Fuzzy Approach Based on Quantum-Inspired MRF for SOFC Anode Optical Microscope Images Segmentation

To develop a multi-modal deep learning method for automatic classification of immune-mediated glomerular diseases based on images of optical microscopy (OM), immunofluorescence microscopy (IM), and transmission electron microscopy (TEM). We retrospectively collected the pathological images from 273 patients and constructed a multi-modal multi- instance model for classification of 3 immune-mediated glomerular diseases, namely immunoglobulin A nephropathy (IgAN), membranous nephropathy (MN), and lupus nephritis (LN). This model adopts an instance-level multi-instance learning (I-MIL) method to select the TEM images for multi-modal feature fusion with the OM images and IM images of the same patient. By comparing this model with unimodal and bimodal models, we explored different combinations of the 3 modalities and the optimal methods for modal feature fusion. The multi-modal multi-instance model combining OM, IM, and TEM images had a disease classification accuracy of (88.34±2.12)%, superior to that of the optimal unimodal model [(87.08±4.25)%] and that of the optimal bimodal model [(87.92±3.06)%]. This multi- modal multi- instance model based on OM, IM, and TEM images can achieve automatic classification of immune-mediated glomerular diseases with a good classification accuracy.

Biomass gasification has acquired considerable interest as a sustainable and environmentally friendly way to produce heat, hydrogen or electricity from agro-industrial wastes or other kinds of biomass. A very effective solution for the achievement of high electrical efficiency (up to 55%) is the integration of biomass gasification with solid oxide fuel cell (SOFC) technology, including the necessary gas cleanup to avoid degradation of the SOFC. For this reason, this paper first shows in detail the risk and the impact of carbon deposition, exposure to tar, hydrogen sulphide, hydrogen chloride and alkali metals on SOFC anode and then, considering the tolerance limit for inorganic and organic contaminants (<1 ppmv for H2S, HCl and alkali and <10 ppmv for tar), offers an overview of the most relevant and effective technologies to remove these contaminants and to feed safely a SOFC system.

Mathematical approaches to modelling the mass transfer process in solid oxide fuel cell anode

High operating temperature affords solid oxide fuel cells (SOFCs) fuel flexibility, favorable kinetics, enhanced transport properties and high quality heat for secondary thermodynamic cycles.1 Elevated temperatures, however, present challenges to ensuring cell durability.2 Coarsening of nickel in the Ni-YSZ anode is one such challenge that can lead to significant performance degradation. The fundamental driving force Δμ for coarsening phenomena is given by Eq. 1.3 The expression, which assumes isotropic interfacial energy, indicates that the chemical potential μ of a curved interface differs from that of a flat interface μ 0 by the factor VmγH, where H is mean curvature, γ interfacial energy and Vm molar volume. Δμ = μ - μ 0 = VmγH (1) Eq. 1 makes evident that variations in interface curvature, i.e., interface shape, directly correspond to variations in chemical potential. Furthermore, it follows from Eq. 1 that microstructural coarsening is fundamentally related to variations in interface shape. The link between interface shape and coarsening propensity is well known and methods have been developed to directly measure interfacial curvature distributions for complex morphologies in 3-D.4,5 In this work, these techniques are applied to 3-D images obtained by x-ray nanotomography to study coarsening in microstructures obtained from Ni-YSZ solid oxide fuel cell anodes aged for varying lengths of time. This work builds on a previous characterization of the same samples.6 The curvature measurements collected suggest that a combination of coarsening and morphological instability, which leads to channel pinch-off, severely diminish the connectivity of the anode’s Ni network and, in addition, lead to a significant loss of both nominal and effective triple-phase boundary (TPB) density. Both the loss of connectivity and TPB density coincide with cell performance degradation that was observed in the aging experiment7 from which the anode samples were taken. References Singhal, S. C.; Kendall, K. High Temperature Solid Oxide Fuel Cells, Elsevier, 2003.Yokokawa, H.; Tu, H.; Iwanschitz, B.; Mai, A. Fundamental mechanisms limiting solid oxide fuel cell durability. J. Power Sources 2008, 400-412.Voorhees, P. W. The Theory of Ostwald Ripening. J. Stat. Phys. 1985, 231-252.Glicksmann, M. E.; Voorhees, P. W. Ostwald Ripening and Relaxation in Dendritic Structures. Metall. Trans. A, 1984, 995-1001.Mendoza, R.; Savin, I.; Thornton, K.; Voorhees, P. W. Topological complexity and the dynamics of coarsening. Nat. Mater., 2004 385-388.Nelson, G. J.; Grew, K. N.; Izzo, J. R. Jr.; Lombardo, J. J.; Harris, W. M.; Faes, A.; Hessler-Wyser, A.; Van herle, J.; Wang, S.; Chu, Y. S.; Virkar, A. V.; Chiu, W. K. S. Three-dimensional microstructural changes in the Ni-YSZ solid oxide fuel cell anode during operation. Acta Mater., 2012 3491-3500. 7. Faes, A.; Hessler-Wyser, A.; Presvytes, D.; Vayenas, C. G.; Van herle, J. Nickel-Zirconia Anode Degradation and Triple Phase Boundary Quantification from Microstructural Analysis. Fuel Cells, 2009 841-851. Acknowledgements Financial support from the National Science Foundation (Award CBET-1134052) and an Energy Frontier Research Center on Science Based Nano-Structure Design and Synthesis of Heterogeneous Functional Materials for Energy Systems (HeteroFoaM Center) funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (Award DE-SC0001061) is gratefully acknowledged. X-ray nanotomography was performed with Dr. Steve Wang at the Advanced Photon Source supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357. Ni-YSZ samples were provided by MER Dr. J. Van herle (Ecole Polytechnique Federale de Lausanne, Switzerland).

