bluuebunny/crossref_metadata_2025 huggingface dataset:
Material Stability and Cation Transport of La0.6Sr0.4Co0.2Fe0.8O3-δ in SOFC Cathodic Conditions
Authors: Oh Miyoung , Unemoto Atsushi , Amezawa Koji , Kawada Tatsuya
Published: April 2011

Material stability and cation transport of La0.6Sr0.4Co0.2Fe0.8O3-δ were investigated by long-term annealing of the sintered pellets with and without applying oxygen potential gradients. The heat treatments at 1073 - 1273 K under uniform p(O2) of 1.0 x 10-4 - 0.21 bar for one week did not make any notable changes on the pellets. However, significant changes were observed when the pellets were placed under oxygen potential gradient between 1.0 bar oxygen and diluted oxygen (1.0 x 10-4 - 1.0 x 10-1 bar of p(O2)). On the high p(O2) side, many particles of cobalt and strontium oxide were found on the surface at 1273 K. The amount of the deposited particles increased with decreasing oxygen potential on the opposite side and/or increasing temperature. The results indicated that the cobalt and strontium ions are faster than the other cations and the cobalt ions are fastest among the cations involved in the LSCF.
Electrode and Electrolyte Layers for Solid Oxide Fuel Cells Applied by Physical Vapor Deposition (PVD)
Authors: Uhlenbruck Sven , Nédélec Ronan , Sebold Doris , Buchkremer Hans Peter , Stöver Detlev
Published: April 2011

Physical vapor deposition (PVD) technologies allow for a variety of microstructural morphologies. PVD is especially qualified for the production of dense ceramic layers at comparatively moderate substrate temperatures. This paper discusses the physical vapor deposition of SOFC functional layers, comprising perovskites, NiO/8YSZ and composite electrolyte layers, with a thickness between 300 nanometres and several micrometres and lateral dimensions of 100 mm⋅100 mm. Magnetron sputtering and electron beam evaporation were used as PVD techniques, with and without additional ion bombardment of the layers during deposition. Scanning electron microscopy analysis revealed that an additional ion bombardment during layer growth increasingly promotes the creation of a continuous and dense layer morphology instead of a columnar microstructure.
Fabrication and Characterization of La0.6Sr0.4Co0.2Fe0.8O3-δ-Yttria Stabilized Zirconia Composites Cathode Prepared by Infiltration Method
Authors: Han Min Fang , Liu Ze , Qian Jin
Published: April 2011

Composite cathodes of yttria stabilized zirconia (YSZ) with Sr-, Co- doped LaFeO3 (LSCF) are prepared by infiltration of a porous YSZ matrix with different weight of aqueous solutions of the stoichiometric metal salts, followed by firing at various temperatures. X-ray diffraction measurements show that the LSCF perovskite phase had formed at 800-900oC and that solid-state reaction with the YSZ does not occur below approximately 950 oC. Various contents of LSCF from 15wt.% to 60wt.% are loaded in porous YSZ of anode supported cell (porous YSZ||YSZ||NiO-YSZ). The cell with 45wt.% LSCF exhibits better performance and lower interfacial resistance. The cell performance of LSCF fired at 850oC is better than that of LSCF fired at 800 and 900oC. The peak power densities of YSZ anode supported cell with 45 wt.% LSCF fired at 850oC are about 640, 869, and 972mWcm-2 at 700, 750, and 800oC, respectively. The infiltrated LSCF cathode displays high catalytic activity and performance for the unique nano film coating fabricated with certain content at low temperature.
Investigation of the Particle Size Change of a La(Ni, Fe)O3 as a Cathode
Authors: Yoshida Yoshiteru , Chiba Reiichi , Komatsu T. , Yokoo Masayuki , Hayashi Katsuya , Orui Himeko , Arai Hajime
Published: April 2011

We have been investigating an La (Ni, Fe)O3 as a cathode. The particle size changes were analyzed by SEM before and after durability test for 1,000 h, and 10,000h. We found that little change was observed between before and after the durability test even after 10,000h operation. It was also appeared that Cr species around the electrolyte were not observed after 10,000h operation by EPMA. We described the detail of the result of the particle size changes and the distribution of the Cr species in this paper.
Simple Infiltrated Microstructure Polarization Loss Estimation (SIMPLE) Model Predictions of Today and Tomorrow's Nano-Composite SOFC Cathodes
Authors: Wang Lin , Nicholas Jason D.
Published: April 2011

The Simple Infiltrated Polarization Loss Estimation (SIMPLE) model was used to predict the performance of a variety of mixed ionic electron conductor (MIEC) - ion conductor (IC) Solid Oxide Fuel Cell (SOFC) nano-composite cathodes. These predictions agree with the reported values to within 70% or better (without the use of fitting parameters) at all temperatures. Systematic SIMPLE model variation of typical nano-composite cathode geometrical parameters reveals little change in cathode performance with cathode thickness and/or porosity above a critical cathode thickness. Further, SIMPLE modeling suggests that conventionally structured nano-composite cathodes with MIEC surface resistances 10 times lower than Sm0.5Sr0.5CoO3-x (SSC) and ionic conductivities 10 times higher than Ce0.9Gd0.1O1.95 (GDC) could achieve polarization resistances of 0.1 Ωcm2 at ~450oC. Likewise, conventionally structured cathodes with 100 times and 1000 times better materials than SSC and GDC could achieve polarization resistances of 0.1 Ωcm2 at ~375oC, and ~300oC, respectively.
Influence of Cathode Thickness on the Oxygen Reduction Kinetics at the Intermediate Temperature SOFC Cathodes
Authors: Kivi Indrek , Drovtar Imre , Anderson Erik , Aruväli Jaan , Tamm Kadi , Nurk Gunnar , Möller Priit , Vestli Mihkel , Kanarbik Rait , Lust Enn
Published: April 2011

