bluuebunny/crossref_metadata_2025 huggingface dataset:
Protective Coatings for Metallic Components in Solid Oxide Fuel Cell Systems
Authors: Kidner Neil J , Ibanez Sergio , Arkenberg Gene , Seabaugh Matthew M , Swartz Scott L
Published: July 2015

For successful implementation of low cost stainless steels in solid-oxide fuel cell (SOFC) systems, protective coatings are necessary to protect the air-facing metal surfaces from high temperature oxidation and to minimize chromium volatilization from the metal, because chromium volatiles poison the cathode and degrade cell performance. This paper outlines the performance of a manganese cobaltite (MCO) coating tailored for the cathode active-area of metallic interconnects. The coating demonstrates excellent long-term stability and chromium volatility resistance.
Coatings for SOFC Interconnects in Fuel Side Environments
Authors: Sachitanand Rakshith , Sattari Mohammad , Svensson Jan-Erik , Froitzheim Jan
Published: July 2015

This study focuses on examining the effect of PVD coatings on the oxidation performance of interconnects in fuel side environments. The ferritic steels Sanergy HT and AISI 441 were coated with nanoscale thick rare earth oxides of Ce and La. Additionally, Sanergy HT was also coated with Cu, Co and Ce/Co .The samples were exposed at 850°C in Ar-5 %H2-3% H2O in a tubular furnace. Chemical analysis on the samples was subsequently performed with SEM/EDX and XRD. It was established that the Ce and La coatings brought about a ≈4x reduction in the oxidation rate while the Cu and Co coatings remained metallic and negatively affected oxidation performance. Additionally, reaction of the La coating with the thermally grown oxide resulted in the formation of a perovskite phase which could be further developed to improve the electronic properties of the oxide.
Properties of Spinel Protective Coatings Prepared Using Wet Powder Spraying for SOFC Interconnects
Authors: Hong Jong-Eun , Bianco Manuel , Van herle Jan , Steinberger-Wilckens Robert
Published: July 2015

A wet powder spraying (WPS) method was applied to prepare protective layers of manganese cobalt spinel oxide (MCO) on commercial stainless steels of solid oxide fuel cell (SOFC) interconnects. Densification of the MCO layer was dependent on the thermal treatment condition in which a reactive sintering increased the coating density. An applied MnO sublayer reacted with the MCO layer during sintering, and resulted in secondary phase formation and limited densification. Both MCO and MnO-MCO coatings were adhering to the steel substrates and suppressed chromium diffusion during oxidation. The area specific resistance (ASR) of a test specimen including the MCO layer was 0.03 Ωcm2 at 700 °C after 800 h, lower than with MnO-MCO, which is believed to be due to the denser protective layer of the single phase and more limited chromia scale growth. Thus, an effective protective layer of metallic interconnects could be prepared using a simple wet coating method after optimization of the sintering conditions.
High Durability Electrodeposition Painting for SOFC Metal Interconnector
Authors: Inoue Shuichi , Nonaka Hidemasa , Saito Tadashi , Yoda Masakazu , Nakao Tadayuki , Takuwa Yuya
Published: July 2015

An electrodeposition painting method had the advantage of coating thickness uniformity regardless of the interconnector structure and mass productivity. But the firing process of the interconnectors coated by this method had to be developed because non-coated area of the interconnector was severely oxidized if the interconnectors were fired in air. Burning out the acrylate resin in the coating and sintering the spinel type oxide powders were possible in the same reduction atmosphere. The non-coated area was not oxidized. ASR(Area Specific Resistance) test showed excellent durability at both the continuous condition and the thermal cycle condition. The Cr diffusion from the stainless steel was also evaluated; it showed the high prevention of Cr diffusion. The variation of coating weight in the manufacturing process was very small, we concluded that this electrodeposition painting method is suitable for mass production.
Evaluation of Protective Coatings for SOFC Interconnects
Authors: Tallgren Johan , Bianco Manuel , Himanen Olli , Thomann Olivier , Kiviaho Jari , van Herle Jan
Published: July 2015

Chromium poisoning is a widely recognized degradation process in solid oxide fuel cells (SOFC). Stainless steel interconnect plates, in direct contact with the cathode, have been identified as the major chromium source, raising a need for electrically conducting protective coatings for the interconnects. This work evaluates four different manganese-cobalt protective coatings manufactured on thin steel foils, made by three commercial companies and a research centre. Area specific resistance, coating microstructure, and chromium retention are compared. Measurements were done in a humid atmosphere over 1000 hours at 700 °C. An innovative measurement setup was used, in which the coated steel samples are stacked adjacent to thin palladium foils with a screen-printed lanthanum strontium cobalt layer, replicating an SOFC cathode. As a conclusion, TeerCoating Ltd’s and Turbocoating S.p.A’s coatings performed similar to the Sandvik Material Technology’s cerium-cobalt reference coating, and could be employed as such in SOFC applications.
Fabrication of Mn1.5Co1.5O4 by Electrostatic Spray Deposition for Application as Protective Coating on Alloy Interconnects for Solid Oxide Fuel Cells
Authors: Conceição Leandro Da , Djurado Elisabeth , Dessemond Laurent , Muccillo Eliana Navarro Santos
Published: July 2015

