bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Tubular Type Cell Stack
Authors: Tomida Kazuo , Kabata Tatsuo , Hisatome Nagao , Yamashita Akihiro , Tsukuda Hiroshi , Ohkuma Shigeru , Kiyabu Toshiyasu
Published: May 2007

Mitsubishi Heavy Industries (MHI) has been developing tubular type SOFC since 1984. With the support of NEDO during the fiscal years 2003 to 2004, some materials have been investigated in order to reduce resistance. The cell tube which is applied advanced materials had been developed, and was operated at 900{degree sign}C, 0.4MPa, 300 mA/cm2. Its output density of 0.21W/cm2 was achieved. The consignment research of NEDO is continued from 2005 to 2007. In this project, we are now developing a simulation technology of performance in order to optimize the cell tube configuration and advanced materials for a high power density cell tube. In 2006, a cell tube that was optimized by advanced simulation technology was developed. The cell tube was operated at 900°C, 0.6MPa, 750mA/cm2. Its output density of 0.5W/cm2 was achieved. This paper reports the current status of improvement of high power density tubular type SOFC at MHI.
Strategy of the Development of Cr-tolerant Cathodes of Solid Oxide Fuel Cells
Authors: Zhen Yongda , Jiang San Ping , Tok A.I.Y
Published: May 2007

The significant development of solid oxide fuel cells (SOFCs) operating in the intermediate temperature range of 600-800oC enable the use of cheap alloys as metallic interconnects. However, at the SOFC operating temperatures, the volatile Cr species are generated over the chromia scale, poisoning the cathodes such as (La,Sr)MnO3 (LSM) and (La,Sr)(Co,Fe)O3 (LSCF) and leading to the rapid degradation of the cell performance. Thus, the development of Cr-tolerant SOFC cathode is important for the SOFCs with metallic interconnect. In this work, a strategy based on our systematic studies of the Cr deposition process under SOFC operating conditions is proposed. Based on this strategy, Mn- and Sr-free materials are developed as Cr- tolerant cathodes. Initial results show that Mn and Sr-free materials such as La(Ni,Fe)O3 and (La,Ba)(Co,Fe)O3 have very stable performance and Cr deposition at La(Ni,Fe)O3 and (La,Ba) (Co,Fe)O3 cathodes is substantially retarded as compared to that on LSM and LSCF cathodes.
Electrocatalytic Properties of Intermediate Temeprature-SOFC Cathode/LSGMC Interfaces
Authors: Qin Ya G. , Lu Xinyu , Brouwer Jack , Mumm Daniel R.
Published: May 2007

La0.8Sr0.2Ga0.8Mg0.115Co0.085O3-d (LSGMC) has been reported as an optimized composition for LSGM-based electrolytes used in intermediate temperature solid oxide fuel cells (SOFCs). Electrocatalytic properties of the interfaces between LSGMC electrolyte and various cathodes: comprised of Sm0.5Sr0.5CoO3-d (SSC), and La0.7Sr0.3Co0.2Fe0.8O3-d (LSCF) in composite forms (70wt.%) with LSGMC (30wt.%) were investigated under both oxygen reduction and evolution conditions. All the oxides were synthesized using the glycine-nitrate process (GNP) followed by unique powder processing to produce the desired phase purity and particle properties. Symmetrical electrochemical cells were fabricated by a screen-printing technique with precisely controlled alignment. Three-electrode linear dc polarization and ac impedance spectroscopy were used to characterize the kinetics of the interfacial reactions in detail. For the composite SSC-LSGMC cathode/LSGMC interface, the cathodic overpotential under 1 A/cm2 current density was as low as 0.085 V at 973 K, 0.062V at 1023K and 0.051V at 1073K in air. Composite LSCF-LSGMC cathode/LSGMC interfaces were found to have about twice the exchange current density of composite SSC- LSGMC/LSGMC interfaces for the same temperature and overpotential conditions.
Regeneration of Anodes Exposed to Sulfur
Authors: McEvoy Augustin J. , Smith Martin J.
Published: May 2007

In any type of fuel cell, impurities in the fuel may be incompatible with either the anode material or the reforming catalyst, with potentially serious consequences. As a result a fuel-processing step is normally required before use of a commercial fuel. In the SOFC case sulfur is the element most likely to degrade a nickel cermet anode. In the present work a method based on the hydrodesulfurisation processes employed in the petrochemicals industry was used to desensitise cermet anodes to sulfur in the fuel gas stream. The mechanisms of sulfur poisoning on nickel are indicated. The desensitising catalyst is a dispersion of a refractory heavy transition metal, introduced into the pores of the cermet anode as a solution of an ammonium salt, followed by pyrolysis. A treated anode can be regenerated after several cycles of sulfur poisoning.
Micro-Hotplate Devices for Micro-SOFC
Authors: Beckel Daniel , Danick Briand , Courbat Jérôme , Bieberle-Hütter Anja , de Rooij Nico F. , Gauckler Ludwig J.
Published: May 2007

Special high temperature Si/SiN based micro-hotplates were used as a platform for preparation and testing of SOFC cathode thin films. The micro-hotplates consist of a free standing SiN film (1 μm thick) spanning over an area of 1 mm2. These membranes withstand thermal stresses up to a maximum temperature of 800 {degree sign}C and several hours of operation at 600{degree sign}C. On top of the membrane a 500 nm thick La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) thin film was deposited by spray pyrolysis. This amorphous film crystallized around 600{degree sign}C. The microstructure and the electrical conductivity of the LSCF was characterized and measured on the micro-hotplate as a function of temperature. Very fast heating and cooling rates of several 100{degree sign}C/min were obtained enabling fast thermal cycling tests. This technology eventually should enable the integration of an electrolyte and an anode with gas channels forming a micro- SOFC on a micro-hotplate with an integrated heating system for start up operation.
Portable Propane Micro-Tubular SOFC System Development
Authors: Finnerty Caine , Robinson Charles , Andrews Stanley , Du Yanhai , Cheekatamarla Praveen , DeWald Paul , Lu Yixin , Schwartz Timothy
Published: May 2007

