Grant: Discovery Grants Program - Individual

My long-term goal is to develop a materials physics framework, based on structural disorder in solids, for answering scientific, technological, and cultural questions. As long as humans have existed, we have used solids around us in creative ways to enhance our lives. Imperfections that are introduced during the formation and use of a solid material can have a dramatic influence on its physical properties. Through fruitful collaborations, I have found that ubiquitous materials in archaeology are ideal prototypes to investigate interesting problems in the physics of disordered solids. In the next 5 years, I will use this convergence of physics and archaeology to study how structural imperfections affect vibrational properties in solids by focusing on two questions: (1) How rapidly do structural changes occur within a solid when its environment changes due to heat, pressure, or exposure to fluids? Isotopes are ideal tracers for tracking structural properties of solids through vibrational spectroscopy because isotopes are chemically identical (the same number of electrons), but have a slightly different mass (a different number of neutrons). The most novel aspect will be working with extremely short-lived radioactive isotopes -- with lifetimes of tens of minutes -- in order to track the early stages of gas-based and water-based structural changes in carbon-rich solids. The final goal is to use this new knowledge to design materials that are less prone to environmental degradation. (2) How do different kinds of imperfections affect the way that vibrations propagate in a solid? Imperfections in solids can take many forms, ranging from Angstrom-scale differences in atomic arrangements, to nm-scale variations in a solid's periodicity, to microscopic pores and cracks. An innovative aspect of this project will be our use of different material characterization techniques on the same material to study it at different length scales, since it is rare to see multi-length-scale studies of structural imperfections. These results will help us to identify specific disorder signatures in a material that can tell us how it formed or evolved over time. The insights I will gain can be applied to research problems in archaeology, geochemistry, and technology sectors. This is because assessing disorder in solid materials can help us understand how a material formed or evolved over time, and can help us identify and design materials that are less prone to environmental degradation. For example, micro- and nano-scale structural defects in layered calcium carbonate materials are important for resource extraction because they affect drilling strategies, and how easily water, oil, and gas can flow within and between layers. Furthermore, understanding the formation and structural stability of graphite oxide will help develop new radiocarbon dating strategies for oxidized wood-based charcoal.