bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of Yttria Doped Zirconia Composites for Solid Oxide Fuel Cells
Authors: Charojrochkul Sumittra , Wannakitti Suda , Limthongkul Pimpa , Ueda Johji , Sato Kazunori
Published: May 2007

Composites of 3 mol % Y2O3 in ZrO2, Ce0.9Gd0.1O1.95, and Sc0.1Ce0.01Zr0.89O1.95 were mixed with 8 mol % Yttria Stabilized Zirconia (YSZ) in 50:50 weight ratio to compare the influences in mechanical and electrical properties using a 3- point bending test and AC-impedance spectroscopy, respectively. An SEM was used for a morphological analysis and an XRD was used to identify phases. The composite of 3YSZ+8YSZ has shown a mixed phase between small and large grains referring to the cubic and tetragonal phases. From AC-impedance measurements, the composite of 8YSZ+ScSZ shows the maximum bulk and grain boundaries conductivities. The mechanical strength of 8YSZ has been proved to increase tremendously when mixed with the tetragonal phase of 3YSZ. However, The maximum bending strength is obtained from 8YSZ+ScSZ composite after sintering for 4 hours. The results have shown very positive solution using a composite of 8YSZ+ScSZ for the intermediate temperature electrolyte for SOFCs.
P/M Processing and Coating Technologies for Fabrication of Interconnect for Stationary and Mobile SOFC Applications
Authors: Venskutonis Andreas , Kunschert Georg , Mueller Eduard , Hoehle Hans-Michael
Published: May 2007

Plansee is pursuing the development as well as the pilot series production of metallic interconnect materials and components for planar SOFCs. Sulzer Metco has developed high efficient coating solutions to apply protective coatings using advanced plasma spray technology. Both companies are working closely together, in a partnership that leverages the specialist competencies of both. Additionally from the perspective of the industrial partners, an outline is given on the future commercialization and scaling-up capabilities of the fabrication of ready-to-use high performance metallic interconnects with optimized functional coatings.
Initiation and Performance of a Coating for Countering Chromium Poisoning in a SOFC-stack
Authors: Nielsen Karsten , Persson Aase , Beeaff Dustin , Ho̸gh Jens , Mikkelsen Lars , Hendriksen Peter V.
Published: May 2007

Minimising transport of chromium from the metallic interconnect (e.g. of Crofer 22APU) in a planar solid oxide fuel cell to the fuel cell cathode is done by application of a coating between the two parts. The coating is applied by slurry coating, and taken through stack initialisation it transforms into a stable and densely grown barrier layer, which minimises both the evaporation of chromium from the interconnect surface and the electrical contact resistance between the interconnect and the cathode. Between comparable stack element tests with and without coatings at 750ºC, the degra-dation rate in terms of power density decreased from 6.5% per 1000h to very low levels (<0.84% per1000 hour) during the first 1000 hours of stack element testing when using such type of coat-ing, indicating that the cathode poisoning from chromium has reached levels interesting for commercial development.
Study on the Ohmic Resistance of Solid Oxide Fuel Cells Based on YSZ Membrane Fabricated by Slurry Spin Coating
Authors: Lü Zhe , Wang Jiaming , Chen Kongfa , Huang Xiqiang , Ai Na , Zhu Ruibin , Su Wenhui
Published: May 2007

In this paper, four fuel cells were prepared using anode supported YSZ electrolyte membranes with different thickness by slurry spin coating technique and tested at 700{degree sign} C to 800{degree sign}C. By fitting the AC impedance spectra of fuel cells, the ohmic and electrochemical polarization resistances were distinguished. It has been found that the directly calculated conductivity and activation energy data of ohmic resistance based on impedance spectra measurement are much lower than that from bulk electrolyte. This phenomenon is discussed by analyzing the ohmic resistance data of four fuel cells with different membrane thickness. According to the analysis, an approach for measuring the conductivity of electrolyte membrane was developed to improve the calculation accuracy by fitting the ohmic area specific resistances to thicknesses of membrane, at the same time, it also can be used to evaluate the resistance contribution of anode supporter, cathode and current collector.
Sol Gel Synthesis of Nano-Sized Powder Precursors for Y2O3-HfO2-ZrO2 Ceramics
Authors: Vladimirovich Soudarev Anatoly , Ivanova Elena A. , Konakov Vladimir G.
Published: May 2007

Evolution of the current power requires developments of advanced materials that would have specific properties. To solve this task, the most promising approach seems to be fabrication of structural ceramic parts using nano-size powders- precursors. To produce the powders-precursors the paper's authors took use of the sol-gel reversed - coprecipitation technique. Water-soluble salts, namely HfOCl2 2 H2O, ZrO(NO3)2 2H2O and Y(NO3)3 6H2O were selected as initial components. The synthesis was carried out at various temperatures ranging 0 to 250C and, also, with the ultra sound affecting the reaction environment. A special attention was paid to a suppression of the agglomeration processes occurring at the final gel drying; whereas the pressurized drying technique proved to be the most effective. Thus, in some cases, monodispersive powders of sizes ranging 100nm to some micrometers depending on the synthesis conditions and the base-line reagents concentrations were produced. To identify the powder sizes, the LSPZA and BET techniques were employed.
Sintering of Thin Zirconia SOFC Electrolyte Films
Authors: Mücke Robert , Menzler Norbert H. , Buchkremer Hans-Peter , Stoever Detlev
Published: May 2007

