are presented for MEAs that were aged in a model test to cause carbon corrosion in the cathode layer via localized anode starvation. These include follow‐up materials characterization, where it is shown that the results of this electrochemical diagnostic correlate well with postmortem materials characterization. Finally, results are shown for a part aged in a model start‐up/shutdown aging test and compared with modeling results to explain the spatial characteristics of the observed degradation.
Methane reforming kinetics, carbon deposition, and redox durability ofNi/8 yttria‐stabilized zirconia (YSZ) anodes
Authors: Ivers‐Tiffée E. , Timmermann H. , Leonide A. , Menzler N. H. , Malzbender J.
Published: December 2010

Anodes for stationary SOFC systems are most likely to be operated with natural gas at temperatures above 800 °C, whereas mobile SOFC applications such as APUs (auxiliary power units) operated below 800 °C use (liquid) hydrocarbons. The fuel (gasoline or diesel) cannot be converted by 100% in the reformer and so a reformate containing higher hydrocarbons has to be converted at the anode. In operation with hydrocarbons, at high fuel utilization or at sequential redox cycles, the nickel catalyst is subject to various degradation processes. The dominating process depends on the anodic oxygen partial pressure applied and possibly deteriorates the electrochemical performance of the anode.

Sequential cyclic reduction and oxidation (redox) can quickly lead to an aging of the anode or even a complete failure of the cell (fracture of the thin film electrolyte). In operation with hydrocarbons, i.e., at low oxygen partial pressures, degradation ranging from (i) reversible damage by occupancy of the Ni catalyst surface with various deposits to (ii) irreversible damage to the Ni catalyst by carbon whisker growth occurs.

Moreover, the kinetics of methane conversion under various operating conditions, the carbon formation in the presence of higher hydrocarbons (acetylene), and the analysis of electro‐oxidation and gas diffusion in stable operation with hydrogen or biomass‐derived gas are also treated in this article.
Ferromagnetism and Morphology of Annealed Fe2O3/CoXOY/ZnO Thin Films
Authors: Zolotaryov Andriy , Goetze Silvana , Bachmann Julien , Goerlitz Detlef , Hesse Dietrich , Nielsch Kornelius
Published: December 2010

We have studied thermal solid‐state reactions in the Fe2O3/CoXOY/ZnO thin film systems grown using the atomic layer deposition technique. The compound produced after annealing at 700 °C is found to be a complex mixture of three different spinel phases: ZnCo2O4, CoFe2O4, and ZnFe2O4. The magnetic properties of the compound strongly depend on the atomic ratio of Fe3+ and Co2+ atoms, which can be set by choosing the corresponding thicknesses of the Fe2O3 and CoXOY films. In addition, we also find a formation of 100 nm voids at the interface between Fe–Co–Zn–O compound and remaining ZnO film after 1h annealing at 700 °C in argon atmosphere. The formation of these voids shows indirectly the preferential outward diffusion of Zn2+ ions from ZnO into the Fe2CoO4 phase layer what we prove via our magnetic measurements.
Image Analysis of Endothelial Microstructure and Endothelial Cell Dimensions of Human Arteries – A Preliminary Study
Authors: Garipcan Bora , Maenz Stefan , Pham Tam , Settmacher Utz , Jandt Klaus D. , Zanow Jürgen , Bossert Jörg
Published: December 2010

