bluuebunny/crossref_metadata_2025 huggingface dataset:
Real-SOFC - A Joint European Effort in Understanding SOFC Degradation
Authors: Steinberger-Wilckens Robert , Tietz Frank , Smith Martin J. , Mougin Julie , Rietveld Bert , Bucheli Olivier , van Herle Jan , Rosenberg Rolf , Zahid Mohsine , Holtappels Peter
Published: May 2007

The Integrated Project Real-SOFC joins 26 partners from throughout Europe active in planar SOFC technology. The project is funded by the European Commission within the Sixth Framework Programme and aims at improving the understanding of degradation in SOFC stacks and extending the durability of planar SOFC devices such that they become viable for stationary applications. The project consortium comprises of universities, research institutions and industrial companies. The project concept is based on improving materials and materials processing by the provision of extensive test results allowing the identification of degradation mechanisms, and then to supply industrial components of enhanced quality for repeated testing analysis. An iterative programme of component development is employed resulting in the production of '2nd' and '3rd' Generations of SOFC components/stacks. This paper offers recent results on the degradation issues and covers selected aspects of other project-related output such as testing conditions, environmental impact assessment and educational activities.
Development Status of a Planer Type of 1 kW Class SOFC System
Authors: Shimano Jun , Yamazaki Hiroshi , Mizutani Yasunobu , Hisada Koji , Ukai Kenji , Yokoyama Misuzu , Nagai Kohki , Kashima Shoichi , Orishima Hiroshi , Nakatsuka Suguru , Uwani Hiroyuki , Hirakawa Makoto
Published: May 2007

Toho Gas Co., Ltd. and Sumitomo Precision Products Co., Ltd. have been jointly developing a SOFC system using scandia stabilized zirconia electrolyte cells. The previous two models of 1 kW class SOFC systems (α and β-model) have been developed and described. In this paper, the third generation 1 kW class SOFC system (γ-model) which has the steam reformer integrated with cell stack and the burner for starting up is reported. Firstly, it was confirmed that the steam reformer operated successfully compared the results of the gas analysis with the equilibrium calculation. Next, the electrical power output of 1180 W was achieved at fuel utilization of 73 % and the electrical efficiency of 53% (DC, LHV) was obtained. Moreover, it was concluded that the thermal design of the hot module was important to achieve highly efficient SOFC system from the evaluation of heat balance.
Development of High Power Density Seal-Less SOFCs
Authors: Vora Shailesh
Published: May 2007

Siemens is the recognized leader in the development of solid oxide fuel cell (SOFC) technology and has developed materials and processes that have produced robust and reliable SOFCs. Siemens tubular seal-less SOFCs have demonstrated long life and ability to thermal cycle with no noticeable performance degradation over several years of operation. Siemens is developing a new cell design that incorporates integral ribs to reduce the current path length, and hence lower cell resistance. This new design, referred to as High Power Density (HPD) cell retains the advantages of a seal-less design, while increasing power density. The HPD cells also utilize advance cell materials that further improve power density. Results of testing of a prototype system with HPD5 cells and progress on different options for HPD cell design, cell fabrication and power enhancement are presented.
Development of SOFC-Micro Gas Turbine Combined Cycle System
Authors: Nishiura Masanori , Koga Shigenori , Kabata Tatsuo , Hisatome Nagao , Kosaka Kenichiro , Ando Yoshimasa , Kobayashi Yoshinori
Published: May 2007

SOFC is able to attain extremely high efficiency over 70% as LHV, as gas turbine combined cycle system. Mitsubishi Heavy Industries (MHI) has been developing SOFC since 1984. Based on developed technologies, now MHI is on the step of integrating SOFC power generation system. MHI has improved the components and the control technology for the combined cycle system, that is, improvement of cell stack, verification of pressurized operation and control of SOFC module and the combustor for low- calorie fuel. In 2006, MHI managed to operate the combined cycle system with maximum combined power output of 75kW, for the first time in Japan. And now, MHI is ready to manufacture a 200kW class SOFC-MGT combined cycle system, which will be operated in 2007.
GE SECA Prototype System Development and Testing
Authors: Zhou Qiong , Goodman Joe , Powers Jim , Campbell Tony
Published: May 2007

This paper summarizes the prototype system development and testing under Solid State Energy Conversion Alliance (SECA) Solid Oxide Fuel Cell Program. There were two generations of the SECA prototype systems developed. The Gen 1 prototype system met or exceeded the SECA requirements over a 1720h test, achieving 41% peak system efficiency and 5.4 kW peak net power. The Gen 2 prototype achieved 49.6% peak efficiency and 5.6 kW peak net power over a 120h commissioning test. The Gen 2 prototype system has been delivered to National Energy Technology Laboratory (NETL) for final testing.
Development of 1 kW Class SOFC System at KEPRI
Authors: Lee Taehee , Park Jae-Keun , Oh Je-Myung , Yoo Young-Sung , Bae Joongmyeon , Park Jin-Woo , Kim Jung Han
Published: May 2007

Korea Electric Power Research Institute (KEPRI) is developing a SOFC system for a combined heat and power unit. KEPRI has studied an anode supported planar cell and a 1 kW class stack operated at intermediate temperature. A 1 kW class SOFC stack was composed of 37 cells with 10×10cm2 and stainless steel interconnects. It showed the maximum power density of 0.35 W/cm2 at 750{degree sign}C. When a 1 kW class SOFC system was operated at 750{degree sign}C with a reformate gas of city gas, the stack showed 1.13 kW electrical power at 40 A and 1.3 kW at 50 A respectively. Hot water was made by recuperated heat from combustion of unreacted anode off-gas and heat of 0.57-1.2 kW was recovered according to the loaded current.
Comparison of the Numerical Calculations on Cell Performance Between Ordinary Planar Cell and Segmented Cell
Authors: Yakabe Hisataka
Published: May 2007