Ni-YSZ | YSZ | GDC | LSC single cells with different thickness of the electrodes have been prepared and studied at temperatures from 773 K to 1073 K. Single cells with high power density (~ 700 mWcm-2) and good time stability have been analyzed in detail using impedance spectroscopy data. Influence of the cathode thickness and synthesis temperature (i.e. porosity) on the rate limiting parameters has been demonstrated.
Characterization of SOFC Cathodes Prepared by Pulse Laser Deposition
Authors: Napolitano Federico , Baqué Laura , Cho Sungmee , Su Qing , Wang Haiyan , Casanova Jorge R. , Lamas Diego G. , Soldati Analia L. , Serquis Adriana
Published: April 2011

We studied the electrochemical performance and microstructural characteristics of La0.5Sr0.5CoO3-d (LSCO) cathodes prepared by pulse laser deposition (PLD). This technique allows the growth of nanostructured cathode layers with vertically-aligned nanopores (VANP). In some samples, a vertically aligned nanocomposite (VAN) LSCO/CGO layer was introduced between the cathode and the Ce0.9Gd0.1O1.95 (CGO) electrolyte. The structure and morphology of several film configurations were characterized by X-ray diffraction, transmission and scanning electron microscopy, and synchrotron X-ray reflectometry, while the electrochemical properties were evaluated by means of impedance spectroscopy. We found that cathode area specific resistances (ASR) for VANP LSCO samples are almost independent of film thickness and are within the lowest reported values. A significant decrease in the ASR values was observed while heating the sample, but after this first heating, the ASR values were reproducible, indicating that these nanostructures are stable in the used temperatures and oxygen partial pressure ranges.
Low-Chromium Alloys for Solid Oxide Fuel Cell Interconnects
Authors: Fergus Jeffrey , Zhao Yu
Published: April 2011

Ferritic stainless steel alloys have a combination of good oxidation resistance and appropriate coefficient of thermal expansion that makes them attractive for use as the interconnect in solid oxide fuel cells. However, chromia can be oxidized to vapor species, which can lead to poisoning of the cathode, so ceramic coatings are applied to reduce chromium volatilization. With the use of coatings, alloys with lower chromium contents could potentially be used. In this work, the oxidation behaviors of a series of ferritic steel alloys, Mn1.5Co1.5O4-coated and uncoated, with chromium contents from 13-18% and other alloying additions typical of those of AISI 441 (i.e. small amounts of niobium and titanium) were evaluated.
Oxide Protective Coatings for Solid Oxide Fuel Cell Interconnects
Authors: Seabaugh Matthew , Ibanez Sergio , Beachy Michael , Day Michael , Thrun Lora
Published: April 2011

The long-term stability of SOFC stacks is a critical hurdle to their commercial success. To maintain low stack and system costs, metallic interconnect materials are required; to achieve long life, protective coatings must stabilize metal interconnect performance. Further, these coatings must exhibit sufficient bulk conductivity to achieve low stack area specific resistance. To exploit the cost advantages offered by metallic interconnects, coating approaches must be size-scalable and allow high volume throughput at low capital cost. NexTech has systematically developed cost-effective approaches to synthesizing and depositing oxide coatings through value-conscious materials processing and deposition processes. Recently, manganese cobalt spinel synthesis and deposition has been demonstrated using production process designed to allow high throughput production.
Electrodeposition Of CoMn Onto Stainless Steels Interconnects For Increased Lifetimes In SOFCs
Authors: Hall Timothy D. , McCrabb Heather , Wu Junwei , Zhang Hui , Liu Xingbo , Taylor Jennings
Published: April 2011

A pulse and pulse reverse electrochemical deposition process is being developed for cost effective coating of solid oxide fuel cell (SOFC) interconnects. Faraday Technology and WVU demonstrated that the developed process could produce uniform dense, crack-free, well-adhered CoMn alloy coatings of various compositions on a 5 cm x 5 cm 441 stainless steel interconnect surface. The post-deposition thermal treatment converted the CoMn alloy coatings to (Mn,Co)3O4 spinels in which a coating thickness of ~3 µm was shown to be sufficient to mitigate chromia diffusion and oxidation. Various electrochemical deposition-processing parameters are examined to determine their affect on the coatings performance, while the coatings thickness and composition are also varied in order to obtain preliminary coating performance limits. Additionally, a preliminary economic analysis based on using batch manufacturing for the pulse reverse electrodeposition process demonstrated that the innovative coating technology can meet DOE's high volume target of 1,600,000 plates per annum for 250 MW of fuel cell stacks at a cost of ~$1.23 per 25 cm x 25 cm coated interconnect.
Analysis of Joint Strength between a Metallic Interconnect and Glass-Ceramic Sealant for Use in Solid Oxide Fuel Cells
Authors: Lin Chih-Kuang , Chen Jun-Yu , Chiang Lieh-Kwang , Wu Si-Han
Published: April 2011

The joint strength between a newly developed glass-ceramic sealant and metallic interconnect for application in planar solid oxide fuel cells (pSOFCs) was investigated. A methodology of evaluating the joint strength at room temperature (RT) and 800 oC was developed in testing two types of sandwich-like specimens under shear and tensile loading. Effects of number of sealant-spreading side and aging treatment on the joint strength at RT and 800 oC were studied. Regardless of the testing temperature and loading mode, the joint strength of specimens with two sides of glass-ceramic sealant was greater than that of single-side ones due to a better wetting effect. An aging treatment at 800 oC for 250 or 500 h degraded the shear joint strength at 800 oC by 17%. A longer aging time of 1000 h further reduced the high-temperature shear joint strength by a slightly additional extent from 17% to 19%.
Synthesis and Electrical Properties of Strontium Titanate-Based Materials for Solid Oxide Fuel Cells
Authors: Park Beom-Kyeong , Lee Jong-Won , Lee Seung-Bok , Lim Tak-Hyoung , Park Seok-Joo , Song Rak-Hyun , Shin Dong-Ryul
Published: April 2011