The sintered thickness of electrolytes in SOFCs prepared via wet-chemical powder routes usually ranges between 5-10 µm. It has been shown that free-standing layers of 8 mol% yttria stabilised zirconia (8YSZ) of this thickness exhibit the same sintering shrink-age behaviour as thicker free layers and bulk ceramics. Sintering strain data of free layers and anode substrates has been used to optimise the sintering programme for firing the electrolyte, in order to improve its gas tightness. In this context, a dwelling period at lower temperatures seems beneficial. The existence of singular leaks in the electrolyte made it difficult to evaluate the relationship between sintering regime and leak rate more comprehensively.
Fabrication of Porous Structure with Scandia Stabilized Zirconia Electrolyte for Solid Oxide Fuel Cell
Authors: Peck Dong-Hyun , Choi Young-Hoon , Woo Sang-Kuk , Song Rak-Hyun , Wackerl Jürgen , Markus T.
Published: May 2007

This paper reports on the investigations on powder synthesis and fabrication of single cell using prepared powders. ScSZ powders for electrolyte of SOFC were synthesized using ultrasonic spray pyrolysis (USP) and Pechini method. The mean particle size diameter (d50) of the particle with the composition of ScMnSZ ((ZrO2)0.89(Sc2O3)0.1(MnO2)0.01) powders prepared by Pechini and USP method was about 0.35μm and 0.67μm. The electrical conductivity of sintered ScMnSZ sample prepared by Pechini and USP method was 0.112 S/cm and 0.091 S/cm at 800{degree sign}C, respectively. The performance of anode-supported single cell prepared using ScMnSZ electrolyte and LSM and Ni/YSZ electrodes was evaluated. The structure of the additional porous electrolyte layer was fabricated using polymer precursor as pore forming materials. The anode-supported cell with the additional porous electrolyte layer shows the maximum power density of 0.82 W/cm2 (0.55V) at 800{degree sign}C.
Synthesis of ZrO2-Sc2O3 Nanopowders by Gel-Combustion Routes
Authors: Abdala Paula M. , Kempf Rodolfo , Lamas Diego G.
Published: May 2007

ZrO2-6 mol% Sc2O3 nanopowders were synthesized by gel- combustion routes using different amino acids as fuel (glycine, alanine and lysine). They exhibited average crystallite sizes in the range of 8-16 nm and BET specific surface areas of 8-12 m2/g. Dense ceramics with excellent electrical properties were prepared by uniaxial pressing and sintering in air at relatively low temperatures (1350{degree sign}C). Specimens prepared from the different nanopowders evaluated in this work exhibited similar ionic conductivities, comparable to those reported in the literature for solid electrolytes with similar composition.
Processing and Properties of Scandia-doped Zirconia Electrolyte for Intermediate Temperature SOFC
Authors: Singh Raj , Chavan Sandeep B.
Published: May 2007

Lower temperature operation of a solid oxide fuel cell (SOFC) is highly desirable for achieving lower cost because less expensive metallic materials can be used for the complete system. Towards this goal, use of a more conducting electrolyte based on scandia-doped zirconia is a promising choice of an electrolyte. A composition with 9.2 mole % Sc2O3 in ZrO2 (scandia stabilized zirconia) is studied as an electrolyte for the SOFC operation at intermediate temperature range of 600-800oC. The electrolyte powder is prepared by a gel-combustion technique using citric acid as the fuel. The reaction product is calcined, tape cast, sintered, and characterized by x-ray diffraction. A single-phase cubic structure belonging to the cubic stabilized zirconia phase is obtained with a lattice parameter of a = 5.086? and coefficient of thermal expansion in the range of 9.9 to 10.2 ppm/oC.
A Comparison and Characterization of CeO2-doped and Bi2O3-doped Scandia Stabilized Zirconia as IT-SOFC Electrolytes
Authors: Bai Bing , McPhee William A. , Smirnova Alevtina L. , Sammes Nigel M.
Published: May 2007

Scandia stabilized zirconia has the highest ionic conductivity of zirconia based electrolytes. From the scandia-zirconia phase diagram 6-9 mol% scandia is cubic at room temperature, however, the cubic phase transforms to tetragonal with annealing at elevated temperatures. Increasing the scandia concentration to 10-12 mol% results in a stable cubic phase at above 600ºC, however, the stable phase at room temperature is rhombehedral. An addition of a third oxide can be used to suppress the rhombehedral to the cubic phase change to below room temperature. This study was a comparison of CeO2-doped and Bi2O3-doped 10 mol% scandia stabilized zirconia (10ScSZ) by X-ray diffraction and AC impedance spectroscopy. For both compositions pellets sintered at 1200ºC and 1300ºC resulted in a cubic phase. Both CeO2 and Bi2O3 additions stabilized the cubic phase at room temperature. 2 mol% Bi2O3 + (Sc2O3)0.10 (ZrO2)0.90 pellets had a comparable conductivity when sintered at 1300{degree sign}C and 1400{degree sign}C, and a lower conductivity when sintered at 1500{degree sign}C compared to (Sc2O3)0.10Ce0.01(ZrO2)0.89.
High Sinterability Doped Scandia Zirconia Powders
Authors: de Carvalho Eduarda Maria Soares , Irvine John T.
Published: May 2007

The compound (CeO2)1(Y2O3)0.2(Sc2O3)9.2(ZrO2)89.6 can be considered as a low ceria substituted Scandia Zirconia and has been investigated as a model composition for possible intermediate temperature electrolytes for SOFCs. The compound was produced by an innovative sol-gel and combustion method in an attempt to obtain a compositionally homogenous dense material. X-ray diffraction confirmed the expected cubic fluorite structure. Particle size analysis and SEM show a wide size range and indicate nano-particle agglomerates with platelet shape. The effects of milling have been investigated. The conductivity was measured by AC impedance spectroscopy. There were observed two linear regions in Arrhenius plots. The lower temperature region exhibited activation energy around 1.24 eV and the high temperature region 0.73 eV. The ionic conductivity at 800 {degree sign}C was 0.07 Scm-1.
Nano-scale Analysis of Low Temperature Solid Oxide Fuel Cell Electrolytes
Authors: Lee Shu-Feng , Cheng Chin-Hsien , Chen Wei-Huei , Hong Che-Wun
Published: May 2007

