Morphological Modelling of a Metal Foam Supported SOFC Configuration

Risø National Laboratory has conducted R&D on solid oxide cells for almost 20 years—all the time together with industries with interest in deploying the technology when mature. Risø National Laboratory (Risø) and Topsoe Fuel Cell A/S (TOFC) have for several years jointly carried out a development programme focusing on low cost manufacturing of flat planar anode-supported cells and stacks employing metallic interconnects. The consortium of Risø and TOFC has up-scaled its production capacity of anode-supported cells to about 1,100 per week. New generations of SOFCs are being developed by the consortium, e.g. a metal-supported cell. TOFC has an extended program to develop the SOFC technology all the way to a marketable product.

Solid oxide fuel cells (SOFCs) have been developed while pursuing low production cost and high performance with anode-supported planar type single cells at Korea Electric Power Research Institute. Anode-supported single cells have been manufactured by press molding, screen printing, and co-firing. They have been formed in the size 5 x 5 cm 2 and about 1.8 mm thick. The structure of anode-supported planar cells was used to investigate internal resistance and anode polarization resistance for improved performance. In our study, an important factor for determining cell performance was found to be the anode raw material quality assurance. The manufactured cells were evaluated on the basis of their microstructure and electrochemical performance. We have significantly improved cell performance during the past few years.

Research into the use of Rh and Ce0.80Gd0.20O1.90 (CGO20) co-impregnated La0.20Sr0.25Ca0.45TiO3 (LSCTA-) anodes for electrolyte-supported Solid Oxide Fuel Cells (SOFC) has yielded extremely impressive durability and robustness at industrial short stack scales over the past decade. These anodes have exhibited the ability to rival the degradation and RedOx/thermal/thermo-RedOx cycling tolerance of state-of-the-art SOFC anodes at short stack scales, in addition to providing the ability to operate under sulfur-laden fuel gas streams and high fuel utilisation/overload conditions. (1)Given the success of implementation of LSCTA- anodes into Electrolyte Supported Cells (ESC) and the reasonable mechanical strength of LSCTA- as a support material, (2,3) successful attempts have also been made to employ LSCTA- as an anode support for SOFC at button cell scales, (4,5) in addition to appraisal of the upscaling of thick-film ceramic processing techniques used to prepare larger (20 cm by 20 cm) SOFC anode supports. (3) These studies performed by Lu et al., Ni et al. and Verbraeken et al. (3-5) focussed upon production of LSCTA- anode supports by aqueous tape casting followed by either co-casting or screen printing of a 8 mol. % yttria-stabilised-zirconia (8YSZ) electrolyte layer.Therefore, using these studies as a basis for the current research, we present results concerning the ceramic processing of Anode Supported Cells (ASC) that employ LSCTA- anode ‘backbone’ microstructures, with the ultimate aim of testing SOFC whose anodes have been decorated with Rh and CGO20 catalysts through wet impregnation. Here, we detail a thermal compatibility study of a variety of electrode and electrolyte material sets using dilatometric analysis, leading to the conclusion that the shrinkages of LSCTA- and 8YSZ are sufficiently matched to allow co-sintering of the anode support and electrolyte layers. Subsequently, the thick-film aqueous ceramic processing of LSCTA- anode supports, via tape casting, is discussed in addition to an appraisal of the most appropriate method to produce dense 8YSZ electrolyte layers (i.e., electrolyte deposition by co-casting or screen printing), with the aim of co-sintering the structure up to 1400 °C in air. Finally, an evaluation of the microstructural characteristics of LSCTA − supports, prepared using a typical graphite pore former (commonly used with organic solvent systems) or without the use of a pore former, will be provided, in comparison to microstructures resulting from the incorporation of poly(ethyl/methyl methacrylate) pore formers that are compatible with the aqueous solvent system employed. References R. Price, M. Cassidy, J. G. Grolig, G. Longo, U. Weissen, A. Mai and J. T. S. Irvine, Adv. Energy Mater., 2003951, 1 (2021).V. Vasechko, M. Ziegner and J. Malzbender, Ceram. Int., 40, 13179 (2014).M. C. Verbraeken, B. R. Sudireddy, V. Vasechko, M. Cassidy, T. Ramos, J. Malzbender, P. Holtappels and J. T. S. Irvine, J. Eur. Ceram. Soc., 38, 1663 (2018).L. Lu, C. Ni, M. Cassidy and J. T. S. Irvine, J. Mater. Chem. A, 4, 11708 (2016).C. Ni, L. Lu, D. N. Miller, M. Cassidy and J. T. S. Irvine, J. Mater. Chem. A, 6, 5398 (2018).