Computer simulations of cell performance for common planar cells and segmented cells were carried out. The ohmic resistance, concentration over potential, and activation over potential affect the cell performance in a different manner between the planar cells and the segmented cells. Besides, the change of the Nernst potential along the fuel flow is different between the two types of cells. The characteristic features of these cells were simulated using computational fluid dynamics models and the results of the simulations were compared. From the numerical simulations, the physical properties for the planar cells and the segmented cells were made clear.
Refractory Cathode Investigation for Single-Step Co-fired Solid Oxide Fuel Cells
Authors: Zink Peter , Yoon Kyung J. , Huang Wenhua , Pal Uday B. , Gopalan Srikanth
Published: May 2007

A single-step co-firing process for fabricating planar solid oxide fuel cells (SOFCs) requires refractory electrodes to prevent excessive sintering of the electrode while facilitating full-density sintering of the electrolyte. Single cell current-potential curves and impedance measurements indicate that the majority of the performance losses occur in the cathode and are due to activation polarization. A-site deficient calcium and cerium doped lanthanum ferrite cathode powders were synthesized and investigated as possible refractory cathode materials with low activation polarization losses. Four-probe conductivity measurements indicated that all compositions were suitable as cathodes. However, reactivity with YSZ reduced the conductivity by as much as two orders of magnitude. Future experiments will investigate the applicability of a doped- ceria barrier layer to prevent reaction of lanthanum ferrite cathodes with YSZ electrolyte.
Performance Degradation of Solid Oxide Fuel Cells with Metallic Interconnects
Authors: Guan Jie , Zecevic Strahinja , Liu Ying , Lam Patrick , Klug Ric , Alinger Matthew , Taylor Seth , Ramamurthi Badri , Sarrafi-Nour Reza , Renou Stephane
Published: May 2007

Factors influencing the performance degradation of solid oxide fuel cells (SOFCs) include oxide scale growth on metallic interconnects, Cr poisoning, interfacial interactions, contact losses, and cell component aging. This research was to investigate the transport and interaction mechanisms of Cr- containing species with SOFC cathode/contact materials and evaluate the impact on the electrochemical performance. To reduce the degradation rate, a protective coating has been developed and evaluated with long-term cell/stack testing. Degradation rate has been significantly reduced with the coating on commercially available ferritic steel interconnects, primarily due to significant reduction in Cr formation and transport through the coating.
Robust and Reliable Cells for an Easy Stack Operation
Authors: Ihringer Raphaël
Published: May 2007

Cell failures are often the cause for stopping a running stack. Staxol, a new company active in the SOFC area is developing thick cells that will provide robustness and reliability. Keeping in mind that fuel utilisation has to be high to allow power efficiency, strong efforts will be dedicated to optimise the structure and the proportion of the porosity in the cell. In order to keep as low as possible the ohmic resistance, thin electrolyte (5-20 μm), made of yttria or scandia stabilized zirconia equips the cell. A thin top layer of doped ceria is added when reactive cathodes are used.
Development of the Stacked Micro SOFC Modules using New Approaches of Ceramic Processing Technology.
Authors: Fujishiro Yoshinobu , Awano Masanobu , Suzuki Toshio , Yamaguchi Toshiaki , Arihara Kayo , Funahashi Yoshihiro , Shimizu Sota , El-Toni Ahmed M. , Sakuragi Satomi
Published: May 2007

Fabrication and development of the compact modules using SOFCs are promising for various electrical applications. Furthermore, both good electrochemical and high thermo-mechanical properties  of the prepared ceramic devices are strongly required for the commercial system under quick start-up at low operating temperature. We are developing the new design of micro SOFC modules by using a novel approach of ceramic processing. Gd-doped CeO2 (GDC) based micro cells have been developed with assembling method of the cells. In this paper, we show the stacked micro SOFC modules in consisting of < 2.0 mm in diameter cells into compact spaces.
SOFC Cells and Stacks for Complex Fuels
Authors: Sabolsky Edward M. , Seabaugh Matthew , Sabolsky Katarzyna , Ibanez Sergio A. , Zhong Zhimin
Published: May 2007

Reformed hydrocarbon and coal (syngas) fuels present an opportunity to integrate solid oxide fuel cells into the existing fuel infrastructure. However, these fuels often contain impurities or additives that may lead to cell degradation through sulfur poisoning or coking. Achieving high performance and sulfur tolerance in SOFCs operating on these fuels would simplify system balance of plant and sequestration of anode tailgas. NexTech Materials, Ltd., has developed a suite of materials and components (cells, seals, interconnects) designed for operation in sulfur-containing syngas fuels. These materials and component technologies have been integrated into an SOFC stack for testing on simulated propane, logistic fuel reformates and coal syngas. Details of the technical approach, cell and stack performance will be reported.
Geometric Effects on Tubular Solid Oxide Fuel Cells
Authors: Finnerty Caine , Du Yanhai , Emley Benjamin J. , Cheekatamarla Praveen , Zhu Weizhong , Cai Jun , Sharp Rebecca
Published: May 2007