SrTiO3 materials co-doped with La in Sr-sites and Nb or Mn in Ti-sites were synthesized by the citric acid-assisted Pechini method. The method led to the formation of nano-sized, single phase SrTiO3-based oxides with a perovskite structure. The electrical property was analyzed under a reducing atmosphere at different temperatures. The conductivity of Sr1-xLaxTiO3 showed a maximum value for x = 0.2 and then decreased with further increasing x, which might be due to the presence of the Ruddlesden-Popper and La2Ti2O7-type phases. Nb doping into Ti-sites resulted in a conductivity increase and a decrease in the activation energy for conduction, whereas Mn doping decreased slightly the conductivity.
First 3D-Modeling of Proton-Conducting SOFC's Interconnect
Authors: Sailler Sébastien , Deseure Jonathan , Doche Olivier , Bultel Yann
Published: April 2011

The development of solid oxide fuel cells has reached a new stage with intermediate temperature SOFCs. The protonic ceramic fuel cell is fundamentally different because it relies on proton conductivity through the electrolyte and not oxygen ions like SOFCs. Only few experimental results on PCFC are reported in literature compare to SOFC devices. The present work deals with three-dimensional geometry in steady state conditions and the role of interconnect for circular PEN PCFC is investigated. The gas flow inlet is at the centre of the cell. It is impossible to consider the problem using only two directions due to symmetry plan absence. To overcome the difficulty of high memory capacity required for 3D simulations, axes make it possible to consider only an eighth part of this configuration The present study reveals a strong edge effects to collect the current and a limiting access of oxygen due to water production.
High-Temperature Stress-Rupture Properties of a Ferritic Steel for Solid Oxide Fuel Cell Interconnect
Authors: Chiu Yung-Tang , Lin Chih-Kuang
Published: April 2011

The high-temperature stress-rupture properties of a ferritic steel (Crofer 22 H) for use as an interconnect material in planar solid oxide fuel cells are investigated. Constant-load creep tests are carried out at 650 to 800oC. For a given applied stress, the creep rupture time is decreased with an increase in temperature. The creep rupture time is well correlated with the applied stress by a simple power law for each testing temperature. The fitted power-law curves of 650-750oC look somewhat parallel to each other while the curve of 800oC is steeper than the others. A greater reduction of creep strength in the long-life region is present at 800oC. Larson-Miller relationship also does well in correlating the creep rupture time with applied stress and temperature. Fractographic and microstructural observations indicate such a significant reduction of creep strength in the long-life region at 800oC can be partially attributed to a precipitate coarsening effect.
Characterization of Vaporization Rates on SOFC Interconnect Alloys
Authors: Casteel Micah , Lewis Dan , Renko Ashley , Willette Peter
Published: April 2011

Ferritic stainless steels are an attractive option for interconnect applications in solid oxide fuel cells due to their low coefficient of thermal expansion (CTE) and potentially low cost. However, a key problem with ferritic stainless steels (and other high chromium materials) in these applications is the vaporization of chromium bearing species(1-6). This vaporized chromium poisons the cathode, which can significantly impact cell performance(1,6-9). In order to understand this problem we have incorporated a solution-based ionic conductivity method into the more traditional transpiration measurement method. Using this novel, hybrid method the vaporization rates of chromia, Crofer 22 APU, E-brite, ZMG-232, Haynes 230, and 441 have been determined. Good agreement was found with literature values; however, large variation was discovered in literature values.
Method for Measuring Chromium Evaporation from SOFC Balance-of-Plant Components
Authors: Thomann Olivier , Pihlatie Mikko H. , Schuler J. Andreas , Himanen Olli , Kiviaho Jari
Published: April 2011

Chromium poisoning is a well-identified performance degradation process in solid oxide fuel cells (SOFC). While stainless steel interconnects have been identified to be a significant source of chromium, the contribution of the chromium from balance-of-plant (BoP) components located upstream of the cathode still needs to be ascertained. The aim of this work was to develop and validate a method to quantify the amount of chromium evaporating from hot BoP components. An austenitic stainless steel (253MA) pipe was exposed to humidified air at high temperatures. The volatile chromium species were then collected by sampling through a quartz tube coated with sodium carbonate. The chromium evaporation rate was reduced by a factor of 4 when a varying temperature history between 650 and 750oC was followed by 100 h operation at 800oC. Scanning electron microscopy was performed on pipe cross sections to show the relationship between the microstructure of the oxide layer and chromium evaporation. The method developed can be used to measure chromium concentration levels at different locations in a complete SOFC system.
Cathode Contact Materials for Solid Oxide Fuel Cells
Authors: Tucker Michael , Cheng Lei , DeJonghe Lutgard
Published: April 2011

Various cathode contact paste material (CCM) candidates are fabricated and screened for CTE, conductivity, sintering behavior, and reactivity with LSCF and (Mn,Co)3O4. The most promising candidates, LSCF, SSC, LSCuF, LSC, and NCC are subjected to ASR testing on LSCF and MCO-coated 441 steel coupons. LSC provides the lowest and most stable ASR on both substrate types.
SOFC Power Generation from Biogas: Improved System Efficiency with Combined Dry and Steam Reforming
Authors: Dietrich Ralph-Uwe , Lindermeir Andreas , Oelze Jana , Spieker Carsten , Spitta Christian , Steffen Michael
Published: April 2011

