bluuebunny/crossref_metadata_2025_split huggingface dataset:
Durability of cathodes includingCrpoisoning
Authors: Menzler N. H. , Mai A. , Stöver D. 
Published: December 2010

AbstractThis article deals with the durability of solid oxide fuel cell (SOFC) cathodes, especially perovskites of the lanthanum–strontium–manganite (LSM) and lanthanum–strontium–cobalt–ferrite (LSCF) types. Both cathode materials were characterized with respect to either the intrinsic degradation behavior depending on, for example, time, temperature, current density, chemical composition, or the influence of the gaseous chromium species that originate from the oxide layer on the metallic interconnects. Results are presented for single‐cell tests and stack tests. Additionally, in the sections describing the influence of Cr on cathode degradation, some basic results are presented on the interaction of single oxides or oxide mixtures with chromium‐containing atmospheres.
Durable sealing concepts with glass sealants or compression seals
Authors: Buchkremer H. P. , Conradt R. 
Published: December 2010

AbstractSolid oxide fuel cell (SOFC) systems allow efficient direct conversion from chemical to electrical energy. But the commercialization of the technology is strongly dependent on the development of cost‐effective, long‐term stable materials and seals. Sealing components in SOFC stacks have to fulfill a large variety of requirements. Primarily, they should separate the oxidants and fuel gases under all operating conditions, e.g. thermal cycling, rapid heating/cooling, temperature gradients. In this article, the state‐of‐the‐art knowledge in SOFC sealing technology is described for the two main development directions—glass sealants and compressive sealants
Design approaches for determining local current and membrane resistance in polymer electrolyte fuel cells (PEFCs)
Authors: Freunberger S. A. , Reum M. , Büchi F. N. 
Published: December 2010

AbstractIn polymer electrolyte fuel cells, several relevant scales determine the local current distribution. For the scales of flow field structures, the full cell and in‐between‐cells in a stack, different methods have been developed for the local current measurement. The respective measurement principles on the three scales are introduced and discussed. On the full cell scale, a number of methods based on some sort of segmented cell have been developed and have become a standard diagnostic tool, whereas on the channel/rib scale only one method, which uses the current drain asin situshunt resistor has been put forward.The methods for measuring local current density on the different scales form a basis for all methods determining the local membrane resistance.
Proton exchange membrane fuel cell (PEMFC) flow‐field design for improved water management
Authors: Allen J. S. , Son S. Y. , Collicott S. H. 
Published: December 2010

AbstractChannel blockage in the form of liquid water or ice can result in severe degradation of fuel cell components. Thus, the durability of PEM fuel cells is dependent upon effective water management. Many mechanisms affect water management. The mechanism responsible for liquid plug formation is capillarity. Water does not appear in the channels in the form of a plug, rather water enters the channel as a drop through the diffusion media. Capillarity is responsible for the transition from a drop or a film of water into a plug which occludes the channel. The purpose of this chapter is to review the destabilization mechanisms responsible for plug formation in the flow channels. We also discuss analytical and computational tools that may be used to predict the behavior of the liquid water in the flow‐field channels. These tools may also be used to design channel features that can improve water management in the flow field.
Performance impact of cationic contaminants
Authors: Pivovar B. S. , Kienitz B. , Rockward T. , Uribe F. A. , Garzon F. H. 
Published: December 2010

Abstract
Although a major amount of research has been undertaken on failure modes of fuel cell durability, relatively little research has been carried out on cationic contamination. One of the primary issues of cationic contamination is the low level of contaminant needed to impact a cell. The uptake of contaminant cations leads to dramatically decreased performance even at low levels of incorporation. Foreign cations replacing protons in the ionomer phase likely increase ohmic, kinetic, and mass transport losses in the cell and may alter cell thermodynamics. At this point in time, little is known about the rates of exposure, uptake, and escape of contaminant cations in operating fuel cells. The extent of performance loss following cationic contamination and recovery of performance after contamination are discussed in terms of cation contaminant impact on fuel cell durability.
Performance modeling and cell design for high concentration methanol fuel cells
Authors: Shaffer C. E. , Wang C. Y. 
Published: December 2010