The traditional electrolyte for solid oxide fuel cells (SOFC), such as the Yttria Stabilized Zirconia (YSZ), is not suitable for the low temperature operation. Its ionic conductivity decreases dramatically when the operation temperature is below 1023K. This paper investigates the replacement of the YSZ by the Yttria doped Cerium (YDC) and Gadolinium-doped Ceria (GDC). A nano-scale analysis was carried out beforehand to predict the oxygen ion transfer inside the ceria-based solid electrolytes by the molecular dynamics (MD) technique. Simulation results showed that the hopping migration of oxygen ions dominates the transfer process instead of continuous diffusion. Different doping concentrations of the Yttria and the Gadolinium showed strong influence on the ionic conductivity. The molecular dynamics simulations of the YSZ, YDC and GDC were carried out at different operating conditions. They were compared with published experimental results and showed acceptable agreements. The conclusion has been reached that the YDC and GDC exhibit the potential to replace the traditional YSZ at low operation temperature and further promote the performance of the SOFCs.
Effect of Sintering Aids on the Formation of Zirconia-Ceria Solid Solution
Authors: Decès-Petit Cyrille , Zhang Xinge , Maric Radenka
Published: May 2007

Bi-layers electrolytes have been envisioned as a solution to improve fuel efficiency of ceria based materials for solid oxide fuel cells operating at intermediate temperature, but performance could be degraded if interface reaction occurs. In the present work, interactions between Samarium Doped Ceria (SDC) and Yttria or Scandia Stabilized Zirconia (YSZ or SSZ) were investigated. A new phase was observed on the XRD pattern for each mixture. On SDC-YSZ mixture, the new phase was completely formed at 1300{degree sign}C, with further shrinkage observed when temperature increased to 1400{degree sign}C. Adding the sintering aids such as Copper or Cobalt significantly decreased the sintering temperature of the mixtures, and it also decreased the temperature from which the new phase appears. The new phase appeared at 1100{degree sign}C with Copper and at 1200{degree sign}C with Cobalt.
Development of Proton Conducting Thin Films from Nanoparticulate Precursors
Authors: Taillades Gilles , Jacquin Mélanie , Khani Zohreh , Jones Deborah , Marrony Mathieu , Roziere Jacques
Published: May 2007

Three different routes allowing preparation of nanoparticulate yttrium-doped barium cerate have been developed: flash combustion, hydrolysis of complexed metal acrylates, and the use of inverse micelles. These methods allow preparation of doped perovskites of particle size in the range 5 - 50 nm. Water uptake characteristics have been determined after high temperature sintering, and proton conduction properties characterized between 400 and 600 {degree sign}C. The availability of sufficiently small particles opens up the possibility of using deposition techniques from colloidal suspensions of powders: In this work, nonporous BaCe0.9Y0.1O2.95 thin films have been synthesised on porous NiO/BCY10 substrates by spin coating. Scanning electron microscopy show that these films are dense, homogenous and with a thickness of 40 µm.
Ceramic Protonic Electrolyte Supported Fuel Cell for Operation with Methane and Ethanol
Authors: Muccillo Reginaldo , Oliveira Olavo R. , dos Santos Eliel , de Florio Daniel Z. , Fonseca Fabio Coral C. , Muccillo Eliana N.
Published: May 2007

Unitary planar solid oxide fuel cells with gadolinium-doped barium cerate protonic conductor solid electrolyte, slurry- coated thin film La0.6Ca0.4Fe0.8Co0.2O2.74 anode, and thin film Pt cathode have been put into operation in the temperature range 500ºC-900ºC using different fuel-oxidant combinations: H2-air, (30%H2,70%N2)-air, (10%CH4,90%Ar)-air, and C2H5OH-air. The sintered ceramic protonic conductors with dimensions φ=25mm and 1 mm thickness were characterized by determination of density by He picnometry, structural phase by X-ray diffraction and electrical behavior from 500 ºC to 1000 ºC by electrochemical impedance spectroscopy in the 5 Hz - 13 MHz frequency range. An experimental setup has also been built for testing electrolyte-supported cells fueled by H2, H2-Ar, CH4-Ar, C¬2H5O-N2. Several ceramic sealants were tested for allowing thermal cycling of the cells without cracking. The OCV time dependence, the current-voltage plot, and the Z' x Z' impedance diagrams, collected in the 300ºC-900ºC range, show the possibilities of operation of the cell.
Improvement in Sintering of Barium Zirconate by Doping with Scandium
Authors: Imashuku Susumu , Uda Tetsuya , Awakura Yasuhiro
Published: May 2007

From the view point of phase relationship, sintering behavior of 15 % yttrium-doped barium zirconate (BaZr0.85Y0.15O3-d) and 15 % scandium-doped barium zirconate (BaZr0.85Sc0.15O3-d) are investigated. Relative density of more than 99 % was achieved for BaZr0.85Sc0.15O3-d and the value was larger than that for BaZr0.85Y0.15O3-d. Larger grain was obtained for BaZr0.85Sc0.15O3-d. On the other hand, grain microstructures of sintered BaZr0.85Y0.15O3-d were a mixture of larger and smaller grains. Scandium is a more promising dopant for barium zirconate in their point of the low density of the grain- boundary and uniform grain.
BaZrxY1-xO3-d and BaCe1-x-zZrxYzO3-d Proton Conductors For Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs)
Authors: D'Epifanio Alessandra , Fabbri Emiliana , Di Bartolomeo Elisabetta , Licoccia Silvia , Traversa Enrico
Published: May 2007