Direct comparison between X-ray nanotomography and scanning electron microscopy for the microstructure characterization of a solid oxide fuel cell anode

Solid oxide fuel cells (SOFCs) are being extensively researched for clean power generation from coal-derived syngas. Some of the contaminants in syngas such as phosphine (PH3) may interact with the SOFC anode material, and degrade its electrochemical performance and material properties. In this paper, a modified Sagnac interferometry method is utilized to monitor the anode surface transient temperature as a function of applied current densities under hydrogen and simulated coal syngas. Moreover, the poisoning effects of PH3 contaminant on the SOFCs performance are investigated in dry and moist conditions. The experimental results indicate that the Ni-cermet-based SOFC anode is more susceptible to degradation due to PH3 in the presence of steam than under dry conditions. These experiments are valuable for the validation and the development of SOFC electrochemical models, and understanding the anode-contaminant interaction.

Coupling inline autothermal reformers (ATR) and air heat exchangers (HX) within solid-oxide fuel cell (SOFC) stacks provides a compact solution for integrating SOFCs into methane-fueled gas-turbine cycles. This study utilizes computational fluid dynamics to investigate the integrated ATR and air-preheating HX within an SOFC stack. For integration with gas-turbine cycles for aviation or ground power, the system employs controlled bleed air and anode exhaust recycling to drive the ATR. Simulations of the integrated ATR/HX/SOFC at 5.0 bar for a range of bleed air and anode recycle ratios reveal that a short-residence-time ATR can preheat the compressor air entering the HX at 400°C to SOFC inlet temperatures over 600°C for yttria-stabilized zirconia (YSZ) electrolyte cells and over 500°C for gadolinium-doped ceria (GDC) electrolyte cells. Results show that the inline ATR produces CH 4 -H 2 mixtures into the SOFC anode that support power densities exceeding 1.0 W cm{ -2 } with internal CH 4 reforming for stack thermal management. The superior ionic conductivity of the GDC electrolyte can sustain higher power densities at conditions with maximum temperatures below 680°C, but the GDC cells require higher excess air ratios to mitigate electronic leakage. This study highlights the potential of the integrated ATR/HX/SOFC architecture for methane-fueled gas turbine systems.

Inverse dynamical photon scattering (IDPS), an artificial neural network based algorithm for three-dimensional quantitative imaging in optical microscopy, is introduced. Because the inverse problem entails numerical minimization of an explicit error metric, it becomes possible to freely choose a more robust metric, to introduce regularization of the solution, and to retrieve unknown experimental settings or microscope values, while the starting guess is simply set to zero. The regularization is accomplished through an alternate directions augmented Lagrangian approach, implemented on a graphics processing unit. These improvements are demonstrated on open source experimental data, retrieving three-dimensional amplitude and phase for a thick specimen.