NanoDynamics Energy Inc. is developing a family of compact, integrated micro-tubular SOFC systems with high volumetric power density and multiple fuel options including methane, propane, diesel and JP8. The development program aims to bring to the market highly efficient, clean, and cost competitive fuel cell systems with outputs above 50We for portable power generation applications. Balance-of-plant (BoP), electronic controls, and power management systems have been identified and integrated with a partial oxidation reformer and SOFC stack. A system test for the integrated process chain was performed with our proprietary cell and system technologies. The performance of a system developed using a micro-tubular SOFC stack is evaluated for different operating conditions. The results from these studies will be presented. System design, integration, and control methodologies are also discussed.
Evaluation and Modelling of the Cell Resistance in Anode Supported Solid Oxide Fuel Cells
Authors: Leonide André , Sonn Volker , Weber Andre , Ivers-Tiffee Ellen
Published: May 2007

The impedance of anode supported single cells (Ni/8YSZ anode; La0.58Sr0.4Co0.2Fe0.8O3 cathode; 8YSZ electrolyte; Area=1 cm²) was characterized in a broad measuring range of temperature and air/fuel gas composition. The data has been analysed by calculating the distribution function of relaxation times (DRT). DRT computations enabled us to separate five different loss mechanisms occurring inside the cathode and anode without the need of an equivalent circuit. Two processes exhibit a systematic dependency on changes in the oxygen partial pressure of the cathode gas and thus can be attributed to diffusional and electrochemical losses on the cathode side. The remaining three processes are very sensitive to changes in the fuel gas, but are not affected by variations of the cathode gas. These resistances are classified as a gas diffusion polarisation within the anode-substrate and as an electrooxidation reaction at the triple-phase-boundary respectively.
Electrochemical Study of IT-SOFC Unit Cell Prepared By Tape Casting Process and Co-sintering
Authors: Kim Ho-Sung , Song Jung-Hoon , Park Sun-Il , Oh Sung-Hwa , Chang Duk-Rye
Published: May 2007

Anode-supported electrolyte with a large electrode area of 7.5×7.5 cm2 was fabricated using tape casting method aided by co-sintering process, in which the thickness of electrolyte layer is about 10 μm. SEM morphology showed the thin film of electrolyte with dense and crack-free structure which was formed between anode and cathode. As a result, open circuit voltage (OCV) of unit cell was around 1.1 V and its maximum power density was 0.214 W/cm2 at 800{degree sign}C. Impedance results of unit cell indicated that the ohmic resistance was 0.267 Ωcm2 at 800{degree sign}C, which was a suitable for the operation of SOFC at the intermediate temperature. In this study, we demonstrated that the tape casting process aided by co-sintering method is a suitable method for the mass production of planar SOFC unit cell with large electrode area.
High Performance Low Cost Co-Fired Solid Oxide Fuel Cells
Authors: Yoon Kyung J. , Zink Peter , Pal Uday B. , Gopalan Srikanth , Seccombe Don
Published: May 2007

Anode-supported planar SOFCs were fabricated by a single step co-firing process. The cells comprised of Ni+yttria-stabilized zirconia (YSZ) anode, YSZ electrolyte, (La,Ca)MnO3 (LCM)+YSZ cathode active layer, and an LCM cathode current collector. The fabrication process involved tape casting of the anode, screen printing of the electrolyte and the cathode, and single step co-firing between 1300-1330{degree sign}C. Cells were tested between 700-800oC with humidified hydrogen and air. Modeling of cell- test results showed that most of the polarization losses were due to ohmic losses associated with the electrodes, activation polarization loss in the cathode, and concentration polarization loss in the anode. The ohmic loss was lowered by improving electrical contact, activation polarization was reduced by improving microstructure of the cathode active layer and the anode concentration polarization loss was lowered by increasing anode porosity. With all these improvements maximum power density of 1.5W/cm2 was achieved at 800oC with humidified H2(g) and air.
Development of Micro-Tubular SOFCs with an Improved Performance via Nano-Ag Impregnation for Intermediate Temperature Operation
Authors: Liu Yu , Hashimoto Shin-Ichi , Nishino Hanako , Mori Masashi , Funahashi Yoshihiro , Fijishiro Yoshinobu , Hirano Atsushi , Imanishi Nobuyuki , Takeda Yasuo
Published: May 2007

Electrochemically catalytic Ag particles in nano-range were in situ incorporated into the 15 um thick cathode consisting of La0.6Sr0.4Co0.2Fe0.8O3-d and Ce0.8Gd0.2O1.9 (GDC) via a citrate infiltration method. The Ag-impregnation route ensures very homogeneous particle dispersion and good adhesion of Ag to the ceramic matrices. The functional cathode was successfully operated on the Ni-cermet-supported (ZrO2)0.89 (Sc2O3)0.1(CeO2)0.01 electrolyte with a GDC buffer layer under a micro-tubular configuration, producing maximum power density of 1.06 W cm-2 (1.43 A cm-2, 0.74 V), 0.98 W cm-2 (1.78 A cm- 2, 0.55 V), 0.49 W cm-2 (1.44 A cm-2, 0.34 V) at 650, 600, 550 {degree sign}C, respectively.
Electrochemical Testing of Solid Oxide Fuel Cells with Sol Gel Impregnated Plasma Sprayed Electrolytes
Authors: Rose Lars , Kesler Olivera , Tang Zhaolin , Burgess Alan
Published: May 2007