A Mn1.5Co1.5O4 (MCO) protective coating was deposited by Electrostatic Spray Deposition on the SS446 alloy used as interconnects in Solid Oxide Fuel Cells. The main purpose of this work was to verify the feasibility this technique to inhibit the Cr volatilization and the subsequent SOFC cathode poisoning. Phase crystallization was obtained by thermal annealing at 800 °C in air, after deposition. The corrosion resistance behavior of the uncoated and coated steels was investigated by electric and thermogravimetric measurements. The coated films, 400 nm thick, were found efficient in reducing the oxidation rate, by limiting the outward Cr3+ diffusion. The area specific resistance of the coated SS446 alloy was found to be much lower (6.7 mΩ.cm2) and more stable as compared to the uncoated one (80 mΩ.cm2), after oxidation for 200 h at 800 °C in ambient air. These results evidence the good performance of the deposition technique for fabricating thin, crack free and dense conductive Mn1.5Co1.5O4 coatings on ferritic alloys.
Pre-Coated Ce/Co-Coated Steel: Mitigating Cr Vaporization, Increasing Corrosion Resistance at Competitive Cost
Authors: Falk Windisch Hannes , Mertzidis Ioannis , Svensson Jan-Erik , Froitzheim Jan
Published: July 2015

Cr vaporization and oxide scale growth are probably the two most detrimental degradation mechanisms associated to Cr2O3-forming alloys as interconnect material in SOFC. Both issues can be improved by the application of coatings. However, the use of coatings increase material cost. To reduce coating costs it is suggested that large amounts of steel can be coated before shaping the pre-coated material into an interconnect. The present study investigates the effectiveness of thin Ce and Co coatings on the cost effective steel AISI 441 with respect to Cr vaporization and corrosion resistance. Furthermore, the effect of mechanical deformation of the coated steel is examined. The results revealed that when the pre-coated steel is deformed, large cracks are formed. However, upon exposure those cracks can heal forming a continuous surface oxide rich in Co and Mn. As an effect of the rapid healing, no increase in Cr vaporization was measured.
Interaction between Crofer 22 APU Current Collector and LSCF Cathode Contacting Layer under Cell Operation
Authors: Spotorno Roberto , Piccardo Paolo , Perrozzi Francesco
Published: July 2015

In this work the oxidation of Crofer 22 APU and its interaction with La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) applied as contacting layer have been investigated in air at 750°C under a current load of 0.5 Acm-2 with the aim to reproduce as close as possible the interconnect interface in real operating conditions. The effects of such interaction and of the pre-oxidation treatment have been studied by means of ASR measurement and post-experiment characterizations. The behavior of such samples has been compared with the results on a working Crofer 22 APU bipolar plate tested as cathode current collector of an anode-supported cell reproducing the stack cathode compartment conditions.
Dependence of Electrical Properties on Thermal Reduction of Protecting Oxides for SOFC Interconnect Applications
Authors: Tsai Shu-Yi , Fung Kuan-Zong , Ni Chung-Ta , Ho Hsin-Chia
Published: July 2015

In this study, plasma sprayed (Mn,Co)3O4 (MCO) coatings with spinel structure are used to formprotective layer for metallic interconnects of solid oxide fuel cells.The temperature during thermal spraying is high enough to change the crystal structure and conductivityof protective oxides. The structure change is caused by the removal of oxygen ions at highertemperature. This behavior is so-called thermal reduction. Furthermore, the transformation of MCOSpinel to a NaCltypestructure causes the degradation in its conductivity by several orders ofmagnitude. With better understanding and control of thermal reduction and/or phase transformation, it isbelieved that the proper heat treatment is an adequate method to obtain desired properties for protectiveoxide.Thus, the objective of this study are (1) to investigate the influence of thermal reduction on theconductivity and crystal structure; (2) to improve the performance of interconnect through properannealing at desired temperatures. XRD, SEM, and impedance spectroscopy are used to characterizethe protective oxides before and after annealing and thermal reduction.
Self Healing of Precoated AISI 441 for Solid Oxide Fuel Cell Interconnects
Authors: Berger Robert , Lundberg Mats W , Westlinder Jörgen , Holmberg Håkan
Published: July 2015

Sandvik Materials Technology develops nanocoatings for SOFC stainless steel interconnects. The self-healing properties of cerium cobalt coated AISI441 (EN 1.4509) have been studied. A partially coated sample was oxidized in air at 800°C for a total of 504 hours. Prior to oxidation a focused ion beam (FIB) was used to mill a trench on the uncoated surface to be used as a reference point relative the coated border. A second FIB trench, made after oxidation, revealed that the oxide formed on the uncoated part adjacent to the coated area contained both cobalt and cerium. Cerium was detected with EDS in the surface oxide of the uncoated area as far as 10 µm away from the coated edge, cobalt had diffused even further. These findings are encouraging since they suggests that cracks introduced in the coating during stamping and/or forming, which are usually in the 1-3 µm range, are likely to self- heal (i.e. become enclosed by the forming Co, Mn, Cr-spinel) upon oxidation.
A Time Resolved Study of Precoated AISI 441 for SOFC Interconnects Using STEM-EELS - Part I
Authors: Karlsson Lisa S , Lundberg Mats W , Berger Robert , Westlinder Jörgen
Published: July 2015

Precoated AISI441 for SOFC interconnectors were investigated by STEM-EELS looking at the diffusion processes in the initial stage of the oxidation. The electron beam physical vapour deposition (EB-PVD) coating contained Ce and Co/Mn-alloy in two layers with at total thickness of 800 nm. The samples were exposed up to 1000 hours at 800°C, and then characterized by STEM-EELS. Multiple linear least squares (MLLS) fitting of reference spectra aids the interpretation of the elemental maps due to overlapping edges. Within 4 min heat treatment the oxidation front has reached the substrate steel and Cr2O3 is forming at the stainless steel interface. CeO2 acts as the barrier line for Cr and is situated between the Cr-containing spinels and the (Co,Mn)-spinel after up to 168 h heat treatment.
A Time Resolved Study of Precoated AISI 441 for SOFC Interconnects Using STEM-EELS - Part II
Authors: Karlsson Lisa S , Lundberg Mats W , Berger Robert , Westlinder Jörgen
Published: July 2015