This report summarizes the work done during the entire project period, between October 1, 1999 and March 31, 2003, which includes a six-month no-cost extension. During the project, eight research papers have, either been, published, accepted for publication, or submitted for publication. In addition, several presentations have been made in technical meetings and workshops. The project also has provided support for four graduate students working towards advanced degrees. The principal technical objective of the project was to analyze the role of electrode microstructure on solid oxide fuel cell performance. Prior theoretical work conducted in our laboratory demonstrated that the particle size of composite electrodes has a profound effect on cell performance; the finer the particle size, the lower the activation polarization, the better the performance. The composite cathodes examined consisted of electronically conducting perovskites such as Sr-doped LaMnO{sub 3} (LSM) or Sr-doped LaCoO{sub 3} (LSC), which is also a mixed conductor, as the electrocatalyst, and yttria-stabilized zirconia (YSZ) or rare earth oxide doped CeO{sub 2} as the ionic conductor. The composite anodes examined were mixtures of Ni and YSZ. A procedure was developed for the synthesis of nanosize YSZ by molecular decomposition, in which unwanted species were removed by leaching, leaving behind nanosize YSZ. Anode-supported cells were made using the as-synthesized powders, or using commercially acquired powders. The electrolyte was usually a thin ({approx}10 microns), dense layer of YSZ, supported on a thick ({approx}1 mm), porous Ni + YSZ anode. The cathode was a porous mixture of electrocatalyst and an ionic conductor. Most of the cell testing was done at 800 C with hydrogen as fuel and air as the oxidant. Maximum power densities as high as 1.8 W/cm{sup 2} were demonstrated. Polarization behavior of the cells was theoretically analyzed. A limited amount of cell testing was done using liquid hydrocarbon fuels where reforming was achieved internally. Significant polarization losses also occur at the anode, especially at high fuel utilizations. An analysis of polarization losses requires that various contributions are isolated, and their dependence on pertinent parameters is quantitatively described. An investigation of fuel composition on gas transport through porous anodes was investigated and the role of fuel diluents was explored. This work showed that the molecular weight of the diluent has a significant effect on anode concentration polarization. This further showed that the presence of some molecular hydrogen is necessary to minimize polarization losses. Theoretical analysis has shown that the electrode microstructure has a profound effect on cell performance. In a series of experiments, cathode microstructural parameters were varied, without altering other parameters. Cathode microstructural parameters, especially three phase boundary (TPB) length, were estimated using techniques in quantitative stereology. Cell performance was quantitatively correlated with the relevant microstructural parameters, and charge transfer resistivity was explicitly evaluated. This is the first time that a fundamental parameter, which governs the activation polarization, has been quantitatively determined. An important parameter, which governs the cathodic activation polarization, and thus cell performance, is the ionic conductivity of the composite cathode. The traditional composite cathode is a mixture of LSM and YSZ. It is well known that Sr and Mg-doped LaGaO{sub 3} (LSGM), exhibits higher oxygen ion conductivity compared to YSZ. Cells were fabricated with composite cathodes comprising a mixture of LSM and LSGM. Studies demonstrated that LSGM-based composite cathodes exhibit excellent behavior. Studies have shown that Ni + YSZ is an excellent anode. In fact, in most cells, the principal polarization losses, at least at low fuel utilizations, are associated with the cathode. Theoretical analysis conducted in our group has also shown that anode-supported cells exhibit lower polarization losses compared to cathode-supported or electrolyte-supported cells. It is essential, however, that Ni + YSZ anode be not subjected to a re-oxidation step, such as may occur accidentally, as this can cause anode disintegration. A theoretical model was developed for reduction and re-oxidation kinetics of Ni-based anodes. The model was experimentally verified. In addition, criteria for the development of redox tolerant, yet Ni-based, anodes were established.