Abstract
For direct methanol fuel cells (DMFCs) to compete with and replace lithium‐ion batteries as power sources for mobile devices, they must be designed to increase their energy density. One major hurdle in accomplishing this task is being able to use high concentration methanol fuel, thereby reducing the size of the fuel tank and the amount of water carried as part of the system (water is a reactant in methanol oxidation). Much effort has been made to reduce the methanol crossover from anode to cathode, but there has been relatively less awareness of water transport and its importance in enabling the use of high concentration methanol fuel. In this article, we review the scientific principles and state‐of‐the‐art technology for high concentration methanol fuel cells (HC‐MFCs). We demonstrate a direct link between water crossover through the membrane and the allowable methanol concentration in the fuel through intuitive examples and pertinent case studies, and further review current means by which water loss to the cathode side of a DMFC is reduced. Future HC‐MFC designs are expected to include the continued progress in membrane electrode assemblies (MEAs) that use unique porous layer properties to simultaneously reduce methanol crossover and enhance water backflow from cathode to anode, as well as development of membrane materials with increased resistance to methanol transport and simultaneous increased diffusivity of water.
New diagnostic methods for polarized state
Authors: Kawada T. 
Published: December 2010

AbstractElectrode polarization is a key to determine the dynamic feature of solid oxide fuel cells (SOFCs). Recently, various methods have been proposed for the evaluation of the electrode under the polarized state. Photoelectron spectroscopy and infrared spectroscopy have been applied to detect the surface intermediate species. Raman spectroscopy is a useful tool for high‐temperaturein situmeasurements, and is used for the study of carbon deposition and sulfur poisoning, etc. Attempts were made to measure the local oxygen potential in the electrode layer in order to evaluate the oxygen reaction pathway. The potentiometric method and X‐ray absorption were employed for thein situmeasurement. Isotope exchange and secondary ion mass spectrometry analysis were also used to trace the oxygen reaction path. Although most of the new techniques are still under development, the information obtained from these measurements gives new insight on electrode reaction kinetics.
Carbon‐support corrosion mechanisms and models
Authors: Gallagher K. G. , Darling R. M. , Fuller T. F. 
Published: December 2010

Abstract
The most significant challenges to the commercialization of fuel cells are cost and durability. The electrochemical oxidation of carbon in low‐temperature fuel cells reduces the lifetime of these power plants. This article presents a current understanding of carbon oxidation and corrosion mechanisms that accelerate the reaction. Carbon is oxidized under various conditions including the reverse‐current mechanism, which occurs when a fuel cell is started or stopped and during localized fuel starvation. Models and mitigation strategies are presented to enhance the understanding of the reverse‐current mechanism. We conclude that a combined system and material mitigation strategy is necessary to overcome this corrosion mechanism.
Field experience with fuel cell vehicles
Authors: Wipke K. , Sprik S. , Kurtz J. , Garbak J. 
Published: December 2010

AbstractThe “Controlled Hydrogen Fleet and Infrastructure Demonstration and Validation Project”, also known asthe Fuel Cell Vehicle and Infrastructure Learning Demonstration, is a 5‐year US Department of Energy (DOE) project started in 2004. The purpose of this project is to conduct an integrated field validation that simultaneously examines the performance of fuel cell vehicles and the supporting hydrogen infrastructure. NREL has now analyzed data from almost 3 years of the 5‐year project. During this time, 92 vehicles have been deployed, 15 project refueling stations have been placed in use, and no fundamental safety issues have been identified. We have analyzed data from over 200 000 individual vehicle trips covering 1, 770, 278 km traveled and over 40 000 kg hydrogen produced or dispensed.Public analytical results for this project are in the form of composite data products, which aggregate individual performance into a range that protects the intellectual property and the identity of each company, while still publishing overall status and progress. One of the key metrics from the project is fuel cell durability. We analyze all of the field data from the fuel cell vehicles, and make degradation projections based on a theoretical 10% drop in voltage at high current. Recent projections show that a four‐team average projected time to a 10% drop in voltage is 1200 h. In the next 6 months, we will work to improve the accuracy of the voltage degradation projections by adding a fixed initial voltage and/or a nonlinear fit to avoid potentially overestimating the projected time that could occur as the accumulated hours continue to grow. To understand the cause of the gradual degradation of the stacks, we characterize how each stack is used and then perform multivariate analysis on this dataset to examine dominant variables affecting stack voltage degradation rate. High‐level public results have been extracted and detailed individual team results are also useful to the teams and for feeding back trends into the research and development program. Fuel cell system efficiency at one‐fourth power has been analyzed and compared with the DOE target of 60%; system efficiency results from the four teams ranged from 52.5 to 58.1%. A total of 47 composite data products have been published to date and made directly accessible to the public from our Hydrogen Technology Validation web site.
Field experience with molten carbonate fuel cells (
MCFCs
) and solid oxide fuel cells (
SOFCs
) with an emphasis on degradation
Authors: Frey H. , Kessler A. , Münch W. , Edel M. , Nerlich V. 
Published: December 2010