A wet chemistry route to produce barium zirconate BaZrxY1-xO3- d (BZY) and barium cerium zirconate BaCe1-x-zZrxYzO3-d (BCZY) with controlled chemical structure and microstructural properties was optimized. A single phase was obtained at temperatures as low as 1100{degree sign}C for BZY and 1200 {degree sign}C for BCZY. To verify their chemical stability, all the calcined oxides were exposed to CO2 and the phase composition of the resulting specimens was investigated using X-ray diffraction (XRD) analysis. Dense electrolytes were obtained sintering BZY and BCZY pellets at 1600{degree sign}C for 10 hours, as shown from field emission scanning electron microscopy (FE-SEM) images. To compare the cell performance of the different oxides, fuel cell polarization curves on symmetric (Pt/BZY/Pt and Pt/BCZY/Pt) cells were measured at 700{degree sign}C.
Design and Evaluation of SOFC Based on BaIn0.3Ti0.7O2.85 Electrolyte and Ni/BaIn0.3Ti0.7O2.85 Cermet Anode
Authors: Prakash Deep , Delahaye Thibaud , Joubert Olivier , Caldes Maria Teresa , Piffard Yves , Stevens Philippe
Published: May 2007

BaIn0.3Ti0.7O2.85 (BIT) exhibits high anionic conductivity above 700{degree sign}C. Electrolyte-supported as well as anode-supported single cells based on BIT were fabricated and tested. A Ni/BIT cermet was used as anode and La0.7Sr0.3MnO3-d as cathode. Electrolyte-supported cells were fabricated by coating slurries of anode and cathode materials on the circular faces of thick (~550 mm) electrolyte pellets. The maximum power (Pmax) drawn was limited to 13 mW cm-2 at 30 mA cm-2 due to high internal resistance. In anode-supported cells made by co-pressing and co-sintering anode and electrolyte powders, the thickness of electrolyte was reduced to 80 mm and Pmax increased to ~90 mW cm-2. In order to further decrease the internal resistance, a thin and dense layer of BIT was deposited on the anode substrate by a spray pyrolysis technique. As a result, the internal resistance decreased further and Pmax was estimated to be up to 500 mW cm-2.
Synthesis of Lanthanum Silicates Electrolyte for Intermediate Temperature SOFC
Authors: Gao Wei , Zhang Chao , Lapostolle Frédéric , Liao Hanlin , Ji Vincent , Codden Christian
Published: May 2007

The emergence of lanthanum silicate as an electrolyte is required to accelerate the development of synthesis techniques for intermediate temperature solid oxide fuel cells (IT- SOFCs). Recently apatite-type lanthanum silicates and germinates of general formula La10-x(RO4)6O3-1.5x (R=Si and Ge) are considered as electrolyte exhibiting high oxide ion conductivity at intermediate temperature (600-800{degree sign} C) and low activation energies associated with the migration of oxygen ions. In this work, apatite-type oxide powders of La10(SiO4) 6O3 have been fabricated through the atmospheric plasma spraying (APS) using micro-size mixtures of La2O3 and SiO2 powders. Granulometer and scanning electron microscopy have indicated the result of high temperature reaction and rapid solidification in the evolution of multi-scale microstructure.
Effect of Y2O3 Addition on Crystal Structure and Electrical Conductivity of WO3 Doped Bi2O3 Solid Electrolyte
Authors: Hsieh Cheng-Yen , Fung Kuan-Zong
Published: May 2007

WO3-doped Bi2O3 was found to exhibit stable fluorite-based structures. However, the electrical conductivity of WO3-doped Bi2O3 is significantly lower than that of Y2O3-doped Bi2O3. The structure and electrical conductivity of samples formulated as (YXW0.15Bi0.85-X)2O3.45 (X=0.1~0.4) were investigated. The as- sintered (Y0.1W0.15Bi0.75)2O3.45 exhibited a single cubic structure that is isostructural with d-Bi2O3. However, the cubic fluorite structure may decompose into cubic structure and rhombohedral Y6WO12 after heat-treatment at 900{degree sign}C for 3 hours. For X=0.2, 0.3 and 0.4, the as-sintered samples consisted of a cubic fluorite structure and rhombohedral Y6WO12. The conductivities of (YXW0.15Bi0.85-X)2O3.45 (X=0.1~0.4) decrease with increasing X value. For X=0.1, the conductivity is 1.97 ´ 10-3 S cm-1 at 700{degree sign}C and slightly lower than that of (W0.15Bi0.85)2O3.45. The Bi 6s2 lone pairs of electrons are known to lead to enough oxygen ion mobility. Thus it is reasonable to expect that ionic conductivity drops as Y substituting for Bi.
Oxide Scales of Modified Fe-Cr Alloy (Low Si and Al Concentrations) in Reducing Atmospheres
Authors: Horita Teruhisa , Katsuhiko Yamaji , Sakai Natsuko , Yokokawa Harumi , Toji Akihiro , Uehara Toshihiro , Seo Takehisa , Ogasawara Kei , Kameda Harukuni , Matsuzaki Yoshio , Yamashita Satoshi
Published: May 2007

Oxide scale formation was examined on the modified Fe-Cr alloys (Si and Al reduced concentrations) in H2-H2O or CH4-H2O atmospheres to simulate SOFC fuels. The formed oxide scales were characterized by surface and depth profile analyses. The oxide scale was composed of the following oxide phases from surface to inner oxide scale: Mn-Cr-(Fe) spinel layer, Cr2O3 layer, and Si-rich interface, and Al2O3 internal oxide. Although the scale formation mechanism is similar between modified and conventional alloys, the oxide scale growth rates were decreased in the modified Fe-Cr alloy. The electrical conductivity of oxidized Fe-Cr alloys was improved in the modified Fe-Cr alloy due to thinner oxide scale thickness and less distribution of insulating Si and Al internal oxides.
Carburization Resistance of Nb Added-16Cr Alloy at 1073 K
Authors: Ito Takuya , Ueda Mitsutoshi , Kawamura Kenichi , Maruyama Toshio
Published: May 2007

