bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Shakedown Boundary and Failure-Assessment-Diagrams of Cracked Pipe Bends
Authors: Elsaadany Mostafa S. , Younan Maher Y. A. , Abdalla Hany F.
Published: October 2013

Determination of shakedown (SD) boundaries of 90-degree plain smooth pipe bends has recently received substantial attention by several researchers. However, scarce or almost no solid information is found within the literature regarding the determination of the shakedown boundary of cracked pipe bends. The current research presents two additions to the literature, namely, determination of shakedown boundary for a circumferentially cracked 90-degree pipe bend via a simplified technique utilizing the finite element (FE) method and introduction of failure-assessment diagrams (FADs) in compliance with the API 579 failure-for-service assessment of pressure vessel and piping components. The analyzed cracked pipe bend is subjected to the combined effect of steady internal pressure spectrum and cyclic in-plane closing (IPC) and opening (IPO) bending moments. Line spring elements (LSEs) are embedded in quadratic shell elements to model part-through cracks. FAD is obtained through linking the J-integral fracture mechanics parameter with the shakedown limit moments of the analyzed cracked 90-degree pipe bend. The LSE outcomes illustrated satisfactory results in comparison to the results of two verification studies: stress intensity factor (SIF) and limit load. Additionally, full elastic-plastic (ELPL) cyclic loading finite element analyses are conducted and the outcomes revealed very good correlation with the results obtained via the simplified technique. The maximum load carrying capacity (limit moment) and the elastic domain are also computed thereby generating a Bree diagram for the cracked pipe bend. Finally, Crack growth analysis is presented to complement the FAD.
A Unified Viscoplastic Model for High Temperature Low Cycle Fatigue of Service-Aged P91 Steel
Authors: Barrett R. A. , Farragher T. P. , Hyde C. J. , O'Dowd N. P. , O'Donoghue P. E. , Leen S. B.
Published: October 2013

The finite element (FE) implementation of a hyperbolic sine unified cyclic viscoplasticity model is presented. The hyperbolic sine flow rule facilitates the identification of strain-rate independent material parameters for high temperature applications. This is important for the thermo-mechanical fatigue of power plants where a significant stress range is experienced during operational cycles and at stress concentration features, such as welds and branched connections. The material model is successfully applied to the characterisation of the high temperature low cycle fatigue behavior of a service-aged P91 material, including isotropic (cyclic) softening and nonlinear kinematic hardening effects, across a range of temperatures and strain-rates.
Linkage-Based Analysis and Optimization of an Underactuated Planar Manipulator for In-Hand Manipulation
Authors: Ma Raymond R. , Dollar Aaron M.
Published: October 2013

This paper investigates the in-hand manipulation capabilities of a compliant, underactuated planar robotic hand by treating the system as a simple, symmetric, 6-bar linkage mechanism with compliant joints. Although underactuated hands are generally not considered to be adept at dexterous tasks, we have found through past work that an underactuated manipulator can control n degrees of freedom with n actuators by leveraging the passive compliance to satisfy contact constraints on the object. Assuming the system to be quasi-static, the workspace of the underactuated mechanism is found through constraint-based energy minimization by sweeping through the set of allowable inputs. In this study, we investigate achievable workspaces by exploring the nondimensionalized design space, consisting of linkage ratio, joint stiffness ratio, transmission ratio, base linkage length, and object linkage length. The results of this study are useful in motivating the design of dexterous, underactuated manipulators, as well as to predict the achievable workspace of specific hand/object configurations.
Evaluation of Ductile Fracture Models in Finite Element Simulation of Metal Cutting Processes
Authors: Liu Jian , Bai Yuanli , Xu Chengying
Published: October 2013

In this paper, a systematic evaluation of six ductile fracture models is conducted to identify the most suitable fracture criterion for metal cutting processes. Six fracture models are evaluated in this study, including constant fracture strain, Johnson-Cook, Johnson-Cook coupling criterion, Wilkins, modified Cockcroft-Latham, and Bao-Wierzbicki fracture criterion. By means of abaqus built-in commands and a user material subroutine (VUMAT), these fracture models are implemented into a finite element (FE) model of orthogonal cutting processes in abaqus/Explicit platform. The local parameters (stress, strain, fracture factor, and velocity fields) and global variables (chip morphology, cutting forces, temperature, shear angle, and machined surface integrity) are evaluated. The numerical simulation results are examined by comparing to experimental results of 2024-T3 aluminum alloy published in the open literature. Based on the results, it is found that damage evolution should be considered in cutting process FE simulation. Moreover, the B-W fracture model with consideration of rate dependency, temperature effect and damage evolution gives the best prediction of chip removal behavior of ductile metals.
Modeling Study of a Combined Fuel-Cell Stack/Switch Mode DC-DC Converter
Authors: Vazquez-Oviedo E. I. , Ortiz-Lopez M. G. , Diaz-Saldierna L. H. , Leyva-Ramos J.
Published: October 2013

A fuel-cell stack produces a low and unregulated dc voltage; therefore, a dc-dc converter is required to step up and regulate the output voltage. A major drawback is that the output voltage of the fuel-cell stack exhibits a nonlinear behavior since the output voltage drops when more current is drawn. This output voltage will be later connected to a switch-mode dc-dc converter to step up its value; therefore, it is very important to consider the dynamic behavior of fuel-cell stack as input to a switching converter. In this work, a model is proposed for a combined fuel-cell stack/boost converter system. The interest of this model is clearly motivated by the need to have a model compatible with the standard techniques for controller design as current-mode control. The model is tested using a power module and a boost converter delivering an output power of 740 W. The power module uses polymer electrolyte membrane fuel cells (PEMFCs) and delivers a variable output dc voltage between 24 V to 42 V. Experimental results verify the theoretical results given within.
Association of membranoproliferative glomerulonephritis with mantle cell lymphoma
Authors: Chu Jamie R , Dierksen Jennifer E , Glass William F , Aisenberg Gabriel Marcelo
Published: October 2013

