Author ORCID Identifier
Year of Publication
Doctor of Philosophy (PhD)
Arts and Sciences
Physics and Astronomy
Dr. Yang-Tse Cheng
The demand for robust materials in energy-based applications such as solid electrolytes for batteries, piezoelectric composites for mechanical energy harvesting, or new polymer materials for polymer binders in composite electrodes is on the rise. Mechanical degradation is the most common way for devices to fail in operation, thus a thorough understanding of a material’s mechanical properties is essential for application purposes.
In this dissertation, the mechanical characterization of novel boron cluster solid electrolytes is presented. Therein, we determine the elastic modulus and hardness of these compounds using instrumented indentation. A comparison is made against other solid electrolytes. It is found that the boron cluster family of electrolytes are significantly more compliant than other common electrolytes, such as garnet.
A study on the structure-property relationship of 0D hybrid chlorometallates is also presented. In this work, we find that the elastic modulus depends significantly on the density of the compound as well as the number of hydrogen bonding sites located on the organic cation. These results are rationalized by comparing them with organic crystals, where it was found that the energy framework of hydrogen bonds within the crystal play a substantial role in determining the stiffness of this family of crystals.
A critical assessment of a novel energy-based method of determining the fracture toughness of materials using indentation is also presented. In this work, we find that the energy-based techniques found in literature give inaccurate values of fracture toughness when compared against more traditional methods. An improved method is proposed by introducing a calibration step into this process. Our results indicate that, once calibrated, this method provides significantly more accurate fracture toughness values.
Lastly, an in situ AFM study on anodized aluminum coated aluminum anodes is presented. It is determined that defects in the insulating layer can lead to unwanted inhomogeneous lithiation. The process of this lithiation is imaged directly in real time with the AFM and is presented.
The collection of this work demonstrates the importance of characterizing the mechanical properties of energy-based materials.
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The study presented in Chapter 3 was generously supported by Toyota Research Institute of North America in 2022.
Some of the work presented in Chapter 5 was supported in part by the Vehicle Technologies Office of the U.S. Department of Energy Battery Materials Research (BMR) Program under contract number DE-EE0007787 and DD-EE0008863 in 2020
Hempel, Jacob, "MECHANICAL AND MORPHOLOGICAL CHARACTERIZATION OF ENERGY MATERIALS BY NANOINDENTATION AND SCANNING PROBE MICROSCOPY" (2023). Theses and Dissertations--Physics and Astronomy. 117.
Available for download on Monday, September 15, 2025