Blind 3D image quality assessment based on self-similarity of binocular features

PurposeAccurate presentation of the rock microstructure is critical to the grain-scale analysis of rock deformation and failure in numerical modelling. 3D granite microstructure modelling has only been used in limited studies with the mineral pattern often remaining poorly constructed. In this study, the authors developed a new approach for generating 2D and 3D granite microstructure models from a 2D image by combining a heterogeneous material reconstruction method (simulated annealing method) with Voronoi tessellation.Design/methodology/approachMore specifically, the stochastic information in the 2D image is first extracted using the two-point correlation function (TPCF). Then an initial 2D or 3D Voronoi diagram with a random distribution of the minerals is generated and optimised using a simulated annealing method until the corresponding TPCF is consistent with that in the 2D image. The generated microstructure model accurately inherits the stochastic information (e.g. volume fraction and mineral pattern) from the 2D image. Lastly, the authors compared the topological characteristics and mechanical properties of the 2D and 3D reconstructed microstructure models with the model obtained by direct mapping from the 2D image of a real rock sample.FindingsThe good agreements between the mapped and reconstructed models indicate the accuracy of the reconstructed microstructure models on topological characteristics and mechanical properties.Originality/valueThe newly developed reconstruction method successfully transfers the mineral pattern from a granite sample into the 2D and 3D Voronoi-based microstructure models ready for use in grain-scale modelling.

Effects of Halloysite Nanotubes on Ionic Conductivity, Morphology, Crystallinity and Mechanical Properties of PEO-based Solid Polymer Electrolyte

Phosphonium-based poly(Ionic liquid) membranes: The effect of cation alkyl chain length on light gas separation properties and Ionic conductivity

Porous materials have become a burgeoning research interest in materials science because of their intrinsic porous characteristics, versatile chemical compositions, and abundant functionalities. Re...

A unitary approach for locally apertured orientation analysis of 2D and 3D scalar images is proposed. The size of the local aperture (the scale) needed for the orientation representation induces in general a loss of spatial acuity, or blur. Our construction permits a compensation of the blur by a reconstruction procedure. For this purpose, a special scale-dependent orientation bundle (map of the visual space into a function of both position and orientation) is built from the local Gaussian-derivatives jet of a scalar image. In this construction there is an invertible relation between the orientation bundle and the original image in the space domain. This invertible transformation is used to regain the original acuity in the spatial domain after analyzing orientation features at any given scale. This type of orientation encoding might contribute to understand both the role of orientation columns and the hyper-acuity phenomenon in biological visual systems. The approach turns out to be highly effective for the detection of elongated structures and for removal of elongated artifacts in 2D images. The results from the detection task can be enhanced by applying an anisotropic diffusion of the orientation field and thus closing missing contour segments.

Reconstruction of three-dimensional heterogeneous media from a single two-dimensional section via co-occurrence correlation function

This report summarizes the results of Phase II of this program, 'Low-Cost Manufacturing Of Multilayer Ceramic Fuel Cells'. The objective of the program is to develop advanced ceramic manufacturing technologies for making planar solid oxide fuel cell (SOFC) components that are more economical and reliable for a variety of applications. Phase II development work focused on three distinct manufacturing approaches (or tracks) for planar solid oxide fuel cell elements. Two development tracks, led by NexTech Materials and Oak Ridge National Laboratory, involved co-sintering of planar SOFC elements of cathode-supported and anode-supported variations. A third development track, led by the University of Missouri-Rolla, focused on a revolutionary approach for reducing operating temperature of SOFCs by using spin-coating to deposit ultra-thin, nano-crystalline YSZ electrolyte films. The work in Phase II was supported by characterization work at Ohio State University. The primary technical accomplishments within each of the three development tracks are summarized. Track 1--NexTech's targeted manufacturing process for planar SOFC elements involves tape casting of porous electrode substrates, colloidal-spray deposition of YSZ electrolyte films, co-sintering of bi-layer elements, and screen printing of opposite electrode coatings. The bulk of NexTech's work focused on making cathode-supported elements, although the processes developed at NexTech also were applied to the fabrication of anode-supported cells. Primary accomplishments within this track are summarized below: (1) Scale up of lanthanum strontium manganite (LSM) cathode powder production process; (2) Development and scale-up of tape casting methods for cathode and anode substrates; (3) Development of automated ultrasonic-spray process for depositing YSZ films; (4) Successful co-sintering of flat bi-layer elements (both cathode and anode supported); (5) Development of anode and cathode screen-printing processes; and (6) Demonstration of novel processes for composite cathode and cermet anode materials. Track 2--ORNL's development work focused solely on making anode-supported planar cells by tape casting of a porous anode substrate, screen printing of a YSZ electrolyte film, co-sintering of the bi-layer element, and screen-printing of an opposite cathode coating. Primary accomplishments within this track are summarized below: (1) Development and scale-up of anode tape casting and lamination processes; (2) Development of proprietary ink vehicle for screen-printing processes; (3) Development of screen-printing process for depositing YSZ films; (4) Successful co-sintering of flat bi-layer anode-supported elements; and (5) Development of cathode screen-printing process. Track 3--UMR's process development work involved fabrication of a micro-porous cathode substrate, deposition of a nano-porous interlayer film, deposition of nano-crystalline YSZ electrolyte films from polymeric precursor solutions, and deposition of an anode coating. Primary accomplishments within this track are summarized below: (1) Development and scale up of tape casting and sintering methods for cathode substrates; (2) Deposition of nano-porous ceria interlayer films on cathode substrates; (3) Successful deposition of dense YSZ films on porous cathode substrates; and (4) Identification of several anode material options.