Precoated AISI441 for SOFC interconnectors were investigated by STEM-EELS looking at the diffusion processes in the initial stage of the oxidation. The electron beam physical vapour deposition (EB-PVD) coating contained Ce and Co/Mn-alloy in two layers with at total thickness of 800 nm. The samples were exposed up to 1000 hours at 800°C, and then characterized by STEM-EELS. Multiple linear least squares (MLLS) fitting of reference spectra aids the interpretation of the elemental maps due to overlapping edges. Within 4 min heat treatment the oxidation front has reached the substrate steel and Cr2O3 is forming at the stainless steel interface. CeO2 acts as the barrier line for Cr and is situated between the Cr-containing spinels and the (Co,Mn)-spinel after up to 168 h heat treatment.
Multilayered Precoated AISI 441 for Solid Oxide Fuel Cell Interconnects
Authors: Lundberg Mats W , Berger Robert , Westlinder Jörgen , Holmberg Håkan
Published: July 2015

Sandvik Materials Technology develops nanocoatings for SOFC stainless steel interconnects. In this study a multilayered PVD-coating has been investigated. Cyclic oxidation for more than 20,000 hours at 800°C, chromium volatilization and area specific resistance studies has been conducted on three different coatings and compared with the uncoated steel, in this case AISI441 (EN 1.4509). In this work we have shown that pre-coated AISI 441 show very promising results for SOFC interconnectors at 800°C. We have studied and compared state of the art CeCo coating with a new four layered coating that shows slightly higher cumulative chromium volatilization, similar ASR values and reduced mass gain in the cyclic oxidation experiments. SEM micrographs show the multilayered the total oxide layer is less than 10 microns after more than 20,000 hours of exposure.
Modeling of Ni Diffusion Induced Austenite Formation in Ferritic Stainless Steel Interconnects
Authors: Chen Ming , Molin Sebastian , Zhang Lijun , Ta Na , Hendriksen Peter Vang , Kiebach Wolff-Ragnar , Du Yong
Published: July 2015

Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell (SOFC) or electrolysis cell (SOEC) stacks. During stack production and operation, nickel from the Ni/YSZ fuel electrode or from the Ni contact component diffuses into the IC plate, causing transformation of the ferritic phase into an austenitic phase in the interface region. This is accompanied with changes in volume and in mechanical and corrosion properties of the IC plates. In this work, kinetic modeling of the inter-diffusion between Ni and FeCr based ferritic stainless steel was conducted, using the CALPHAD approach with the DICTRA software. The kinetics of inter-diffusion and austenite formation was explored in full detail, as functions of layer thickness, temperature, time, and steel composition. The simulation was further validated by comparing with experimental results. Growth of the austenite phase in commercial interconnect materials is predicted to take place under practical stack operation conditions.
Metallic/Ceramic (Fe-22Cr mesh/ LaNi0.6Fe0.4O3-δ) Composite as Contact Material for SOFCs
Authors: Morán-Ruiz Aroa , Vidal Karmele , Larrañaga Aitor , Slater Peter Raymond , Arriortua María Isabel
Published: July 2015

A Fe-22Cr mesh/LaNi0.6Fe0.4O3-δ
(LNF) composite, obtained via dip coating technique, was machined using a femtosecond laser as a possible gas permeable contact layer for solid oxide fuel cells (SOFCs). Both electrical performance and processing reproducibility of {Crofer22APU channeled interconnect-ablated composite contact material-La0.6Sr0.4FeO3 (LSF) cathode} structure were studied through electrochemical measurements on four replicas. For comparison, the obtained area specific resistance (ASR) data, under similar measurement conditions, for {flat Crofer22APU/LNF contact perovskite/LSF} and {channeled Crofer22APU/contact composite} setups are also presented. The results support the reproducibility for the measured ablated final systems, obtaining average ASR value of 0.06(1) Ω cm2 at 800 ºC, in air.
Electrical and Oxidation Resistance of Surface Oxide of Porous Fe-Cr-Al Alloy for the Application of Metal Supported SOFCs
Authors: Pham Hung-Cuong , Taniguchi Shunsuke , Inoue Yuko , Chou Jyh-Tyng , Izumi Toru , Matsuoka Koji , Sasaki Kazunari
Published: July 2015

We have investigated the property of Fe-Cr-Al-type stainless steel as a porous alloy substrate for metal-supported SOFCs especially on the cathode side. We confirmed not only good heat resistance but also low electrical resistance at the interface between the porous substrate and a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) coating at 700 °C in air. Long-term durability of the oxidation resistance of the LSCF-coated Fe-Cr-Al alloy at 700 °C was investigated by measuring the mass gain, surface oxide thickness, and electrical resistance at different temperatures from 700 to 900 °C.
Development of Metal Supported Solid Oxide Fuel Cell Based on Interconnect Coating
Authors: Lee Kunho , Jin Sangbeom , Kang Juhyun , Lee Sanghun , Bae Joongmyeon
Published: July 2015