Micro-tubular solid oxide fuel cell systems have many desirable characteristics compared with their planar counterparts; however, there are many obstacles and difficulties that must be met to achieve a successful and economically viable manufacturing process and stack design. One of the most important parameters is the cell size and geometries. Anode-supported tubes provide an excellent platform for individual cells. A thin electrolyte layer applied to the outside of the tube helps to minimize polarization losses thus avoiding the difficulty of coating the inside of electrolyte or cathode-supported tubes. The stack design with anode supported tubes also avoids using a fuel chamber on the outside of the tube. Various geometries of the cell support, in terms of diameter, length, cross-section shape and arrangement were investigated. The results of geometric effects on micro-tubular SOFCs will be discussed and presented in this paper.
Optimization of Configuration for Cube-Shaped SOFC Bundles
Authors: Funahashi Yoshihiro , Suzuki Toshio , Fujishiro Yoshinobu , Shimamori Toru , Awano Masanobu
Published: May 2007

Solid oxide fuel cells (SOFCs) have serious problems under heating cycle. As a solution for this problem, use of micro- tubular SOFCs is considered for robustness under rapid changes of operating temperature. We fabricated cube-shaped SOFC bundles with following method; Micro-tubular Gd-CeO2(GDC)-NiO anode was fabricated by extrusion, and then was co-fired with GDC electrolyte coated on the surface of the anode tube. La0.6Sr0.4Co0.2Fe0.8O3-x (LSCF) cathode matrices with grooves were also prepared by extruding of a mass with LSCF powder and pore-former. Then, the tubes were arranged in the grooves of LSCF cathode matrices, where the tubes and the matrices were jointed with LSCF pastes. Optimization of the micro tubular cell configuration in cube-shaped SOFC bundles and microstructure of cathode is important to achieve our target power density (2W/cm3). In this study, we considered the configuration of cube-shaped SOFC bundles and investigated the character of single tubular cell and cathode porous matrices.
A Numerical Approach to Predict the SOFC Fracture: The Case of an Anode Supported Cell
Authors: Laurencin Jérôme , Delette Gérard , Dupeux Michel , Lefebvre-Joud Florence
Published: May 2007

The purpose of this work has been focused on the calculation of the stress field inside planar anode supported cells. The cell fracture has been estimated through the statistical approach of Weibull. After elaboration, a high residual compressive stress has been calculated in the thin electrolyte layer. A slight tensile stress has been pointed out in the anode in a region close the anode/electrolyte interface. For high electrolyte thickness (>20 μm), this tension leads to low survival probabilities of the anode. At SOFC operating temperature, the elaboration stress is partially relaxed. In this condition, the thermal cycling between the room temperature to the SOFC operating one should not induced any cell degradation. The first cermet re-oxidation step has been also analyzed. This study has shown that the cathode is damaged as soon as the anodic expansion reaches values between 0.05-0.09 %. The electrolyte fracture has been predicted to occur for anodic expansion ranging between 0.12-0.15 %.
Improving Reliability of Microtubular SOFCs for Direct Use on Methane
Authors: Dhir Aman , Kendall Kevin
Published: May 2007

The main problems of small scale SOFC devices are the interconnections, durability and operation on available fuels such as methane. This paper shows how anode supported micro tubular SOFCs can be interconnected more reliably then run on methane. Theory showed that by coiling a wire on the outside of the micro tube, a more reliable connection could be achieved, when compared to traditional methods of internal wiring. Experiment showed that micro tubular SOFCs can be operated for 60 hours to give a steady power output. The enhanced reliability has been tested on methane, which showed better and consistent performance by up to 9% compared to hydrogen.
Enhancing Cathode Performance and Anode Sulfur/Carbon Tolerance of SOFCs by Nano-Infiltration
Authors: Sholklapper Tal , Kurokawa Hideto , Jacobson Craig P. , Visco Steven J. , De Jonghe Lutgrad C.
Published: May 2007

The positive cost benefit associated with the use of metallic interconnects in SOFCs have led commercial developers to target operating temperatures in the range of 600{degree sign}C-800 {degree sign}C; however maintaining high electrode performance at reduced temperatures remains a challenge. One approach to increase electrode performance is to enhance the active catalytic area by infiltrating the electrode with dispersed catalyst. LBNL has developed an infiltration method that deposits a continuous network of nano-particles throughout existing electrodes, in a single processing step. In the case of mixed ionic electronic conductor (MIEC) nanoparticles infiltrated into LSM-YSZ electrodes, electrode performance is greatly improved by both the catalytic properties of the MIEC and the triple-phase boundary extension across the surfaces of both the electrode and electrolyte particles in the electrode. The infiltration method has additionally been used to deposit MIEC nanoparticles in Ni-YSZ electrodes, leading not only to improved performance, but to impressive sulfur tolerance as well.
Influence of H2S Poisoning on Anode Layer of SOFC
Authors: Ishikura Akira , Sakuno Shinichi , Komiyama Norio , Sasatsu Hiroshi , Masuyama Naoto , Itoh Hibiki , Yasumoto Kenji
Published: May 2007

The influence of sulfur compounds on Ni-YSZ anode of SOFC cell has investigated by measuring cell voltage under a constant current density for Ni-YSZ anode / YSZ electrolyte / (La,Sr) MnO3 cathode cell. Two-step degradation of cell voltage was observed by supplying H2S contained fuel. The first-step degradation of cell voltage was recovered completely by switched to sulfur-free fuel, while the cell voltage wasn't recovered completely once the cell voltage went down under 0V. After the cell with irreversible degradation was cooled down under pure N2 atmosphere, it was analyzed by FE-SEM, EDX and Raman Spectroscopy. The results of these analyses of cross-section of the cell revealed nickel sulfides formation by supplying H2S contained fuel. It is supposed that melted nickel sulfides diffused in the anode and electrolyte layer. The irreversible cell poisoning might be caused by these nickel sulfides.
Performance of Single-Chamber Intermediate-Temperature SOFCs Operated in Methane/Air Mixtures using PdO/NiO/CeO2-Sm2O3 Anodes
Authors: Cabezas Marcelo D. , Lamas Diego G. , Bellino Martín G. , Fuentes Rodolfo O. , Walsöe de Reca Noemí E.
Published: May 2007