Solid Oxide Fuel Cells (SOFCs) have been fabricated on tape cast anode substrates with plasma sprayed (PS) electrolytes and screen printed cathodes. To reduce the porosity in the PS electrolyte layers, spin coating was used to impregnate the as-sprayed electrolytes with yttria stabilized zirconia (YSZ) sols and YSZ composite sol powder suspensions. Fuel cells with electrolytes impregnated with different techniques were electrochemically tested and compared to fuel cells with no sol gel coatings to correlate the sol gel processing parameters with the resulting electrochemical performance changes. The sol gel impregnation significantly increased the open circuit voltage, slightly decreased the series resistance, and substantially decreased the polarization resistance compared to the cells with as-sprayed electrolytes. Impregnation of electrolytes offers the possibility of producing thinner electrolytes in simpler low-energy plasmas (100% nitrogen, no hydrogen) while lowering gas permeability through the electrolyte and improving fuel cell performance.
Fabrication and Properties of Honeycomb-type SOFCs Accumulated with Multi Micro-cells
Authors: Shimizu Sota , Yamaguchi Toshiaki , Suzuki Toshio , Fujishiro Yoshinobu , Awano Masanobu
Published: May 2007

An electrode-supported honeycomb-type SOFC with multi sub- millimeter sized channels can hold large electrode area per a unit volume, which leads to space saving and cost reduction. In this study, a cathode-supported honeycomb-type SOFC has been prepared from integrating multi micro-cells via the fabrication processes; extrusion method for a cathode honeycomb monolith (LaSrMnO3 (LSM)) and new novel slurry injection method for subsequent inner wall coating (electrolyte/anode layers) of multi channels. The complete honeycomb-type SOFC has the cell density of about 1000 cpsi (channels per square inch) with wall thickness of 160 mm, dense electrolyte layer about 20 mm and anode layer about 10mm.
Development of Honeycomb-type SOFCs with Accumulated Multi Micro-cells
Authors: Yamaguchi Toshiaki , Shimizu Sota , Suzuki Toshio , Fujishiro Yoshinobu , Awano Masanobu
Published: May 2007

SOFC based on honeycomb support is known as one of the most compact SOFCs due to its large electrode area per a unit volume, which is attractive with regard to space saving, cost reduction and thermal control. In this study, the effects of material configuration and honeycomb channel number on the performance of SOFC were investigated using the simulation of equivalent electrical circuit. It was revealed that cathode- supported honeycomb type could be better for maximizing net electrode area per a unit volume and minimizing current collecting loss than any other types such as electrolyte- or anode-supported types due to its small current collecting loss.
Development of Estimation of SOFC System Performance
Authors: Yoshiba Fumihiko , Yamamoto Tohru , Yoshikawa Masahiro , Mugikura Yoshihiro , Watanabe Takao
Published: May 2007

Development of an estimation method of a SOFC system performance has been conducted in the NEDO SOFC project from 2004-2008. There are two factors that indicate SOFC system performance. One is a current versus voltage relation includes parameters of a reactive gas composition and an operating temperature of the cell; the other is a heat management method that offers thermally self sufficient condition of the SOFC stack for the purpose to decrease its fuel gas supply. Two 1kW class SOFC system operating tests were carried out and energy balances of the systems were evaluated. Based on the results of the current and voltage relation test and the evaluated energy balance of the systems, the system efficiency and a qualitative analysis of an energy recirculation of the system are discussed.
Ceramic Diffusion Barrier Layers for Metal Supported SOFCs
Authors: Franco Thomas , Schibinger Karlheinz , Ilhan Zeynep , Schiller Günter , Venskutonis Andreas
Published: May 2007

Metal supported solid oxide fuel cells (MSCs) show a high poten- tial predominantly for an application as light-weight planar cells for electricity supply systems in cars and other mobile systems. One of the most promising MSC concepts is the plasma sprayed thin film concept of DLR-Stuttgart in which powder metallurgi-cally manufactured substrates, developed within a collaboration of Plansee and DLR, serves as mechanical cell support. In MSCs gen-erally problems can occur in particular by a mutual diffusion of Ni, Fe and Cr on the substrate/anode interface that causes significant cell degradation. To avoid this mass transport ceramic diffusion barrier layers consisting of Cr2O3 and/or MnCr2O4 or doped LaCrO3-type perovskites are provided. The paper focuses on a ma- terial study of different substrate materials performed with inte-grated diffusion barrier layers. Furthermore, the electrochemical long term behaviour of cells with different plasma sprayed barrier layers is shown demonstrating the barrier effect and the electro-chemical compatibility.
Measurement of Concentration Profile of Gaseous Species in Seal-less Disc-type SOFC Anode Operating on Reformed Fuel
Authors: Momma Akihiko , Takano Kiyonami , Tanaka Yohei , Negishi Akira , Kato Ken , Amano Masatsugu , Nozaki Ken , Kato Tohru , Inagaki Toru , Kawano Mitsunobu , Hosoi Kei , Hoshino Koji , Shibata Makoto , Akbay Taner , Akikusa Jun , Chitose Norihisa
Published: May 2007

Measurements of the concentration profile of gaseous species along the flow direction in seal-less disc-type SOFC anode channel were performed using partially reformed methane as a fuel. Gas chromatography was used for the analysis. The inlet gas to the anode was found to be in its equilibrium composition dictated by the temperature of the reformer. The osmosis of ambient gas was found to be noticeable when the cell was operated under low fuel utilization just as observed previously using hydrogen as a fuel. The effect of internal reforming was observed when the modified anode current collector was used instead of pure Ni. In this case, it was found that the cell works up to fuel utilization values as high as 80%, even if the temperature of the reformer was 550 {degree sign}C. Observed H/C ratio suddenly decreases at the outer rim of the cell.
Liquid-Hydrocarbon Internal Reforming In Catalyst-Assisted SOFCs
Authors: Kim Ilwon , Pillai Manoj R. , Barnett Scott A.
Published: May 2007

Direct internal reforming of hydrocarbon fuels such as gasoline and diesel has been problematic due to coking on Ni-based SOFC anodes. This paper describes stable direct internal reforming SOFCs (Ni-YSZ/YSZ/LSM-YSZ) using anode reforming catalysts. Button cells were tested with a separate catalyst piece placed against the anode. Button cell power densities of ~ 0.5W/cm2 at ~ 800oC have been demonstrated with n-dodecane and n-tridecane mixed with H2O-CO2-air. Life tests with n-dodecane showed stable operation for > 140 h. Flattened-tube segmented-in- series modules with 14 cells on each side were tested with a catalyst layer coating on the fuel side of the zirconia support tube. For iso-octane mixed with either air or H2O-CO2-air, a stable maximum power density of ~ 0.6W/cm2 was obtained at ~ 800oC.
In-situ Observation on the Active Reaction Sites for the Oxygen Reduction in Solid Oxide Fuel Cells
Authors: Wang Wei , Jiang San Ping
Published: May 2007