Manufacturing cost remains one of the major issues facing the solid oxide fuel cell (SOFC) industry. In the anode supported SOFC design, the cermet anode constitutes around 90% of the total material required to build a cell, making the technology very sensitive to anode raw material price. A new patent-pending process called “nickel yttria reaction-sintered zirconia (NiYRSZ)” has been developed for manufacturing SOFC anodes at a fraction of the cost. Typically, the solid component of the anode consists of about 50/50 volume percent nickel and 8 mole percent yttria stabilized zirconia, the latter being a rather costly material. It was discovered that zirconia and yttria powders sintered in the presence of nickel oxide readily form the cubic phase at moderate temperature. Cells manufactured using this process show excellent microstructures for anode supports: a strong bond between the electrolyte and the anode, and a high porosity without addition of pore formers. The strength of the anode was 100 MPa making the material equivalent or slightly superior to an anode fabricated with the traditional NiO/8YSZ material of similar porosity. The resistivity of the material was measured at 850°C and found to be less than 2 mΩ·cm. Cell performance was also compared to cells manufactured with traditional material. Every indication is that SOFC anodes fabricated with this new method perform as well as anodes made with the conventional material set.

The electrochemical reduction of CO2 was studied via solid oxide electrolysis cell (SOEC), a type of device that can work reversely into a solid oxide fuel cell (SOFC) to generate electricity. Application of SOEC for CO2 electrolysis possesses potential rewards both in energy and environmental aspects, as it offers a way to recycle CO2 into chemicals and value-added fuels, which helps to reduce the accumulation of atmospheric CO2 and realize the carbon neutral cycling of fuels. Secondly, SOEC techniques provide a means to utilise the intermittent renewable sources, such as wind, tide, etc., as energy input to store excess electricity in the form of H2, CO and hydrocarbons and use these chemicals when necessary. Yet it is a challenging task to realize an efficient reduction of CO2 by SOEC due to the non-polar nature of CO2 fuels which are hard to be chemically absorbed and activated in high temperature range. The CO product from CO2 reduction is also demanding for the choice of fuel electrode (i.e. cathode in SOEC and anode in SOFC) materials, which has been an issue for the CO/hydrocarbon-fuelled SOFCs. To date, the CO2 electrolysis by SOEC is still at the starting point, and the mechanisms on the electrochemical reduction of CO2through SOECs are not fully understood. Extensive efforts need to be dedicated to the material developments, mechanism study, and system designs etc. Effort was made in our lab to find a highly performed, long-term durable cathode material for electrochemical reduction of CO2 by SOEC and to obtain more understandings of the mechanism of CO2 electrochemical reduction process. Different cathode materials were employed, including Ni-8 mol% yttria stabilised zirconia (YSZ) cermet, (La,Sr)(Cr,Mn)O3 (LSCM)-YSZ composite, and LSCM-(Gd, Ce)O2 (GDC) composite. Focus was casted on LSCM based cathodes which were found to be carbon-resistive, and the microstructure of LSCM-based cathodes was tuned to high performance and efficient CO2 electrolysis by the strategy of applying a gradient composite cathode and of adopting wet impregnation as cell fabrication procedures. The electrochemical performance of CO2 electrolysis was characterized in various CO2-CO mixtures and applied potentials in 900-750oC with the aid of impedance spectroscopy, on YSZ electrolyte supported three-electrode SOECs. In this paper, impedance behaviour of the electrochemical reduction reaction of CO2 from different cathode SOECs was correlated with the variations in gas composition, operating temperature and loading potential. As both charge transfer and surface adsorption/desorption equilibration and surface diffusion of activated species were found to be dominant processes taking place in the scope of cathodes under examination, with the later being significant in CO2-rich fuels, areas of discussion will be the effects of operational conditions on the impedance arcs associated with these steps, and how the cathode microstructure impacts the impedance behaviour and the corresponding elementary steps from CO2electrochemical reduction. By introducing a LSCM-YSZ 30-70/LSCM-YSZ 60-40 graded cathode and by incorporating extra catalyst into LSCM-GDC composite, the cathode performance was greatly improved, and the surface activity was profoundly accelerated. However, the most effective way to promote cathode performance was to introduce the cathode components in separate steps via wet impregnation. A competitive CO2 electrolysis performance to Ni-YSZ cermet was obtained from the GDC impregnated LSCM-YSZ cathode with 0.5% Pd extra catalyst, which also showed a comparable performance between SOEC and SOFC when operating in CO2-CO 50-50 mixture.