The aim of this study was to broaden the relatively small number of qualitative and quantitative data available on the endothelium of human blood vessels by scanning electron microscopy (SEM) imaging and computer based image analysis of the human endothelial microstructure and dimensions. Endothelium of the arterial blood vessels (common iliac artery and hepatic artery) was imaged directly by using SEM. From high quality images, precise information on the microstructure and dimensions of endothelial cells was obtained by using GIMP and Leica QWin image analysis software. The mean endothelial cell width, length, and area of common iliac artery endothelial cells were found to be 13.2 ± 4.1 µm, 25.8 ± 8.5 µm, and 245.0 ± 115.1 µm2, respectively. For hepatic artery endothelial cells, mean values of cell width, length, and area were found to be 4.9 ± 1.5 µm, 21.9 ± 6.6 µm, and 70.7 ± 34.8 µm2, respectively. Morphology and dimension of the endothelial cells were different depending on the donor, type, and diameter of the arteries due to the effect of blood flow direction and volume rate. The presented method is useful for obtaining quantitative data on human endothelial cells. This study provides a first basis for future studies with larger numbers of samples on morphological changes secondary to pathological conditions, such as hypertension and atherosclerosis. Furthermore, the data may support the development of a template for a novel artificial vascular graft with superior performance.
Nanocomposite Elastomeric Biomaterials for Myocardial Tissue Engineering Using Embryonic Stem Cell‐derived Cardiomyocytes
Authors: Jawad Hedeer , El Fray Miroslawa , Boccaccini Aldo R. , Harding Sian E. , Wright Jamie S. , Chen Qizhi , Piegat Agnieszka , Ali Nadire N.
Published: December 2010

Regeneration or repair of the damaged myocardium requires different strategies including engineered constructs for more efficient cell delivery. This study was undertaken to examine the potential of a new nanostructured elastomer to deliver embryonic stem cell‐derived cardiomyocytes (ESC‐CM) to an infarcted area of the myocardium. Engineered materials were biocompatible, mechanically stable, and elastomeric nanocomposites serving as substrates for delivery of ESC‐CM and as a left ventricular support device in myocardial regeneration strategies. Materials investigated were soft and strong poly(aliphatic/aromatic‐ester) multiblock thermoplastic elastomers with poly(ethylene terephthalate) (PET) hard segments and dimerized fatty acid, i.e., dilinoleic acid (DLA) soft segments, respectively, with and without addition of 0.2 wt% TiO2 nanoparticles to form nanocomposites. The PET/DLA‐TiO2 nanocomposite exhibited over 8 MPa tensile strength and 900% elongation at break. Addition of TiO2 nanoparticles significantly altered surface roughness and enhanced adhesion and spreading of ESC‐CM derived from mouse and human embryonic stem cells. The newly developed materials did not affect the functional activity of spontaneously beating hESC‐CM, as demonstrated by unaltered rate of their beating, and the cells continued to demonstrate contractile activity on the materials for more than two months in culture (the longest time tested). Quantitative proliferation and survival assays using fibroblasts confirmed the ability of the new materials to support cells as well as or better than the present commercial‐type thermoplastic elastomer analog. The results indicate that PET/DLA and PET/DLA‐TiO2 are promising candidates for the manufacture of engineered patches to deliver ESC‐CMs.
Organic D‐A‐π‐A Solar Cell Sensitizers with Improved Stability and Spectral Response
Authors: Zhu Weihong , Wu Yongzhen , Wang Shutao , Li Wenqin , Li Xin , Chen Jian , Wang Zhong‐sheng , Tian He
Published: December 2010

A novel concept “D‐A‐π‐A” organic sensitizer instead of traditional D‐π‐A ones is proposed. Remarkably, the incorporated low bandgap, strong electron‐withdrawing unit of benzothiadiazole shows several favorable characteristics in the areas of light‐harvesting and efficiency: i) optimized energy levels, resulting in a large responsive range of wavelengths into NIR region; ii) a very small blue‐shift in the absorption peak on thin TiO2 films with respect to that in solution; iii) an improvement in the electron distribution of the donor unit to distinctly increase the photo‐stability of synthetic intermediates and final sensitizers. The stability and spectral response of indoline dye‐based DSSCs are improved by the strong electron‐withdrawing benzothiadizole unit in the conjugation bridge. The incident‐photon‐conversion efficiency of WS‐2 reaches nearly 850 nm with a power conversion efficiency as high as 8.7% in liquid electrolyte and 6.6% in ionic‐liquid electrolyte.
Investigation of the kinetics of fluidized bed spray agglomeration based on stochastic methods
Authors: Terrazas‐Velarde Korina , Peglow Mirko , Tsotsas Evangelos
Published: December 2010