The active reaction sites for the oxygen reduction in SOFCs were investigated by atomic force microscopy (AFM) under extremely strong cathodic polarization conditions. It has been found that cathodic polarization treatment has significant promoting effect for the oxygen reduction on the in-situ sintered LSM electrode, which could be related to the increasing active reaction sites at the LSM/YSZ interface. The three-phase boundary (TPB) points between un-sintered LSM particles and the YSZ electrolyte increased with increasing cathodic polarization currents, leading to enhancing LSM electrode performance.
Fabrication of Tubular Solid Oxide Electrolysis Cells for Hydrogen Production
Authors: Kato Tohru , Nguyen Tuong Lan T. , Honda Takeo , Tanaka Yohei , Negishi Akira , Tanaka Seiko , Amano Masatsugu , Momma Akihiko , Kato Ken , Iimura Youko
Published: May 2007

Tubular SOECs whose operating temperature is reduced to 700~800oC are developed to apply to the nuclear power systems without losing the SOECs merit. To improve cell performance at the low temperature, Sc2O3 stabilized ZrO2 is chosen as electrolyte material and the thickness of the electrolyte layer is tried controlling about 10μm. Tubular testing electrolysis cells are fabricated by using slurry coating method. Dependence of the cell performance on operating conditions is measured. Further, AC impedance method is applied to the cells to estimated interfacial overvoltage. From the experiment, it is clarified that the hydrogen production rate at 800 oC is achieved 2.5~2.7 sccm/cm2 at the thermoneutral voltage (1.3V) under practical steam utilization. This value is comparable to that of the commercial electrolysers.
NiO/ZrO2-CeO2 Anodes for Single-Chamber Solid-Oxide Fuel Cells Operating on Methane/Air Mixtures
Authors: Lamas Diego G. , Cabezas Marcelo D. , Fábregas Ismael O. , Walsöe de Reca Noemí E. , Lascalea Gustavo E. , Kodjaian Armen , Vidal María A. , Amadeo Norma E. , Larrondo Susana A.
Published: May 2007

Single-chamber SOFCs have received much attention in recent years due to their simple design and low cost. In this work, we evaluated single-chamber SOFCs that operate in methane/air mixtures at high temperatures (900-1000{degree sign}C). YSZ was used as electrolyte, La0.8Sr0.2MnO3 as cathode, and NiO and NiO/ZrO2-50; 70 or 90 mol% CeO2 composites as anode. ZrO2-CeO2 solid solutions were previously characterized by several techniques and results of their structural and catalytic characterization are presented. Our results demonstrate that the incorporation of ZrO2-CeO2 catalysts in the anode significantly improves the performance of the cell.
SOFC Based on Proton Conductors
Authors: Balachandran U. Balu , Lee Tae H. , Dorris Stephen E.
Published: May 2007

We have fabricated a solid oxide fuel cell (SOFC) using BaCe0.8Y0.2Ox (BCY20) proton conductor as the electrolyte. An ≈10-μm-thick dense BCY film was prepared on a porous Ni/BCY cermet (i.e., ceramic/metal composite) substrate by a dip coating process. The gas-permeable Ni/BCY cermet substrate backed with nickel mesh was used as the anode, and a platinum paste backed with platinum mesh served as the cathode. The current-voltage characteristics of the BCY-based SOFC were measured in the temperature range 450-800{degree sign}C using wet air on the cathode side and hydrogen on the anode side. The power density of the fuel cell was ≈90 and ≈1500 mW/cm2 at 450 and 800{degree sign}C, respectively.
Promotion of Oxygen Surface Reaction at the Hetero-Interface of (La,Sr)CoO3 / (La,Sr)2CoO4
Authors: Sase Maya , Hermes Florian , Nakamura Takashi , Yashiro Keiji , Sato Kazuhisa , Mizusaki Junichiro , Kawada Tatsuya , Sakai Natsuko , Yamaji Katsuhiko , Horita Teruhisa , Yokokawa Harumi
Published: May 2007

The preferential site for oxygen isotope exchange was investigated on layered films of (La2-xSrx)CoO4 (x = 0.5, 1.0) / (La0.6Sr0.4)CoO3 prepared by PLD on a polycrystalline Ce0.9Gd0.1O1.95. An isotope exchange experiment was performed at 723 K in 18O enriched oxygen of 0.2 ×105 Pa. Three- dimensional imaging of Secondary Ion Mass Spectrometry (SIMS) was carried out to visualize the isotope distribution. The SIMS image suggested that there are fast oxygen-incorporation paths along the triple phase boundary of (La2-xSrx)CoO4/(La0.6Sr0.4) CoO3/oxygen. The results have reproduced our former results with (La2-xSrx)CoO4/(La0.6Sr0.4)CoO3 composite polycrystals.
Improving LSM Cathode Performance Using (Cu,Mn)3O4 Spinel Coated UNS430 Ferritic Stainless Steel SOFC Interconnects
Authors: Paulson Scott , Bateni M.Reza R. , Wei Ping , Petric Anthony , Birss Viola
Published: May 2007

