Three-Dimensional Imaging Methods and Analytical Transport Network Theory to Guide the Characterization and Design of Energy Materials

Energy materials are a class of composites used in energy conversion and storage technologies (e.g., batteries, fuel cells, etc.). They must meet a diverse and demanding set of performance criteria (including mechanical, thermal, transport, electrochemical, and economic considerations). The work in this dissertation aims to obtain an improved understanding of how the morphology and topology of an energy material’s microstructure influences its transport performance. This is accomplished by two parallel streams of research: (1) the use of three-dimensional imaging techniques, in particular, synchrotron-based x-ray nanotomography, to characterize energy material microstructures; and (2) the development of an analytical transport network theory to relate microstructural features (both morphological and topological) to energy material transport performance and activity. The portion of this work dedicated to three-dimensional imaging includes a comprehensive review of three-dimensional imaging methods for energy materials and an imaging study of ceramic waste form materials using synchrotron-based x-ray nanotomography. The waste form materials characterization revealed a minority composition within a single-phase hollandite material with a characteristic rod-like morphology. The modeling portion of this work resulted in the development of an analytical model that links 3-D features of an energy material’s microstructure, specifically local morphology and network topology, to its effective conductivity as well as to approximate metrics of its activity. In addition, the model provides a number of morphological and topological microstructural characteristics that are explicitly related to performance. The extensive morphological and topological information provided by the model along with its relative ease of use and computational efficiency make it well-suited for application in the design of energy material microstructures with respect to their transport performance