Fe-Cr ferritic alloy is one of the candidates of interconnects. This alloy has a good oxidation resistance by formation of a protective Cr2O3 scale, which also protects from carburization. Using hydrocarbon gas as fuel, Cr concentration near the alloy surface may decrease by the formation of Cr carbides. The formation of the protective Cr2O3 scale is failed. It is expected that Nb addition to Fe- Cr alloy prevents from carburization because Nb has stronger affinity to carbon than Cr. Fe-16 mass%Cr and Fe-16 mass%Cr- 1.0 mass%Nb alloys were exposed to the atmosphere with S/C=1.1 at 1073 K up to 604.8 ks. In the case of Fe-16Cr alloy, carburization occurred extensively and internal Cr oxides and carbides were formed inside of the alloy. No Cr carbides were observed in all parts of the Nb added alloy. This indicates that carburization resistance is improved by the addition of Nb.
Oxidation Studies on Crofer 22 APU Alloy Under Simulated SOFC Operating Conditions
Authors: Huang Wenhua , Gopalan Srikanth , Pal Uday B. , Basu Soumendra N.
Published: May 2007

The oxidation of Crofer 22 APU was studied under simulated SOFC interconnection operating conditions. Crofer 22 APU samples were exposed to cathodic conditions, i.e. air on one side, and anodic conditions, i.e. fuel (hydrogen) on the other side, with an externally imposed current flow simulating the passage of current. Preliminary results indicate that the composition of the oxide scale formed on the fuel side of the alloy with the externally imposed current flow was significantly different from that of the oxide scale formed when there was no current flow. However, the results indicate that the current flow has no significant effect on the composition of the oxide scale on the air side.
Effects of REM Coatings on Electrical Conductivity of Ferritic Stainless Steels for SOFC Interconnect Applications
Authors: Jun Jaeho , Kim Dohyeong , Jun Joonghwan
Published: May 2007

The purpose of this study is to examine the influences of rare earth metal (REM) coatings on electrical conductivity of ferritic stainless steel for planer SOFC interconnect applications. In this work, La and Y were selected as REMs and coated on AISI-444 by using an evaporation process. Subsequently, the La- and Y-coated AISI-444 specimens with various coating thickness from 10 to 50nm were oxidized in air for 500hrs at 700{degree sign}C. The electrical conductivities of each oxidized specimens were evaluated by measuring their values of ASR at 700{degree sign}C. The test results indicated that La and Y coating noticeably reduced the ASR value of AISI-444, and the change in ASR values with coating thickness and coating material were not apparent at the beginning. However, Y coating displayed a better performance than La coating with the lapse of time.
Electrodeposition of Ceria on Stainless Steel for SOFC Interconnect Applications
Authors: Elbelghiti Hanane , Lair Virginie , Ringuedé Armelle , Cassir Michel
Published: May 2007

Cerium-based oxides usually find application as electrolyte for SOFC applications, but can also be considered as potential protective coating of interconnect materials. Films of ceria were obtained on stainless steel via a cathodic electrolytic deposition method, at elevated temperature. The submicronic films were characterized using X-ray diffraction, showing that the cubic phase was directly obtained. Scanning electron microscopy revealed small grain size, and a no-cracked coating. The electrical properties of the ceria films were investigated by impedance spectroscopy measurements.
Use of SOFC Metallic Interconnect Coated with Spinel Protective Layers using the APS Technology
Authors: Vargas Maria Jose Garcia , Zahid Mohsine , Tietz Frank , Aslanides Antoine
Published: May 2007

The use of metallic interconnects for SOFC application leads to the degradation of the cell performance due to Cr migration. In order to avoid the cathode poisoning, spinel type coatings were developed and deposited on the cathode contact side of a ferritic interconnect, using Atmospheric Plasma Spraying. A porous contact layer was then deposited by Wet Powder Spraying on the top of the dense protective layer. This contact layer favours the adjustment between cathode and interconnect, reducing the possible stress caused by the difference in thermal expansion coefficients. This study shows the performance of a single repeating unit, i.e. cell and coated interconnect, tested at 800{degree sign}C during 600 h. After a decrease of the interconnect Area Specific Resistance during the first hours a low value, which remains stable until the end of the test, is reached. Post mortem analysis of both the cell and the interconnect confirmed the effectiveness of this coating against Cr poisoning.
Ceramic PVD Coatings as Dense/Thin Barrier Layers on Interconnect Components for SOFC Applications
Authors: Kunschert Georg , Schlichtherle Stefan , Strauss Georg N. , Kailer Karl
Published: May 2007

In the last decade of SOFC metallic interconnect component development barrier coatings have proven being indispensable as functional layers and therefore gained serious attention. Diffusion processes at the interface between metallic and other cell materials have demonstrated harmful influence on degradation of SOFC stacks. Recent scientific developments of perovskite barrier layers show that innovative pulsed PVD technologies make it feasible to deposit thin films of highest density and conductivity. Simultaneously, through applying PVD methods it is possible to drastically reduce the employed perovskite material. PVD coatings in the thickness range of around 1 µm have been applied on porous substrates of Plansee's P/M ODS ferritic FeCr- alloy ITM for MSC type SOFC as well as on bulk components. Long term oxidation tests at 850{degree sign}C in combination with SEM/EPMA imaging and element sensitive mappings are shown and verify the functionality of described coatings as diffusion barrier layers.
Analysis of Structural Phase Transition Behavior of La1-x-yCaxSryCrO3
Authors: Mitsui Akio , Homma Kenji , Kumekawa Yuh , Nakamura Fumihiko , Ohba Norifumi , Hashimoto Takuya
Published: May 2007