In recent years, new concepts have been explored in order to find anodes adequate for operation with hydrocarbon fuels with high catalytic activity at intermediate temperatures, since the usual internal reforming of methane requires very high temperatures. In this sense, single-chamber SOFCs have attracted great attention because they take advantage of the ambient oxygen to produce H2 and CO by the partial oxidation of the hydrocarbon. In this work, we studied the performance of single-chamber intermediate-temperature SOFCs operated with methane as fuel using PdO/NiO/CeO2-Sm2O3 anodes. CeO2-Sm2O3 and Sm0.5Sr0.5CoO3 were used as electrolyte and cathode, respectively. All these materials were prepared by low-cost wet chemical methods. Our results showed that the incorporation of PdO in the anode allows to reach high peak power densities, of about 100 mW/cm2 at 600{degree sign}C.
Microstructure Control Using Impregnation of LSM in a Thin Porous Electrolyte Layer
Authors: Shimada Hiroyuki , Takizawa Koichi , Michibata Hideo , Hagiwara Akifusa
Published: May 2007

A high performance LSM/ScSZ composite cathode was prepared by a novel fabrication method where LSM/ScSZ in the form of solid particles was impregnated in a porous electrolyte layer with a thickness of approximately 5-10μm. In the proposed method, a porous ScSZ electrolyte structure is first fabricated on a dense ScSZ electrolyte, and LSM powder in slurry is then printed on this surface structure. Since this surface layer is very thin and has appropriate electrolyte pore structure, LSM particles can be effectively impregnated. SEM observation has revealed that the impregnated LSM forms electronic conduction paths on the porous electrolyte structure without severe blockage of channels for gas phase diffusion, thus confirming the successful impregnation. The prepared cathode actually showed a significant improvement in polarization performance. Also, a cathode structure model is discussed by considering the effect of surface roughening and layer thickening for the interface between LSM/electrolyte
Characterisation of La0.6Sr0.4Co0.2Fe0.8O3-d and Ba0.5Sr0.5Co0.8Fe0.2O3-d as Cathode Materials for the Application in Intermediate Temperature Fuel Cells
Authors: Ried Peter , Bucher Edith , Preis Wolfgang , Sitte Werner , Holtappels Peter
Published: May 2007

Capable materials for solid oxide fuel cell cathodes have to provide high electrocatalytic activity for oxygen reduction as well as sufficient electronic conductivity and good ionic transport properties. This study compares the electrical transport properties and the oxygen exchange properties of two promising cathode materials for operating temperatures between 600 and 800 {degree sign}C: La0.6Sr0.4Co0.2Fe0.8O3-d and Ba0.5Sr0.5Co0.8Fe0.2O3-d. Both materials were synthesized by spray pyrolysis and characterised with respect to phase purity and to the element ratio by XRD and ICP-AES analysis. The sintering behaviour of the calcined powders and the coefficients of thermal expansion of dense sintered samples were studied by dilatometry. As important parameters for the oxygen exchange reaction the chemical surface exchange coefficients and chemical diffusion coefficients as well as the electrical conductivities are compared.
Passivation and Activation of SOFC Nanostructured Cathodes
Authors: Wang Wei Guo , Bentzen Janet , Jensen Soeren H. , Bonanos Nicolas , Hendriksen Peter V. , Mogensen Mogens
Published: May 2007

In a solid oxide fuel cell the cell performance is largely determined by the cathode properties, in particular at low operating temperature (<700{degree sign}C). Intensive cathode studies have made a great improvement in reducing the polarization resistance (Rp) in many systems. This has led to reduction of fuel cell operating temperature to use stainless steel as interconnect, and by this to reduce cost. However, our studies showed a significant increase of Rp over time when samples were kept at low temperature and open circuit voltage. We have systematically investigated these passivation phenomena in LaSrMnO3, LaSrCoFeO3 and BaSrCoFeO3 systems. On the other hand, Rp was reduced significantly by a high temperature annealing, close to the initial value and sometimes series resistance (Rs) could be recovered completely. Cation diffusion and defect disordering are considered to be the main effects contributing to the passivation and activation.
Conversion of Simulated Biogas in a SOFC: The Effect of Organic Compounds
Authors: Dekker N. J. J. , Ouweltjes Jan Pieter P. , Rietveld Bert
Published: May 2007

Fuel from a gasifier contains a series of organic compounds, mainly in the range of C1-C16. CH4 is known to be converted by the SOFC, far less is known about the conversion of higher hydrocarbons and the effect on the degradation of the SOFC. In the EU project Green-Fuel-Cell , a SOFC stack will be connected to a biomass gasifier. For the determination of the allowable concentration of higher hydrocarbons for the stack test, single cell tests with simulated gas from a gasifier containing various hydrocarbons were performed. From these single cell tests it was concluded that C2H2, C2H4 and C7H8 were completely converted without degradation of the performance of the SOFC. The addition of C10H8, C14H10 and C16H10 resulted in a strong cell voltage degradation, which appeared to be due to the blocking of the reforming of CH4. The electrochemical conversion of H2 was hardly effected by these organic compounds
Performance Assessment of Bioethanol-Fed Solid Oxide Fuel Cell System Integrated with Distillation Column
Authors: Jamsak Wasana , Assabumrungrat Suttichai , Douglas Peter L. , Croiset Eric , Laosiripojana Navadol , Suwanwarangkul Rapeepong , Charojrochkul Sumittra
Published: May 2007