To develop interconnect-coating based metal supported solid oxide fuel cells (SOFCs), a new coating process which can deposit dense electrolyte at relatively low temperature of 1000℃ was studied. And then, the newly developed coating method was applied to interconnect-coating-based metal supported SOFC, and open circuit voltage of interconnect-based-metal supported SOFC was measured to identify whether dense electrolyte was formed on the interconnect-based-metal supported SOFC.
Electrical Conducting Properties of LSF-Based Composites as an Interconnection of Tubular Type of Solid Oxide Fuel Cells
Authors: Yu Ji Haeng , Lee Hee Lak , Shin Hyung Chul , Cho Sangyoung , Joo Jong Hoon , Yoo Chung-Yul
Published: July 2015

We investigated La0.8Sr0.2FeO3
-δ(LSF)-based composite materials as the interconnection for tubular SOFCs. LSF is a mixed ionic and electronic (hole) conducting material and thus shows low electrical conductivity in reducing (H2) atmosphere. However, composite materials with LSF and ceria show moderate electrical conductivity by electronic leakage current through doped ceria and LSF. LSF-GDC composite and LSF layers were successfully deposited on NiO-YSZ anode substrate by conventional co-firing process. The area specific resistance of LSF/LSF-GDC bilayer on Ni-YSZ measured in air//H2 condition was initially ~50 mΩcm2.
Manufacture of Solid Oxide Fuel Cells Using Electroless Co-Deposition: A Review of Work Carried out at Edinburgh Napier University
Authors: Davidson Alan , Wilson Callum , Shearer Neil
Published: July 2015

This paper reviews work carried out at Edinburgh Napier University on the manufacture of anodes and cathodes for solid oxide fuel cells (SOFCs) using electroless co-deposition of nickel and ceramic powders. Most of the work has been focused on anodes where the co-deposition of nickel and yttria stabilised zirconia (YSZ) negates the need for traditional manufacturing methods such as screen printing and removes the need for expensive and time consuming high temperature consolidation of the ceramic part of the composite. Work has also been carried out manufacturing cathodes by electroless co-deposition replacing YSZ with lanthanum strontium manganite and lanthanum nickel ferrite. Anodes and cathodes of both planar and tubular designs of SOFCs have been successfully manufactured using this technique and process variables have included ceramic particle size, bath pH, ceramic loading, the inclusion of pore-formers and tubular orientation in the electroless bath. Testing of the electrodes included impedance analysis, long term degradation testing at 850oC for 500 and 1000-hours, high temperature electrical conductivity measurements, scanning electron microscopy and energy dispersive X-ray analysis. The cost benefits of the electroless co-deposition process compared with other conventional processes are also discussed.
Results for a New SOFC-Stack Design with Parallel-Connected Cells
Authors: Szepanski Christian , Immisch Christoph , Lindermeir Andreas , Faulstich Martin , Dörrer Lars , Schmidt Ute , Borchardt Günter , Hamje Jens , Wesling Volker
Published: July 2015

The TU Clausthal and CUTEC have teamed up to design, build and test a new SOFC stack architecture, based on repeating units with cells connected in parallel. This approach allows the use of electrically conducting seals like brazes and can be realized without any glass sealing. Unlike conventional (serially connected) stacks, where all cells operate at the same current but individual voltage, in this setup each cell contributes as much current as possible at a common voltage. Thereby accelerated degeneration caused by undervoltage and the associated oxidation of the nickel catalyst can be completely overcome. The concept uses two cells in electrical parallel connection with the anodes facing each other to form a repeating unit. Two designs have been realized: An all ceramic housing made from 3YSZ, sealed with reactive air brazing (RAB) and a metallic one with Crofer 22 APU housing, joined by laser beam welding.
Mobilty of Sr in Gadolinia Doped Ceria SOFC Chemical Barrier Layers Prepared Using Spray Pyrolysis, Pulsed Laser Deposition and Magnetron Sputtering Methods
Authors: Nurk Gunnar , Möller Priit , Vestli Mihkel , Jaaniso Raivo , Kodu Margus , Mändar Hugo , Kanarbik Rait , Lust Enn
Published: July 2015

Gadolinia doped ceria Ce0.9Gd0.1O2-
d (GDC) barrier layers with thickness approximately 0.7 mm were deposited onto the YSZ electrolyte using pulsed laser deposition (PLD), magnetron sputtering (MS) and spray pyrolysis (SP) method. One set of layers were studied without additional sintering and other set were sintered for 30 h at 1300 °C before using as barrier layer. Sr mobility from Pr0.6Sr0.4CoO3-
d and La0.6Sr0.4CoO3-
d cathodes through PLD, MS and SP layers caused by thermal treatment at 950 °C and at 1100 °C, respectively, were systematically studied. Concentration profiles of Zr ion in GDC, Ce in YSZ, Sr in GDC and Sr in YSZ were recorded using TOF-SIMS analysis. XRD, SEM and electrochemical studies were performed. Influence of synthesis method and thermal treatment of layer on the Sr mobility was demonstrated. Changes in layer microstructure caused by thermal treatment of cathode as well as GDC layer during preparation were demonstrated.
Microstructure-Based Damage Modelling of Plasma Sprayed Ceramic Coatings in SOFC-Layer Systems
Authors: Guski Vinzenz , Krebs Axel , Weber Ulrich , Schmauder Siegfried
Published: July 2015

Solid oxide fuel cells (SOFC) promise interesting energy conversion systems for mobile and stationary usage. High temperatures enable the use of a variety of hydrocarbons fuels. These temperatures intensify chemical reactions, and a compromise between beneficial and harmful side effects on a SOFC has to be defined. For economical reasons, a SOFC design is required, applicable for batch-production leading to a staple of finely arrange structures to separate fuel and oxidizing agent reliably. In this work, we apply a holistic approach to include macro- and microstructural details into a holistic numerical model. A newly developed self-healing material is investigated. Using subroutine techniques in ABAQUS, we could simulate self-healing materials under realistic conditions, derive understanding of failure mechanism paths to forecast material over service lifetime.
Atmospheric Plasma-Sprayed Metal-Supported Solid Oxide Fuel Cells with Varying Cathode Microstructures
Authors: Harris Jeffrey , Kuhn Joel , Kesler Olivera
Published: July 2015