The structural phase transition behavior of La1-x-yCaxSryCrO3, which can be regarded as promising material for interconnector of SOFC due to high sintering property, has been investigated by differential scanning calorimetry. Temperature and variation of enthalpy at the structural phase transition decreased with increase of Sr content among the specimens with the same alkaline earth content. It was also revealed from X- ray diffraction that crystal symmetry of orthorhombic phase became lower whereas that of rhombohedral one higher with Sr substitution. Assuming that the standard Gibbs free energy of formation of La1-x-yCaxSryCrO3 with higher crystal symmetry is lower, the variation of the phase transition behavior on Sr substitution can be qualitatively explained by using thermodynamics.
Investigation of Electrical Conductivity and Oxidation Behavior of TiC and TiN Based Cermets for SOFC Interconnect Application
Authors: Pang Yukun , Xie Hua , Koc Rasit
Published: May 2007

Titanium carbide and titanium nitride based cermets were produced and investigated to evaluate potential application for SOFC interconnect in terms of electrical conductivity and oxidation resistance. TiC and TiN cermets with 30, 50 and 70 wt% of Ni were fabricated using wet milling and hot pressing, and were then subjected to electrical conductivity measurements in air at 800 ºC for 100 hours. Although all samples tested were slightly oxidized, no degradation has been observed and high electrical conductivity values of the order of 10^3 S/cm have been recorded. The oxide scale strongly adhered to the substrate and protected the sample from further oxidation. With reference to the mixture rules, SEM and EDS results were presented and interpreted to discuss impact of characteristics of the oxide scales on their electrical conductivities.
Altered biomechanical properties of carotid arteries in two mouse models of muscular dystrophy
Authors: Dye W. W. , Gleason R. L. , Wilson E. , Humphrey J. D.
Published: May 2007

Muscular dystrophy is characterized by skeletal muscle weakness and wasting, but little is known about possible alterations to the vasculature. Many muscular dystrophies are caused by a defective dystrophin-glycoprotein complex (DGC), which plays an important role in mechanotransduction and maintenance of structural integrity in muscle cells. The DGC is a group of membrane-associated proteins, including dystrophin and sarcoglycan-δ, that helps connect the cytoskeleton of muscle cells to the extracellular matrix. In this paper, mice lacking genes encoding dystrophin ( mdx) or sarcoglycan-δ ( sgcd−/−) were studied to detect possible alterations to vascular wall mechanics. Pressure-diameter and axial force-length tests were performed on common carotid arteries from mdx, sgcd−/−, and wild-type mice in active (basal) and passive smooth muscle states, and functional responses to three vasoactive compounds were determined at constant pressure and length. Apparent biomechanical differences included the following: mdx and sgcd−/− arteries had decreased distensibilities in pressure-diameter tests, with mdx arteries exhibiting elevated circumferential stresses, and mdx and sgcd−/− arteries generated elevated axial loads and stresses in axial force-length tests. Interestingly, however, mdx and sgcd−/− arteries also had significantly lower in vivo axial stretches than did the wild type. Accounting for this possible adaptation largely eliminated the apparent differences in circumferential and axial stiffness, thus suggesting that loss of DGC proteins may induce adaptive biomechanical changes that can maintain overall wall mechanics in response to normal loads. Nevertheless, there remains a need to understand better possible vascular adaptations in response to sustained altered loads in patients with muscular dystrophy.
Flow-induced shear strain in intima of porcine coronary arteries
Authors: Zhang Wei , Liu Yi , Kassab Ghassan S.
Published: May 2007

The in vivo circumferential strain has a small variation throughout the vascular system (aorta to arterioles). The axial strain has also been shown to be nearly the same as the circumferential strain under physiological loading. Since the endothelium is mechanically much softer than the media-adventitia in healthy arteries, the porcine intima was considered as a mechanically distinct layer from the media-adventitia in a two-layer computational model. Based on the simulation result, we hypothesize that the flow-induced shear strain in intima can be of similar value as the pressure-induced circumferential strain in healthy coronary arteries, even though the shear stress is orders of magnitude smaller than the circumferential stress. The nearly isotropic deformation (circumferential, axial, and shear strains) may have important implications for mechanical homeostasis of endothelial cells, mechanotransduction, growth, and remodeling of blood vessels.
Distinct Functions between Toll-Like Receptors 3 and 9 in Retinal Pigment Epithelial Cells
Authors: Ebihara Nobuyuki , Chen Lizhong , Tokura Tomoko , Ushio Hiroko , Iwatsu Minoru , Murakami Akira
Published: May 2007

Retinal pigment epithelial cells (RPE cells) are key players in the first-line defense against invading organisms such as viruses and bacteria. The interaction between RPE cells and viral or bacterial components is very important for clearance of these organisms. Toll-like receptors are a family of recognition receptors involved in innate immunity. Each TLR acts as a primary sensor of conserved microbial components and drives the induction of specific biological responses. TLR 3 is involved in the recognition of viral components, such as double-stranded RNA (dsRNA) and poly(I:C), while TLR 9 recognizes viral or bacterial DNA without methylation at CpG motifs. In the present study, we investigated the expression and function of TLR 3 and 9 in RPE cells. PCR analysis revealed expression of genes for TLR 3 and 9 in RPE cells. Expression of TLR 3 and 9 protein was detected in RPE cells by flow cytometry. TLR 3 and 9 showed strong intracellular expression. To detect angiogenetic factors produced by RPE cells, culture supernatant was examined with the Human Angiogenesis Antibody Array, which can simultaneously detect 20 different angiogenetic factors including cytokines, chemokines, soluble cytokine receptors, and growth factors. RPE cells showed high production of interleukin-8 (IL-8) and monocyte chemotactic protein-I (MCP-I). Furthermore, stimulation of RPE cells with the dsRNA analogue poly(I:C) enhanced the secretion of IL-8 and MCP-I, as well as enhancing the expression of junctional adhesion molecule-I (Jam-I) and intracellular adhesion molecule-I (ICAM-I), and promoted the adhesion of monocyte to these cells. In contrast, stimulation with the CpG-DNA motif only enhanced the secretion of IL-8. However, CpG-DNA motif enhanced phagocytosis in RPE cells. These results may indicate that TLR 3 and 9 play a distinct role in the inflammatory response that clears viruses from the retina.
Eccentric Lamellar Keratolimbal Grafts Harvested with a Manually Guided Microkeratome
Authors: Grueterich Martin , Kenyon Kenneth R. , Priglinger Siegfried , Welge-Luessen Ulrich , Lackerbauer Carlo , Kampik A.
Published: May 2007