This work focuses on assessing the ability of the (Cu,Mn)3O4 spinel oxide coating to limit Cr2O3 film growth and chromia loss from ferritic 430 stainless steel (UNS430). Several orders of magnitude more conductive than the native Cr2O3 oxide film, this material and other spinel coatings have been applied to UNS430 samples using a low cost fabrication method that is amenable to many interconnect geometries. Coated UNS430 samples were tested under simulated half-cell conditions via direct contact to a porous (La0.8Sr0.2)0.98MnO3 (LSM) cathode supported on 8%YSZ in flowing dry air at 600 to 800 oC. As compared to uncoated UNS430 contacts, spinel-coated interconnects greatly enhance the stability of the cathode when cathodically polarized over a 250+ hour period. WDX analyses show that these films prevent Cr transfer to the LSM-YSZ interface, but are susceptible to long-term loss of Cu.
Dry Coating Technique for Nanosized La0.8Sr0.2MnO3 Powder for SOFC Cathode
Authors: Abe Hiroya , Shimoda Hirofumi , Sato Kazuyoshi , Naito Makio
Published: May 2007

A simple and effective dry coating technique was applied to fabricate La0.8Sr0.2MnO3 (LSM) cathode electrode of SOFC. The specific surface area of the LSM used was 12.4 m2/g of which corresponding diameter was about 80 nm. The LSM powder was coated with Poly vinyl butyral (PVB) binder on a YSZ electrolyte substrate followed by firing at 1100 ºC for 2 h. Finally, the thick porous LSM cathode (~50 μm) with consisting of fine grains (<0.5 μm) was obtained. The interfacial area specific resistance (ASR) of the cathode was measured as 0.49 Ω cm2.
Synthesis and Performance of La0.6Ca0.4Fe0.8Ni0.2O3-δ Material for Intermediate-Temperature SOFC Cathode
Authors: Ruiz de Larramendi Idoia , Ortiz Nagore , Ruiz de Larramendi José I. , Rojo Teófilo
Published: May 2007

A major research goal on solid oxide fuel cells (SOFC) is to develop cost-effective component materials for operation temperatures lower than 800ºC. In this way, the La0.6Ca0.4Fe0.8Ni0.2O3-δ (LCFN) phase with perovskite-type structure was obtained by a liquid mix method. The product was characterized by X-ray diffraction and an orthorhombic structure (Pnma) was found. The particle size was studied by scanning electron microscopy obtaining a mean particle size less than 300 nm.The polarization resistance was studied using two different electrolytes: Y-doped zirconia (YSZ) and Sm-doped ceria (SDC). Chemical reactivity of the LCFN and the electrolytes was studied. Electrochemical Impedance Spectroscopy measurements of LCFN/YSZ/LCFN and LCFN/SDC/LCFN test cells were conducted. These electrochemical experiments were performed at equilibrium from room temperature up to 850{degree sign}C, under zero dc current intensity and under air. The obtained ASR values at 700{degree sign}C for the SDC and YSZ cell tests were 3.23 Ω•cm2 and 85.87 Ω•cm2 , respectively.
Properties of Gd Substituted Lanthanum Cobalt Iron Oxide as Cathode for IT-SOFCs
Authors: Limthongkul Pimpa , Tsuchiya Hiromasa , Somroop Kittichai , Sansernnivet Mayuree , Sato Kazunori , Charojrochkul Sumittra
Published: May 2007

In an effort to reduce TEC of the LSC materials while maintaining enough conductivity Gd substitution on A site of La0.6Sr0.4Co0.4Fe0.6O3-δ (LGSCF) perovskite materials were investigated as a potential cathode material for ITSOFCs in this study. La0.6-xGdxSr0.4Co0.4Fe0.6O3-δ (LGSCF) powders with x = 0.1-0.6 were prepared via solid state reaction method by ball milling the starting precursor in ethanol and calcining the starting powder at 1100oC for 10 hours. X-ray diffraction analysis performed on the samples reveal the perovskite rhombohedral structure for all samples. An increase in Gd substitution amount was found to decrease thermal expansion coefficient and conductivity of the compounds.
Lanthanum Doped Barium Cobaltite as a Novel Cathode for Intermediate-temperature SOFC Using Lanthanum Gallate Electrolyte
Authors: Kawasaki Masami , Chitose Norihisa , Akikusa Jun , Akbay Taner , Eto Hiroyuki , Inagaki Toru , Ishihara Tatsumi
Published: May 2007

A new research and development program to increase the output power density of cell-stack of intermediate-temperature (IT) solid oxide fuel cells (SOFCs) has been started. In order to increase the mechanical strength of the lanthanum gallate electrolyte, starting powder preparation methods and sintering temperature were examined. Manufacturing of dense ceramic bodies with smaller grain sizes were enabled using smaller submicron powder source. An alternative cathode material lanthanum doped barium cobaltite and the effect of dispersed Ag particles were investigated. Power generation characteristics were measured as a function of the dopant concentration in Ba1-xLaxCoO3-δ. Although observed variation between x = 0.3 and 0.5 was insignificant, the maximum terminal voltage was obtained at x = 0.5. Using Ag-dispersed Ba0.5La0.5CoO3-δ cathode, output power density of 0.4 W/cm2 was obtained at the current density of 0.5 A/cm2 at 750{degree sign}C for hydrogen fuel.
LSCF-Ag Composite Cathode for Reduced-temperature SOFCs
Authors: Sakitou Yuki , Hirano Atsushi , Hanai Kazuma , Matsumura Tadaaki , Imanishi Nobuyuki , Takeda Yasuo
Published: May 2007

Operating temperature is high and long start-up time, and there is a problem of the material deterioration etc. The electrode development to obtain the catalyst revitalization even at the low temperature is advanced now. We attracted to attention because of Ag is high the electron conductivity in the metal and the oxide ion conductivity. In this study, to improve the performance, we impregnated Ag particles in the LSCF-GDC cathode using Ag(NO)3. These new cells showed the high cell performance.
Influence of Mesoporosity of the Anode on the Characteristics of Mediumtemperature SOFC Single Cells
Authors: Nurk Gunnar , Küngas Rainer , Kivi Indrek , Kurig Heisi , Grozovski Vitali , Kallip Silvar , Lust Enn
Published: May 2007

