bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Indium Diffusion into Solution-Processed Oxide TFTs with ZTO Active Layer and IZO Source/Drain Electrodes
Authors: Kim Yong-Jin , Lee Jeong-Soo , Lee Yong-Uk , Cho Seung-Hwan , Kim Yong-Hoon , Han Min-Koo
Published: April 2011

We have investigated the indium diffusion in oxide-based thin film transistors (TFTs) fabricated with zinc tin oxide (ZTO) active layer and indium zinc oxide (IZO) source/drain electrode by employing a solution-process. Oxide TFTs were fabricated with spin-coating process using solution with chloride-, acetate- and nitrate- based precursors. After spin-coating, ZTO active layer and IZO source/drain electrodes were annealed sequentially by rapid thermal annealing (RTA). Rutherford backscattering spectrometry (RBS) result shows that 16.8% of indium atoms in IZO source/drain electrodes are diffused into ZTO active layer after annealing process. The In-diffusion into ZTO active layer cause a considerable negative shift of threshold voltage in solution-processed ZTO TFTs.
The Perspective of Nanotechnology and Its Convergence with Future Information Technology
Authors: Kim Jong Min
Published: April 2011

We present the current and future of nanotechnology, especially focusing on the convergence of nanotechnology with electronics, photonics, energy, and biology. Nano-electronics aspect addresses the nano carbon and its applications with graphene and carbon nanotubes. These will be covering displays, lighting, THz radiation, network transistors and many applications. As a part of nano-photonics, quantum dot and its related application for LED and displays are addressed. We also discuss nano energy generator for energy harvesting. Concept of e-nose and e-tongue with nano wires is presented. Printable and flexible electronics is discussed with nano materials. The convergence of nanotechnology is covered in details.
(Thomas D. Callinan Award of the Dielectric Science and Technology Division) Ge-Source TFETs for Ultra-Low-Power Electronics
Authors: Liu Tsu-Jae K. , Kim Sung Hwan , Jacobson Zachery
Published: April 2011

An electronic switching device that can achieve better performance than a MOSFET at low operating voltages is needed to mitigate the CMOS power crisis. The tunnel field effect transistor (TFET) can potentially meet this need. Germanium (Ge) is an attractive material to use in the source region of a silicon-based TFET, because it can provide for a small effective tunneling bandgap and hence large on-state tunneling current, and it is relatively easy to integrate into a CMOS process. Optimally designed Ge-source TFETs can achieve on/off current ratio well beyond the limit for MOSFETs at low operating voltages (<0.5 V), and hence are promising for future ultra-low-power digital integrated circuit applications.
Polarity Behavior and Adjustment in Silicon Nanowire Schottky Junction Transistors
Authors: Weber Walter M. , Heinzig Andre , Mikolajick Thomas
Published: April 2011

Silicon nanowires are currently being considered as possible candidates for Beyond-CMOS electronic applications. One attractive nanowire transistor concept is the Schottky junction FET where the source and drain regions are metallic. The most appropriate device geometry to couple the gate potential to the junctions is an axial metal / semiconductor / metal nanowire heterostructure. Here, NiSi2 / Si / NiSi2 nanowire heterostructures are fabricated and used as the core of our transistors. Characteristic advantages of these structures are the abrupt and homogeneous Schottky interfaces formed. In contrast to most Schottky FETs the clear definition of the junction area, as given by the nanowire cross-section has the prospect of reducing device to device variability.
Modeling and Simulation of High-κ Gate GaSb Nanowire Field Effect Transistor for Ultra High Speed and Low Power Applications
Authors: Jahangir Ifat , Jahangir Shafat , Khosru Quazi D.
Published: April 2011

In this work, we have presented a numerical model for calculating drain current, gate capacitance, gate leakage current and several other important metrics of GaSb nanowire field effect transistor (NWFET). A 2-D simulator is used to calculate gate capacitance, surface potential, charge profile and direct tunneling gate leakage current under different gate biases. Drain current is simulated using a 3-D simulator based on mode-space approach. Dependence of drain current on several device parameters like film thickness, gate length and source/drain Fermi level is also investigated. Gate delay, power-delay and energy-delay products are calculated to show these devices' applicability in ultra high speed and low power applications. To investigate the effects of using ternary alloys of GaSb and InSb, the same metrics are also calculated for GaxIn1-xSb NWFET.
Spectroscopic Ellipsometry of CVD Graphene
Authors: Nelson Florence , Kamineni Vimal , Zhang Tianhao , Comfort Everett , Lee Ji Ung , Diebold Alain
Published: April 2011

Spectroscopic Ellipsometry (SE) was used to characterize the complex refractive index of Chemical Vapor Deposition (CVD) graphene grown on copper (Cu) foils and transferred to glass and SiO2/Silicon substrates. Previously, we reported the complex refractive index of single layer graphene on glass substrates. Here, we describe the challenges in characterizing the optical properties of graphene on SiO2/Silicon substrates. We also discuss whole measurements of patches of graphene on 300 mm silicon wafers. This establishes the ability of in-line metrology methods to measure graphene thickness. This builds on previous use of an Effective Medium Approximation (EMA) for optical dispersion modeling of incomplete graphene films.
Thermal Properties of Graphene: Applications in Thermal Interface Materials
Authors: Shahil Khan M. , Goyal Vivek , Balandin Alexander
Published: April 2011