Background: To perform lamellar keratolimbal allograft transplantation in a one-step procedure with a single graft, we investigated the feasibility of harvesting eccentric lamellar keratolimbal grafts from conventionally processed corneoscleral buttons using a manually guided microkeratome in conjunction with an artificial anterior chamber system. Methods: We used the Moria LSK-One microkeratome and the automated lamellar therapeutic keratoplasty (ALTK) system (Antony, France). Ten human donor eyes were used to obtain single-piece lamellar keratolimbal grafts. Specimens were processed for light and electron microscopy. Results: Eccentric keratolimbal grafts could be obtained from all human donor buttons. Grafts include a crescent-shaped limbal and a large corneal portion. No visible damage to the limbal region was discernible. Conclusion: Our data show that the LSK-One microkeratome in conjunction with the ALTK system allows harvesting eccentric keratolimbal grafts from donor corneoscleral buttons.
A 12-Month Prospective Study of Gasserian Ganglion Stimulation for Trigeminal Neuropathic Pain
Authors: Machado A. , Ogrin M. , Rosenow J.M. , Henderson J.M.
Published: May 2007

Aims: Trigeminal neuropathic pain is a broad diagnostic category that includes pain of several etiologies and excludes trigeminal neuralgia. The authors report a prospective series of percutaneous gasserian ganglion stimulation for trigeminal neuropathic pain. Methods: Patients who experienced >50% reduction in pain from a 7- to 10-day trial period underwent permanent implantation and were prospectively followed. Results: Eight of 10 trialed patients received a permanent implant. At the 12-month follow-up, 2 patients had been explanted and 1 was lost to follow-up. Three (all working at that the time) continued to experience >50% improvement in pain. Discussion: The results in this series were variable but 3 patients showed long-term improvements. Patients who continued to work responded better to treatment.
A New Mechatronic Assistance System for the Neurosurgical Operating Theatre: Implementation, Assessment of Accuracy and Application Concepts
Authors: Rachinger Jens , Bumm Klaus , Wurm Jochen , Bohr Christopher , Nissen Urs , Dannenmann Tim , Buchfelder Michael , Iro Heinrich , Nimsky Christopher
Published: May 2007

Objective: To introduce a new robotic system to the field of neurosurgery and report on a preliminary assessment of accuracy as well as on envisioned application concepts. Based on experience with another system (Evolution 1®, URS Inc., Schwerin, Germany), technical advancements are discussed. Material/Methods: The basic module is an industrial 6 degrees of freedom robotic arm with a modified control element. The system combines frameless stereotaxy, robotics, and endoscopy. The robotic reproducibility error and the overall error were evaluated. For accuracy testing CT markers were placed on a cadaveric head and pinpointed with the robot’s tool tip, both fully automated and telemanipulatory. Applicability in a clinical setting, user friendliness, safety and flexibility were assessed. Results: The new system is suitable for use in the neurosurgical operating theatre. Hard- and software are user-friendly and flexible. The mean reproducibility error was 0.052–0.062 mm, the mean overall error was 0.816 mm. The system is less cumbersome and much easier to use than the Evolution 1. Conclusions: With its user-friendly interface and reliable safety features, its high application accuracy and flexibility, the new system is a versatile robotic platform for various neurosurgical applications. Adaptations for different applications are currently being realized.
Dominant Negative Suppression of Rad Leads to QT Prolongation and Causes Ventricular Arrhythmias via Modulation of L-type Ca
2+
Channels in the Heart
Authors: Yada Hirotaka , Murata Mitsushige , Shimoda Kouji , Yuasa Shinsuke , Kawaguchi Haruko , Ieda Masaki , Adachi Takeshi , Murata Mitsuru , Ogawa Satoshi , Fukuda Keiichi
Published: May 2007

Disorders of L-type Ca
2+
channels can cause severe cardiac arrhythmias. A subclass of small GTP-binding proteins, the RGK family, regulates L-type Ca
2+
current (
I
Ca,L
) in heterologous expression systems. Among these proteins, Rad (Ras associated with diabetes) is highly expressed in the heart, although its role in the heart remains unknown. Here we show that overexpression of dominant negative mutant Rad (S105N) led to an increase in
I
Ca,L
and action potential prolongation via upregulation of L-type Ca
2+
channel expression in the plasma membrane of guinea pig ventricular cardiomyocytes. To verify the in vivo physiological role of Rad in the heart, a mouse model of cardiac-specific Rad suppression was created by overexpressing S105N Rad, using the α-myosin heavy chain promoter. Microelectrode studies revealed that action potential duration was significantly prolonged with visible identification of a small plateau phase in S105N Rad transgenic mice, when compared with wild-type littermate mice. Telemetric electrocardiograms on unrestrained mice revealed that S105N Rad transgenic mice had significant QT prolongation and diverse arrhythmias such as sinus node dysfunction, atrioventricular block, and ventricular extrasystoles, whereas no arrhythmias were observed in wild-type mice. Furthermore, administration of epinephrine induced frequent ventricular extrasystoles and ventricular tachycardia in S105N Rad transgenic mice. This study provides novel evidence that the suppression of Rad activity in the heart can induce ventricular tachycardia, suggesting that the Rad-associated signaling pathway may play a role in arrhythmogenesis in diverse cardiac diseases.
Sex Disparity in the Access of Elderly Patients to Acute Stroke Care
Authors: Foerch Christian , Misselwitz Bjoern , Humpich Marek , Steinmetz Helmuth , Neumann-Haefelin Tobias , Sitzer Matthias
Published: May 2007

Background and Purpose—

Sex differences in the management of acute coronary symptoms are well documented. We sought to determine whether sex disparities exist in acute stroke management, particularly with regard to early hospital admission and thrombolytic therapy.