Ultra fine Pr0.6Sr0.4CoO3-δ nanopowder as a cathode material for intermediate temperature solid oxide fuel cell has been synthesized by a solution combustion method. The X-ray diffraction, SEM, EDX, AFM, BET and electrochemical impedance methods have been used for the analysis of Pr0.6Sr0.4CoO3-δ cathodes and Ni/Ce0.9Gd0.1O1.95 anodes, prepared at different co-firing temperatures with Ce0.9Gd0.1O1.95 electrolyte. Development of microporous cathode with specific surface area SBET = 217 m2 g 1 and medium pore radius R = 16 Aå, and Ni anode with SBET = 13 m2 g 1 and R = 16 Aå was established using NLDFT method. The weak influence of the co-sintering temperature of the anode and electrolyte on the power density has been observed. The shape of the Nyquist plots, phase angle and logZ vs. logf plots show that there is only one main rate-determining process and therefore it is impossible to analyze separately the anode and cathode processes.
Synthesis and Electrical Characterization of the Ceramic Anode La1-xSrxMn0.5Cr0.5O3
Authors: Fonseca Fabio Coral C. , de Florio Daniel Z. , Muccillo Eliana N. , Muccillo Reginaldo
Published: May 2007

The synthesis and electrical characterization of La1- xSrxMn0.5Cr0.5O3 compounds are reported. Such a perovskite has been pointed out as a promising alternative for the nickel- based cermet anode. Polycrystalline samples, with x = 0.3, 0.4, and 0.5, have been prepared by the citrate technique. The crystalline phase and the chemical compatibility with zirconia- based electrolytes were studied by X-ray diffraction analyses. The electrical properties were studied by 4-probe dc electrical conductivity sig(T) measurements under both oxidizing and reducing atmosphere. The main results show that the sig(T) has a thermally activated behavior, and increasing Sr content increases sig(T). Compounds with x = 0.3 exhibited no appreciable chemical reaction with the zirconia electrolyte after heat treatment at high temperature. The sig(T) measurements evidenced the redox stability of the ceramic anode. However, some degradation of the sig(T) was observed on thermally treated samples in fuel conditions.
Development of Solid Oxide Fuel Cell Operated at Intermediate Temperature for Direct Utilization of Dimethylether Fuel - Investigation of Anode Catalysts
Authors: Takeuchi Ken , Ishida Yousuke , Tai Ryousuke , Ui Koichi , Koura Nobuyuki , Koyanaka Hideki
Published: May 2007

We have developed the intermediate-temperature solid oxide fuel cell (SOFC) with a proton conducting oxide BaCe0.8Y0.2O3-d(BCY20) as the electrolyte for direct utilization of dimethyl ether (DME) fuel. In present study, we tried to improve the cell performance of the SOFC with using Fe as a catalyst for the anode. The maximum power density of the SOFC (DME+H2O, Fe|BCY20|Pt, dry air) was 44mW•cm-2 at 600{degree sign}C. The SOFC was able to perform at even 500{degree sign}C. Consequently, direct DME SOFC performance is substantially enhanced at temperatures 500{degree sign}C - 600{degree sign}C by use of Fe as anode catalyst.
Electrochemical Characteristics of Anode with SrZr0.95Y0.05O3-α for SOFC in Dry Methane Fuel
Authors: Jin Yongcheng , Levy Caroline , Saito Haruyuki , Hasegawa Shinichi , Yamahara Keiji , Hanamura Katsunori , Ihara Manabu
Published: May 2007

The feasibility of a Ni/YSZ anode with proton-conductor was investigated for direct hydrocarbon SOFCs. In the present paper, the infiltration method was selected to fabricate the Ni/YSZ anode with a proton-conductor of SrZr0.95Y0.05O3-α(SZY). The electrochemical characteristics of Ni/YSZ-SZY were examined in humidified hydrogen(1% H2O) fuel and in dry methane fuel at 900ºC respectively. The durability of Ni/YSZ and Ni/YSZ-SZY anodes were also studied using adapted degradation tests. Results indicate that the addition of the proton-conductor of SZY to the Ni/YSZ anode made the Ni/YSZ-SZY anode operated more stably than the Ni/YSZ anode in dry methane. Thus, Ni/YSZ anode infiltrated with SZY was more suitable to be used than Ni/YSZ anode in dry methane fuel.
Effect of Specific Surface Area and Zr Doping Content on Oxygen Storage Capacity (OSC) and Methane Steam Reforming Reactivity of CeO2-ZrO2
Authors: Sutthisripok Weerawan , Laosiripojana Navadol , Sikong Lek
Published: May 2007

This paper investigated the effect of specific surface area and Zr doping content on oxygen storage capacity (OSC) and methane steam reforming reactivity of CeO2 and Ce-ZrO2. It was found that the specific surface area of ceria and the doping of Zr present important role on the oxygen storage capacity (OSC) and the reactivity toward methane steam reforming. After calcination at 900{degree sign}C, ceria prepared by Surfactant- assisted method (SF) was observed from the present work to have significantly higher surface area than those prepared by Templating (TP) and Precipitation (PP) methods; this material showed strong OSC and better reforming reactivity compared to others. In detail, the degree of OSC was measured by the number of hydrogen uptake from the temperature programmed reduction (TPR). It was found that the value of hydrogen uptake from the TPR of ceria prepared by SF was 2084 mmol/g, whereas those of ceria prepared by TP and PP were 1724 and 781 mmol/g, respectively. According to the reactivity toward methane steam reforming, after purging in 3 kPa methane at 900 C for 8h, the methane conversion for ceria prepared by SF was approximately 38%, whereas those of ceria prepared by TP and PP were 22%.
Thermodynamic Analysis of a SOFC Aystem for CHP Applications: Influence of Operation Parameters on Global Efficiency
Authors: Corradetti Alessandro , Desideri Umberto , Lunghi Piero , Lisbona Pilar
Published: May 2007

