Materials Science Research Lecture
***Refreshments at 3:45pm in Noyes lobby
Abstract:
Not all mechanical deformation events can be observed in situ, so discerning the conditions at the time of an event after the fact requires a type of forensic science. Failure analysis from unexpected component breakage is a common example in engineering applications, but its principles are also relevant to understanding prehistoric geologic events that shaped our planet. In this talk, I will discuss how we are uncovering the fascinating deformation behavior of rare earth orthophosphates, a class of ceramics garnering current interest in both aerospace applications and geochronology. We have explored behaviors including twinning and pressure-induced phase transformation using nanoindentation, dynamic mechanical analysis, and diamond anvil cells with a variety of structural probe modalities. We find that these materials exhibit an anomalous decoupling of stiffness from damping behavior due to reversible twinning. In high-pressure experiments, superimposed shear stress dramatically reduces the onset pressure of the phase transformation by facilitating the distortion of the polyhedral molecular units. Novel use of direct excitation photoluminescence spectroscopy both detects the xenotime-monazite phase transition, while also showing more subtle spectra changes diagnostic of previous stress history. Greater understanding of mechanical deformation, including its dependence on stress state and its reversibility is getting us closer to answering "What happened here?" more definitively in situations that are fundamentally unobservable.
More about the Speaker:
Dr. Corinne Packard recently joined the University of Southern California as a Professor in the Mork Family Department of Chemical Engineering & Materials Science. From 2010-2024, Packard progressed through the professorial ranks in the George Ansel Department of Metallurgical and Materials Engineering at the Colorado School of Mines while simultaneously jointly appointed at the National Renewable Energy Laboratory. Prior to appointment at Mines, Packard earned her Ph.D. in Materials Science & Engineering from MIT. Packard researches fundamental and applied mechanics of materials, with a focus on ceramics for solar energy, electronics, and aerospace. Her research has elucidated principles and mechanisms of deformation behavior in brittle materials at the micro- and nanoscales under complex stress states. Specific examples include determining the role of chemistry in controlling the deformation behavior in rare-earth orthophosphate ceramics; engineering fracture in photovoltaic semiconductors to enable dramatic cost reduction through wafer reuse; and high-throughput materials discovery and optimization to design for durable thin film coatings. She has an impactful research portfolio with more than 60 archival publications and 4 issued patents, and has been recognized with notable awards including the Acta Materialia Silver Award, AIME Robert Lansing Hardy Award, a National Science Foundation Faculty Early Career Development (CAREER) Award, and the Colorado School of Mines Faculty Excellence Award.