Particle formation during fluidized bed spray agglomeration is modeled by a Monte Carlo method. The methodology is based on the micromechanisms occurring within the bed. The most important model parameters are identified as interparticle collision time, deposited droplet drying time and droplet addition time. It is found that a high number of collisions leads to a negligible role of the drying mechanism. In the real bed, however, the process is dependent on the gas inlet temperature. This indicates that the number of collisions relevant to agglomeration is relatively low. The accordance of the model with experimental results for variations of several process parameters demonstrates that the approach is a promising way to simulate the formation of agglomerates. In addition, the model is able to reproduce slower agglomeration at increased temperatures. This result is, for the first time, based on physical mechanisms rather than on the use of fitted agglomeration kernels. © 2011 American Institute of Chemical Engineers AIChE J, 2011
Link between bubbling and segregation patterns in gas‐fluidized beds with continuous size distributions
Authors: Chew Jia Wei , Hrenya Christine M.
Published: December 2010

Experiments involving a bubbling, gas‐fluidized bed with Gaussian and lognormal particle‐size distributions (PSDs) of Geldart Group B particles have been carried out, with a focus on bubble measurements. Previous work in the same systems indicated the degree of axial species segregation varies non‐monotonically with respect to the width of lognormal distributions. Given the widely accepted view of bubbles as “mixing agents,” the initial expectation was that bubble characteristics would be similarly non‐monotonic. Surprisingly, results show that measured bubble parameters (frequency, velocity, and chord length) increase monotonically with increasing width for all PSDs investigated. Closer inspection reveals a bubble‐less bottom region for the segregated systems, despite the bed being fully fluidized. More specifically, results indicate that, the larger the bubble‐less layer is, the more segregated the system becomes. The direct comparison between bubbling and segregation patterns performed provides a more complete physical picture of the link between the two phenomena. © 2011 American Institute of Chemical Engineers AIChE J, 2011
The incidence of thrombocytopenia in children with Cornelia de Lange syndrome
Authors: Lambert Michele P. , Jackson Laird G. , Clark Dinah , Kaur Mani , Krantz Ian D. , Deardorff Matthew A.
Published: December 2010

Thrombocytopenia was first reported in Cornelia de Lange syndrome (CdLS) by Froster in 1993. Despite early reports, thrombocytopenia has been rarely reported in this disorder. We performed a retrospective analysis of a large cohort of patients with CdLS. We calculated prevalence of thrombocytopenia in three subsets of this cohort: the entire cohort (n = 1,740), a subset of subjects with substantial clinical records (n = 695) and a subset of subjects with clinical information regarding platelet counts (n = 85). This analysis revealed that 15 have had thrombocytopenia (18% of those with available blood counts); seven had immune thrombocytopenia (ITP). The reported prevalence of pediatric ITP is between 5 and 13 per 100,000 persons. The prevalence of ITP in this cohort is between 7/1,740 and 7/85, giving a relative risk of ITP of between 30 (CI 12–77) and 633 (CI 259–1,549). Contrary to the reported cases in the literature, none of our patients have had progression of the thrombocytopenia nor have they developed other cytopenias. All 15 patients with thromobocytopenia had CdLS based on clinical criteria. Of the 10 patients tested for mutations in NIBPL, 8 had mutations identified. These data support an increased incidence of thrombocytopenia and ITP in CdLS. Subsequently, patients are at risk for spontaneous hemorrhage, and likely increased risk secondary to the high frequency of self‐injurious behavior. Although further studies are needed to better define the scope of the problem and to define the mechanisms of thrombocytopenia in CdLS, we would recommend screening for thrombocytopenia upon diagnosis and at 5‐year intervals thereafter. © 2010 Wiley‐Liss, Inc.
Dandy–Walker malformation associated with heterozygous ZIC1 and ZIC4 deletion: Report of a new patient
Authors: Tohyama Jun , Kato Mitsuhiro , Kawasaki Sari , Harada Naoki , Kawara Hiroki , Matsui Takeshi , Akasaka Noriyuki , Ohashi Tsukasa , Kobayashi Yu , Matsumoto Naomichi
Published: December 2010