Solid oxide fuel cell systems (SOFC) can improve the efficiency of electrical power generation from biogas compared to small scale CHP units. The SOFC requires a reforming step converting biogas into synthesis gas (hydrogen and carbon monoxide). . Dry reforming of methane with the carbon dioxide contained in biogas is a promising approach to produce high caloric SOFC fuel gas, but carbon formation is predicted for all typical biogas compositions. To avoid carbon formation and to compensate fluctuating biogas compositions additional supply of steam is essential leading to a combined dry and steam reforming. The paper describes the system approach, upfront analysis, biogas monitoring results, process unit design and evaluation as well as the system setup to demonstrate a biogas to electricity route with a gross efficiency of 45 % using a commercial 1 kW SOFC stack.
Transient Operation Effects of SOFCs Driven with Tar Loaded Synthesis Gas
Authors: Hauth Martin , Kienberger Thomas , Karl Jürgen
Published: April 2011

This paper describes recent results from the utilization of tar loaded synthetic wood gas in a planar single SOFC (Ni-GDC/YSZ/LSM) at OCV conditions. The distinct influence of naphthalene, toluene and xylene on direct steam reforming of methane is investigated. It is shown that the high reactivity of naphthalene causes a reduction of the conversion of other hydrocarbons such as methane which eventually impacts the OCV. While toluene and xylene are converted almost completely, a transient response time for naphthalene is observed until steady conversion is achieved. This transient behavior is detected not only by FID measurements but also by the OCV curve. This overlaying effect occurs during the use of tar loaded wood gas with fluctuating PGCs and tar concentrations and is finally discussed to estimate the operation characteristic for real wood gas.
Liquid Tin-Lead Anode Solid Oxide Fuel Cell Fueled by Coal
Authors: LaBarbera Mark , Fedkin Mark , Lvov Serguei
Published: April 2011

Liquid tin-lead alloy, liquid bismuth, and liquid tin-lead-bismuth alloy were investigated as potential anodes for a solid oxide fuel cell powered directly by coal. Power generation from direct oxidation of solid coal was demonstrated with a good stability only in the case when liquid tin-lead anode was used. The tests were carried out at 900 °C under ambient pressure. The open circuit potentials of the SOFC with tin-lead and bismuth anodes operated under nitrogen were compared, and those values were found to correspond to the metal-metal oxide redox potentials for tin and bismuth, respectively. When the SOFCs were fueled by hydrogen, only the tin-lead anode showed a direct electrochemical reaction between hydrogen and oxygen. When 60-mesh coal powder was fed to the liquid tin-lead anode, SOFC showed increase in open circuit potential and generated power from direct electrochemical oxidation of coal.
Startup Characteristics of Propane-Fueled Solid Oxide Fuel Cell Hot Zones
Authors: Du Yanhai , Cui Daan , Reifsnider Kenneth , Chen Fanglin
Published: April 2011

For portable applications, a fuel cell often experiences frequent startups and shutdowns. Therefore the startup and shutdown behaviors are critical to a portable solid oxide fuel cell (SOFC) and SOFC system. This paper discusses propane-fueled and thermally self-sustained SOFC hot zones and their startup characteristics in terms of temperatures, time, fuel and air utilization, O/C ratio, and repeatability.
Direct-DME SOFC for Intermediate Operation Temperature Using Proton Conductor as the Electrolyte
Authors: Takeuchi Ken , Tai Ryosuke , Ui Koichi , Fujimoto Kenjiro , Ito Shigeru , Koyanaka Hideki , Koura Nobuyuki
Published: April 2011

We have developed intermediate-temperature solid oxide fuel cell (SOFC) with a proton conducting oxide BaCe0.8Y0.2O3-δ(BCY20) as the electrolyte for direct utilization of dimethylether (DME) fuel. We tried to improve the cell performance of the SOFC by using Fe, Fe-Ni and Fe-Pd/MnO2 as a catalyst for the anode. Fe showed high catalytic activity for DME, furthermore attending Ni or Pd/MnO2 catalysts to Fe remarkably improved the cell performance.
Electrocatalysis and Reforming in Oscillatory Reaction of Methane on a Pt-LSC/Ceria Anode for Solid Oxide Fuel Cells
Authors: Medvedev Valentin , Adler Stuart B. , Stuve Eric M.
Published: April 2011

Distributions in reacting species during oscillations of methane oxidation were studied to obtain information on the relative rates of electrocatalysis and reforming. Spontaneous oscillations in total pressure and current occur for reaction at 637 °C on a Pt-modified, LaSrCoO (LSC) anode and gadolinium-doped ceria electrolyte. The oscillations have the form of sharp peaks (spikes) of 8 min duration and a period of 40 min. Reaction rates of H2, CO, CH4, CO2, H2O, and O2 were followed as a function of time. The results show that electrooxidation of CH4 occurs between spikes and that an increase in electrooxidation initiates the spike. Catalytic steam reforming then ensues to produce H2 and CO, which provide the main current in the spike. The cause of the oscillatory behavior is ascribed to dynamic effects of site blocking by surface carbon and oxygen, as controlled by processes of carbon removal and oxygen accumulation.
Towards Understanding the Hydrocarbon Oxidation Activity of Oxides for Direct Hydrocarbon SOFC Anodes
Authors: McIntosh Steven , Van den Bossche Michael
Published: April 2011