We review results of the thermal conductivity studies of graphene, which revealed its excellent heat conduction properties. Using the liquid solutions of graphene and few-layer graphene flakes, we produced composites with graphene as the filler material. The measurements of thermal properties of the resulting graphene composites have been measured with the "laser flash" and transient planar-source "hot disk" techniques. We have demonstrated that graphene flakes can substantially increase the effective thermal conductivity of the composite materials even at small volume loading fractions. The thermal conductivity enhancement exceeded a factor of five at 5% of the volume loading fraction and reached a factor of ten for some specific composites. We argue that graphene and few-layer graphene flakes can become efficient fillers for the thermal interface materials.
Molecular-Scale Tailoring of Graphene Surface Chemistry via Organic Functionalization
Authors: Wang Qing H. , Hossain Md. Zakir , Walsh Michael A. , Hersam Mark C.
Published: April 2011

Graphene has emerged as one of the leading materials in condensed matter physics due to its superlative electrical and mechanical properties. With an eye towards expanding its functionality and applications, this paper highlights efforts to tailor the surface chemistry of graphene via organic functionalization. At the molecular scale, ultra-high vacuum (UHV) scanning tunneling microscopy (STM) is employed to characterize and nanopattern organically modified graphene. For example, a suite of perylene-based molecules form highly ordered self-assembled monolayers (SAMs) on graphene via gas-phase deposition in UHV. Due to their noncovalent bonding, these SAMs preserve the superlative electronic properties of the underlying graphene while providing uniform and tailorable chemical functionality. Alternatively, via aryl diazaonium chemistry, functional polymers are covalently grafted to graphene. In addition to presenting opportunities for graphene-based chemical and biological sensing, covalent grafting allows local tuning of the electronic properties of the underlying graphene.
Measuring Graphene Piezoreisistance via In-Situ Nanoindentation
Authors: Huang Mingyuan , Greer Julia R.
Published: April 2011

We report piezoresistance measurements of uniaxially strained graphene ribbons obtained by performing in-situ nanoindentation experiments on suspended graphene devices with simultaneous electrical measurements. We find the Young's modulus of graphene to be ~335 N/m, which is consistent with previous reports. We measure the gauge factor of graphene ribbons to be ~2, a value close to that predicted by a tight binding model.
Carbon-Based Nanomaterial for Nanoelectronics
Authors: Chen Xiangyu , Lin Albert , Wei Lan , Patil Nishant , Wei Hai , Chen Hong-Yu , Mitra Subhasish , Wong H.-S. Philip
Published: April 2011

Carbon-based nanomaterials such as carbon nanotubes (CNT) and graphene have been known for their outstanding transport, thermal and mechanical properties, and their great potentials in nanoelectronic device applications such as CNT field effect transistors (CNFET), interconnects, nano-electromechanical systems (NEMS). Using an energy-delay optimization approach, we showed that the current available best CNT FETs is about 2-3 times more energy efficient than 32nm state-of-art silicon MOSFETs, evaluated at the same delay. At the 11nm technology node, CNFET is projected to outperform the ITRS target for logic devices by 2-3 times. In spite of the great performance potentials, challenges still exist on the way towards commercial carbon-based device technology. In this paper, we review some of the recent advances such as wafer-scale fabrication of CNFET-based logic circuit, circuit-level solution for removal of metallic CNTs, and integration of multi-walled CNTs and graphene interconnects with CMOS circuit.
Klein Tunneling in Graphene p-n-p Junctions
Authors: Rossi Enrico , Bardarson Jens H. , Brouwer Piet W.
Published: April 2011

We study the effect of the Klein tunneling on the transport properties of graphene p-n-p junctions. We first analyze the ideal case of a clean system and then study the realistic case in which disorder is present. To take into account the effect of disorder we develop a method for obtaining quantum transport properties in graphene that uniquely combines three crucial features: microscopic treatment of charge disorder, fully quantum mechanical analysis of transport, and the ability to model experimentally relevant system sizes. Our results allow us to conclude unambiguously that recent transport experiments on graphene p-n-p junctions have indeed observed signatures of Klein tunneling. The analysis presented is based on Rossi et al. Phys. Rev. B 81, 121408R.
Multi-Gate Modulation Doped In0.7Ga0.3 As Quantum Well FET for Ultra Low Power Digital Logic
Authors: Liu Lu , Saripalli Vinay , Hwang Euichul , Narayanan Vijay , Datta Suman
Published: April 2011

Multi-gate modulation doped In0.7Ga0.3As quantum well FETs (MuQFETs) are simulated, fabricated and analyzed in detail. The devices operate in both classical and non-classical quantum regime. Due to its robust electrostatics, its excellent channel transport properties and its versatile classical and quantum mode operation capability, In0.7Ga0.3As MuQFET is promising device architecture for future ultra low power information processing applications.
Interfacial and Electrical Properties of GaAs Metal-Oxide-Semiconductor Device with TiOxNy High-k Gate Dielectrics
Authors: Das T. , Mahata Chandreswar , Sutradhar G , Bose P K , Maiti C.K.
Published: April 2011

Fermi level pinning attributed to oxides at the GaAs/high-k interface is a major obstacle to develop GaAs-based metal-oxide-semiconductor devices. In this paper, plasma nitridation of GaAs surface prior to the high-k deposition is shown to solve the issue of interface pinning. X-ray photoelectron spectroscopy (XPS) study confirms that nitridation passivation effectively suppresses the oxides formation and minimizes the Fermi level pinning at the interface between the GaAs and TiO2. Plasma-nitrided TiO2 (TiOxNy) films on n-GaAs show better metal-oxide-semiconductor (MOS) capacitor characteristics, such as interface state density, accumulation capacitance, hysteresis, and leakage current.
III-V/Si Electronics
Authors: Fitzgerald Eugene A. , Yang Li , Cheng Cheng-Wei
Published: April 2011