This paper investigated the performance of a bioethanol-fed Solid Oxide Fuel Cell (SOFC) system integrated with a distillation column (SOFC-D). Excess heat from the SOFC system was directly utilized in the distillation column where bioethanol (5 mol%) was purified to a desired concentration before feeding to the SOFC system consisting of an air heater, an ethanol/water heater, a reformer, an SOFC preheater, an SOFC stack and an afterburner. The SOFC-D system was simulated using Aspen PlusTM for the distillation portion and MatlabTM for the SOFC portion. The effects of operating parameters; i.e., ethanol concentration, ethanol recovery, fuel utilization and operating voltage on the performance and energy involved in the SOFC-D system (e.g. distillation energy: QD and the net exothermic heat of the SOFC system: QSOFC,Net) were examined. In addition, the performance of the SOFC-D system at the energy sufficient point where QD = QSOFC,Net was considered. The integration of the distillation column with the SOFC system was found to offer superior SOFC performance. The ethanol recovery and fuel utilization significantly influenced the overall electrical efficiency and power density. Quite low performances are obtained when one operated the SOFC-D without an external heat source. The maximum overall efficiency and power density (~35% and 0.22 W cm-2) occured at an ethanol recovery of 80% and Uf of 90%.
Development of Functional SOFC Anode
Authors: Basu Rajendra , Mukhopadhyay J , Banerjee M , Das Sharma A , Maiti H S.
Published: May 2007

For anode-supported planar SOFC, the most widely accepted anode material is nickel-8 mol% yttria stabilized zirconia (Ni- YSZ) cermet. For the required electrical conductivity during intermediate temperature SOFC operation (~800oC), conventionally 35-40 vol% Ni is used. Reduction of nickel content solves not only nickel coarsening problem during long- term SOFC operation but also makes thermal expansion coefficient much closer to YSZ. In this investigation, a novel electroless technique is employed to prepare uniform coating of metallic Ni onto YSZ to make core-shell anode cermet structure. Compared to conventionally prepared anodes (~35 vol% Ni), in this functional anode, percolation threshold is lowered down to ~20 vol% to achieve almost same electrical conductivity (σ800oC ~150 Scm-1). However, the properties of these cermets depend strongly on several processing conditions like particle size of YSZ powders, sensitization process, electroless bath composition and deposition temperature. A simple adsorption kinetic model for sensitization process is proposed.
Investigation of H2 and CO Oxidation on Ni-CeO2 Electrodes Using a Specially Designed Three-Electrode Configuration
Authors: Cimenti Massimiliano , Hill Josephin M.
Published: May 2007

The electrochemical oxidation of H2 and CO was studied on Ni- CeO2 anodes using a specific cell design characterized by a Luggin-type reference electrode. The consistency of this configuration was verified theoretically using a numerical model. The oxidation rates were measured by cyclic- voltammetry and electrochemical impedance spectroscopy (EIS) at temperatures between 700 and 800{degree sign}C and at different H2 and CO partial pressures. EIS results were analyzed following a validation and deconvolution procedure. EIS fitting parameters were rationalized using a method developed for conventional Ni-YSZ anodes. Typically, two main arcs composed the complex impedance of Ni/CeO2. In H2, the charge transfer reactions were not limiting but the rate of the process related to the lower peak-frequency arc decreased with anodic overpotential, indicating diffusion limitations in this region. In CO, charge transfer limitations were evident. The design and procedure developed in this study is useful for characterizing the processes in SOFC anodes.
Electrochemical Performance of Ni-CGO Nano-Grained Thin Film Anodes for Micro SOFCs
Authors: Muecke Ulrich P. , Akiba Kojiro , Salkus Tomas , Stus Nataliya , Ludwig Gauckler J.
Published: May 2007

NiO-Ce0.8Gd0.2O1.9-x (CGO) thin film anodes with thicknesses around 400 nm were prepared by air blast spray pyrolysis. The film composition was 60/40 vol.% Ni/CGO in the reduced state. The films were deposited on tape-cast YSZ electrolytes. The material was amorphous after deposition and was crystallized by sintering in air between 650 and 1200{degree sign}C. The temperature treatment resulted in films with average grain sizes of the NiO and CGO grains between 5 and 250 nm. The area specific resistance of the thin film anodes was measured in a humidified 1:4 H2:N2 atmosphere as a function of grain size within the temperature interval of 400{degree sign}C- 600{degree sign}C. The area specific resistance (ASR) was predominantly depending on the grain size of the films. At 550{degree sign}C, an ASR of 0.5 Ωcm2 was found for the 5 nm grain size anode. The value increased to 30 Ωcm2 for the 250 nm grain size anode.
Electrical Properties of Nb-Doped SrTiO3 Ceramics with Excess TiO2 for Anodes and Interconnects of SOFCs
Authors: Horikiri Fumimasa , Han Li Q. , Iizawa Naofumi , Sato Kazuhisa , Yashiro Keiji , Kawada Tatsuya , Mizusaki Junichiro
Published: May 2007