We report on a female patient with Dandy–Walker malformation possibly caused by heterozygous loss of ZIC1 and ZIC4. The patient presented with mental retardation, epilepsy, and multiple congenital malformations including spina bifida, mild dysmorphic facial features including, thick eyebrows, broad nose, full lips, macroglossia, and hypoplasia of the cerebellar vermis with enlargement of the fourth ventricle on brain magnetic resonance imaging, which is consistent with Dandy–Walker malformation. A chromosome analysis showed interstitial deletion of chromosome 3q23‐q25.1. Fluorescence in situ hybridization (FISH) and microarray‐based genomic analysis revealed the heterozygous deletion of ZIC1 and ZIC4 loci on 3q24. Her facial features were not consistent with those observed in blepharophimosis–ptosis–epicanthus inversus syndrome (BPES) involving FOXL2 abnormality. Other deleted genes at 3q23‐25.1 might contribute to the dysmorphic facial appearance. A milder phenotype as the Dandy–Walker malformation in our patient supports the idea that modifying loci/genes can influence the development of cerebellar malformation. © 2010 Wiley‐Liss, Inc.
Sulfur removal from coal‐derived syngas: thermodynamic considerations and review
Authors: Dolan Michael D. , Ilyushechkin Alex Y. , McLennan Keith G. , Sharma Sunil. D.
Published: December 2010

Current research into desulfurization sorbents for coal gasification is aimed at maximizing sorption capacity, kinetics and attrition resistance, while minimizing cost and volatility. Isolating the chemical aspects of desulfurization sorbent performance, however, is difficult because sorption performance is highly dependent on the physical form of the sorbent. To guide sorbent development, thermodynamic calculations offer a consistent basis from which to compare various aspects of sorbent performance, which includes conversion, but also speciation, volatility and regeneration. This approach has been used to compare 24 potential sorbents for the removal of sulfur from syngas, including oxides of transition metals, alkaline earths, alkalis and borates. Oxides of copper, manganese and zinc are most favourable for high‐temperature sulfur sorption and these oxides are chemically regenerable. The thermodynamic calculations are confirmed by the available literature, with the ZnO, MnO and CuO receiving the most attention in recent years. Each oxide has characteristic disadvantages, such as the tendency of copper oxide to reduce, the high volatility of zinc oxide and the high regeneration temperature of manganese oxide. This is driving the development of fabrication techniques which maximize sorbent dispersion, stability and tolerance to repeated sulfidation/regeneration cycles. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
Investigation on the correlation between rheology and morphology of PA6/ABS blends using ethylene acrylate terpolymer as compatibilizer
Authors: Mojarrad Alireza , Jahani Yousef , Barikani Mehdi
Published: December 2010

Phase morphology and rheological behavior of polyamide 6 (PA6)/acrylonitrile butadiene styrene (ABS) polymers blends was studied using scanning electron microscopy and rheometry. The results showed that the phase morphology and rheological properties depends on blend composition. We evaluated the effect of addition of ABS as dispersed phase and EnBACO‐MAH (ethylene n‐butyl acrylate carbon monoxide maleic anhydride) as a compatibilizer on the morphological and rheological behaviors of PA6/ABS blends. It was concluded that there is a good agreement between the results obtained from rheological and morphological studies. As a consequence, addition of the ABS and compatibilizer weight percent led to a significant change in morphological structure and a great mounting in the viscosity as well as the elasticity. The rheological properties results demonstrate that adding compatibilizer to polymer blends led to increasing the crossover point, which shows a transition from a high viscous to a considerably more elastic behavior. Also, the slow transition of relaxation time peak from the peak of the PA6 to the peak of the ABS implies increasing the miscibility of the PA6/ABS blend components by increasing compatibilizer content. In addition, the Carreau–Yasuda model was used to extract information on rheological properties (zero shear viscosity and relaxation time) for PA6/ABS/EnBACO‐MAH blends by fitting the experimental data with this model. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011