Mantle cell lymphoma (MCL) is a rare and aggressive lymphoid neoplasm. It can involve the kidney, either by direct lymphomatous infiltration or by a paraneoplastic glomerulonephritis. We present here the case of a man with rectal bleeding and rapidly progressive renal failure, who had MCL in the gastrointestinal tract and paraneoplastic membranoproliferative glomerulonephritis, and whose renal dysfunction normalised after chemotherapy.
Trichophyton tonsurans strains from Brazil: phenotypic heterogeneity, genetic homology, and detection of virulence genes
Authors: Sidrim José Julio Costa , Rocha Marcos Fábio Gadelha , Leite João Jaime Giffoni , Maranhão Fernanda Cristina de Albuquerque , Lima Rita Amanda Chaves , Castelo-Branco Débora de Souza Collares Maia , Bandeira Tereza de Jesus Pinheiro Gomes , Cordeiro Rossana de Aguiar , Brilhante Raimunda Sâmia Nogueira
Published: October 2013

The objective of this study was to establish the phenotypical and molecular patterns of clinical isolates of Trichophyton tonsurans circulating in the state of Ceará, northeastern Brazil. For this purpose, 25 T. tonsurans strains isolated from independent cases of tinea capitis in children were phenotypically evaluated regarding their macro- and micro-morphological characteristics, vitamin requirements, urease production, and antifungal susceptibility. The molecular characterization was carried out with random amplified polymorphic DNA molecular markers and M13 fingerprinting. The presence of the genes CarbM14, Sub2, CER, URE, ASP, PBL, and LAC, which encode enzymes related to fungal virulence, was also evaluated. Finally, melanin production was assessed through specific staining. The data obtained demonstrated that these T. tonsurans strains have considerable phenotypical variation, although they showed a low degree of genetic polymorphism according to the markers used. The genes CarbM14, Sub2, CER, and URE were detected in all the analyzed strains. The gene LAC was also identified in all the strains, and melanin synthesis was phenotypically confirmed. The strains were susceptible to antifungals, especially itraconazole (GM = 0.06 μg/mL) and ketoconazole (GM = 0.24 μg/mL). Therefore, T. tonsurans strains can present great phenotypical heterogeneity, even in genetically similar isolates. Moreover, the presence of the LAC gene indicates the possible participation of melanin in the pathogenesis of these dermatophytes.
A QUANTUM SIMULATOR FOR PROBING MOTT LOBES VIA THE AC JOSEPHSON EFFECT
Authors: HUO MING-XIA , LI YING , SONG ZHI , SUN CHANG-PU
Published: October 2013

In this paper, we propose to directly detect Mott lobes, i.e. the order parameter 〈a〉, describing the Mott insulator (MI) to superfluid (SF) quantum phase transition of the Bose–Hubbard (BH) model. By weakly coupling the system to an environment in the SF phase, the U(1) symmetry breaking of the system is simulated, and the order parameter can be read from the AC Josephson current between the system and the environment. The relation between the order parameter and the Josephson current is obtained from both the mean-field theory approach and an exact numerical simulation of a finite-size example. Our numerical simulations show that the profile of the order parameter read from the Josephson current is different from it predicted by the mean-field theory, but similar to it in a system whose U(1) symmetry is broken by a weak field proportional to a + a†. This proposal is feasible in optical lattices.
INTELLECTUAL PROPERTY MANAGEMENT AND TECHNOLOGICAL ENTREPRENEURSHIP
Authors: WILLOUGHBY KELVIN W.
Published: October 2013

This paper investigates the distinctive technology protection strategies of entrepreneurial technology firms. In contrast with much popular opinion, it is reported that intellectual property features more prominently in the business of small entrepreneurial firms than it does in the business of large, established mature firms. The intellectual property portfolios of technology firms of all sizes and ages exhibit a rich array of instruments in addition to patents for protecting technology, including trade secrets, trademarks and copyright, together with licenses to externally sourced technology. The intellectual property profiles of technology firms appear to be influenced by their context, organizational profiles and corporate goals and by the character of their technology.
Theory and Empirical Evidence for Carbon Cost Pass-Through to Energy Prices
Authors: Gullì Francesco , Chernyavs’ka Liliya
Published: October 2013

Simulation models of emissions trading performance are generally based on the assumption that carbon prices are fully (or almost fully) passed through to energy prices (with pass-through rates equal or very close to one). Unfortunately, empirical analyses of wholesale electricity spot markets do not confirm this simple rule. Pass-through rates can be much lower or much higher than one and can sharply vary over time or across countries and markets. In several cases, such rates are not significantly different from zero and can even be negative. Until now, only a few authors have tried to offer a theoretical justification for the divergence between the assumptions used in simulation models and the results of empirical evidence. The main finding of these theoretical studies is that, when the characteristics of specific energy markets (e.g., organization, vertical and horizontal structure, technology mix, firms’ strategies) are adequately taken into account, the existence and degree of imperfect competition can explain why pass-through rates can vary widely and can even assume negative values. Therefore, if the models carried out to estimate the performance and costs of environmental policies are used to support policy decisions, ignoring the role of imperfect competition and the characteristics of energy markets may induce significant distortions in estimations of the impact of public action and may lead to incorrect policy calibration.
Development of Microtubular SOFCs for Portable Power Sources
Authors: Sumi Hirofumi , Yamaguchi Toshiaki , Hamamoto Koichi , Suzuki Toshio , Fujishiro Yoshinobu
Published: October 2013