We describe the creation of low defect density III-V materials near the lattice constant of InP on Si substrates and the effect of dielectric/III-V interfaces on mobility in InGaAs channels. The GaAsSb metamorphic system appears to be a promising method for achieving a relatively low threading dislocation density when spanning the Ge-to-InP lattice constant. Our mobility studies show that more than 15nm is required between the dielectric/III-V interface and the InGaAs channel to achieve maximum channel mobility, suggesting that ultimate III-V MOSFET performance will require improved dielectric/III-V interfaces.
Study of La2O3/HfO2Gate Dielectric for n-InAs Metal-Oxide-Semiconductor Capacitor
Authors: Lin Yueh-Chin , Chang Chia-Hua , Kakushima Kuniyuki , Iwai Hiroshi , Shie Tin-En , Huang Guan-Ning , Lu Po-Ching , Lin Ting-Chun , Chang Edward Yi
Published: April 2011

In this study, we investigate the composite La2O3/HfO2 high k dielectric as the gate oxide for n-InAs metal-oxide semiconductor (MOS) capacitor. The La2O3 was used for its high k value and HfO2 was used as the diffusion barrier and was deposited between La2O3 and InGaAs to prevent the Inter-diffusion between InAs and La2O3 layers after post deposition annealing (PDA). Finally, we demonstrate the La2O3/HfO2 composite oxide structure as the high K dielectric for n-InAs MOS capacitor with enhanced capacitance for the MOS capacitor.
Si1-xGex-Channel PFETs: Scalability, Layout Considerations and Compatibility with Other Stress Techniques
Authors: Eneman Geert , Hellings Geert , Mitard Jerome , Witters Liesbeth , Yamaguchi Shinpei , Garcia Bardon Marie , Christie Phillip , Ortolland Claude , Hikavyy Andriy , Favia Paola , Bargallo Gonzalez Mireia , Simoen Eddy , Crupi Felice , Kobayashi Masaharu , Franco Jacopo , Takeoka Shinji , Krom Raymond , Bender Hugo , Loo Roger , Claeys Cor , De Meyer Kristin , Hoffmann Thomas
Published: April 2011

Si1-xGex-channel pFETs can combine enhanced intrinsic performance with a threshold voltage shift, therefore this technology possibly facilitates the use of high-k/metal gate stacks in high-performance applications. This review presents imec's work on a new device concept using Si1-xGex-channels, the implant-free quantum well transistor, that can additionally provide improved short-channel scalability, as well as further performance enhancement when compared to conventional silicon and Si1-xGex-channel pFETs. Furthermore, circuit simulations of Si1-xGex-channel pFETs indicate that this technology shows even more enhanced potential at reduced supply voltages, and also in circuits that allow operation at lower electric fields such as stacked transistors. Finally it is demonstrated that the layout sensitivity of Si1-xGex-channel pFETs is an important concern, especially for variations of the device width. The effectiveness of another stress technique, Si1-xGex Source/Drain, is shown to be decreased when used in combination with Si1-xGex-channel pFETs.
Electrical Properties of SiGe MOS Capacitors with Ultrathin ALD Hafnium Dioxide
Authors: Mallik S. , Mahata Chandreswar , Hota M.K. , Dalapati G. K. , Gao H. , Kumar M. K. , Chi D. Z. , Sarkar C. K. , Maiti C.K.
Published: April 2011

Ultra thin HfO2 high-k gate dielectric has been deposited directly on Si0.81Ge0.19 by the atomic layer deposition (ALD) process. HfO2 layers were characterized by grazing incidence x-ray diffraction (GIXRD) to examine crystallinity. In this work it is shown that MIS capacitors annealed in N2 ambient show better electrical properties than the samples annealed in O2 and mixed gas ambient (O2 and N2) and without annealing. Furthermore, trapping and detrapping behavior of charge carriers in N2 annealed ultrathin HfO2 gate dielectrics during constant current stress (CCS) and constant voltage stress (CVS) has been investigated in detail.
Recent Developments in the SECA Program
Authors: Vora Shailesh D.
Published: April 2011

The development of an electric power generation technology that effectively uses coal, our major domestic energy source, and meets environmental requirements and water conservation needs, is of crucial importance to the United States. Work to achieve that objective is being done by the U.S. Department of Energy Office of Fossil Energy. Embodied in the Solid State Energy Conversion Alliance (SECA) program, the development of the required power generation technology is centered on the solid oxide fuel cell as the key enabling technology, and is being done at the National Energy Technology Laboratory. The overall SECA program goal is the development of power generation technology for cost-effective, high-efficiency, central-station (>100 MWe) power systems that are equipped for effective carbon capture, and which restrict to specified levels the emission of other pollutants such as mercury, NOx, and SOx. SECA program status and accomplishments are reviewed.
Status of National Project for SOFC Development in Japan
Authors: Hosoi Kei , Ito Masanori , Fukae Mamoru
Published: April 2011

New Energy and Industrial Technology Development Organization (NEDO) has started the development project of system and elemental technology on SOFC from Fy2008. The objective of this project is to clarify the prospects for 40,000 hours of operation (voltage decrease rate less than 0.25%/1,000 hours) and the prospects for 250 start-up and stop operations. Thermodynamic analysis, a chemical analysis, and a mechanical analysis have been conducted to make clear the deterioration mechanism, to make the countermeasures, and to establish acceleration test method. In addition, start-stop technology aiming at improving operability, and high-pressure operation technology aiming at achieving ultra-high-efficiency operation have been developed. The demonstrative research project on SOFC has been started since Fy2007. In this project, 136 units of 0.7-8 kW SOFC systems were installed in various actual load environments and the operating data were evaluated and analyzed to identify issues which would feed back into the technological development project mentioned above.
European SOFC Technology - Status and Trends
Authors: Steinberger-Wilckens Robert
Published: April 2011