In this work we have developed a novel pulse reactor technique to study the methane oxidation activity of La0.75Sr0.25Cr0.5Mn0.4X0.1O3-d (X=Co, Fe, Ni, V, Mn), and the double-perovskite Sr2MgMoO3-d (SMMO) as a function of lattice oxygen stoichiometry under SOFC anode conditions. The oxidation activity and selectivity towards total oxidation products both decrease with decreasing oxygen stoichiometry for all of the materials tested. The difference in activity between materials is related to the catalytic activity of the B-site cations and the availability of oxygen for reaction (i.e. the reducibility of the underlying bulk lattice). These findings are used to interpret the non-linear electrochemical response of an La0.75Sr0.25Cr0.5Mn0.5O3-d based SOFC anode upon increasing cell current density.
Ceramic Microchannel Heat Exchanger and Reactor for SOFC Applications
Authors: Murphy Danielle M. , Rosen Benjamin , Blasi Justin , Sullivan Neal , Kee Robert J. , Hartmann Marco , McGuire Nicholas E.
Published: April 2011

In this paper, we present the design, fabrication, and performance of novel ceramic microchannel reactors in heat-exchanger and fuel-reforming applications. Reactor design is based on the results of computational fluid mechanics simulations so that uniform fluid flow and thermal gradients are observed across the reactor body. Reactors are fabricated by CoorsTek, Inc. as four-layer Pressure Laminated Integrated Structures using 94% Al2O3 materials. The cost-effective PLIS fabrication produces a single ceramic body with internal microchannels and manifolding. High-temperature performance of the ceramic microchannel reactor is measured through non-reactive heat-exchanger experiments. After coating rhodium catalyst materials over two of the four reactor layers, use of the ceramic microchannel reactor in fuel-processing applications is demonstrated through catalytic partial oxidation of butanol. While significant syngas formation is demonstrated, further work is necessary to improve reforming conditions, increase the selectivity to hydrogen and carbon monoxide, and integrate the microchannel reactor with a tail-gas combustor.
Studies on Direct Ethanol Use in SOFCs
Authors: Corre Gael P. , Irvine John T.
Published: April 2011

We report here on the investigation of the direct use of ethanol in solid oxide fuel cells. While the operation on Ni-YSZ anodes leads to detrimental catalytic carbon deposition even at high steam to carbon ratio, diluted ethanol can be directly used on LSCM anodes. Steady operation seems achievable only at high temperatures (900°C) due to gas-phase reaction carbon deposits. However, it is demonstrated that the initial performance is fully recovered after removal of these deposits. The addition of CGO to the LSCM anode is shown to considerably improve the anode performance, by limiting the gas-phase carbon deposition to a small layer beneficial to the performance. Recorded performance was higher on diluted ethanol than on humidified hydrogen. No degradation was observed on short term tests, and a polarization resistance of 0.3 Ω.cm2 was achieved on ethanol diluted (15 mol. %) in steam.
Solid Oxide Fuel Cell Fueled by Diesel Reformate and Anaerobic Digester Gas
Authors: LaBarbera Mark , Fedkin Mark , Wang Xiaoxing , Chao Xie , Song Chunshan , Lvov Serguei
Published: April 2011

A solid oxide fuel cell with a nickel-yttria stabilized zirconia cermet anode and a porous lanthanum strontium manganite cathode was used to generate electrical power directly from anaerobic digester gas and commercial diesel steam reformate. A diesel reformer was combined with the solid oxide fuel cell system in a single operating unit to convert diesel to electricity. To model anaerobic digester gas (ADG), a fuel gas mixture was prepared based on analytical data on real ADG from a local water cleaning facility. Electrochemical performance characterization involved power generation across a variety of external loads to characterize open circuit potential, maximum power densities and limiting current densities. The effects of anode poisoning from of sulfur compounds and their removal from the ADG fuel were studied.
Experimentally Validated Simulations of Undoped Ceria Electrodes for H2 Oxidation and H2O Electrolysis in Solid Oxide Electrochemical Cells
Authors: DeCaluwe Steven C. , Jackson Gregory
Published: April 2011

We present here the formulation and validation of a one-dimensional model of undoped CeO2-x
electrodes for fuel oxidation and H2O splitting in high-temperature solid oxide cells. The model describes dense thin-film electrodes with a porous Au current collector, dense YSZ supporting electrolyte, and a porous LSM/YSZ composite counter electrode. The model is formulated as a set of differential algebraic equations which are integrated over time to steady-state, and is compared to V-i curves from single cell tests to yield estimates for important transport, thermodynamic, and kinetic parameters governing electrochemical performance of CeO2-x
electrodes in solid oxide cells. These results represent a quantitative framework for the analysis of electrochemical results on ceria electrodes.
Development of Reversible Solid Oxide Fuel Cells (RSOFCs)and Stacks
Authors: Minh Nguyen Q.
Published: April 2011

A reversible solid oxide fuel cell (RSOFC) is a SOFC that can function efficiently under both power generation mode for electricity production and electrolysis mode for hydrogen/chemical production. The RSOFC thus can be used as a fuel cell or an electrolysis cell or both depending on the application. Multi-cell RSOFC stacks have been built and reversible operation has been demonstrated. Experiments on RSOFCs (yttria-stabilized zirconia or YSZ electrolytes, Ni/YSZ hydrogen electrodes, and perovskite oxygen electrodes) showed certain performance irreversibility of the perovskite electrode. Significant performance degradation was observed under electrolysis mode for predominantly electronic-conducting oxygen electrodes such as Sr-doped lanthanum manganite (LSM). Mixed-conducting oxygen electrodes such as lanthanum strontium cobalt iron oxides (LSCF) showed better performance and performance stability. Long-term operation of RSOFC stacks using stainless steel interconnects at 800oC showed elemental (Sr and Cr) migration and interactions at oxygen electrode/interconnect interfaces.
Production of Sustainable Fuels by Means of Solid Oxide Electrolysis
Authors: Hansen John B. , Christiansen Niels , Nielsen Jens Ulrik
Published: April 2011