Microtubular SOFCs with a diameter on the millimeter scale are suitable for portable power sources due to rapid start-up characteristics. The performance of conventional Ni-stabilized zirconia anodes deteriorated rapidly over a period of 3-4 h at 610 oC and a low steam/carbon (S/C) ratio of 0.044 in butane due to a large amount of carbon deposition. For the Ni-Gd doped ceria (Ni-GDC) anode, the electric power could be generated continuously for more than 24 h at 610 oC and S/C = 0.044 in butane. We manufactured and demonstrated a prototype portable SOFC system using a microtubular cell-stack. It can heat up to 400 oC within 2 min by burning an external LPG burner, and drive a USB device for 24 h continuously using a LPG cartridge (250 g; 3.2 kWh). This development has shown the potential of the microtubular SOFC system as portable power sources in disaster and emergency situations, for outdoor use, and for small-scale electric vehicles.
Evolved Materials and Innovative Design for High Performance, Durable and Reliable SOFC Cell and Stack Presentation and Status of the European Project EVOLVE
Authors: Costa Rémi , Ansar Asif
Published: October 2013

Beyond the state of the art, EVOLVE aims at the development of a new cell architecture for SOFC, combining benefits of existing Anode Supported (high power density, lifetime) and Metal Supported cell (redox stability) architectures, while limiting the issue of sulphur poisoning by using enhanced perovskite anode materials. The core component is based on a composite anode substrate made of porous Alumina forming alloy combined with an electron conducting oxide ceramic, without having Nickel as structural component. A first Anode/Electrolyte assembly based on a NiCrAl foam and La0,1Sr0,9TiO3-α
has been produced by means of Vacuum Plasma Spraying, showing the feasibility of this cell concept. With a requirement of a low temperature process, the manufacturing of the electrolyte layer remains the key challenge. Work is under progress for the manufacturing and testing of the first full prototype.
Local Activation and Degradation of Electrochemical Processes in a SOFC
Authors: Wuillemin Zacharie , Antonetti Yannik , Beetschen Cédric , Millioud Olivier , Ceschini Sergio , Madi Hossein , Van herle Jan
Published: October 2013

The local electrochemistry is studied in a SOFC repeat-element using a test setup that allows a local control of the polarization. During long-term tests, the local current densities evolve, following activation and degradation periods. Electrochemical impedance spectroscopy (EIS) measurements performed at regular intervals are used to analyze the activation and degradation of the individual electrochemical processes. By computing the distribution of relaxation times (DRT) from the EIS spectra, a total of 6 electrochemical processes are revealed and their evolution studied separately. It is found that not only the activation/degradation rates but also their spatial evolution are strongly influenced by the choice of materials and by the operating conditions. In particular, the degradation of the anode propagates over the active area with important local differences, and in a wave-like manner that differs from one test to the other. Results are presented and analyzed for several long-term tests operated with hydrogen or steam-reformed methane as fuel.
Chromium Poisoning of La2NiO4+δ Cathodes
Authors: Lee Soo-Na , Atkinson Alan , Kilner John A.
Published: October 2013

It has been reported that Sr-containing materials (such as LSCF) are susceptible to Cr-poisoning by the formation of SrCrO4 and therefore there is interest in Sr-free cathodes such as La2NiO4+δ (LNO). In this study, La2NiO4+δ electrodes were deposited symmetrically onto Ce0.9Gd0.1O1.95 electrolytes by screen printing. The LNO electrodes were solution impregnated with targeted amounts of chromium and then characterised by impedance spectroscopy (520- 800°C). XRD of LNO/Cr2O3 powder mixtures annealed at 900°C showed that there is a reaction between them. Nevertheless, the impedance results indicate that LNO is less prone to chromium deactivation than LSCF.
The Effect of Ferroelasticity of La1-X
Sr
x
Co1-Y
Fe
y
O3-δ

on the Mechanical Stability of Solid Oxide Fuel Cells
Authors: Kimura Yuta , Tolchard Julian , Einarsrud Mari-Ann , Grande Tor , Amezawa Koji , Hashimoto Shin-ichi , Kawada Tatsuya
Published: October 2013

The stress-strain relationships of La0.6Sr0.4CoO3-δ
(LSC), La0.6Sr0.4Co0.2Fe0.8O3-δ
(LSCF6428) and La0.6Sr0.4FeO3-δ
(LSF) was evaluated by uniaxial compression tests in the temperature range between room temperature and 1173 K. A nonlinear stress-strain relationship with a residual strain was observed below the phase transition temperature, while an almost linear relationship with no residual strain was observed above the phase transition temperature. Cyclic tests revealed that the width of the hysteresis in the 2nd cycle was much smaller compared with that of the 1st cycle at room temperature. On the other hand, the difference in the stress-strain relationship and the effective compliance was hardly observed at 873 K. This result suggests that the apparent Young’s modulus of the rhombohedral LSCF depends on the applied stress and the mechanical history due to ferroelasticity. Thus, the stress distribution in SOFCs can be affected by the ferroelasticity of LSCF.
Investigation of Cu-Based Infiltration Coatings for Metal-Supported SOFC
Authors: Blennow Peter , Sudireddy Bhaskar Reddy , Persson Åsa Helen , Nielsen Jimmi , Sachitanand Rakshith Nugehalli , Froitzheim Jan
Published: October 2013