Metal-supported solid oxide fuel cells were manufactured by plasma spraying the cell layers on porous ferritic stainless steel supports. Cathodes with four different microstructures were produced by varying the plasma spray parameters and mixing carbon or starch-based pore forming agents with the ceramic feedstock powders. At 750°C, the best-performing button cell contained cathodes made with a carbon pore forming agent. This cell had an open circuit potential of 1.057 V and peak power density of 562 mW/cm². The lowest cell polarization resistance was 0.29 Ωcm² at 750°C, measured at an operating point of 0.7 V.
Degradation Studies and Sr Diffusion Behaviour in Anode Supported Cell after 3,000 h SOFC Short Stack Testing
Authors: Miguel-Pérez Verónica , Ouweltjes Jan Pieter , Tarancón Albert , Torrell M. , Bongiorno Valeria , Wuillemin Zacharie , Montinaro Dario , Morata Alex
Published: July 2015

One of the most important issues related to the performance of solid oxide fuel cells (SOFCs) is the reduction of performance due to elements diffusion and phase segregation on their ceramic components. Degradation phenomena were investigated on an SOFC stack tested at 780 ºC for 3000 h and an untested reference cell using XRD, Raman spectroscopy, SEM-WDX and STEM-EDX. In the present work, the evolution of the cathode side of the cell is studied, paying particular attention to diffusion taking place at the barrier layer/cathode interface and the barrier layer/electrolyte interface. The results show that insulating phases and solid solutions have formed at both interfaces in both the pristine and the tested cell.
Chromium-Related Degradation of Thin-Film Electrolyte Solid Oxide Fuel Cell Stacks
Authors: Menzler Norbert H. , Sebold Doris , Fang Qingping
Published: July 2015

SOFC short stacks with thin-film electrolyte anode-supported cells were operated for up to ~ 3,000 h and post-test characterized. The cells consisted of thin electrolyte films (≤ 3µm) and LSCF or LSC cathodes. Typical manganese-oxide chromium evaporation protection layers and cathode contact layers were used. Operating parameters were: temperatures between 600°C and 750°C, a current density of 500 mA/cm², hydrogen with 20% water vapor as fuel, and a fuel utilization of ~40%. Microstructural characterization revealed that Cr-containing phases formed at different locations. SEM and TEM analysis of some cells additionally showed microstructural changes within the GDC layer. A possible explanation for the different chromium-containing phase locations based on theoretical assumptions is given.
Current Status of Rapid Evaluation of Durability of Six SOFC Stacks within Nedo Project
Authors: Yokokawa Harumi
Published: July 2015

Six solid oxide fuel cell stacks manufactured by Kyocera, Mitsubishi Hitachi Power Systems (MHPS), TOTO, NGK SPARK PLUG, NGK INSULATORS, and Murata Manufacturing have been investigated to identify their performance degradation behavior, extract major sources of degradations, clarify the degradation mechanism, and predict the time dependent contributions of such degradations to life time. Stack performance was analyzed into several contributions, and in addition to identification of respective degradation rates, an interesting correlation between the overpotential values and the ohmic losses has been extracted. Respective degradation issues have been examined experimentally with SIMS, FIB-SEM, STEM and described as key simulation matters to predict the long life up to 90,000 h. Emphases have been placed on degradation of cathodes with Cr or S; to ensure the appropriateness for overcoming such poisoning effects, care was exercised to measure the impurity level after long term operations in various environments. For simulation, focus was made to overcome some gaps between knowledge on stacks and on single (or buttons) cells appearing in several degradations.
Effect of Nanocrystalline Perovskite-Based Cathode Compositions on SOFC Performance: An Aspect of Cell Stability with Composite Interlayer
Authors: Banerjee Koyel , Mukhopadhyay Jayanta , Basu Rajendra Nath
Published: July 2015

Multicomponent nanocrystalline Sr-doped lanthanum manganite (La0.65Sr0.3MnO3, LSM) and a composite cathode comprising of Sr-doped lanthanum ferrite (La0.54Sr0.4Co0.2Fe0.8O3, LS-1) and cobaltite (La0.54Sr0.4Fe0.2Co0.8O3, LS-2) were synthesized. Powder was characterized thoroughly. Sintering characteristics of all the cathode compositions were correlated with densification of the bulk cathode material and the electrical characterization of the sintered cathode compositions showed that the composite cathode exhibits higher electrical conductivity compared to LSM. Another composite (L80-C20) material has been synthesized to be used as a part of the intermediate bilayer containing 80% (50%LS-1+50%LS-2) cathode composite and 20% Co-doped CGO. Symmetric cell study showed that the electrode polarization of this composite as low as 0.012 ohm-cm2. Systematic stability studies of the electrochemical performance using single cells with different configurations revealed that use of intermediate bi-layer, one layer of CoCGO and another interlayer containing L80-C20 increases the cell stability in conjunction with doped lanthanum ferrite and cobaltite based composite electrodes.
Multi Length-Scale Quantification of Hierarchical Microstructure in Designed Microtubular SOFC Electrodes
Authors: Cooper Samuel J , Li Tao , Bradley Robert S , Li Kang , Brandon Nigel P. , Kilner John A.
Published: July 2015