Electrolysis by means of Solid Oxide Cells (SOC) offers unique possibilities with respect to production of sustainable fuels from carbon dioxide and steam. High temperature waste heat can be utilized to reduce the consumption of electric power and the ability to co-electrolyze carbon dioxide and steam makes it possible to generate synthesis gas suitable for production of a range of fuels. The synergies between SOEC and production of SNG or methanol will be explored. The requirements for feedstock purification, limitations due to potential carbon formation problems and overall efficiencies will be addressed taking into account the properties of existing as well as emerging SOEC electrodes.
Hydrogen Production by High Temperature Electrolysis Using Solid Oxide Electrolyzer Cells
Authors: Kim Sundong , Yu Jihaeng , Seo Doowon , Han Insub , Woo Sangkuk
Published: April 2011

Experimental studies have been performed to understand the influence of the temperature and water vapor contents on the performance of high temperature electrolysis. The single cell composed of Ni-YSZ cathode support, YSZ electrolyte, LSM anode and, especially, ceramic interconnector. The experiments were performed over a range of steam inlet volume percent (30 and 50 vol%) and the operating temperature was 650∼800 °. Finally, the 3-cell short stack test was also investigated.
A Proposed Method for High Efficiency Electrical Energy Storage Using Solid Oxide Cells
Authors: Bierschenk David M. , Wilson James R. , Miller Elizabeth , Dutton Emma , Barnett Scott A.
Published: April 2011

Large-scale electrical energy storage is becoming increasingly necessary due to the continued growth of intermittent renewable sources such as wind and solar. Reversible solid oxide cells (SOCs) have many desirable attributes for this application, but round trip efficiency is expected to be relatively low. Here we use thermodynamic calculations and gas chromatography measurements to demonstrate a reversible SOC storage chemistry where the fuel cycles between H2O-CO2-rich and CH4-H2-rich gases, enabled by operating at reduced temperature and/or increased pressure. The CH4-forming electrolysis reactions are less endothermic than the usual H2- or CO-forming reactions, thereby allowing an improved round-trip efficiency. SOC requirements for this application are discussed.
Development of Tubular Solid Oxide Electrolysis Stacks for Hydrogen Production
Authors: Kato Tohru , Sato Katsutoshi , Honda Takeo , Negishi Akira , Tanaka Yohei , Momma Akihiko , Kato Ken , Iimura Yoko
Published: April 2011

Slurry coating method for fabricating tubular solid oxide electrolysis stacks operated at 700~800oC is developed. To improve cell performance at the low temperature, the thickness of the electrolyte layer is tried controlling about 10μm. By using this process, the SOEC stack whose input power is about 100 W is fabricated and its performance is measured. From the measurement, it is clarified that the hydrogen production rate at 750oC goes up to 678 sccm (3.08 sccm/cm2) at the thermoneutral voltage and steam utilization of 75 %. Furthermore, impedance of the stack is analysed by AC impedance method.
Novel Micro-Tubular High Temperature Solid Oxide Electrolysis Cells
Authors: Jin Chao , Yang Chenghao , Chen Fanglin
Published: April 2011

NiO-YSZ (yttria-stabilized zirconia) supported micro-tubular LSM ((La0.75Sr0.25)0.95MnO3)-YSZ/YSZ/NiO-YSZ solid oxide electrolysis cells (SOECs) have been prepared by a phase-inversion method. SEM results show that a novel asymmetric microstructure was obtained, with large finger-like pores on inner wall which can be used as gas delivery layer and small finger-like pores adjacent to the electrolyte thin film which can be used as electrochemical functional layer. High temperature steam electrolysis was carried out with H2 as gas carrier and maximum 80 vol. % absolute humidity (AH) steam fed to the micro-tubular cell. The electrolysis cell resistance increased with increase in the fed steam concentration under open circuit voltage conditions. An encouraging H2 generation rate of 3.8 ml min-1 cm-2 was obtained with 60 Vol. % AH steam under an electrolysis voltage of 1.3 V at 850 oC.
Au-Catalyst Induced Low Temperature (∼250 ºC) Layer Exchange Crystallization for SiGe On Insulator
Authors: Park Jong-Hyeok , Kurosawa Masashi , Kawabata Naoyuki , Miyao Masanobu , Sadoh Taizoh
Published: April 2011

The gold-induced crystallization technique has been investigated to achieve poly-SiGe films on insulators at low temperatures (300ºC). By annealing of the amorphous SiGe (Ge concentration: 0-100%)/Au stacked structures formed on insulating substrates, positions of the SiGe and Au layers are inverted, and the Au/SiGe stacked structures are obtained. Crystallization of the SiGe layers in the inverted samples is confirmed by the Raman scattering spectroscopy analysis. Moreover, the Raman measurements reveal that the Ge fractions in the crystallized SiGe layers are almost the same as those of the initial amorphous SiGe layers. This gold-induced layer-exchange crystallization technique of SiGe layers at a low temperature (~250ºC) will be very useful to obtain poly-SiGe layers on plastic substrates, which are essential to realize flexible high-speed thin-films transistors and high-efficiency solar cells.
Strain Nano-Engineering: SSOI as a Playground
Authors: Moutanabbir Oussama , Hähnel Angelika , Reiche Manfred , Erfurth Wilfred , Tarun Alvarado , Hayazawa Norohiko , Kawata Satoshi , Naumann Falk , Petzold Matthias
Published: April 2011