Metal-supported solid oxide fuel cells are candidates for the next generation of SOFCs. However, the cell design with an FeCr/YSZ-based anode backbone suffers from corrosion when the cells are run at high fuel utilization, which limits the long term durability. In this work, new infiltration coatings based on Cu in combination with Ni:Ce0.8Gd0.2O1.9 (Ni:CGO) have been studied. The candidates for a corrosion resistant coating should limit the formation of Cr2O3 on the surface of FeCr particles. Promising fuel cell performance with an ASR of 0.5 Ωcm2 was obtained at 650 ºC with H2 as fuel. However, various analysis techniques showed no improved corrosion resistance with the addition of a Cu coating.
Flow Channel Configurations of an Anode-Supported Honeycomb Solid Oxide Fuel Cell
Authors: Kotake Shota , Nakajima Hironori , Kitahara Tatsumi
Published: October 2013

An anode-supported honeycomb SOFC can achieve high power density and improve thermo-mechanical durability at high temperatures. We have fabricated the honeycomb cell with an electrolyte layer of 8YSZ on an anode honeycomb substrate of Ni/8YSZ. The cathode layer is LSM-YSZ composite. Current-voltage and current-power density characteristics of the cells having different anode and cathode flow channel configurations are measured under different hydrogen flow rates and partial pressures. We also evaluate the hydrogen mole fraction distributions in the honeycomb cell using finite element method, and discuss appropriate anode and cathode flow channel configurations.
Improvement of Cell Performance and Stability by Optimizing Microstructure of Cathode Contact Materials for Planar-Type SOFC
Authors: Duan Jianbin , Yan Dong , Pu Jian , Chi Bo , Li Jian
Published: October 2013

The cell testing was performed to investigate the performance and degradation of single cell stack that is related to the cathode contact materials of solid oxide fuel cells (SOFCs). Two different particle size of perovskite LCN (LaCo0.6Ni0.4O3-δ) were used as cathode current collectors. When compared with the thin LCN powders, the coarse powders showed that the materials are appropriate for long-term stability of cell, whereby the cell exhibited almost undetectable degradation over 100h. The degradation mechanism has been further investigated on the electrical contact between cathode current collection/metallic interconnect. The microstructure stability of LCN powder was proved to play critical roles in depressing degradation of SOFC stack.
Nanostructure Electrodes for Metal-Supported Solid Oxide Fuel Cells
Authors: Zhan Zhongliang , Zhou Yucun , Wang Shaorong , Liu Xuejiao , Meng Xie , Wen Tinglian
Published: October 2013

Metal-supported solid oxide fuel cells (MS-SOFCs) use thick porous alloy substrates as the mechanical supports for thin functional anode-electrolyte-cathode layers and have gained increasing interest due to their advantages over the traditional all-ceramic counterparts such as increased structural robustness, improved tolerance toward rapid thermal cycling, simplified stack assembling and reduced materials costs as well. However, issues such as coarsening of the active nickel anode catalysts, metalic interdiffusion between the alloy substrates and the anodes, and application of appropriate cathode layers remain to be addressed. Here we report some of recent progress in nano-scale electrode catalysts for MS-SOFCs using the liquid phase impregnation technique.
Micro-Protonic Ceramic Fuel Cells with Y:BaZrO3 Electrolyte Prepared by Pulsed Laser Deposition (PLD)
Authors: Bae Kiho , Jang Dong Young , Jung Hojean , Kim Jun Woo , Son Ji-Won , Shim Joon Hyung
Published: October 2013

BaZr0.85Y0.15O3-ä (BZY) thin film was prepared by pulsed laser deposition (PLD) at of 400oC and 700oC and performance was compared as free-standing electrolyte of micro ceramic fuel cells. Structural and electrochemical analyses were conducted using scanning electron microscopy (SEM) and a customized fuel cell measurement set-up, respectively. As a result, we have identified that chemical stability of PLD BZY deposited at 700oC (PLD BZY-700) was improved showing stable open circuit voltage (OCV) close to 0.9V compared to one made at 400oC (PLD BZY-400). Fully densified structure was identified in PLD BZY-700 with clear separation of electrodes.
Ultimate Performance of Anode-Supported SOFC by Realizing Thin-Film Electrolyte and Nano-Structure Electrode
Authors: Noh Ho-Sung , Yoon Kyung Joong , Kim Byung-Kook , Je Hae-June , Lee Hae-Weon , Lee Jong-Ho , Son Ji-Won
Published: October 2013

Thin-film electrolytes and nano-structure electrodes are essential components to lower the operation temperature of SOFCs. We will discuss how to precisely assess the impact of the thin-film electrolyte and the nano-structure electrodes which are realized on the anode supports, a realistic SOFC platform (anode-supported TF-SOFC). A peak power density over 500 mWcm-2 at 500 oC is obtained, which we believe is nearing the highest level that the SOFC can reach while using the common SOFC materials and platforms, by changing the dimension of the cell components. The potential and limitations of anode-supported TF-SOFCs in achieving the critical low-temperature performance will be discussed.
YSZ Films Prepared by Reactive Magnetron Sputtering: Effect of the Thickness on the Electrical Properties
Authors: Briois Pascal , Yu Li , Arab Pour Yazdi Mohammad , Georges Samuel , Billard Alain
Published: October 2013

Lowering the SOFC operating temperature is a major challenge. Using conventional electrolyte materials, a solution consists in preparing thin layers to limit the ohmic losses. The coatings are synthesized by sputtering a metallic Zr-16 at%Y target in the presence of a reactive argon-oxygen discharge. The deposition stage is controlled by Plasma Emission Monitoring in order to guarantee a high sputtering rate. The influence of the thickness on the electrical properties is determined by impedance spectroscopy.
Characterizations of Co-Ionic Neodymium-Doped Ceria/Carbonate Composite Electrolytes
Authors: Kim Ji-Tae , Baek Seung-Seok , Lee Tae-Hee , Song Sun-Ju , Park Jun-Young
Published: October 2013