The transport properties of a micro-tubular solid oxide fuel cell (MT-SOFC) anode have been analysed by imaging and simulation at multiple length-scales. The anode support investigated was manufactured using a phase inversion-assisted co-extrusion process, which generated a hierarchical and highly anisotropic microstructure. The resulting pore network was observed to contain two distinct, but interacting transport systems. The features in these systems spanned several orders of magnitude and as such it was not possible to image or model them simultaneously. The simulations indicated that the design of the microstructure was beneficial for the radial transport required by these cells; however this conclusion was only obtained by considering diffusive systems at many length-scales.
Design and Fabrication of a 600W Anode Supported Flat Tubular SOFC Stack
Authors: Ji Weijie , Zhang Lei , Ming Li , Jiang Yousong , Xie Bin
Published: July 2015

A 600W anode supported flat tubular SOFC stack is designed and fabricated. FeCrAl alloy is applied as metallic cassette. Ag-Cu serve as seal to the anode and metallic cassette and electrical connect to anode. After tested for 1000 hours, the jointing of FeCrAl, Ag-Cu braze and anode shows good stability. With cells of Ni-YSZ/YSZ/LSM-YSZ, a maximum output of 614W and an average power density of 213mw/cm2 are obtained in this stack configuration. The fuel utilization efficiency is high as 51%.
Development of Modelling and Testing for Analysis of Degradation in Solid Oxide Fuel Cells
Authors: Maillard John Geoffrey , Steinberger-Wilckens Robert
Published: July 2015

The ability to predict the lifetime performance of an SOFC can give guidelines for where improvements and alterations can be made in terms of production, operating parameters and cell design. This study focuses on continuous degradation mechanisms and the impact they have on the components of a single repeating unit level, i.e. the anode, cathode, electrolyte, metal interconnect and sealants. Currently the model being developed deals specifically with anode and electrolyte degradation. Depending on operating conditions, SOFC cells suffer from Ni particle agglomeration, coarsening, and volatilisation which lead to increased overpotential in the anode. A loss in the ionic conductivity in the electrolyte is also observed. Matlab® coding has been developed to outline the loss of performance in a single repeating unit for a given set of operating parameters. These equations will be tested against real life data to establish their validity and, where necessary, adjusted for accuracy.
Beyond the 3rd Generation of Planar SOFC: Development of Metal Foam Supported Cells with Thin Film Electrolyte
Authors: Han Feng , Semerad Robert , Constantin Guillaume , Dessemond Laurent , Costa Rémi
Published: July 2015

The manufacturing of thin and gas tight electrolyte in solid oxide fuel cells (SOFCs) remains challenging especially when alloys are used for the substrate. In this work, we present a porosity graded multi-layer structure supporting thin film electrolyte, as a further evolution of the metal supported planar cell architecture. The substrate is made of NiCrAl metal foam impregnated with La0.1Sr0.9TiO3-α (LST) ceramic. Furthermore, a 20 µm thick composite anode functional layer with LST and Gd0.1Ce0.9O2-α (GDC) was deposited onto the substrate. The surface of the anode functional layer is later engineered with a suspension of nano-particles with 40 nm average particle size of yttria-stabilized zirconia (YSZ). This results in a mesoporous layer with a smooth surface. Finally, a gas-tight GDC electrolyte was deposited by EB-PVD method. The thickness of the thin-film YSZ layer and the gas-tight CGO layer was approximately 1 µm and 2 µm, respectively. Button half cells with size up to 25cm² were successfully produced showing an air leakage rate down to 0.7 Pa·m·s-1 satisfying the gas-tightness quality control threshold of the state of the art metal supported SOFCs at DLR. Full cells with La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes showed an OCV of 0.97 V at 750°C and power density of about 80mW/cm² was obtained at 0.7 V.
Solid Oxide Cell and Stack Testing, Safety and Quality Assurance (SOCTESQA)
Authors: Auer Corinna , Lang Michael , Couturier Karine , Nielsen Eva Ravn , McPhail Stephen J. , Tsotridis Georgios , Fu Qingxi , Chan Siew Hwa
Published: July 2015

In the EU-funded project "SOCTESQA" partners from Europe and Singapore are working together to develop uniform and industry wide test procedures and protocols for solid oxide cells and stacks SOC cell/stack assembly. New application fields which are based on the operation of the SOC cell/stack assembly in the fuel cell (SOFC), in the electrolysis (SOEC) and in the combined SOFC/SOEC mode are addressed. This covers the wide field of power generation systems, e.g. stationary SOFC µ-CHP, mobile SOFC APU and SOFC/SOEC power-to-gas systems. This paper presents the results which have been achieved so far. Besides a summary of existing test procedures a so called "test matrix" was created. This document includes generic test modules, e.g. current-voltage curves, electrochemical impedance spectroscopy, thermal cycling, electrical current cycling and long-term tests both under steady -state and dynamic operating conditions. The application specific test programs are created by combining several of these test modules.
Development of Toho Gas SOFC Cell Stack
Authors: Masuda Soichiro , Ogura Yusuke , Shimano Jun
Published: July 2015

Toho Gas has developed a planar type of scandia stabilized zirconia (ScSZ) electrolyte supported cell, and has been researching ways to improve performance of the cell stack. The present paper reports about a glass seal which is one of the major challenge in a planar type cell stack. The seal performance of two types of seals, paste and sheet, has been evaluated. As a result, it was indicated that the sheet seal improved the gas seal performance compared to the paste seal. Furthermore, the investigation for sheet seal contraction during seal forming process suggested that a load to seal should be controlled in order to define seal thickness after seal forming process.
Fabrication of Large-area Multi-scale-architectured Thin-Film SOFC via Commercially Viable Thin-film Technology
Authors: Noh Ho-Sung , Hong Jongsup , Kim Hyoungchul , Yoon Kyung Joong , Kim Byung-Kook , Lee Jong-Ho , Son Ji-Won
Published: July 2015