Ultrathin strained silicon-on-insulator (SSOI) has been in the limelight of device scientists and engineers as one of the materials that can possibly extend the lifetime of the current silicon technology. In this paper, we show that, beyond this technological interest, SSOI also provides a rich platform to explore and explain a number of fundamental phenomena. In particular, ultrathin SSOI substrates are exploited to elucidate basic nanomechanical properties of silicon. Particularly, the bending associated with free surface-induced relaxation upon nanoscale patterning are investigated using micro-Raman scattering, high resolution transmission electron microscopy, and nano-beam electron diffraction. The observed morphological changes in SSOI nanostructures cannot be explained by the classical Stoney's formula or related formulations developed for nanoscale thin films. Instead, a continuum mechanical approach is employed to describe these observations through three-dimensional numerical calculations of relaxation-induced lattice displacements. The use of SSOI to implement novel nanoscale devices is also discussed.
Growth-Direction Dependent Rapid-Melting-Growth of Ge-On-Insulator (GOI) and its Application to Ge Mesh-Growth
Authors: Yokoyama Hiroyki , Ohta Yasuharu , Toko Kaoru , Sadoh Taizoh , Miyao Masanobu
Published: April 2011

Single crystal Ge-on-insulator (GOI) structures with various crystal orientations are necessary for realization of advanced high-speed and multi-functional devices. SiGe mixing triggered rapid-melting-growth of GOI is investigated as a function of seed-orientations and growth-directions. Single crystal growth of (100)-Ge strips is possible for all growth directions using (100)-oriented Si-seeds. However, rotational-growth is observed for some directions when Si-seeds with (110) and (111) orientations are employed. Such rotational-growth is completely suppressed by selecting the growth-directions deviating from the <111> direction by more than 35o. Based on this finding, growth of large mesh-patterned Ge layers with (100), (110), and (111) orientations are demonstrated.
Hysteresis Effects in FinFETs with ONO Buried Insulator
Authors: Chang Sungjae , Bawedin Maryline , Xiong Wade , Lee Jonghyun , Cristoloveanu Sorin
Published: April 2011

FinFETs fabricated on SiO2-Si3N4-SiO2 (ONO) buried insulator are investigated for flash memory application. The Si3N4 layer can trap charges by tunneling at high back-gate bias. The amount of trapped charges is sensed, via gate coupling effects, by the drain current. The trapped charges in Si3N4 layer also induce a drain current hysteresis when the back-gate is dynamically scanned. Systematic measurements reveal that the charge trapping and drain current hysteresis are useful memory effects. The memory window depends on bias conditions and geometrical parameters.
Humidity Effects on Substrate Bonding for Silicon-On-Glass
Authors: Usenko Alex
Published: April 2011

Glass-to-silicon bonding quality has been studied as a function of air relative humidity in a pre-bonding tool. Two bond-activation techniques, wet and plasma, were used. Optimum ranges of air humidity that ensure high bonding yield are determined. The bonding is finalized by annealing and types of defects appearing in the cases of low and high humidity are indicated. Results prove that humidity control is required for high yield glass-to-silicon bonding.
Research of SOI Microelectromechanical Sensors with a Monolithic Tensoframe for High-Temperature Pressure Transducers
Authors: Sokolov Leonid V.
Published: April 2011

This paper is devoted to an integrated piezoresistive pressure sensors based on novel concept of high-temperature microelectromechanical SOI sensors with a monolithic tensoframe. The SOI and integrated MEMS technologies are of especial interest for this sensors. The research enables main technology problems due to the features of a photolithography process on a relief surface with the high aspect ratio and resulted restrictions on the design parameters of SOI sensor three-dimensional micromechanical structures to be defined.
Transport Properties of 3D Vertically Stacked SiGe and SiGeC Nanowires
Authors: El Hajj Diab Amer , Saracco Emeline , Ionica Irina , Bonafos Caroline , Damlencourt Jean-François , Cristoloveanu Sorin
Published: April 2011

One of the trends in microelectronics is to explore nanowire gate-all-around structures and alternative channel materials with interesting electrical transport properties. We present the electrical transport in three-dimensional vertically stacked germanium-enriched nanowires. Two starting materials have been used for the nanowire fabrication: SiGe and SiGeC. Measurements show that the transport in the nanowires is controlled by the voltage applied on the substrate, as in a metal-oxide-semiconductor field effect transistor. Interestingly, the substrate bias effect depends on the designed geometry of the nanowire: For high width/length ratio nanowires, we show the possibility of turning on both electrons and holes channels. For small width/length ratio nanowires, the only visible channel is that of the holes. Transport modification with the concentration of germanium in the finite nanostructures is also discussed.
Nonlinear Properties of Si Based Substrates for Wireless Systems and SoC Integration
Authors: Roda Neve César , Raskin Jean-Pierre
Published: April 2011

The nonlinear behaviour of silicon substrates with different resistivities is analyzed using coplanar structures. In order to compare the nonlinear performance for different substrates and technologies, the harmonic distortion of crosstalk test structures is investigated, as well as the dependence on the distance. The generated harmonic components due to a large signal at 900 MH are measured using a one-tone network analyzer based setup. Below the crosstalk tap, harmonic levels as high as -43 and -54 dBc for 15 dBm are generated for standard and high-resistivity (HR) Si substrate, respectively. The introduction of a trap-rich layer at the interface between the BOX and the high-resistivity Si (HR-Si) provides a reduction of at least 45 dB in the harmonic distortion generated into the substrate. It has been proven that these results can be easily extrapolated to crosstalk structures with different dimensions.
FDSOI Process Technology for Subthreshold-Operation Ultra-Low-Power Electronics
Authors: Vitale Steven A. , Wyatt Peter W. , Checka Nisha , Kedzierski Jakub , Keast Craig L.
Published: April 2011