Solid Oxide Fuel Cells (SOFCs) operate under harsh environments, which cause the deterioration of anode material properties and reduce their service life. In addition to electrochemical performance, structural integrity of the SOFC anode is essential for successful long-term operation. Anode-supported SOFCs rely on the anode to provide mechanical strength to the positive-electrolyte-negative (PEN) structure. The stress field in the anode may arise from a variety of phenomena including thermal expansion mismatch between layers in the PEN structure, thermal/redox cycles and external mechanical loads. Moreover, some fuel contaminants such as phosphine (PH3) interact with the anode materials which lead to the formation of secondary phases and grain growth. These mechanisms result in the formation of microcracks, and degrade anode structural and electrochemical properties. Assessments of the evolution of anode mechanical properties during long-term operation are therefore essential to predict SOFC working life.;The principal objective of this research is to develop a structural durability model for the SOFC anode that takes into account thermo-mechanical and fuel contaminants effects on the anode material properties. The model is implemented in finite element analysis through a user defined subroutine to predict anode long-term structural integrity. The model is exploited to predict the stress-strain relations of Ni-YSZ at temperatures and porosities which are difficult to generate experimentally. Accelerated exposure tests under high contaminant concentrations dictate that the electrochemical degradation is the principal mode of cell failure while the cell structure is still intact. However, the model predicts that under lower contaminant concentrations, the anode structural degradation may be significant as compared to the electrochemical degradation in long-term operation.;The proposed model is enhanced for the planar-SOFC configurations exposed to PH3. The model predicts that under pure thermo-mechanical effect, the critical location for structure failure is near the corner of highest thermal gradient. However when fuel contaminant structural effect is superimposed on the thermo-mechanical effect, the critical location may shift depending on the flow configuration. Under similar operating conditions, i.e. same current density, co-flow configuration yields a higher anode structural life than counter-flow or cross-flow configurations. The knowledge obtained from this research will be useful to establish control parameters to achieve desired service life of the SOFC stack under various operating conditions.

Solid Oxide Fuel Cells (SOFCs) are an interesting energy conversion device due to their fuel flexibility feature and high fuel conversion efficiency. Reducing the performance losses associated with fuel electrode is critical, especially when SOFCs are operated on hydrocarbon fuels. The fuel electrode in an SOFC has typically been a cermet of Ni-YSZ whose degradation mechanisms have been thoroughly studied. Recently, the focus of SOFC research has shifted towards a lower operating temperature range (400-650 oC) to achieve reliability and cost competitiveness among other energy conversion technologies. The use of a Ni-GDC cermet anode allows SOFCs to operate on hydrocarbon fuels at lower temperatures compared to (>800 oC) for Ni-YSZ. However, Ni-based anodes have several challenges that have to be resolved for efficient operation of SOFCs. Evaluating the microstructural changes such as coarsening and carbon formation when exposed to hydrocarbon fuels is essential to understand the underlying degradation mechanism and to overcome the issues. This study focuses on a) evaluating the chemical compatibility of Ni-GDC cermet anode when exposed to harsh operating conditions and b) to propose a possible degradation mechanism at low temperature ranges by carefully examining the microstructural changes on samples that are aged in hydrocarbon containing fuels.