Solid Oxide Fuel Cells are gradually evolving from the laboratory stage to technology being introduced to the market. New products address real consumers, though in first niche areas only. In European SOFC development planar designs prevail. Several companies are already offering cells, stack components, stack modules and complete units, at least at a pre-competitive level, e.g. for demonstration projects. This contribution offers an overview of European developments and summarizes the activities around the Fuel Cell and Hydrogen Joint Undertaking (JTI) and the projects conducted with JU funding.
Solid Oxide Fuel Cells Canada NSERC Strategic Research Network
Authors: Birss Viola I. , Petric Anthony , Thomas Sharon
Published: April 2011

The SOFC Canada Network is an association of about 20 research groups from both university and government, partnered with industry. A sub-program provides funding for student workshops, as well as opportunities for student travel both within the Network and internationally. The technical objectives of the Network include enhancing the sulfur/coke tolerance of the fuel processor, improving the performance of cells with sulfur-containing fuels through the development of new sulfur and coke tolerant anodes, as well as increasing cell robustness and lowering cost through alternative cell manufacturing methods and design. Some key research highlights arising from the Network are described here.
The Strategic Electrochemical Research Center in Denmark
Authors: Mogensen Mogens , Hansen Karin
Published: April 2011

A 6-year strategic electrochemistry research center (SERC) in fundamental and applied aspects of electrochemical cells with a main emphasis on solid oxide cells was started in Denmark on January 1st, 2007 in cooperation with other Danish and Swedish Universities. Furthermore, 8 Danish companies are taking part in the center. Now after 4 years both new equipment and methods have been developed and new scientific and technical results have been generated in relation to four technical applications, namely fuel cells, electrolysers, gas cleaners and oxygen sensors. Selected techniques and results are presented.
Recent Results in Solid Oxide Fuel Cell Development at Forschungszentrum Juelich
Authors: Steinberger-Wilckens Robert , Blum Ludger , Buchkremer Hans Peter , De Haart Bert , Malzbender Jürgen , Pap Michael
Published: April 2011

The JÜLICH SOFC group has assembled and tested more than 430 SOFC stacks rated between 100 W and 15 kW during the last 15 years. The main focal points of current development are the improvement of SOFC stack lifetime, increased performance, especially at relatively low temperatures (<700°C), increased robustness of stacks and an improved understanding of degradation phenomena. Recently, 30 000 hours of continuous operation were reached with a short stack test.
Development of Solid Oxide Fuel Cells at Versa Power Systems
Authors: Borglum Brian , Tang Eric , Pastula Michael
Published: April 2011

Versa Power Systems (VPS) is a developer of solid oxide fuel cells (SOFCs) for clean power generation. VPS has been working with its development partner FuelCell Energy within the U.S. Department of Energy (DOE) Office of Fossil Energy's Solid State Energy Conversion Alliance (SECA) program to apply SOFC technology in large-scale power plant systems. As a result, initiatives such as scale-up of the cell and stack are being actively pursued for these applications.
CFCL's BlueGen Product
Authors: Payne Richard J. , Love Jonathan , Kah Michael
Published: April 2011

Ceramic Fuel Cells Limited is manufacturing the BlueGen product that is being sold in a number of markets around the world. This paper describes the consistency achieved for all BlueGen units manufactured in 2010 delivering 60% AC electrical efficiency (LHV) on start up. The consistency in performance over time is described and 55% efficiency is achieved after 1 year operation. The power modulation and turn down performance are also described with greater that 50% AC electrical efficiency (LHV) achieved as low as 750 W exported power.
Progress on SOFC Power Generation Module and System Developed by NTT, SPP and THG
Authors: Hayashi Katsuya , Miyasaka Akihiro , Katou Naoki , Yoshida Yoshiteru , Arai Hajime , Hirakawa Makoto , Uwani Hiroyuki , Kashima Shoichi , Orisima Hiroshi , Kurachi Seigo , Matsui Akira , Katsurayama Koichi , Tohma Eiji
Published: April 2011

An SOFC system generating a 5 kW-class AC output power has been developed to demonstrate high electrical efficiency over 1000 hours. The SOFC mono-generation system, consisted of a power generation module and a balance of plant. We have measured the characteristics of the SOFC system, namely, the electrical efficiency at the rated output power, the power consumption of the BOP, and the DC/AC conversion efficiency of an inverter. This paper describes the system configuration and design points that make it possible to achieve high performance. In addition, the experimental results reveal the long-term voltage stability and the electrical efficiency of the SOFC system.
Latest Update on Delphi's Solid Oxide Fuel Cell Stack for Transportation and Stationary Applications
Authors: Mukerjee Subhasish , Haltiner Karl , Kerr Rick , Kim Jin-Yong , Sprenkle Vince
Published: April 2011

Delphi is developing Solid Oxide Fuel Cell (SOFC) technology for applications in a variety of markets, in participation with the U.S. Department of Energy (SECA, EERE). This paper outlines the development of SOFC stacks and discusses the latest results, including key features of the cell and stack developed under the SECA program, Delphi's progress in demonstrating the technology as an Auxiliary Power Unit for trucks and key achievements toward meeting goals for commercialization.
Characterization of Propane-Fueled SOFC Portable Power Systems
Authors: Du Yanhai , Cui Daan , Reifsnider Kenneth
Published: April 2011

