Three-phase porous composites containing electrolyte (ionic conductor), electronic conductor, and porosity phases are frequently used for solid oxide fuel cell (SOFC) electrodes. Performance of such electrodes is microstructure sensitive. Topological connectivity of the microstructural phases and total length of triple phase boundaries are the key microstructural parameters that affect the electrode performance. These microstructural attributes in turn depend on numerous process parameters including relative proportion, mean sizes, size distributions, and morphologies of the electrolyte and electronic conductor particles in the powder mix used for fabrication of the composites. Therefore, improvement of the performance of SOFC composite electrodes via microstructural engineering is a complex multivariate problem that requires considerable input from microstructure modeling and simulations. This dissertation presents a new approach for geometric modeling and simulation of three-dimensional (3D) microstructure of three-phase porous composites for SOFC electrodes and provides electrode performance optimization guidelines based on the parametric studies on the effects of processing parameters on the total length and topological connectivity of the triple phase boundaries. The model yields an equation for total triple phase boundary length per unit volume (LTPB) that explicitly captures the dependence of LTPB on relative proportion of electrolyte and electronic conductor phases; volume fraction of porosity; and mean size, coefficient of variation, and skewness of electrolyte and electronic conductor particle populations in the initial powder mix. The equation is applicable to electrolyte and electronic conductor particles of any convex shapes and size distributions. The model is validated using experimental measurements performed in this research as well as the measurements performed by other researchers. Computer simulations of 3D composite electrode microstructures have been performed to further validate the microstructure model and to study topological connectivity of the triple phase boundaries in 3D microstructural space. A detailed parametric analysis reveals that (1) non-equiaxed plate-like, flake-like, and needle-like electrolyte and electronic conductor particle shapes can yield substantially higher LTPB; (2) mono-sized electrolyte and electronic conductor powders lead to higher LTPB as compared to the powders having size distributions with large coefficients of variation; (3) LTPB is inversely proportional to the mean sizes of electrolyte and electronic conductor particles; (4) a high value of LTPB is obtained at the lowest porosity volume fraction that permits sufficient connectivity of the pores for gas permeability; and (5) LTPB is not sensitive to the relative proportion of electrolyte and electronic conductor phases in the composition regime of interest in composite electrode applications.

This work deals with microstructural characterisation, modelling and simulation of SOFC electrodes with the goal of optimizing the electrode microstructures. Methods for a detailed electrode analysis based on focused ion beam (FIB) tomography are presented. A 3D FEM model able to perform simulations of LSCF cathodes based on 3D tomography data is shown. A model generating realistic, yet synthetic microstructures is presented that enables the optimization of microstructural characteristics.

This work deals with microstructural characterisation, modelling and simulation of SOFC electrodes with the goal of optimizing the electrode microstructures. Methods for a detailed electrode analysis based on focused ion beam (FIB) tomography are presented. A 3D FEM model able to perform simulations of LSCF cathodes based on 3D tomography data is shown. A model generating realistic, yet synthetic microstructures is presented that enables the optimization of microstructural characteristics. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.

Solid Oxide Fuel Cells (SOFCs) have received great attention among researchers in the past few decades due to their high electrochemical energy conversion efficiency, environmental friendliness, fuel flexibility and wide range of applications. This volume is a contribution from renowned researchers in the scientific community interested in functional materials for SOFCs. Chapters in this volume emphasize the processing, microstructure and performance of electrolyte and electrode materials. Contributors review the main chemical and physical routes used to prepare ceramic/composite materials, and explain a variety of manufacturing techniques for electrode and electrolyte production and characterization. Readers will also find information about both symmetrical and single fuel cells. The book is a useful reference for students and professionals involved in SOFC research and development.

Solid Oxide Fuel Cell (SOFC) has been considered as a promising technology to replace the traditional fossil fuels due to high efficiency, low emission, and silent operation. The configuration of microstructures throughout the electrodes plays a significant role in improving cell performance. However, current research did not capture the connections of the microstructure parameters, which is vital to simulate the SOFC behavior under practical circumstances. This study explored the correlations of microstructure parameters from a micro scale level, together with mass transfer and electrochemical reactions inside the electrodes, providing a novel approach to predict the SOFC performance numerically. The results then compared with available experimental data with encouraging outcome. Sensitivity of each microstructure parameter is also tested aiming to deliver a benchmark for micro-scale analysis of SOFC in the future. Additional effort focuses on exploring the cell performance of functionally graded electrodes by taking the microstructure sub-model correlations into consideration. Present results exhibit that micro-scale graded electrodes have the potential to enhance SOFC efficiency by boosting mass diffusion and fastening electrochemical reactions and hence demonstrate a strong improvement of cell performance compared with conventional uniform composite electrodes.

In this book well-known experts highlight cutting-edge research priorities and discuss the state of the art in the field of solid oxide fuel cells giving an update on specific subjects such as protonic conductors, interconnects, electrocatalytic and catalytic processes and modelling approaches.Fundamentals and advances in this field are illustrated to help young researchers address issues in the characterization of materials and in the analysis of processes, not often tackled in scholarly books.

This study aims to correlate microstructure and performance of purely electronic and mixed conducting cathodes for solid oxide fuel cells. AC impedance was used for performance evaluation, as measured by the polarization resistance values (Rp). Serial sectioning by FIB/SEM and 3D reconstruction was successful in producing volumetric representations of the porous composite cathode. These volumes were quantitatively analyzed for triple phase boundary and surface area. The results are discussed in terms of implications for design of optimal SOFC composite electrode microstructure.