The electrical properties of Nb-doped SrTiO3 ceramics with and without excess TiO2 were investigated for anodes and interconnects of SOFCs by a DC four-probe conductivity measurement. The microstructures and the grain boundary properties were revealed by SEM, EDX, SEM-EBSP-OIM and HRTEM. It was found that addition of excess TiO2 reduces the influence of the grain boundary on the conductivity of Nb-doepd SrTiO3 ceramics and the conductivity turned to be metallic in SOFCs operating temperatures. The second phases such as TiO2 and Nb2O5 were found in the composition of excess TiO2. No grain boundary segregation was found, and randomly distributed grain boundaries were found predominant in the Nb-doped SrTiO3 ceramics with and without excess TiO2. The defects at the grain boundary were discussed.
SOFC Anodes for Direct Oxidation of Alcohols at Intermediate Temperatures
Authors: Cancellier Marina , Sin Agusti , Morrone Michele , Caracino Paola , Sarkar Partho , Yamarte Luis , Lorne J , Liu Man , Barker-Hemings Emma , Caligiuri Andrea , Cavallotti Carlo
Published: May 2007

Anode electrodes with suitable performance towards the direct oxidation of alcohols avoiding the reforming step are presented in this paper. The reforming process increases the complexity of the whole device and increases the cost. It is shown the synthesis of nanoparticles that are used for the fabrication of button cells suitable to be used with alcohols as anodic fuel, avoiding preliminary reforming operation unit. Also, it is investigated the theoretical thermodynamic conditions and correlated with the electrochemical performance
Power Generations of Rechargeable Direct Carbon Fuel Cells with Ni/GDC Anodes and Ni/ScSZ Anodes
Authors: Ihara Manabu , Hasegawa Shinichi , Saito Haruyuki , Jin Yongcheng
Published: May 2007

A rechargeable direct carbon solid oxide fuel cell (RDCFC) that used a solid carbon fuel supplied by thermal decomposition of a hydrocarbon has been developed. Because a solid fuel has a higher energy density compared with gas fuel or liquid fuel, the RDCFC can be expected as a compact, portable power unit. In our previous papers, we reported that the RDCFC with the nickel (Ni) / Gadolinia doped ceria (GDC) anode after a propane charging time of only 5 min, maintained a power density of 44.2~50.4 mW/cm2 for 83 min. In this report, the power-generation characteristics of RDCFC with Ni/GDC anode after a charging of methane were compared with those with Ni/Scandia stabilized zirconia (ScSZ) anode. The fuel utilizations of solid carbon were also evaluated. The RDCFC with Ni/GDC anode showed high and stable characteristics of power generation. However, the performance of the RDCFC with Ni/ScSZ anode had much lower than that with Ni/ GDC anode although the Ni/ScSZ anode had the high performance in dry methane fuel as well as Ni/GDC anode. The fuel utilization of carbon fuel in the RDCFC with Ni/GDC anode charged by methane was ranged from 48 to 58%. Furthermore, by increasing charging time, we demonstrated the power density of RDCFC charged by dry methane was comparable to that of the RDCFC charged by propane.
Investigation of Composite Ni-Doped Perovskite Anode for Direct Oxidation of Hydrocarbons
Authors: Massimiliano Lo Faro , La Rosa Daniela , Brunaccini Giovanni , Minutoli Maurizio , Antonucci Vincenzo , Aricò Antonino Salvatore
Published: May 2007

Ni-doped perovskite anodes have been investigated for direct oxidation of hydrocarbon in IT-SOFC. Perovskite materials are characterized by mixed electronic-ionic conductivity that combined to the high intrinsic catalytic activity of Ni allows to achieve high reaction rates in both direct oxidation and internal reforming processes while minimizing the cracking and carbon deposition processes. Suitable power densities of about 300mW•cm-2 for the direct oxidation of propane were achieved at 800{degree sign}C. Temperature programmed reduction analysis carried out in methane on a reduced catalyst has shown that Ni-doped perovskite has good catalytic activity at higher temperatures than 600{degree sign}C in absence of humidity. No carbon formation was observed in the discharged catalysts as confirmed by XRD analysis that however showed a modification of the perovskite structure.
Numerical Study of Heterogeneous Reactions in an SOFC Anode With Oxygen Addition
Authors: Hao Yong , Goodwin David G.
Published: May 2007

Previous experimental studies have shown that addition of small amounts of oxygen to a hydrocarbon fuel stream can control coking in the anode, while relatively large amounts of oxygen are present in the fuel stream in single-chamber SOFCs. In order to rationally design an anode for such use, it is important to understand the coupled catalytic oxidation / reforming chemistry and diffusion within the anode under SOFC operating conditions. In this study, the heterogeneous catalytic reactions in the anode of an anode-supported SOFC running on methane fuel with added oxygen are numerically investigated, using a model that accounts for catalytic chemistry, porous media transport, and electrochemistry at the anode/electrolyte interface. Using an experimentally validated heterogeneous reaction mechanism for methane partial oxidation and reforming on nickel, we identify three distinct reaction zones at different depths within the anode: a thin outer layer in which oxygen is nearly fully consumed in oxidizing methane and hydrogen, followed by a reforming region, then a water-gas shift region deep within the anode. Based on these insights into the chemistry, the possibility of a composite anode with different layers of metal catalysts is also explored for the improvement of fuel cell performance.
Modeling Distributed Charge-Transfer Processes in Membrane Electrode Assemblies with Mixed-Conducting Composite Electrodes
Authors: Zhu Huayang , Kee Robert
Published: May 2007