Abstract
Fuel cells are a very important technology for a utility because they could affect our core business in the future. In the near future, if an increasing number of households produce their own electricity, then we might have to cope with a decline in sales. For this reason, Energie Baden‐Württemberg AG (EnBW) had embarked on the first fuel cell project at the end of the year 2001 to gain experience with the technical and economical maturity of this technology. Since then, more than 20 projects have followed; hence, we have good experience concerning the operation of fuel cell systems. For our business, it is important to assess the state of the art of the systems. Therefore, we are carrying out a great variety of demonstration projects.
In this report, we summarize the results of the operation of our fuel cell systems and our experience concerning degradation issues. The relevant systems are 16 solid oxide fuel cell (SOFC) HXS 1000 PREMIERE from Hexis, 1 Galileo 1000 N from Hexis, and 2 molten carbonate fuel cells (MCFCs) Hot Modules from CFC Solutions (formerly MTU). The SOFC systems are suited for home energy supply in different buildings. The two MCFC systems have an electrical output of a maximum of 250 kW and a thermal output of a maximum of 180 kW. One of these has been operated with natural gas and the other with biogas for the first time worldwide.
Local transient techniques in polymer electrolyte fuel cell (
PEFC
) diagnostics
Authors: Schneider I. A. , Scherer G. G. 
Published: December 2010

Abstract
The polymer electrolyte fuel cell (PEFC) is a complex macroscopic electrochemical reactor. Its performance is governed by the interplay of various processes, which occur on different length and timescales. Transient techniques provide a basis for understanding limiting processes, material properties, and degradation phenomena. A variety of transient techniques have entered the field of PEFC diagnostics: linear sweep and cyclic voltammetry (LSV, CV), potential and current step, and electrochemical impedance spectroscopy (EIS). Transient techniques have been used for the in situ characterization of a PEFC up to the complex stack level. Yet, by contrast, conclusions deduced from transient response are almost exclusively limited to phenomena within the most elemental part of a PEFC, the membrane electrode assembly (MEA). This perception, however, neglects the fact that in a technical PEFC processes in three spatial dimensions determine local cell performance and therefore, transient response. In contrast to integral measurements, local transient techniques account for the inhomogeneous operation of a PEFC. In this article, key results obtained by using local CV, EIS, and current step technique are discussed. Thereby, we focus on phenomena in local and overall transient response of a PEFC, which are linked to processes along the flow channels. It is shown that their identification and consideration is crucial for a meaningful interpretation of results
Properties of Flame Sprayed Ce0.8Gd0.2O1.9‐δ Electrolyte Thin Films
Authors: Karageorgakis Nikolaos I. , Heel Andre , Rupp Jennifer L. M. , Aguirre Myriam H. , Graule Thomas , Gauckler Ludwig J. 
Published: December 2010