The feasibility of realizing large-area multi-scale-architectured thin-film solid oxide fuel cell (TF-SOFC) by using commercially viable thin-film technology, sputtering in the present study, is investigated. By using a 2-inch sputtering system, the multi-scale-architectured platform consisting of a nanostructure NiO-yttria-stabilized zirconia (YSZ) interlayer and an ultra-thin YSZ electrolyte is successfully fabricated over a 5 cm by 5 cm NiO-YSZ anode support. An open circuit voltage of 1.1 V and a peak power density exceeding 1 Wcm-2 are obtained, thus a total power output from the cell reaches 16 W at 600 oC. The present study demonstrates the possibility of transferring the multi-scale-architectured TF-SOFC technology to the industrial sector using commercial thin-film technologies.
Thermo-Mechanical Reliability of SOFC Stacks during Combined Long-Term Operation and Thermal Cycling
Authors: Greco Fabio , Nakajo Arata , Wuillemin Zacharie , Van herle Jan
Published: July 2015

Thermo-mechanical issues in solid oxide fuel cells (SOFC) must be understood and overcome to meet the reliability standards for market implementation. This study presents a thermo-mechanical model of an SOFC-stack SRU. The analysis starts with the simulation of stack conditioning procedures, which aims at capturing the stresses during the stack components production and assembly. The simulated stresses after the initialisation sequence provide the initial stress-state for the simulation of stack operation, which consists in importing into FEA software the temperature profiles from thermo-electrochemical simulations. The study includes long-term steady-state operation in co-flow configuration, interrupted by thermal cycling. The SRU contact pressure was found to decrease significantly after a first thermal cycle to RT, after stack qualification. Thermal cycling after long-term operation worsens the extent of loss of contact pressure at room temperature. Similarly to the evolution of contact pressure, long-term operation increases the risks of sealant failure during thermal cycling.
Effect of LSCF Microstructure on GDC Interlayer Stability and Cation Diffusion in Porous and Dense LSCF/GDC/YSZ Triplets
Authors: De Vero Jeffrey , Bagarinao Katherine Develos- , Cho Do-Hyung , Kishimoto Haruo , Yamaji Katsuhiko , Yokokawa Harumi , Horita Teruhisa
Published: July 2015

We evaluated the effect of LSCF microstructure on the stability of GDC interlayer by performing cation diffusion experiments on LSCF/GDC/YSZ triplets. For this purpose, we prepared porous and dense LSCF layers on pre-annealed dense GDC/YSZ diffusion couples and performed subsequent heat treatments. Here we observe that the pre-annealing of GDC/YSZ couples, results in microstructural changes in GDC interlayer and preferential diffusion of Zr from YSZ electrolyte. Our results show that after annealing at high temperature of porous LSCF/GDC/YSZ triplets, enhanced Sr–diffusion from the grains of LSCF layers to the GDC resulted in the severe formation of SrZrO3 at the LSCF/GDC interface, while Sr and Zr diffusion along the grains of GDC dominate in the formation of SrZrO3 at the YSZ electrolyte than the diffusion through the cracks. On the other hand, for dense LSCF/GDC/YSZ, the cracks or crack–walls in the GDC interlayer are fast diffusion paths for cation diffusion. Our results show that the microstructure of LSCF plays an important role in understanding the formation of SrZrO3 as well as the stability of GDC as a reaction barrier.
Accelerated Lifetime Tests for SOFCs
Authors: Weber André , Szász Julian , Dierickx Sebastian , Endler-Schuck Cornelia , Ivers-Tiffée Ellen
Published: July 2015

Conventional lifetime analysis for Solid Oxide Fuel Cells requires considerable testing time and capacities. In case of application oriented testing durations of several years the results can not be used for the continued development of cells and stacks before the test is finished. Therefore accelerated lifetime tests, which enable a rapid degradation analysis, would be highly desirable. In this paper we will show that the overall degradation rate of a single cell can hardly be used in accelerated lifetime tests. It is required to evaluate the degradation of the electrochemical processes in each cell component. The degradation of cathode, electrolyte and anode was deconvoluted by (i) impedance spectroscopy, (ii) distribution of relaxation times data analysis and (iii) a subsequent CNLS-Fit. Such approach can provide stress level dependencies for the aging of individual electrochemical processes in the cell.
Shaping of a Dual Membrane SOFC and First Electrochemical Tests in a Dedicated 3-Chamber Set-up
Authors: Masson David , Perrozzi Francesco , Piccardo Paolo , Viviani Massimo , Pilot Claire , Stoynov Zdravko , Vladikova Daria , Chesnaud Anthony , Thorel Alain
Published: July 2015