Solid oxide fuel cells (SOFCs) have the capability to use hydrocarbon fuels and the potential to offer high efficiency and reliable power to many end users. Propane is a popular and readily available commercial fuel for a wide range of portable applications. This paper discusses various aspects of several propane-fueled and thermally self-sustained SOFC portable power systems, such as startup and shutdown characteristics, thermal cycling, load cycling, power output stability, effects of environmental temperatures and humidity on performance, and durability.
System Tests and Operation Control Strategies of an SOFC-CHP-Device for Field Testing
Authors: Belitz Rico , Heddrich Marc Philipp , Jahn Matthias , Näke Ralf Michael , Paulus Jochen , Pohl Markus
Published: April 2011

As SOFC microCHP systems come closer to commercial application, Vaillant GmbH as one of Europe's largest heating appliance manufacturers and their development partner Fraunhofer IKTS focus on system development for large scale demonstration.
Development of Metal-Supported Solid Oxide Fuel Cells
Authors: Franco Thomas , Haydn Markus , Mücke Robert , Weber André , Rüttinger Matthias , Büchler Oliver , Uhlenbruck Sven , Menzler N.H. , Venskutonis Andreas , Sigl Lorenz S.
Published: April 2011

A novel generation of a thin-film, metal supported solid oxide fuel cell (MSC) has been developed and demonstrated in the scope of the NextGen MSC project (funded by the German Federal Ministry of Economics and Technology) by Plansee, Forschungszentrum Jülich (FZ-J), and the Karlsruhe Institute of Technology (KIT), respectively. In the scope of this work, due to consequent electrolyte and electrode development, a novel cell configuration, based on Plansee's well-known porous FeCr alloy as mechanical cell support, could be established. Thus, first cell measurements at KIT indicate the feasibility and the reliability of the established cell manufacturing process. The tested cell has shown a current density of 1.52 A/cm² at 0.7 V and 820 °C. This corresponds with an area specific cell performance of 1,064 mW/cm2. Furthermore, during a cell operation time of approx. 300 hrs., the cell degradation was relatively low.
Metal Supported Solid Oxide Fuel Cell by Freeze Tape Casting
Authors: Wei Ping , Sofie Stephen , Zhang Qi , Petric Anthony
Published: April 2011

Freeze tape casting was used to fabricate a porous metal support for the solid oxide fuel cell (SOFC). The parameters that affect tape quality, such as casting temperature, solid loading, amount of additives and particle size of steel powders, have been investigated. It was found that that casting temperatures between -40°C and -80°C did not affect pore size and structure of the metallic tapes. The porosity and shrinkage rate of the metallic tapes is highly influenced by the solid loading, but not by the particle size of the steel powders. Multiple layers of the single cell structure were deposited on the freeze cast green tape by screen printing. A composite cathode of nano-size lanthanum strontium manganite (LSM) plus YSZ was obtained by infiltration.
Transient Performance of Micro-Tubular Solid Oxide Fuel Cells and Stacks
Authors: Howe Katie , Kendall Kevin
Published: April 2011

The transient performance of micro-tubular solid oxide fuel cells and six-cell stacks was investigated, with promising results. It was found that a single cell can take less than 0.5 seconds to adjust to load changes, even when the change crosses the majority of the cell's range. When steps of equal size were ranged across the current-voltage spectrum, more distortion was seen at the higher voltages. Six-cell stacks were tested with the cells arranged both in series and parallel. The response time was marginally longer for these stacks, being 0.6 to 0.7 seconds, irrespective of step size. Again, very good load-following characteristics were observed, with no observable degradation in performance. In addition, no under-shooting of the voltage was seen in any of these tests, despite several predictions of such in the literature.
Performance and Energy Efficiency of a Microtubular Solid Oxide Fuel Cell
Authors: Suzuki Toshio , Sugihara Shinichi , Hamamoto Koichi , Yamaguchi Toshiaki , Fujishiro Yoshinobu
Published: April 2011

Performance and energy efficiency of a single microtubular solid-oxide fuel cell (SOFC) has been studied in various experimental conditions and directly correlated to the character of the cell. The performance of the cell with Ni-YSZ anode supported, ScSZ electrolyte increases from 0.25 to 0.42 Wcm-2 by increasing the fuel flow rate at 620 oC cell temperature. On the other hand, the energy efficiency of the cell simply improves by decreasing the fuel flow rate, and reaches 26% (LHV) in flowing 20% H2 - Ar fuel inside the tube. Impedance analysis has suggested that the improvement of polarization resistances will effectively increase the energy efficiency of the cell at lower operation temperatures.
Impact of Sintering Mechanism Evolution on Electrochemical Performance of Cathode Support Tubular Solid Oxide Fuel Cells
Authors: Zhou Juan , Zhao Chunhua , Ye Xiaofeng , Wang Shaorong , Wen T. L.
Published: April 2011

Cathode-supported tubular solid oxide fuel cells (CS-T-SOFCs) have been regarded as promising energy conversion devices; However, their commercialization was blocked by high manufacturing cost. We have been researching dip-coating and co-sintering techniques for fabricating CS-T-SOFCs in order to reduce the cost. In this paper, we improved the sintering process and found that the degree of co-sintering has significant effects on the microstructure of electrodes and the electrolyte. The co-sintering temperature is limited by the reaction between the (La0.8Sr0.2)0.95MnO3+δ (LSM95) cathode and the Zr0.89Sc0.1Ce0.01O2+δ (SSZ) electrolyte; However, by changing the co-firing temperature of the cathode-supported electrolyte tube, the relative density of electrolyte and the connection of anode particles to CS-T-SOFC could be improved. As a result, the maximum power density of a CS-T-SOFC reached 740, 635and 489 mW•cm-2 at 850, 800 and 750 oC, respectively, with hydrogen as fuel. The long-term stability of the improved CS-T-SOFC was also investigated.
Materials for Proton Conducting Solid Oxide Fuel Cells (H-SOFCs)
Authors: Thangadurai Venkataraman , Kan Wang Hay H. , Mirfakhraei Behzad , Bhella Surinderjit , Trinh Trang T.
Published: April 2011