Introduction For many potential mobile robot applications, current power supply technology (such as the lithium ion battery technology) is in fact a key limiting factor due to its low energy density. Solid oxide fuel cells (SOFCs) are a promising alternative and can overcome limitations of current battery technology. This is because SOFCs can, in principle, use not only hydrogen but also hydrocarbon fuels which have high energy density such as gasoline and so on.Ni-YSZ cermet is the most promising anode material for SOFCs because of its low cost, chemical stability, and closely matched thermalexpansion coefficients with the dense YSZ electrolyte. Ni is an excellent catalyst for hydrocarbon fuel reforming and cracking, which leads to rapid carbon deposition inside the SOFC anode and causes coking and deactivation1). In principle, the carbon deposition on Ni can be depressed by adding steam in the hydrocarbon fuel2,3), whereas few detailed investigations of SOFCs that operate on gasoline fuel have been reported.In this work, we studied the effect of steam content and demonstrated the direct operation of SOFCs by octane which is a main ingredient of gasoline. In the case of the Ni-YSZ anode, the operation temperature must be high in order to avoid sulfur poisoning4 -6 ), because most commercially available fuels contain sulfur. Therefore, in this study, the SOFCs operation was conducted at high temperature of 950 oC. Experimental Surface-polished YSZ pellets of 2 mm in thickness were used for the electrolyte. Pt cathode electrode and Pt reference electrode were prepared on the surface and side of the pellets, respectively, by firing Pt paste at 1300 oC. Then, NiO powder and GDC powder (NiO/YSZ=6/4 (wt)) were thoroughly mixed in a vacuum using the planetary ball mill (200 rpm, 12 h), and made into NiO-YSZ pastes using ethyl-cellulose and organic solvent. The NiO-YSZ paste was screen-printed in diameter of 8 mm on the YSZ pellets and sintered at 1200 oC for 1 h.Octane and steam were supplied to the SOFC cell by bubbling carrier gas (He) at a constant rate. Octane bubbler temperature was 30 oC, and Steam/Carbon ratio (S/C) were controlled by changing the temperature of the water bubbler from 40 to 70 oC. Electrochemical properties (open circuit voltage, anode electrode resistance, I - V and I - P characteristics, stable power generation property) were measured over a temperature range of 950-700 oC. During the constant current generation, exhaust gas was analyzed by gas chromatography. Results and Discussion Figure 1 shows I - V and I - P characteristics for the cells at 950 oC in wet octane. Maximum power density of 35 mW/cm2 was obtained by S/C of 8.9. The power density decreased with S/C quickly.Figure 2 shows the time course of cell voltage at a drawn current density of 5.2 mA/cm2 for S/C of 3.5. The cell voltage was stable. That is, carbon deposit does not arise even in the cell of the Ni-YSZ anode in low S/C of 3.5 when the operation temperature is high of 950 oC. References 1) S. Mclntosh and R.J. Gorte, “Direct Hydrocarbon Solid Oxide Fuel Cells,” Chemical Reviews, 104 (2004) 4845- 4865.2) K. Sasaki and Y. Teraoka, “Equilibria in Fuel Cell Gases: I. Equilibrium Compositions and Reforming Conditions,” Journal of Electrochemical Society, 850 (7) (2003) A878-A884.3) K. Sasaki and Y. Teraoka, “Equilibria in Fuel Cell Gases: II. The C-H-O Ternary Diagrams,” Journal of Electrochemical Society, 850 (7) (2003) A885-A888.4) K. Sasaki, K. Susuki, A. Iyoshi, M. Uchimura, N. Imamura, H. Kusaba, Y. Teraoka, H. Fuchino, K. Tsujimoto, Y. Uchida, N. Jingo, “H2S Poisoning of Solid Oxide Fuel Cells,” J. Electrochem. Soc., 153 (2006) A2023–A2029.5) P. Lohsoontorn, D.J.L. Brett, N.P. Brandon, “Thermodynamic predictions of the impact of fuel composition on the propensity of sulphur to interact with Ni and ceria-based anodes for solid oxide fuel cells,” Journal of Power Sources, 175 (2008) 60–67.6) H. Kishimoto, Y-P Xiong, K. Yamaji, T. Horita, N. Sakai, M.E. Brito, H. Yokokawa, “Stability of Ni base anode for direct hydrocarbon SOFCs, ” Journal Chemical Engineering of Japan, 40 (13) (2007) 1178-1182.

Assessment of a methanol-fueled integrated hybrid power system of solid oxide fuel cell and low-speed two-stroke engine for maritime application

A perovskite related material, La0.75Sr0.25Cr0.5Fe0.5O3−δ (LSCF), has been synthesised and examined as a potential anode material for solid oxide fuel cells (SOFC). The material exhibits an overall orthorombic structure with a = 5.4926 ± 0.0005 Å, b = 5.5339 ± 0.0004 Å, c = 7.7646 ± 0.0008 Å. V = 236.01 ± 0.05 Å3 according to the X-ray data. It is chemically stable under SOFC anode conditions. The conductivity of LSCF at 900°C is 14.3 and 0.21 S/cm respectively in air and 5% H2. An 11% methane conversion was observed at 900°C when the steam to methane ratio is 1:1. A methane conversion of 68% with CO2-selectivity of 99% is achieved at 900°C when equal molar of CH4 and O2 were introduced into the reactor. The anode polarisation resistance in wet 5% H2/Ar and wet H2 are about 1.79 Ωcm2 and 1.15 Ωcm2 respectively at 850°C. A fuel cell with a maximum current density of 640 mA/cm2 was achieved in wet H2 at 900°C. LSCF itself is not an ideal SOFC anode material although it is redox stable in reducing atmosphere at high temperatures and exhibits good catalytic effects for methane-reforming.