The present paper offers a discussion about an innovative dual membrane fuel cell concept IDEAL-Cell operating between 600°C-700°C. It is based on the junction of SOFCs anodic part with PCFCs cathodic part through a mixed H+ and O2- conducting porous membrane. This concept was successfully proved and developed during the 4 years of a FET-Energy/FP7 project, through the collaboration between 10 European research and technological institutes. After two stages of development, respectively the proof of concept and the realization of an optimized lab-scale cell, the concept has evolved to a simplified design, called “monolithic”, in which the mixed H+ and O2- conduction of BCY15 is exploited for the fabrication of all the cell components. With the reduction of chemical gradients and thermal expansion mismatches, the cell durability is potentially enhanced. Furthermore, the shaping, the microstructure and the catalytic properties of the central membrane (CM) have been improved by structuring the central membrane with a Ni foam or by including Pt nano-particles. This work presents a complete study of the permeability of the central component of this concept in view of a reversible SOFC/SOEC operation, and the preliminary results obtained on this new Ni-foam based architecture by using a 3-chambers set-up (Real Life Tester) to determine the electrochemical performances of the cell in real operating conditions.
Development of a SOFC Performance Model to Analyze the Powder to Power Performance of Electrode Microstructures
Authors: Gawel Duncan A.W. , Pharoah Jon G. , Beale Steven B.
Published: July 2015

A computational model that evaluates the triple phase boundary length, normalized effective transport coefficients, and charge production within solid oxide fuel cell electrode microstructures is described. Local charge production, within the electrode, is predicted by coupling the species transport equations with an expression for the electrochemical reaction rate. A particle placement model, employing the drop-and-roll algorithm, is used to generate the electrodes studied in this work. Parametric studies with the computational model are then preformed to investigate the influence of the anode porosity and solid volume fraction on charge production. It was found that charge production is jointly influenced by the reaction site (triple phase boundary) density, and ionic transport within the electrode structures. High current densities are observed in electrodes with low porosities and ionic volume fractions greater than 50%, for equal sized particles.
Study on Direct Flame Solid Oxide Fuel Cell Using Flat Burner and Ethylene Flame
Authors: Hossain Md. Moinul , Myung Jaeha , Lan Rong , Cassidy Mark , Burns Iain , Tao Shanwen , Irvine John T. S.
Published: July 2015

This paper presents an experimental investigation of direct flame solid-oxide fuel cell (SOFC) by using a flat-flame burner and fuel-rich ethylene/air premixed flames. A direct flame fuel cell (DFFC) setup is designed and implemented to measure electrochemical characteristics of electrolyte supported (i.e., single cell consisting of Ce0.9Ni0.1O2-δ anode/GDC electrolyte/LSCF-GDC cathode) fuel cell. The fuel cell temperature and cell performance were investigated by operating various fuel/air equivalence ratios and varying distance between burner surface and the fuel cell. A maximum power density of 41 mW/cm2 and current density of 121 mA/cm2 were achieved. Experimental results suggest that the fuel cell performance was greatly influenced by the flame operating conditions and cell position in the flame. The uniformity of the flame temperature and the fuel cell stability were also investigated and calculations of equilibrium gas species composition were performed.
Redox-Stable High-Performance Thin-Film Solid Oxide Fuel Cell
Authors: Keuter Thomas , Roehrens Daniel , Menzler Norbert H. , Vaßen Robert
Published: July 2015

In this work, a mechanically redox-stable SOFC with a 1 µm thin-film sol-gel electrolyte is presented. With this electrolyte a power output larger than 1.25 W/cm2 at 0.7 V and an operating temperature of 600 °C could be demonstrated. Half cells were re-oxidized in excess air, in order to test the redox stability of these SOFCs. No cracks were found in the sol-gel electrolyte after re-oxidation for 4 hours at 600 °C and 30 minutes at 800 °C, respectively. Due to the fact, that the energy release rate is proportional to the thickness of the thin-film, a thinner film is more stable against cracking than a thicker film at constant tensile stresses. The SOFC with the thin-film sol-gel electrolyte can be considered as stable against re-oxidation, because the long re-oxidation time of 4 hours at an operating temperature of 600 °C is unlikely to happen under real conditions.
Electrochemical Impedance Spectroscopy Investigation of the Anodic Functionalities and Processes in LSCM-CGO-Ni Systems
Authors: Boulfrad Samir , Nechache Aziz , Cassidy Mark , Traversa Enrico , Irvine John T. S.
Published: July 2015

Electrochemical impedance spectroscopy was used to characterize anode compositions made of (La0.75Sr0.25)0.97Cr0.5Mn0.5O3 (LSCM) and gadolinia doped ceria (CGO) with and without additional submicron Ni, or exsoluted Ni nanoparticles. In addition, the effects of the anode gas flow rate and the working temperature were investigated. Higher content of the ionic conductor leads to a decrease of the impedance in the frequency range from 100 Hz to 10 Hz. The effect of the catalyst component was investigated while keeping the electronic conductivity unchanged in the tested materials. Enhanced catalytic activity was demonstrated to considerably decrease the impedance especially in the frequency range between 100 Hz to 1 Hz. The change in the gas flow rate affects mainly the impedance bellow 1 Hz.
Towards the Design-Led Optimization of Solid Oxide Fuel Cell Electrodes
Authors: Kishimoto Masashi , Lomberg Marina , Ruiz-Trejo Enrique , Brandon Nigel P.
Published: July 2015

A one-dimensional numerical model of a nickel-infiltrated gadolinium-doped ceria (Ni-GDC) electrode has been developed to investigate the effects of electrode microstructure on performance. Electrode microstructural information was obtained with focused-ion beam tomography and microstructural parameters were quantified. These have been used to estimate the effective transport coefficients and the electrochemical reaction rate in the electrode. GDC was considered as a mixed ionic and electronic conductor and hence the electrochemical reaction was assumed to occur on the GDC-pore contact surface, i.e. double-phase boundaries (DPBs). Sensitivity analysis was conducted to investigate the effect of electrode microstructure on both transport properties and electrochemical activity. The developed model offers a basis to understand the electrode-microstructure relationships and to further optimize the electrode microstructures.