In this paper, we report our steps forward in the search of proton conducting metal oxides possessing disordered perovskite-type and B-site ordered double perovskites for application in solid oxide fuel cells (SOFCs) and mixed proton-electron conductors as anodes for SOFCs. Role of A- and B- site cations in the perovskite structures on electrical properties and their corresponding chemical stability in CO2, H2S and H2O have been studied. Partial substitution of the parent phase is one of the most effective and popular approaches in which certain ions in the lattice are replaced by foreign species. However, "the right recipes" are not usually obvious; optimization on the functional physical and chemical properties is often based upon "the trial and error" strategy. Here, we review our progress since 2005 in the development of the proton conducting solid oxide fuel cells (H-SOFCs).
Anode/Electrolyte Interface Modification in LSGM Electrolyte Supported SOFC
Authors: Kawahara Koichi , Suda S. , Suzuki Masaya , Kawano Mitsunobu , Yoshida Hiroyuki , Inagaki Toru
Published: April 2011

We studied the effects of the introduction of a spinel compound ((Co0.67Mg0.33)Fe2O4) or a perovskite compound (SrFeO3) as a reactive layer between anode and electrolyte on the SOFC performance of Ni-SDC/LSGM/SSC single cells. The SOFC performance was improved by introduction of reactive layer. The improved performance was mainly attributed to the decrease in ohmic loss. TEM/EDX analyses in the vicinity of the anode/electrolyte interface revealed that Fe diffused at the surface of LSGM, and the Fe diffusion would lead to the decrease in ohmic loss.
Fabrication of Solid Oxide Fuel Cell Using the Dual Tape Casting Method
Authors: Ghobadzadeh Amir H. , Mohebbi Hamed , Raoufi Arman , Aslannejad Hamed , Davari Susan
Published: April 2011

SOFC single cell was fabricated by using cost effective and simple methods like tape casting and screen printing. Anodic and anodic active layer and electrolyte layer were made by tape casting method. Properties and characterization of the cell was examined. Results showed fabricated cell has good microstructure and its performance that comparable with the other SOFC.
A New Type of SOFC for Conversion of High Temperature Heat to Electricity without Carnot Limitation
Authors: Jacob K. T.
Published: April 2011

A new type of solid oxide fuel cell (SOFC) is presented which can convert heat absorbed from a high-temperature source to electricity bypassing the Carnot limitation and use solid carbon as the fuel. The essential cell reaction is the partial oxidation of carbon to carbon monoxide, unlike in the case of conventional SOFC where oxidation of hydrogen and carbon monoxide to water vapour and carbon dioxide are the main reactions. The fuel cell is endothermic and absorbs heat from an external source and converts it to electricity. The theoretical basis of the new fuel cell is explained and some preliminary experimental results are presented. A liquid metal is used as the medium for the carbon-oxygen reaction generating carbon monoxide. There is no violation of the second law of thermodynamics since the theoretically loss free conversion of heat to electricity is accompanied by a chemical reaction.
Electrochemical Performance of Cone-Shaped Tubular Anode Supported Solid Oxide Fuel Cells Fabricated by Low-Pressure Injection Moulding Technique
Authors: Xiao Jie , Liu Jiang , Ding Jiao
Published: April 2011

Low-pressure injection moulding (LPIM) technique was successfully developed to fabricate porous NiO-YSZ anode substrates for cone-shaped tubular anode-supported solid oxide fuel cells. A single cell, NiO-YSZ / YSZ/ LSM-YSZ was assembled and tested to demonstrate the feasibility of the technique applied. The single cell provided a maximum power density of 795 mW/cm2 at 850oC with the effective area of the cathode 1.21cm2, using moist hydrogen(75ml/min) as fuel and ambient air as oxidant. The observed open-circuit voltages (OCV) was closed to the theoretical value and the scanning electron microscope (SEM) results revealed that the microstructures of the anode substrate and the cathode layer were porous and the electrolyte film was dense.
Impedance Analysis of Practical Segmented-in-Series Tubular Solid Oxide Fuel Cells
Authors: Liu Bin , Matsui Toshiaki , Muroyama Hiroki , Tomida Kazuo , Kabata Tatsuo , Eguchi Koichi
Published: April 2011

The individual electrode processes from anode and cathode have been clearly identified from practical impedance spectra with high-frequency inductive impedance for the Mitsubishi segmented-in-series tubular solid oxide fuel cell by combining the distribution of relaxation times (DRT) analysis and the complex nonlinear least square (CNLS) fitting. Anodic gas diffusion process and charge transfer reaction near anodic triple phase boundary (TPB) appear at ca. 0.3 Hz and 1000 Hz, respectively. Cathodic oxygen reduction processes appears at ca. 10 Hz at 700 oC, whereas the impedance arc over 10000 Hz is dominated by the cathodic oxygen ion transfer through the LSM/YSZ interface and YSZ of the composite. The results also exhibit an excellent agreement with those from the analysis of difference in impedance spectra (ADIS).
Impedance Behavior of SOFC at High Fuel Utilization and a Way of Evaluating Diffusion Contribution
Authors: Momma Akihiko , Tanaka Yohei , Takano Kiyonami , Kato Tohru
Published: April 2011