AbstractThin films of Ce0.8Gd0.2O1.9‐δ (CGO) are deposited by flame spray deposition with a deposition rate of about 30 nm min−1. The films (deposited at 200 °C) are dense, smooth, and particle‐free and show a biphasic amorphous/nanocrystalline microstructure. Isothermal grain growth and microstrain are determined as a function of dwell time and temperature and correlated to the electrical conductivity. CGO films annealed for 10 h at 600 °C present the best electrical conductivity of 0.46 S m−1 measured at 550 °C. Reasons for the superior performance of films annealed at low temperature over higher‐temperature‐treated samples are discussed and include grain‐size evolution, microstrain relaxation, and chemical decomposition. Nanoindentation measurements are conducted on the CGO thin films as a function of annealing temperature to determine the hardness and elastic modulus of the films for potential application as free‐standing electrolyte membranes in low‐temperature micro‐SOFCs (solid oxide fuel cells).
Rylene and Related Diimides for Organic Electronics
Authors: Zhan Xiaowei , Facchetti Antonio , Barlow Stephen , Marks Tobin J. , Ratner Mark A. , Wasielewski Michael R. , Marder Seth R. 
Published: December 2010

AbstractOrganic electron‐transporting materials are essential for the fabrication of organic p‐n junctions, photovoltaic cells, n‐channel field‐effect transistors, and complementary logic circuits. Rylene diimides are a robust, versatile class of polycyclic aromatic electron‐transport materials with excellent thermal and oxidative stability, high electron affinities, and, in many cases, high electron mobilities; they are, therefore, promising candidates for a variety of organic electronics applications. In this review, recent developments in the area of high‐electron‐mobility diimides based on rylenes and related aromatic cores, particularly perylene‐ and naphthalene‐diimide‐based small molecules and polymers, for application in high‐performance organic field‐effect transistors and photovoltaic cells are summarized and analyzed.
Competition between hydrotreating and polymerization reactions during pyrolysis oil hydrodeoxygenation
Authors: De Miguel Mercader F. , Koehorst P. J. J. , Heeres H.J. , Kersten S. R. A. , Hogendoorn J. A. 
Published: December 2010

AbstractHydrodeoxygenation (HDO) of pyrolysis oil is an upgrading step that allows further coprocessing of the oil product in (laboratory‐scale) standard refinery units to produce advanced biofuels. During HDO, desired hydrotreating reactions are in competition with polymerization reactions that can lead to unwanted product properties. To suppress this polymerization, a low‐temperature HDO step, referred to as stabilization, is typically used. Small batch autoclaves have been used to study at near isothermal conditions the competition between hydrotreating and polymerization reactions. Although fast polymerization reactions take place above 200°C, hydrogen consumption was already observed for temperatures as low as 80°C. Hydrogen consumption increased with temperature and reaction time; however, when the end temperature exceeded 250°C, hydrogen consumption achieved a plateau. This was thought to be caused by the occurrence of fast polymerization reactions and the refractivity of the products to further hydrotreating reactions. The effect of the gas–liquid mass transfer was evaluated by using different stirring speeds. The results of these experiments (carried out at 300°C) showed that in the first 5 min of HDO, gas–liquid mass transfer appears to be limiting the overall rate of hydrotreating reactions, leading to undesired polymerization reactions and product deterioration. Afterward, intraparticle mass transfer/kinetics seems to be governing the hydrogen consumption rate. Estimations on the degree of utilization (effectiveness factor) for industrially sized catalysts show that this is expected to be much lower than 1, at least, in the early stage of HDO (first 30 min). Catalyst particle size should, thus, be carefully considered when designing industrial processes not only to minimize reactor volume but also to improve the ratio of hydrotreating to polymerization reactions. © 2011 American Institute of Chemical Engineers AIChE J, 2011
Undulating topography of HfO2 thin films deposited in a mesoscale reactor using hafnium (IV) tert butoxide
Authors: Li Kejing , Zhang Lin , Dixon David A. , Klein Tonya M. 
Published: December 2010

AbstractHfO2 was deposited by chemical vapor deposition on Si, native SiO2, and borosilicate glass surfaces using hafnium (IV) tert butoxide in a mesoscale flow reactor. Undulating thin film topographies were observed by atomic force microscopy on all substrates with peak‐to‐peak periods between 10 and 25 nm in the presence of a temperature gradient perpendicular to flow of 25°C/mm. A computational fluid dynamic model suggests the phenomenon originates from buoyancy driven roll type flow. The thickness uniformity and roughness of the films depended on the flow rate, reactor temperature, and the substrate type. © 2011 American Institute of Chemical Engineers AIChE J, 2011
Nickel phosphide catalyst for autothermal reforming of surrogate gasoline fuel
Authors: Liu Lei , Hong Liang 
Published: December 2010