Methods—

We analyzed a prospective, countywide, hospital-based stroke registry. Between 1999 and 2005, all cases with a final diagnosis of cerebral infarction (ICD-10 I63) or intracerebral hemorrhage (ICD-10 I61) were selected. Datasets with missing values for sex and time to admission, as well as datasets of patients transferred between hospitals in the acute phase, were excluded. Main outcome measures were the probability of being admitted within the first 3 hours of stroke onset and being treated with thrombolytic agents for both women and men, after adjustment for age, prestroke disability, severity of clinical symptoms, vascular risk factors, and final diagnosis.

Results—

Fifty-three thousand four hundred fourteen patients were included (49.3% female; mean±SD age, 72.1±12.5 years). Women had a 10% lower chance of being admitted within the first 3 hours than men (odds ratio=0.902, 95% CI=0.860 to 0.945,
P
<0.001). This chance further decreased in elderly women. Similarly, the chance of a female stroke patient being treated with thrombolysis was 13% lower than that of a male patient (odds ratio=0.867, 95% CI=0.782 to 0.960,
P
=0.006). For patients admitted within the 3-hour time window, the chance of being treated with thrombolysis was similar for women and men (odds ratio=0.915, 95% CI=0.809 to 1.035,
P
=0.156).

Conclusions—

We identified sex disparities in acute stroke management in terms of early hospital admission and thrombolytic treatment. This is best explained by the sociodemographic fact that “surviving spouses” are more likely to be women than men. Attempts to overcome disadvantages in their access to acute stroke care should focus on increased social support.
Increased Echolucency of Carotid Plaques in Patients With Type 2 Diabetes
Authors: Östling Gerd , Hedblad Bo , Berglund Göran , Gonçalves Isabel
Published: May 2007

Background and Purpose—

Diabetes is associated with the presence of moderate to large atherosclerotic carotid plaques. Previous carotid ultrasound studies have associated plaques with low echogenicity with a higher risk of cerebrovascular events. The aim of this study was to evaluate whether patients with type 2 diabetes have different plaque echogenicity than do nondiabetic subjects.

Methods—

Forty-seven type 2 diabetic and 51 nondiabetic subjects with a carotid plaque in the right artery were included in this study. All patients were born in 1935 to 1936 and were participants in a population-based study. Carotid ultrasonography was performed and the risk factors for cardiovascular disease were determined. Plaque echogenicity was assessed quantitatively on B-mode ultrasound images by standardized gray-scale median values.

Results—

Gray-scale median values were significantly lower, indicating more echolucent plaques, in patients with type 2 diabetes compared with nondiabetics (37.0±14.8 vs 45.5±15.4,
P
=0.007). Of the other risk factors studied, only triglycerides were significantly associated with the echogenicity of the plaque.

Conclusions—

Patients with type 2 diabetes have more echolucent plaques compared with nondiabetic subjects. This might be associated with the higher risk of cardiovascular events among diabetics.
One-Year Follow-Up After Bone Marrow Stromal Cell Treatment in Middle-Aged Female Rats With Stroke
Authors: Shen Li Hong , Li Yi , Chen Jieli , Cui Yisheng , Zhang Chunling , Kapke Alissa , Lu Mei , Savant-Bhonsale Smita , Chopp Michael
Published: May 2007

Background and Purpose—

We sought to evaluate the long-term effects of bone marrow stromal cell (BMSC) treatment on retired breeder rats with stroke.

Methods—

Female retired breeder rats were subjected to 2-hour middle cerebral artery occlusion (MCAO) followed by an injection of 2×10
6
male BMSCs (n=8) or phosphate-buffered saline (n=11) into the ipsilateral internal carotid artery at 1 day after stroke. The rats were humanely killed 1 year later. Functional tests, in situ hybridization, and histochemical and immunohistochemical staining were performed.

Results—

Significant recovery of neurological deficits was found in BMSC-treated rats beginning 2 weeks after cell injection compared with control animals. The beneficial effects of cell transplantation persisted for at least 1 year (
P
<0.01). In situ hybridization for the Y chromosome showed that donor cells survived in the brains of recipient rats, among which 22.3±1.95% of cells expressed the astrocyte marker glial fibrillary acidic protein, 16.8±2.13% expressed the neuronal marker microtubule-associated protein 2, and 5.5±0.42% and <1% of cells colocalized with the microglial marker IB4 and the endothelial cell marker von Willebrand factor, respectively. Only very few BMSCs, however, were found in peripheral organs such as the heart, lung, liver, spleen, and kidney in recipient rats. BMSCs significantly reduced axonal loss (
P
<0.01), the thickness of the lesion scar wall (
P
<0.01), and the number of Nogo-A–positive cells (
P
<0.05) along the scar border; meanwhile, synaptophysin expression (
P
<0.05) was significantly increased in BMSC-treated ischemic brains compared with control untreated brains.

Conclusions—

The beneficial effects of BMSCs on ischemic brain tissue persisted for at least 1 year. Most surviving BMSCs were present in the ischemic brain, but very few were found in other organs. The long-term improvement in functional outcome may be related to the structural and molecular changes induced by BMSCs.