A quantitative evaluation method of gas diffusion resistance is proposed in which measurement of V-I characteristics under constant fuel utilization (Uf) and ac impedance were combined to separate diffusion and electromotive force change contributions from the low frequency semi-circle observed in complex impedance diagrams. Diffusion resistance was evaluated using various hydrogen content mixture diluted with nitrogen, Uf , hydrogen flow rate and current as parameters. From the measurement under various Uf, it was found that the diffusion resistance at low Uf originates mainly from the diffusion of H2O. Also, from the measurement under various hydrogen concentration in inlet fuel, the diffusion resistance was found to become significantly large with decreasing hydrogen content.
Hydrogen-Oxidation Kinetics in Reformate-Fuelled Anode Supported SOFC
Authors: Kromp Alexander , Leonide André , Weber André , Ivers-Tiffée Ellen
Published: April 2011

In this study, the reformate operation of solid oxide fuel cells (SOFC) is characterized by electrochemical impedance spectroscopy. The characterization is performed over a broad measuring range of temperature and H/C/O-ratios of the fuel. The kinetic parameters of the electrochemical oxidation of the fuel are obtained directly from impedance measurements performed on full anode-supported SOFCs. This is done by a combined distribution of relaxation times and an equivalent circuit impedance analysis method, which allows a highly resolved identification and deconvolution of each single polarization mechanism contributing to the overall losses of the cell. The evaluated kinetic parameters in reformate are the same as under hydrogen operation. Obviously only hydrogen is directly electrochemically oxidized in reformate-fuelled cells. The higher overall polarization resistance compared to hydrogen operation has to be attributed to the occurrence of an additional process, which is interpreted in this work.
Operation Characteristics of Tubular Segmented-In-Series Solid Oxide Fuel Cells (SOFC)
Authors: Lim Tak-Hyoung , Yun U. J. , Lee Jong-Won , Lee Seung-Bok , Park Seok-Joo , Song Rak-Hyun , Shin Dong-Ryul
Published: April 2011

A novel design of tubular segmented-in-series solid oxide fuel cell (SOFC) unit bundle was presented in this paper. The tubular ceramic support was fabricated by the extrusion technique. The anode functional layer and the yttria-stabilized zirconia (YSZ) electrolyte are deposited onto the ceramic support by dip coating method. Also, the multi-layered cathode composed of LSM/8YSZ composite, LSM and LSCF were coated onto the co-sintered ceramic support by dip coating method and sintered at 1150°. The performance of first cell in the unit bundle at 800oC showed maximum power of 30.6mW/cm2.
Metal-Supported SOFC with Ceramic-Based Anode
Authors: Blennow Peter , Klemenso̸ Trine , Persson Asa , Brodersen Karen , Srivastava Akhilesh K. , Sudireddy Bhaskar R. , Ramousse Severine , Mogensen Mogens
Published: April 2011

Metal-supported solid oxide fuel cells have shown promise to offer several potential advantages over conventional anode (Ni-YSZ) supported cells, such as increased resistance against mechanical and thermal stresses and a reduction in materials cost. The purpose of this work is to illustrate how the metal-supported cell concept can be combined with ceramic-based anode materials, such as Nb-doped SrTiO3. The paper shows that a metal-supported cell can have excellent performance by only having electronically conducting phases in the anode backbone structure, into which electrocatalytically active materials are infiltrated after sintering. Initial area specific resistance as low as 0.3 Ωcm2 at 700 ºC has been obtained with power densities > 1 Wcm-2. The initial results on the chemical compatibility, electrochemical performance, and galvanostatic durability of a ceramic based (Nb-doped SrTiO3), zirconia-free anode, in a planar metal-supported SOFC concept is discussed.
Anode-Supported Tubular SOFC at Low Temperature Using Ni, Fe, GDC, and YSZ Based Anode Support
Authors: Liang Bo , Suzuki Toshio , Hamamoto Koichi , Yamaguchi Toshiaki , Fujishiro Yoshinobu , Awano Masanobu , Ingram Brian J. , Carter John David
Published: April 2011

NiO-GDC, NiO-YSZ, NiO-Fe2O3-GDC, NiO-Fe2O3-YSZ anode tube supported tubular fuel cells was fabricated at the co-sintering temperature from 1250 oC to 1400 oC to investigate how the co-sintering temperature affect the open-circuit voltage. To focus on the changing of anode tube, all the tubular fuel cells support a ScSZ electrolyte layer and a LSCF cathode layer. The microstructure of the electrolyte layer sintered under 1300 oC included pores inside it, and the densification of the electrolyte completed at the sintering temperatures above 1300 oC. Furthermore, the shrinkage both in length and in diameter of a tubular fuel cell reaches as much as 20% at co-sintering temperature of 1400 oC. The densification of ScSZ electrolyte layer and shrinkage of anode tube will result in the changing of open-circuit voltage of fuel cell from 1.0 V to 1.1 V.
Investigation on the Electrochemical Properties of the Ni-YSZ/Ni-ScSZ/ScSZ/LSM Tubular Solid Oxide Cell for High Temperature Steam Electrolysis
Authors: Shao Le , Wang Shaorong , Qian Jiqin , Xue Yanjie , Liu Renzhu
Published: April 2011