Neodymium-doped ceria (Nd0.2Ce0.8O1.9, NDC)-based composite electrolytes with (Li/0.5Na)2CO3 have a higher conductivity than pure NDC in the intermediate temperature range (500-700°C). This may be attributed to protons that contributes to an improvement in the ionic conductivity across grain boundaries or phase interfaces, thereby providing conduction pathways between NDC and the carbonate material (interfacial super ionic conduction mechanism). In this research, the fundamental properties of the composite materials are characterized by a variety of experimental methods such as XRD, SEM, TEM, and TG-DSC. First, it is confirmed by XRD that the fluorite structure of ceria is maintained in the composite materials. Carbonates, which exist in form of an amorphous phase, as well as NDC particles, which have a cubic fluorite structure, are identified by SEM and TEM. A thermal analysis by TG-DSC is performed to determine the temperature at which the binary eutectic of (Li/Na)-carbonate is formed. Electrical conductivities of composite electrolytes are also analyzed by EIS at 250-650 °C in air atmosphere.
Performance of Atomic-Layer-Deposited Yttria-Stabilized Zirconia Near Room Temperature
Authors: Jang Dong Young , Kim Hokeun , Bae Kiho , Schlupp Meike V.F , Prestat Michel , Shim Joon Hyung
Published: October 2013

The ionic impedance of atomic-layer-deposited yttria-stabilized zirconia thin films was measured in the cross-plane direction in the range 80–300°C. The microstructure of the films was also analyzed using transmission electron microscopy in the high- resolution and scanning modes, and the electrical performance of the films was found to be related to their structural characteristics. We found that the ionic impedance of the films near room temperature was lower than that measured at elevated temperatures, presumably because of proton conduction along the surface of the nanopores in the films.
Long Annealing Effect on Stabilities for Electrical Conductivity of (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 Electrolyte at IT-SOFC Operating Temperature
Authors: Mori Masashi , Itoh Takanori
Published: October 2013

Long annealing effect on electrical conductivity and chemical stability of (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 fluorite has been studied in the temperature range between 600°C and 800°C. The conductivities of the impervious samples before annealing were 8.51×10-3 S/cm at 600°C and 1.16×10-1 S/cm at 800°C. The conductivity at 600°C had a tendency to increase with annealing time and the conductive value increased to be 1.47 ×10-2 S/cm after 1000 h. On the other hand, the conductivity at 800°C decreased and was 6.34 ×10-2 S/cm after 1000 h. From the results of synchrotron X-ray diffraction analysis, the peaks of CeO2 were observed for the samples after annealing at 500 h and increased with the time. The release of CeO2 in the ZrO2-based fluorite should be related to the change of the conductivity during the annealing treatment.
Characterization of Doped Ceria Films as SOFC Electrolyte Prepared by Using Ultrasonic Spray Pyrolysis Method
Authors: Vestli Mihkel , Maide Martin , Nurk Gunnar , Lust Enn
Published: October 2013

Terbium and samarium co-doped ceria was studied as electrolyte membrane for intermediate temperature solid oxide fuel cell single cells. The ceramic doped ceria powders with different composition like Ce0.9Sm0.1O2-
δ and Ce0.9SmxTbyO2-
δ were synthesized using glycine-nitrate thermal decomposition process and the films were deposited using ultrasonic spray pyrolysis method. The samples were characterized using XRD, SEM, AFM and impedance methods. The conductivity measurements of the disk like samples were conducted at different temperatures and gas environments.
Full Ceramic Fuel Cells Based on Strontium Titanate Anodes, an Approach towards More Robust SOFCs
Authors: Holtappels Peter , Irvine John T. S. , Iwanschitz Boris , Kuhn Luise Theil , Lu Lanying , Ma Qianli , Malzbender Jürgen , Mai Andreas , Ramos Tânia , Rass-Hansen Jeppe , Sudireddy Bhaskar Reddy , Tietz Frank , Vasechko Viacheslav , Veltzé Sune , Verbraeken Maarten
Published: October 2013

The persistent problems with Ni-YSZ cermet based SOFCs, with respect to redox stability and tolerance towards sulfur has stimulated the development of a full ceramic cell based on strontium titanate(ST)- based anodes and anode support materials, within the EU FCH JU project SCOTAS-SOFC. Three different compositions (La, Y and Nb substituted ST) have been developed as anode backbones for either 25 cm2 or larger than 100 cm2 cell areas. Cell performances, once infiltrated with suitable electro catalysts, exhibited a maximum power density of 0.5 W/cm2 at 850 °C. While the ST based backbone remains intact and tolerant to redox cycles, cell performance degradation appears linked to the infiltrated electro catalysts. The materials have also been assessed with respect to their electrical and mechanical properties, in order to further evaluate their potential use as anode and anode support layers in SOFCs.
Effects of Metal Additives on Power Generating Property of Direct Hydrocarbon Type SOFC Using LaGaO3 Electrolyte
Authors: Ishihara Tatsumi , Shin Tae Ho , Ida Shintaro
Published: October 2013

Composite oxides have been attracting great interest recently as alternative materials for SOFC anodes with the potential to overcome the serious deterioration in performance associated with the traditional Ni-based cermet; in particular, oxide based anodes show enhanced carbon coke and re-oxidation tolerance compared to present Ni-based cermets. In this study, the anodic performance of a (Ce,Mn,Fe)O2/(La,Sr)(Fe,Mn)O3 composite oxide with additions of catalytically active RuO2 nano particle was studied. Fairly high maximum power densities of 0.3 Wcm-2 (in H2) and 1.5 Wcm-2 (in C3H8) at 800 oC were achieved for anodes with 10 wt% RuO2 addition. The cells showed stable power density, and negligible carbon formation, even after operation for more than 50 h at 1Acm-2. The improved power density was explained by decreased anodic overpotential and IR losses because of the improved electrical conductivity contributed by the RuO2 particles.
Development of Redox Resistant Infiltrated Tubular SOFCs
Authors: Hanifi Amir Reza , Chen Xueyuan , Seens Joshua , Sarkar Partha , Etsell Thomas H.
Published: October 2013