In this paper, a model for a solid oxide fuel cell (SOFC) system for decentralized combined heat and power (CHP) production has been developed and studied. The proposed system, fuelled by natural gas, consists of a SOFC stack of 1 kWe of nominal power and a balance of plant (BoP) which includes gases supply, fuel processing, heat management, start-up equipment, power conditioning and control system. A starting point scenario is calculated based on a simple system flowsheet (external steam generation and no recirculation of exhaust gases) and basic operation parameters. The analysis of the global efficiency of the system is carried out varying the plant concept. The proposed configuration lead to several heat management options which are assessed by energetic balances.
A General Approach for Electrochemical Impedance Spectroscopy Simulation using Transient Mechanistic SOFC Model
Authors: Shi Yixiang , Cai Ningsheng , Li Chen , Bao Cheng , Croiset Eric , Qian Jiqin , Hu Qiang , Wang Shaorong
Published: May 2007

A general approach for electrochemical impedance spectroscopy (EIS) simulation was developed by solving a 1-D transient model based on physical conservation laws. This method is not specific to a certain type of electrochemical system nor is material dependent. This approach is illustrated in this paper by developing a transient model of an anode-supported SOFC button cell consisting of Ni-YSZ|Ni-ScSZ|ScSZ|LSM-ScSZ multiple layers. In this model, instead of being considered as boundary conditions at the electrode/electrolyte interface, the electrochemical reaction zone expanded though the electrode. The transient model has been solved for imposed sinusoidal voltage perturbations at different frequencies. The results have then been transformed into EIS spectra. The EIS simulation results were compared with experimental data under different temperatures using humidified H2 fuel and air oxidant to prove the validity of the EIS modeling approach. The model was further validated by comparing the steady-state results obtained from the transient model with the polarization curves.
A Neural Network Model in LaNixAl1-xO3 Catalyst for Methane Reforming in SOFC
Authors: Ciou Sian-Jie , Jhang Ya-Wun , Lai Ying-Jhih , Kuan-Zong Fung , Hung Min-Hsiung , Chiang Kai-Wei
Published: May 2007

There has been a great interest in application of SOFC using hydrocarbon fuel, and the major issues associated with the improvement of steam reforming is the possibility to extend the area of operation conditions, and lead to low carbon formation. The improvement can be achieved by modifying the design of existing nickel catalysts. Generally, mathematical modeling can be considered as an important element in the methane reforming in terms of the avoidance of extensive experiments. In this article, a two layered feed-forward neural network has been trained with the backpropagation algorithm to learn parameters in the process that the LaNixAl1-xO3(x= 0.1-0.9), reform the methane. The data used during the training procedure are generated by using of mass spectrometer after reforming. The average values of the errors for prediction are well below 5%.ANN model was capable of modeling the relationship between catalytic behaviors and the structure of catalytic well.
Efficiency Analysis of Planar Solid Oxide Fuel Cell at Direct Internal Reforming Conditions
Authors: Janardhanan Vinod M. , Deutschmann Olaf
Published: May 2007

A detailed model is presented for the analysis of temperature, species concentration, and current density profiles as well as the efficiency and power density of a planar solid oxide fuel cell at direct internal reforming condition. The model describes the interactions of mass transport, heat transport, heterogeneous chemistry, and electrochemistry. The heterogeneous chemistry model for the catalytic reactions in the anode structure uses a multi-step reaction mechanism for the steam reforming of methane on Ni based catalysts. The porous media transport is modeled using the Dusty Gas Model, and electrochemistry is modeled using a modified Butler-Volmer setting assuming hydrogen as the only electrochemically active species. The impact of flow rate, anode thickness, and catalyst loading on power density and efficiency is discussed for isothermal and adiabatic operating conditions.
Non Linear Modeling of Mixed Ionic Electronic Conductors
Authors: Ciucci Francesco , Goodwin David G.
Published: May 2007

A nonlinear model for the study of Mixed Ionic Electronic Conductors (MIEC) is presented in this paper. The model is time dependent and takes into account electrical carriers motion, the electrical behavior of the MIEC-metal interface and the kinetics of the chemistry occurring at the MIEC surface. By applying a small potential input complex impedances are computed.
Stability of Oxidation Resistance of Ferritic Fe-Cr Alloy for SOFC Interconnects
Authors: Toji Akihiro , Uehara Toshihiro
Published: May 2007

Ferritic Fe-Cr alloy is suitable for an interconnect material of planar-type SOFC. A ferritic Fe-22Cr alloy with a small addition of La and Zr, ZMG232, which has good oxidation resistance and good electrical conductivity at 750-1000 degrees C, was developed as a metallic interconnect material. Recently, further long-term stability of oxidation resistance of interconnect material has been required. Therefore in order to improve the oxidation resistance of ZMG232, the effect of alloying elements on properties of ferritic Fe-Cr alloys was investigated. As a result, it was found that oxidation resistance and electrical contact resistance of ZMG232 were improved by decreasing Si and Al contents. The oxidation test was carried out in air at 750 degrees C for 5000 hours. The oxidation weight gain of ZMG232L, which was an improved alloy with low Si and Al contents, reduced by about 30% in comparison with that of ZMG232.
Evaluation of Selected Interconnect Alloys at Versa Power Systems: Laboratory Screening and In-stack Testing
Authors: Benhaddad Sofiane , Protkova Julia , Dueck Willy , Sherman Scott
Published: May 2007

Versa Power Systems (VPS) develops planar SOFC operating at intermediate temperature around 750{degree sign}C. At that temperature, metallic interconnects are suitable due to their low cost, availability, matching thermal expansion and easy manufacturing. However their oxidation as a function of time remains one of the main contributors to fuel cell degradation and life performance. At VPS a complete laboratory characterization was developed for a fundamental understanding of the oxidation of those alloys. However, in-stack testing has been an ideal vehicle for in-situ steel comparison in the fuel cell environment. Interconnects are made with different alloys and assembled together in a single stack to be tested. A detailed post-test analysis of numerous tested stacks, including at least two different alloys, has provided valuable information on the relation between steel composition, oxidation and performance. Testing included long holds at various temperatures and a number of transients.
Oxidation Behavior and Conductivity of UNS 430 Stainless Steel and Crofer 22 APU with Spinel Coatings
Authors: Wei Ping , Deng Xiaohua , Bateni M.Reza R. , Petric Anthony
Published: May 2007