Ultralow-power electronics will expand the technological capability of handheld and wireless devices by dramatically improving battery life and portability. In addition to innovative low-power design techniques, a complementary process technology is required to enable the highest performance devices possible while maintaining extremely low power consumption. Transistors optimized for subthreshold operation at 0.3 V may achieve a 97% reduction in switching energy compared to conventional transistors. The process technology described in this article takes advantage of the capacitance and performance benefits of thin-body silicon-on-insulator devices, combined with a workfunction engineered mid-gap metal gate.
Ultra-Thin Film SOI/BOX Substrate Development, Its Application and Readiness
Authors: Schwarzenbach Walter , Cauchy Xavier , Bonnin Olivier , Daval Nicolas , Aulnette Cécile , Girard Christophe , Nguyen Bich-Yen , Maleville Christophe
Published: April 2011

The Ultra-Thin SOI and BOX substrates are the foundation of Fully Depleted planar technology, a CMOS scaling solution for 20 nm node and beyond. Using the Smart CutTM technology, UTSOI substrates development, with SOI & BOX thickness reduced down to 12 & 25 nm respectively, is on the way to High Volume Manufacturing by the end of 2011. To improve device Vt variation control, SOI total layer thickness variation of less than +/- 1 nm for all the measured points and all the preproduction wafers is already achieved and +/- 0.5 nm variation is targeted. Tight SOI thickness variation at device scale and BOX thickness variation are also demonstrated.
TiN/HfSiON for Analog Applications of nMuGFETs
Authors: Rodrigues Michele , Galeti Milene , Martino Joao A. , Collaert Nadine , Simoen Eddy , Claeys Cor
Published: April 2011

This work presents an analysis of the impact of the implementation of a hafnium gate dielectric on triple-gate structures for analog applications. A reduced Early voltage VEA is observed for the hafnium dielectric. This was attributed to a slightly higher physical gate dielectric thickness observed on HfSiON dielectric that could be leading to a increasing on the horizontal electric field contribution on the drain current. As a result, lower intrinsic voltage gain was observed for high-k dielectrics when compared with a SiON gate insulator.
Properties of Silicon Ballistic Spin Fin-Based Field-Effect Transistors
Authors: Osintsev Dmitri , Sverdlov Victor , Stanojevic Zlatan , Makarov Alexander , Weinbub Josef , Selberherr Siegfried
Published: April 2011

We investigate the properties of ballistic fin-structured silicon spin field-effect transistors. The spin transistor suggested first by Datta and Das employs spin-orbit coupling to introduce the current modulation. The major contribution to the spin-orbit interaction in silicon films is of the Dresselhaus type due to the interface-induced inversion symmetry breaking. The subband structure in silicon confined systems is obtained with help of a two-band k·p model and is in good agreement with recent density functional calculations. It is demonstrated that fins with [100] orientation display a stronger modulation of the conductance as function of spin-orbit interaction and magnetic field and are thus preferred for practical realizations of silicon SpinFETs.
Stress Relaxation Empirical Model for Biaxially Strained Triple-Gate Devices
Authors: Trevisoli Renan D. , Martino Joao A. , Simoen Eddy , Claeys Cor , Pavanello Marcelo A.
Published: April 2011

Multiple gate devices provides short channel effects reduction, been considered promising for sub 20 nm era. Strain engineering has also been considered as an alternative to the miniaturization due to the boost in the carrier mobility. The stress non-uniformity cannot be easily considered in a TCAD device simulation without the coupled process simulation which is a cumbersome task. This work analyses the use of an analytical function to compute accurately the dependence of the strain on the device dimensions. The maximum transconductance gain and the threshold voltage shift are used as key parameters to compare simulated and experimental data.
Ultra Low Power 3-D Flow Meter in Monolithic SOI Technology
Authors: Andre Nicolas , Rue Bertrand , Scheen Gilles , Francis Laurent A. , Flandre Denis , Raskin Jean-Pierre
Published: April 2011

Silicon-on-Insulator technology, with unique properties such as harsh environment resistance and lower power consumption, is presented here as a platform for CMOS and MEMS co-integration. An original CMOS-compatible process has been developed for the design and the co-fabrication of out-of-plane movable cantilevers and ring oscillators circuits on the same chip. The measured transducer, by deflection of the out-of-plane MEMS component, shows until 10% variation of the frequency under different flow rates.
Electrical and Proton Conduction Properties of Amorphous TiO2 Nanotubes Fabricated by Electrochemical Anodization
Authors: Hanzu Ilie , Djenizian Thierry , Knauth Philippe
Published: April 2011

Electrolyte contacts were used to investigate the properties of pure and N-doped titania nanotubes (ntTiO2). Mott-Schottky analysis gave a flat-band potential Efb = -0.57V vs. Ag/AgCl for pure ntTiO2 and Efb = -0.22V vs. Ag/AgCl for N-doped ntTiO2. The charge carrier density was ND = 6.7 1020 cm-3 for pure ntTiO2 and ND = 3.9 1020 for N-doped ntTiO2. This investigation also allowed estimation of the apparent diffusion coefficient of H+ in ntTiO2. Following the Randles-Sevcik method, the effective proton diffusion coefficient in ntTiO2 is (2±1)•10-11 cm2s-1 while in N-doped ntTiO2 it is (4±1)•10-11 cm2s-1. Using the Warburg diffusion element determined by electrochemical impedance spectroscopy, the proton diffusion coefficient is (2±1)•10-11 cm2 s-1 for pure ntTiO2 while for nitrogen-doped ntTiO2 a value of (7±3)•10-11 cm2 s-1 is found. These values are consistent with those of the Randles-Sevcik method.