The electrochemical performance of two infiltrated fuel cells and the redox cycling tolerance of such cells are presented. Ni-SDC was infiltrated into a porous YSZ support to form the anode of the infiltrated cells and LSM or Nd-nickelate was infiltrated into a thin porous YSZ layer to form the cathode. The power density of the Nd-nickelate infiltrated cell is higher than that of the LSM infiltrated cell suggesting it as a suitable cathode for intermediate temperature applications. The microstructure of these infiltrated fuel cells shows a reasonable distribution of fine particles (50-100 nm) near the interface of electrodes and electrolyte and within the bulk electrodes. Despite having much lower Ni content than conventional anode supported cells, the infiltrated fuel cells exhibit a reasonable power density at low temperatures and an excellent robustness against redox cycling.
In Situ Spectroscopic Studies of Carbon Formation in SOFCs Operating with Syn-gas
Authors: McIntyre Melissa D. , Kirtley John D. , Halat David M. , Reeping Kyle W. , Walker Robert A.
Published: October 2013

Vibrational Raman spectroscopy has been used to measure the rate and extent of carbon formation in SOFCs operating with CO/H2 mixtures at 675¢ªC. The SOFCs consist of commercial Ni/YSZ anode supported assemblies. Raman data show that carbon forms readily on anodes held at OCV and that the carbon deposits consist of highly ordered graphite as evidenced by a single band at 1561 cm-1. Polarizing the SOFC limits the amount of carbon that forms. At currents approaching 75% Imax, where Imax corresponds to a 0.0V potential difference between the cathode and anode, observed carbon formation is completely suppressed. Interestingly, voltammetry data from these anode supported assemblies are unstable until small amounts of carbon form. This correlation between carbon formation observed in situ and electrochemical performance raises interesting questions about the role played by carbon in charge transfer processes and current collection in functioning devices.
Core-Shell Structured Sr0.88Y0.08TiO3-Ce0.8Sm0.2O1.9 Composite as an Anode for Solid Oxide Fuel Cells Operating with CH4
Authors: Yang Wei , Ma Zhaohui , Sun Chunwen , Chen Liquan
Published: October 2013

A porous Sr0.88Y0.08TiO3 (YST)-Ce0.8Sm0.2O1.9 (SDC) composite with a core/shell structure has been prepared with a sol-gel method and evaluated as an alternative anode for solid oxide fuel cells. The single cells were studied with a YST-SDC anode screened on a 300um LSGM electrolyte and a composite cathode consisting of Sr0.90Ce0.10CoO3-
d-SDC (30wt%). When CH4 was used as fuel, the peak power density of the single cell reached about 150 mW cm-2 at 900oC. This anode material showed good stability, without obvious degradation after operating in CH4 more than 10 hours. The preliminary results demonstrate that YST coated SDC composite is a promising alternative anode in solid oxide fuel cells with hydrocarbon fuels.
Structural Changes of Ni/YSZ Cermet for Solid Oxide Fuel Cells in Hydrocarbon Gas Containing Atmospheres
Authors: Nakamura Takashi , Ohmura Nobuyuki , Yahiro Keiji , Amezawa Koji
Published: October 2013

Macroscopic and microscopic structural changes of Ni/YSZ cermets in CH4, C2H6, and C3H8 containing atmosphere at 1073 K were evaluated by dilatometry and SEM observation. Carbon deposition was observed in low-humidified hydrocarbon atmospheres, accompanying significant expansion of the cermet. SEM observation of the cross section revealed that carbon deposition took place preferentially near the surface and Ni particles seemed to be surrounded by the deposited carbon. The expansion due to carbon deposition did not depend on the kind of hydrocarbon but on the amount of supplied carbon. On the other hand, in high-humidified hydrocarbon atmospheres, e.g. S/C ≥ 1, no carbon deposition and expansion were observed.
Comparative Study on Performance Stability of Ni–Oxide Cermet Anodes under Humidified Atmospheres in Solid Oxide Fuel Cells
Authors: Muroyama Hiroki , Kishida Ryo , Matsui Toshiaki , Eguchi Koichi
Published: October 2013

The influence of the oxide component in Ni–oxide based cermet anodes on the performance stability was examined at 1000°C with a supply of highly humidified hydrogen, 40% H2O–60% H2. Three types of anodes were applied; Ni–samaria-doped ceria (Ni–SDC), Ni–yttria-stabilized zirconia (Ni–YSZ), and Ni–scandia-stabilized zirconia (Ni–ScSZ). Abrupt deterioration in performance was confirmed during constant current operation for the cells with Ni–YSZ and Ni–ScSZ anodes, accompanied with a drastic increase in ohmic resistance between the anode and reference electrode. In contrast, the performance of cell with Ni–SDC anode was pretty stable for 48 h. These differences in performance stability were significantly related to the local partial pressure of steam in the vicinity of the electrochemically active sites because the surface oxidation of nickel particles resulted in the deterioration. The microstructural changes in Ni–YSZ and Ni–SDC anodes upon discharge were also quantified by the dual–beam focused ion beam–scanning electron microscopy (FIB–SEM). The electrochemical behavior observed in each anode had a strong correlation with the anode microstructure such as triple phase boundary length and nickel particle size.
The Effect of Coexisting Oxides Upon Carbon Formation on Ni Surface
Authors: Shindo Taiki , Watanabe Satoshi , Hashimoto Shin-ichi , Yashiro Keiji , Kawada Tatsuya , Taniguchi Takaaki , Kudo Takao , Sato Yasushi
Published: October 2013