Deep-learning-based SEM image denoiser Dorin Cerbu1, Sandip Halder1, Philippe Leray1 1IMEC, Kapeldreef 75, B-3001 Leuven, Belgium We report the development of a new method to denoise SEM images with the help of artificial neural networks. Upon using a preprocessing and training scheme tailored for SEM images of structures, most often encountered in semiconductor manufacturing, we can efficiently denoise images affected with varying degrees of noise severity and origin. In the figure below, we show an example of how we can use this filter efficiently to treat noisy images and improve the image quality. This can help in acquisition of more stable and better metrology data. Fig1(a) original image (b) Image which has been denoised using deep-learning based algorithms This development is of utmost importance for the case of post-litho processing step where resist nanostructures when SEM inspected are usually impacted by the electron beam and shrink, hence skewing critical dimension measurements. This is especially true as we push towards sub N-10 nm nodes. Application of our deep-learning processing scheme allows efficient noise reduction on SEM inspection images and helps us discern minor details previously shadowed by noise. This is extremely important as we move towards using EUV in high volume manufacturing. Small details can be crucial to understand the root-cause of stochastic and process defects. In previous work, we have already shown different approaches to understand stochastic defects [1-2]. The goal of this work is to enhance the image quality as much as possible to gain further fundamental understanding on nano-defects. [1] S. Halder et. al., ‘Using machine learning techniques to understand EUV stochastics, SPIE Photomask Technology + Extreme Ultraviolet Lithography, 2018 [2] K. Sah et.al., ‘EUV stochastic defect monitoring with advanced Broadband optical wafer inspection and e-Beam review systems’, SPIE Photomask Technology + Extreme Ultraviolet Lithography, 2018

With the rapid progress of imaging methods it is now possible to obtain detailed rock structure information on different scales, ranging from nanometers to micrometers. Such knowledge facilitates use of pore-scale modeling approaches to predict numerous physical properties based on three dimensional structural data. Pore-scale modeling approaches can simulate different processes in the rock under natural conditions (pressure, temperature, etc.), which are more difficult to simulate in the laboratory. This is especially important for unconventional reservoir rocks such as the Bazhen formation siliceous rocks (black shales) used in this study. Based on X-ray microtomography and SEM imaging we develop a detailed categorization of different types of porosities (including micro, i.e. larger than µm size, and nano, i.e. sub-micron size, porosities) for samples of Bazhen siliceous rocks. Standard pore-scale modeling techniques do not account for different flow regimes within different pore sizes. Thus, we develop a pore-network model with different physics of gas flow for micro- and nanoporosity. High-resolution images are used for stochastic reconstructions of 3D structure and subsequently used for modeling of gas permeability. Resulting permeability values are in a good agreement with gas permeabilities measured for Bazhenov siliceous rocks. Finally, we present a framework to model gas permeability of unconventional reservoir rocks using multi-scale 3D structure information based on microCT scans and high resolution SEM/FIB-SEM imaging techniques.

Preparation, characterization and ionic conductivity studies of composite sulfide solid electrolyte