Cathode-supported tubular solid oxide cells were fabricated by dip-coating and co-sintering technology. The electrochemical properties of the tubular cell were investigated both in solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC) modes. In SOFC mode, the maximum power density reached 420 mW cm-2 with H2 (105 mL min-1) and O2 (70 mL min-1) as working gases at 850 oC. In SOEC mode, I - V curves and EIS results suggested that steam ratio had a strong impact on the performance of the tubular cell, and the LSM-ScSZ anode polarization predominate the polarization of the whole tubular SOECs. The acceptable resistance values indicated that the fabricated SOECs can be used for high temperature steam electrolysis (HTSE) or electricity production.
Numerical Simulation of Anode-Supported Disc-Type Single Cell at Anode Off-Gas Recycle
Authors: Tanaka Yohei , Momma Akihiko , Sato Katsutoshi , Kato Tohru
Published: April 2011

Numerical simulations were implemented to predict a disc-type single cell performance with gas seal at anode off-gas recycle from the previous experimental results without gas seal. It was clarified that 70% DC electrical efficiency with seal could be expected at 700ºC, 387 mA cm-2 (90% fuel and 45% air utilizations) and recycle ratio r = 0.67 by 17 mV enhancement in the cell voltage with gas sealing. The efficiency would be increased by 1 percent points compared to one without seal. Distribution of current density, anode gas composition, and electromotive force in the cell with seal was also elucidated. Furthermore, it was revealed that change in current density, H2 concentration, and electromotive force between the cell inlet and outlet could become smaller as the recycle ratio increases. It was also found that differences in recycle ratio (r = 0.56, 0.67, 0.74) could influence cell voltage only by ± 1%.
Low Temperature Operating Micro Solid Oxide Fuel Cells with Perovskite Type Proton Conductors
Authors: Iguchi Fumitada , Kubota Kensuke , Inagaki Yu , Tanaka Shuji , Sata Noriko , Esashi Masayoshi , Yugami Hiroo
Published: April 2011

We fabricated micro solid oxide fuel cells with perovskite type proton conductors on silicon substrates, and evaluated their electrical properties using electrochemical impedance spectroscopy (EIS). The cells with 15mol% yttrium-doped BaZrO3 and Pt-Pd electrodes could resist several thermal cycles from room temperature to 317oC, and they showed sufficient open circuit voltage over 1V around 300oC, if physical gas leakage was properly prevented. Maximum power density of cells reached 8.4mW / cm2 at 270oC. This value was quite promising for low temperature operation. But, the results of power generation test were so different each other and difference was sometimes over two orders of magnitude. EIS results indicated the contribution of electrolyte resistance to total resistance was small and those differences were due to the difference of electrode reaction components.
Three-Dimensional Simulation of SOFC Anode Polarization Characteristics Based on Sub-Grid Scale Model
Authors: Kishimoto Masashi , Iwai Hiroshi , Saito Motohiro , Yoshida Hideo
Published: April 2011

Three-dimensional numerical simulation of SOFC anode polarization is conducted with a structure obtained by a focused ion beam and scanning electron microscope (FIB-SEM). Electronic, ionic and gaseous transports with electrochemical reaction are considered. A sub-grid scale model is newly developed and effectively used to evaluate the transport flux in the porous structure. The proposed SGS model shows its potential to reasonably evaluate the transport flux considering the microstructure smaller than the grid size.
Modeling the Electrochemistry of an SOFC through the Electrodes and Electrolyte
Authors: Ryan Emily , Recknagle Kurt , Khaleel Moe A.
Published: April 2011

This paper describes a distributed electrochemistry model of the solid oxide fuel cell (SOFC) electrodes and electrolyte. The distributed electrochemistry (DEC) model solves the transport, reactions, and electric potential through the thickness of the SOFC electrodes. The DEC model allows the local conditions within the electrodes to be studied and allows for a better understanding of how electrochemical and microstructural parameters affect the SOFC performance. In this paper the governing equations and implementation of the DEC model are presented along with several case studies which are used to investigate the sensitivity of the SOFC performance to the microstructural and electrochemical parameters of the cathode and to explore methods of improving the electrochemical performance of the SOFC cathode.
Mathematical Modeling and Simulation for Optimization of IDEAL-Cell Performance
Authors: Bertei Antonio , Nicolella Cristiano , Delloro Francesco , Bessler Wolfgang G. , Bundschuh Nicola , Thorel Alain
Published: April 2011

The IDEAL-Cell is an innovative SOFC concept, comprising the anodic part of a proton conducting fuel cell (i.e., anode and protonic electrolyte) and the cathodic part of a solid oxide fuel cell (i.e., cathode and anionic electrolyte), connected through a porous composite central membrane of proton conducting and anion conducting materials where water recombination reaction between protons and oxygen ions occurs. A mathematical model for the description of transport phenomena and reactions in steady-state conditions is presented. The model is based on charge and mass balances in a continuum approach. Simulations are performed considering negligible polarization resistances due to electrochemical activations in order to evaluate the maximum performance of the cell. Simulations show that the IDEAL-Cell performance is comparable to that provided by the current state of the art for proton conducting fuel cells, and it may be further improved by reducing ohmic losses with thinner layers.
Modeling Segmented-in-Series SOFCs with Distributed Charge Transfer and Internal Reforming
Authors: Zhu Huayang , Kee Robert J.
Published: April 2011

This paper develops and applies a two-dimensional computational model that can be applied to evaluate the performance of unit cells on segmented-in-series (SIS) solid-oxide fuel cell (SOFC) modules. The model accommodates detailed heterogeneous chemistry as well as distributed electrochemical charge transfer throughout the entire membrane-electrode assembly. The local charge-transfer rates depend upon local electric-potential differences between the electrode and electrolyte phases. The results predict optimal performance as a function of unit-cell width.