A model is developed to represent chemistry and transport in a membrane- electrode assembly with porous mixed ionic-and-electronic conducting composite electrodes. Reactive porous media transport within electrodes is represented with a Dusty-Gas model. Charge-transfer chemistry is handled via a modified Butler- Volmer formalism, which depends on the local electric-potential differences. Heterogeneous chemistry (e.g., reforming or partial oxidation) is handled via a detailed surface-reaction mechanism. For typical composite- electrode structures the charge-transfer region extends about 10 to 20 microns from the dense electrolyte. The model is formulated as continuum differential equations, which are solved computationally on a discrete mesh network.
Numerical Analysis of Output Characteristics of a Tubular SOFC with Different Fuel Compositions and Mass Flow Rates
Authors: Barzi Y. Mollayi , Ghassemi M. , Hamedi M. , Afshari E.
Published: May 2007

The purpose of this paper is to present a control volume based numerical model for simulation of fuel/air flow, electrodes, and electrolyte components of a single tubular solid oxide fuel cell. The SOFC uses a mixture of H2, CO, CO2, and H2O (vapor) components (pre-reformed methane gas) as fuel. The developed model determines the effect of fuel and air mass flux on local EMF, state variables (pressure, temperature and species concentration) and cell performance. In addition, the effect of fuel hydrogen concentration on output characteristics of fuel cell is investigated. If we consider a pure hydrogen fuel, we will have maximum Nerenst potential and power Generation. While the hydrogen goes through the channel and is being consumed, vapor is introduced into the flow and hydrogen concentration is reduced along the flow direction. Therefore, the local Nerenst potential decreases. For mixed fuel, output parameters are function of fuel molar composition. In general, this model shows how output parameters of the SOFC can be controlled and adjusted by inlet fuel and air mass flow rate as well as hydrogen Concentration of the fuel. Finally the numerical study is validated by experimental results such as polarization curve and power density.
A Simple Model for Prediction of Polarization Loss Phenomena in a SOFC Stack
Authors: Heddrich Marc P. , Dörrer Lars , Dietrich Ralf-Uwe , Borchardt Günter , Argirusis Christos
Published: May 2007

A simple model for prediction of polarization losses occurring in a solid oxide fuel cell is presented. It is a one-dimensional model taking into consideration ohmic and fuel conversion losses, voltage drop due to fuel crossover and internal currents, losses due to gas diffusion through the porous electrodes as well as activation overpotential. The parameters for the modeling equations are derived from literature values which need only be supported by few initial measurements. The model can be implemented to identify separate experimentally found loss phenomena and to predict SOFC behavior - especially E(i) behavior - for most standard situations. Based on this model it is possible to describe results obtained in the laboratory fairly well.
Novel Design of Compressed Seal Gasket with Higher Thermo-Mechanical Stability
Authors: Lee Hae-Weon , Kim Sung Moon , Kim Hyoungchul , Jung Hwa Young , Jung Hoon-Gi , Lee Jong-Ho , Song Huesup , Lee Jaechun
Published: May 2007

Sealing of SOFCs has been one of the most critical barriers for commercialization of planar SOFCs. Typical rigid bond seals of common glass or glass-ceramic were found to be ineffective due to the lack of their long-term stability at elevated temperatures and brittle behavior below their glass transition temperatures. In the present work, we investigated a novel compressed seal gasket of higher strength and stiffness with multiple reinforcements including ceramic fibers and particles. This novel sealing gasket showed excellent thermal cycle and long-term durability over 1000 hours without significant mechanical or hermetic failure.
Mechanical Properties of Ceria-doped Scandia-stabilized Zirconia Electrolyte Coatings for SOFCs
Authors: Zhang Xiaoyu , Smirnova Alevtina L. , Sammes Nigel M. , Brodnikovskii Egor , Vasylyev Oleksandr
Published: May 2007

Solid Oxide Fuel Cell (SOFC) Electrolyte, specifically 1wt% Ceria-doped 10wt% Scandia-stabilized Zirconia (1Ce10ScSZ) was deposited onto the surface of planar anode supports using screen printing and Electron Beam Evaporation and Condensation (EBEC) technique. The SEM morphological characterization of the 10-20µm layers reveals that after sintering at different temperatures the electrolyte layers deposited by EBEC method are dense and show well defined columnar structure. The mechanical properties of the deposited electrolyte layers deposited were compared using conventional nano-indentation technique. The data indicate that Berkovich Hardness and Young' s modulus values for EBEC coated layers sintered at low temperature (900oC) reach 2.8GPa and 77GPa correspondingly and are uniform across the 10-15µm thick electrolyte surface.
Study of Pr-doped Ceria-based Electrolytes for IT-SOFC
Authors: Chen Mei-Ju , Cheng Soofin , Wang Feng-Yun , Lee J. F. , Tai Y. L.
Published: May 2007

Pr-doped ceria materials were synthesized by Pechini method using citric acid as chelating agent, and the resultant materials were examined for possible application as the electrolyte in ITSOFC. The XRD patterns of Pr doped ceria with the formula Ce1-xPrxO2-δ (abbreviated as xCPO) showed that all the samples with x {less than or equal to} 35% were fluorite-type solid solutions. The Pr L3-edge XANES profiles of xCPO after calcination at 700åC and sintering at 1500åC were similar to that of Pr6O11. For 30CPO, the Pr3+/(Pr3++Pr4+) molar ratio determined by XPS profile analysis was ca. 57%. These results implied that the number of oxygen vacancies created in the samples was lower than original expectation. Among the doped samples with x in 5- 40%, 30CPO gave the highest conductivity of 0.067 S/cm, which exceeded those of CGO and CSO. Moreover, with Mg co-dopant the conductivities were enhanced, while the contrast was seen on Ca co-dopant.
Structural and Electrical Properties of Gadolinia-doped Ceria Mixed with Alkali Earth Carbonates for SOFC Applications
Authors: Benamira Messaoud , Albin Valerie , Ringuedé Armelle , Vannier Rose-Noëlle , Bodén Andreas , Lagergren Carina , Cassir Michel
Published: May 2007