Carbon deposition on Ni anode support causes degradation of cell performance. Using an additive is one of possible solutions to suppress carbon deposition on Ni. In this study, the substrate effect for carbon formation was investigated at 1073 K under CH4/H2O/ Ar (S/C = 0.087) using Ni particles dispersed substrate oxides (8YSZ, SrZr0.95Y0.05O3-δ
, Ce0.9Gd0.1O1.95-δ
, Y2O3, TiO2, CeO2). Independent of the substrate oxides, uniform mm-sized Ni particles were successfully dispersed on the substrate oxides by heat treatment of Ni thin film under the reducing atmospheres. The Ni surfaces after carbon deposition were observed with FE-SEM. As the results of Ni surface texture observation, the order of suppressive effect for carbon deposition can be estimated qualitatively as follows, CeO2, TiO2 > SrZr0.95Y0.05O3-δ
, Ce0.9Gd0.1O1.95-δ
> 8YSZ, Y2O3.
Highlights on the Anisotropic Oxygen Transport Properties of Nickelates with K2NiF4-Type Structure: Links with the Electrochemical Properties of the Corresponding IT-SOFC’s Cathodes
Authors: Bassat Jean-Marc , Burriel Monica , Ceretti Monica , Veber Philippe , Grenier Jean-Claude , Paulus Werner , Kilner John A.
Published: October 2013

Understanding fundamental aspects of oxygen self-diffusion in MIEC materials is crucial for the discovery of next-generation of cathode materials. Perovskite-type oxides are the most studied material, the oxide ion diffusion being based on the vacancy migration in a cubic-like disordered network. According to results of predictive atomistic simulations, a current trend concerns experimental works related to perovskite-derived phases with anisotropic structures where oxide ion transport is no longer based on oxygen vacancies but on oxygen interstitials. Then a particular attention is here paid to the nickelates Ln2NiO4+δ, Ln=La, Nd, Pr, with the orthorhombic K2NiF4-type structure characterized by a high c/a lattice parameters ratio. We have completed our previous work performed on single crystals and thin films aiming at experimentally determining the oxygen diffusion and surface exchange coefficients using the so-called IEDP method, as a function of the crystallographic orientation as well as the rare-earth cation. Highly anisotropic oxygen diffusion properties have been evidenced and the activation energies have been compared. Moreover, the electrochemical performances (polarization resistance measurements) of the corresponding porous cathode materials were previously determined in the literature in the same T-range, using symmetrical half cells including YSZ as electrolyte. The results are discussed with regards to the oxygen diffusion properties of the electrodes.
Boron Poisoning of (La, Sr)(Co, Fe)O3 Cathodes of Solid Oxide Fuel Cells
Authors: Chen Kongfa , Hyodo Junji , Zhao Ling , Ai Na , Ishihara Tatsumi , Jiang San Ping
Published: October 2013

Effect of volatile boron species on the properties of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode materials has been studied in detail by using porous electrode coatings and dense bar samples. Prior to the characterization, the LSCF samples were heat-treated at 800oC in air in the presence of borosilicate glass for 7 and 30 days. Heat-treatment in the presence of glass has a significant detrimental effect on the surface exchange rate, electrical properties, and electrochemical activity of the cathodes. Secondary ion mass spectroscopy (SIMS) detected the deposition of boron as well as sodium and potassium on the surface and in the bulk of the bar samples. The boron deposition results in significant microstructure and composition changes. Sr in the form of SrB2O4 is enriched on the outmost surface of LSCF bar samples, leading to the Sr-deficient in the adjacent layer in the bulk. The present study demonstrates the remarkable detrimental effect of volatile boron species on the microstructure and electrochemical activity degradation of the LSCF cathode materials of solid oxide fuel cells.
An SOFC Cathode Infiltrated with Pr6O11
Authors: Chiba Reiichi , Aono Hiroki , Kato Kiyotaka
Published: October 2013

We fabricated single cells with an 8YSZ electrolyte, a Pt anode, a spin-coated Ce0.8Sm0.2O1.9 (SDC) cathode buffer layer and a LaNi0.6Fe0.4O3 (LNF) cathode infiltrated with mixed conductor of Pr6O11. The cathode performance was investigated by the ac impedance method at 800oC. The initial interface resistance of the Pr6O11 infiltrated cathode was reduced to about one seventeenth of that without the infiltration. The interface resistance increased slightly with 106 mA/cm2 current loading. It increased faster and constantly at 354 mA/cm2. The annealing temperature dependence of the crystallization and grain growth of the spin-coated Pr6O11 films was also investigated.
Optimization of Transport Properties of A-Site Ordered LnBa1-xSrxCo2-yFeyO5+δ Perovskite-Type Cathode Materials
Authors: Świerczek Konrad , Zheng Kun , Klimkowicz Alicja
Published: October 2013

Choice of an appropriate chemical composition in a group of A-site ordered LnBa1-xSrxCo2-xFexO5+δ (Ln - selected lanthanides, Y) oxides may allow to obtain novel, potential cathode materials for IT-SOFC having desirable physicochemical properties, which can surpass those of typical Ln1-xSrxCo1-yFeyO3-δ perovskites. Layered ordering in A sublattice (Ln-Ba1-xSrx), resulting from a significant difference between ionic radii, is observed for compounds having smaller Ln cations, even for a substantial substitution of Ba by Sr. Materials with a high Co content exhibit very high mixed ionic-electronic conductivity and substantial deviation from oxygen stoichiometry, while increase of Fe content improves stability and decreases thermal expansion. The observed relationship between structural properties, oxygen nonstoichiometry and transport properties is discussed.
Long-Term Stability of LSM-YSZ Based Cathodes
Authors: Baqué Laura Cecilia , Jørgensen Peter Stanley , Hansen Karin Vels , Søgaard Martin
Published: October 2013