AbstractAn investigation into the catalytic autothermal reforming (ATR) of a mixture of n‐octane and naphthalene (6 wt %), designed as a surrogate gasoline, is undertaken. Carbon deposition on the metallic Ni catalyst has been aware of the main hurdle for the catalytic reforming of hydrocarbons especially those with high carbon numbers. This work develops NixPy crystallites on a CeO2 powder support by electroless nickel plating and calcination. The catalyst exhibits nil coking extent after reforming the surrogate fuel. The NixPy crystallites are determined by XRD and its Ni‐P bonding is confirmed by XPS, where the Ni carries slightly higher negative charge than the Ni0 as usually observed. The XPS investigation also divulges the presence of Ce3+ species in the CeO2 support on which the NixPy crystallites are distributed, indicating that the support contains oxygen vacancies. These two subtle structural differences are proposed to provide the catalyst with resistance to coking. © 2011 American Institute of Chemical Engineers AIChE J, 2011
Process‐based graphical approach for simultaneous targeting and design of water network
Authors: Deng Chun , Feng Xiao , Ng Denny Kok Sum , Foo Dominic Chwan Yee 
Published: December 2010

AbstractA new process‐based graphical approach (PGA) is presented for the simultaneous targeting and design of water network. The PGA is extended from the limiting water profile which was developed for flow rate targeting for a water network. Via PGA procedure, apart from locating the minimum freshwater and wastewater flow rate targets, the water network that corresponds to the minimum flow rate targets is also synthesized simultaneously. The proposed approach handles both fixed load (including operations with water loss and/or gain) and fixed flow rate problems equally well. In addition, the approach can be used to synthesize direct reuse/recycle, regeneration reuse/recycling, and total water network. Furthermore, the proposed approach is applicable for water network with multiple freshwater sources. Three literature examples are presented to illustrate the proposed approach. © 2011 American Institute of Chemical Engineers AIChE J, 2011
Synthesis and characterization of novel graft copolymers by radiation‐induced grafting
Authors: Işıkel Şanlı Lale , Alkan Gürsel Selmiye 
Published: December 2010

AbstractThe radiation‐induced graft copolymerization of N‐vinyl‐2‐pyrrolidone (NVP), 4‐vinyl pyridine (4VP), and 2‐vinyl pyridine (2VP) monomers onto poly (ethylene‐alt‐tetrafluoroethylene) (ETFE) was investigated. The influence of synthesis conditions particularly the solvent was studied. Various solvents, such as n‐propanol, isoproponol, benzyl alcohol, methanol, ethanol, cyclohexanone, tetrahydrofuran (THF), nitromethane, 1,4‐dioxane, and n‐heptane were examined for this purpose. Graft copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA), and scanning electron microscopy‐energy dispersive spectroscopy (SEM‐EDAX). It was found that the nature of the solvent had profound influence over the grafting reaction. Cyclohexanone, n‐propanol, and isoproponol for 4VP/ETFE grafting, THF and 1,4‐dioxane for NVP/ETFE grafting, and benzyl alcohol and methanol for 2VP/ETFE grafting were found to be the suitable solvents yielding highest graft levels. Isoproponol and n‐propanol are promising in terms of both graft level and mechanical properties for 4VP/ETFE. Grafting of NVP, 4VP, and 2VP onto ETFE were verified through FTIR spectroscopy. Storage modulus and glass transition temperature of the copolymers were found to increase as graft level increased. Surface profile of representative films was also investigated by viewing the distribution of elemental nitrogen using SEM‐EDAX. Results indicated that copolymers of 4VP, NVP, and 2VP are considerably different from each other. 4VP‐based copolymers exhibited relatively more homogenous grafting over the surface compared with NVP‐ and 2VP‐based copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011