Coatings of Cu-Mn, Co-Mn, and Cu-Fe spinels were obtained on UNS 430 and Crofer 22 APU ferritic stainless steel by oxidation of electroplated metal coatings. The thickness of the spinel coatings was 20-30 um. The average weight gain of Crofer 22 APU with Cu-Mn, Co-Mn, and Cu-Fe spinel coatings after 1400 hours oxidation at 750{degree sign}C was 0.00052 g/cm2, 0.00022 g/cm2, and 0.00027 g/cm2, whereas the average weight gain of UNS 430 stainless steel with Cu-Mn, Co-Mn, and Cu-Fe spinel coatings was respectively 0.0003 g/cm2, 0.0001 g/cm2, and 0.00021 g/cm2. The area specific resistance of both Cu-Mn and Co-Mn spinel coated alloys was 0.003 Ω•cm2 after oxidation at 750åC for 1500 hours. Compared with an ASR of 0.189 Ω•cm2 for uncoated UNS 430, it is clear that the coatings can effectively provide a conductive path to the metallic substrate.
Composition Effects in YSZ Electrolyte Tapes for Solid Oxide Fuel Cells Fabricated By Tape Casting
Authors: Chen Chung-Chun , Liau Leo Chau-Kuang , Jung Guo-Bin , Chan Shih H.
Published: May 2007

YSZ electrolyte tapes were produced by a tape casting approach in which slurries were prepared and coated on substrates. The slurry recipe is composed of different amounts of YSZ powders, solvents, dispersants, binders and plasticizers. The effects of the recipes on the surface morphology of the tape samples before and after sintering were analyzed by microscopy and SEM. Results show that formations of the sample defects were greatly influenced by the recipe. The use of methyl ketone/isopropanol instead of ethanol as a solvent can prevent the generation of the cracks for the tapes before sintering. Moreover, the amount of the organic additives in the slurries can affect the defect formation of the tapes during sintering. A better recipe used for the fabrication of the YSZ electrolyte was determined from the analytical results. In addition, kinetics of the removal of the organic contents was analyzed using TGA data and an analytical approach.
Microstructure and Electrical Conductivity of Ce0.85Y0.15-xRExO2-/ (RE=Pr,Tb)
Authors: Tadokoro Sandra K. , Muccillo Eliana N.
Published: May 2007

Ce0.85Y0.15-xRExO2-δ (RE=Pr,Tb) with x = 0.02 and 0.06 solid solutions were synthesized by the coprecipitation technique to study the effect of Pr and Tb additions in the microstructure and electrical conductivity of yttria-doped ceria solid electrolyte. For comparison purposes, the solid solution Ce0.85Y0.13Pr0.02O2-δ was prepared by mixing Pr6O11 to the precipitated gel of ceria-yttria. Reductions in the average grain size and in the full width at half maximum height of the grain size distribution curve were obtained with increasing praseodymium additions to ceria-yttria. In contrast, Tb additions to yttria-doped ceria do not result in any significant microstructural change. Although an increase in grain conductivity with small amounts of Pr was observed at 300 ºC, both co-dopants exert a deleterious effect on the electrical conductivity of yttria-doped ceria at temperatures of typical solid oxide fuel cells operation.
Sintering Mechanism of CuO-doped Ce0.8Gd0.2O2-δ Ceramics
Authors: Mangifesta Patrizia , Sanson Alessandra , Roncari Edoardo
Published: May 2007

This study reports the effect of copper oxide on the sintering mechanism of Ce0.8Gd0.2O2-δ (GDC) studied through dilatometric and microstructural analyses. The addition of 3% CuO into GDC greatly improves its sinterability lowering the sintering temperature of more than 300{degree sign}C and increasing its maximum shrinkage rate. The early-stage sintering has been modeled showing a mechanism substantially different from the one generally accepted for CoO.
Fabrication of Anode Supported Direct Ammonia Solid Oxide Fuel Cells Based on Proton Conducting Y-doped BaCeO3 Electrolyte
Authors: Yoo Yeong , Tuck Mark , Lim Nguon , McFarlan Andrew , Maffei Nicola
Published: May 2007

The high performance anode supported single cells for ammonia fueled SOFCs comprising of BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3- δ)//BCY//NiO-BCY have been fabricated by co-pressing for depositing 50 µm thin film electrolytes. The electrolytes prepared by co-pressing technology were fully dense with no formation of secondary phases and observed to be crack-free. The electrochemical performance of single cells was characterized at the temperature 600-700 {degree sign}C under humid 75% H2 in N2 (3% H2O) similar to cracked ammonia as the fuel gas and air as the oxidant gas at a gas flow rate of 100 mL min-1. The open circuit voltages were around 1.02 V at 600 {degree sign}C indicating little gas leakage or mixed conduction through the electrolyte. Maximum power densities of 220, 190 and 160 mW cm- 2 from single cells were obtained at 700, 650 and 600 {degree sign}C, respectively under humid 75% H2 in N2 (3% H2O) and air.
Genetic Causes of Bronchiectasis: Primary Immune Deficiencies and the Lung
Authors: Notarangelo Luigi D. , Plebani Alessandro , Mazzolari Evelina , Soresina Annarosa , Bondioni Maria Pia
Published: May 2007

Primary immune deficiencies (PID) comprise a heterogeneous group of genetically determined disorders that affect development and/or function of innate or adaptive immunity. Consequently, patients with PID suffer from recurrent and/or severe infections that frequently involve the lung. While the nature of the immune defect often dictates the type of pathogens that may cause lung infection, there is substantial overlap of radiological findings, so that appropriate laboratory tests are mandatory to define the nature of the immune defect and to prompt appropriate treatment. At the same time, the recent identification of a large number of PID-causing genes now allows early, even presymptomatic diagnosis, thus representing an essential tool for prevention of lung damage. This review article describes the most common forms of PID, their cellular and molecular bases, and the associated lung abnormalities, and reports on available treatment.