A transmission line based model was successfully applied to study the ageing effect in LSM-YSZ cathodes after being exposed to humidified air at 900 °C for up to 3000 h. A decrease in the YSZ conductivity was correlated with the formation of the less conducting monoclinic zirconia. The amount of La2Zr2O7, present in the non-aged samples, decreases with ageing time increasing the number of active sites for charge transfer between LSM and YSZ as well as the LSM conductivity values.
Electronic Structures of LaCoO3-Based Oxides Studied by Soft X-ray Absorption Spectroscopy under Controlled Temperatures and Oxygen Partial Pressures
Authors: Oike Ryo , Amezawa Koji , Tamenori Yusuke , Yashiro Keiji , Nakamura Takashi , Kawada Tatsuya
Published: October 2013

In situ soft X-ray absorption spectroscopic measurements were performed to evaluate electronic structures of LaCoO3. X-ray absorption spectra at Co L
II- and L
III-edges were measured under p(O2) = 10-4 bar at room temperature to 873 K. Depending on temperature, the shape and the peak energy of the absorption spectra were varied, indicating thermally induced spin state transition of Co3+ ion. The results demonstrated that our in situ soft X-ray absorption technique is an useful tool to investigate the electronic structures of components for solid oxide fuel cells under operating conditions.
Electrochemical Analysis of Nanoscaled Ba0.5Sr0.5Co0.8Fe0.2O3-δ Thin-Film Cathodes
Authors: Asano Koichi , Klotz Dino , Hayd Jan , Szász Julian , Ivers-Tiffée Ellen
Published: October 2013

Nanoscaled Ba0.5Sr0.5Co0.8Fe0.2O3-δ thin-film cathodes deposited by spin-coating followed by pyrolysis of the metal organic precursors (the metal organic deposition [MOD] process) with a film thickness below 100 nm on Ce0.9Gd0.1O1.95 electrolyte pellets were investigated with a focus on the cathode reaction processes. Electrochemical impedance spectroscopy was carried out under systematic variation of the temperature (T = 500–625 °C) and oxygen partial pressure (pO2 = 0.01–0.5 atm). The impedance data were then analyzed by calculating the distribution of relaxation times (DRT) and performing complex nonlinear least squares (CNLS) fitting. Five processes were identified in the cathode reaction. Area specific polarization resistances as low as ASRpol = 39 mΩ cm2 at 600 °C were found.
Mixed Nickelates Pr2-XLaxNiO4+
δ Used as Cathodes in Metal Supported SOFCs
Authors: Vibhu Vaibhav , Rougier Aline , Grenier Jean-Claude , Bassat Jean-Marc
Published: October 2013

The third generation of IT-SOFCs concerns the metal supported cells. With respect to the sintering conditions of the complete cell, a current challenge is the chemical stability of the components, more especially the cathode, under low pO2 (e.g. under N2, pO2 ≈ 10-4 atm). In this scope, the properties of the mixed rare earth nickelates formulated Pr2-xLaxNiO4+δ have been studied; indeed Pr2NiO4+δ is a very promising material in terms of electrochemical properties while La2NiO4+δ exhibits a higher chemical stability. The aim of this study is to find the best compromise between both characteristics. The properties of mixed phases were found intermediate between those of Pr2NiO4+δ and La2NiO4+δ.
First-Principles Study of the Lattice Strain Effects on the Ionic Migration Barrier of Sm-Doped Ceria
Authors: Alaydrus Musa , Sakaue Mamoru , Aspera Susan Meñez , Wungu Triati Dewi Kencana , Linh Tran P. T. , Kasai Hideaki , Ishihara Tatsumi
Published: October 2013

Recent experiments on thin films and hetero-structures of ionically conducting oxides have indicated to an enhancement of oxygen ion conduction typically ascribed to strain-related effects. We performed first-principles calculations to investigate the effects of biaxial lattice strain on the oxygen anion diffusivity in Sm2O3 doped CeO2 (SDC). The oxygen ion migration paths and barriers in SDC as functions of lattice strain were assessed computationally using density functional theory (DFT) with U correction and climbing image nudged elastic band (CI-NEB) method. Our current results indicate that both expansive and compressive strains lead to decreases in the ionic migration barriers.
Investigations on the Structural and Electronic Properties of Pure and Doped Bulk Pr2NiO4 through First Principles Calculations
Authors: Aspera Susan Meñez , Sakaue Mamoru , Alaydrus Musa , Wungu Triati Dewi Kencana , Linh T. P. T. , Kasai Hideaki , Ishihara Tatsumi
Published: October 2013

Pr2NiO4-based ceramic oxides are known promising MIEC cathodes material for SOFC, owing to its experimentally found good ionic and electronic conductivity compared with other known materials. In this study, the structural and electronic properties of pure and doped Pr2NiO4-based oxides are investigated through first principles calculations based on density functional theory (DFT) in an attempt to investigate the possibility of using this material as an SOFC electrolyte. Substitutional doping at the cation site [Pr2-yRyNi1-x-y-zExTzO4 (R=La, and E=Cu and T=Ga)] shows change in both structural and electronic properties. Higher concentration of La doping increases the lattice parameter along the c direction while maintaining the electronic property of the host system. On the other hand, Cu doping causes tilting of the nickelate octahedral substructures so as to stabilize the whole structure but accompanies emergence of states which can contribute to electronic conduction. However, Ga doping has indications of high O ion diffusion and lower electronic conductivity