The properties of composite materials based on mixtures of gadolinium-doped ceria (GDC) and Li2CO3-K2CO3 are analyzed as potential SOFC electrolytes. In a temperature range higher than 500{degree sign}C, their ionic conductivity is significantly higher than for single GDC. Discontinuities were found in the conductivity Arrhenius diagram (σ vs. 1/T) around the melting point of the carbonate mixture (490{degree sign}C), showing, at least partially, the contribution of molten carbonates. At this stage, precise mechanisms are still under analysis.
Development of Insulating and Conductive Seals for Controlled Conduction Paths
Authors: Suda Seiichi , Kawahara Koichi , Jono Kaori
Published: May 2007

Micro-SOFCs require precise control of conduction paths among small cells or stacks. We have developed both insulating and highly conductive gas-tight seals in order to arrange both the seals and to fabricate the gas-tight sealing interface that has various electric conduction paths. The insulating seals were prepared with amorphous Na2O-SiO2 spherical particles and amorphous SiO2 particles. Porous La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) ceramics were used as a porous cathode to investigate sealing behavior. Firing the insulating sheet at 800oC resulted in gas-tight melt sealing. Penetration of viscous fused glasses into porous LSCF was controlled by changing the particle ratios. On the other hand, the highly conductive seals were prepared with various Ag-Si-Ge alloys by metal rolling. The alloys was melted at 850oC in air and led to highly conduction paths. The bi-layer sheets composed of the insulating and the conductive sheets was also resulted in gas- tight sealing at 850oC in air.
Tailor-made BaO-CaO-Al2O3-SiO2-based Glass Sealant for Anode-supported Planar SOFC
Authors: Basu Rajendra , Ghosh Saswati , Das Sharma A , Kundu P , Maiti H S.
Published: May 2007

In the present investigation, several glasses based on the BaO- CaO-Al2O3-SiO2 (BCAS) system have been investigated to see their applicability as IT-SOFC sealants. The glass transition temperature (Tg) of the developed glasses are within 600- 6350C. The CTE value can be tailored between that of YSZ electrolyte and ferritic steel (FS) interconnect, by varying the amount of alkaline-earth metal content. The electrical resistivities of the developed glasses are quite high (ρ800C ~ 105Ω-cm) and thus suitable for IT-SOFC application. Based on the crystallization behavior, a single glass having matching CTE with FS and a bi-layer glass having different CTE values within the range of 10×10-6 K-1 to 13×10-6 K-1 are found to be very effective for the FS-FS and FS-YSZ sealing.
Geldanamycin inhibits hemorrhage-induced increases in caspase-3 activity: role of inducible nitric oxide synthase
Authors: Kiang Juliann G. , Bowman Phillip D. , Lu Xinyue , Li Yansong , Wu Brian W. , Loh Horace H. , Tsen K. T. , Tsokos George C.
Published: May 2007

Hemorrhage has been shown to increase inducible nitric oxide synthase (iNOS) and deplete ATP levels in tissues and geldanamycin limits both processes. Moreover, it is evident that inhibition of iNOS reduces caspase-3 and increases survival. Thus we sought to identify the molecular events responsible for the beneficial effect of geldanamycin. Hemorrhage in mice significantly increased caspase-3 activity and protein while treatment with geldanamycin significantly limited these increases. Similarly, geldanamycin inhibited increases in proteins forming the apoptosome (a complex of caspase-9, cytochrome c, and Apaf-1). Modulation of the expression of iNOS by iNOS gene transfection or siRNA treatment demonstrated that the level of iNOS correlates with caspase-3 activity. Our data indicate that geldanamycin limits caspase-3 expression and protects from organ injury by suppressing iNOS expression and apoptosome formation. Geldanamycin, therefore, may prove useful as an adjuvant in fluids used to treat patients suffering blood loss.
Genetic Causes of Bronchiectasis: Primary Ciliary Dyskinesia
Authors: Morillas Hilda N. , Zariwala Maimoona , Knowles Michael R.
Published: May 2007

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder reflecting abnormalities in the structure and function of motile cilia and flagella, causing impairment of mucociliary clearance, left-right body asymmetry, and sperm motility. Clinical manifestations include respiratory distress in term neonates, recurrent otosinopulmonary infections, bronchiectasis, situs inversus and/or heterotaxy, and male infertility. Genetic discoveries are emerging from family-based linkage studies and from testing candidate genes. Mutations in 2 genes, DNAI1 and DNAH5, frequently cause PCD as an autosomal recessive disorder. A clinical genetic test has been recently established for DNAI1 and DNAH5, which involves sequencing 9 exons that harbor the most common mutations. This approach will identify at least one mutation in these 2 genes in ∼25% of PCD patients. If biallelic mutations are identified, the test is diagnostic. If only one mutation is identified, the full gene may be sequenced to search for a trans-allelic mutation. As more disease-causing gene mutations are identified, broader genetic screening panels will further identify patients with PCD. Ongoing investigations are beginning to identify genetic mutations in novel clinical phenotypes for PCD, such as congenital heart disease and male infertility, and new associations are being established between ‘ciliary’ genetic mutations and clinical phenotypes.