MSE Special Speaker: Dr. Kinga Unocic, Oak Ridge National Laboratory

Insight into Materials Degradation in Extreme Environments with in situ/operando Electron Microscopy

Materials utilized in advanced technologies such as power plants, nuclear reactors and aviation are constantly exposed to severe and extreme conditions of temperature, stress and environmental exposure, the combination of which is known to have a deleterious effect on materials performance, durability and lifetime. Advanced electron microscopy-based characterization techniques play a vital role in correlating materials microstructure to materials degradation phenomena because of multi-length scale imaging and microanalysis capabilities. However, new insight into materials behavior under extreme environments can be further elucidated using in situ microscopy techniques. Recent development of specialized holders for in situ experimentation, coupled with state-of-the-art scanning transmission electron microscopes, are enabling a new level of mechanistic understanding into interfacial chemical reactions for a broad range of materials systems and as a function of temperature, flowing gas, pressure, and/or mechanical stimuli. In this presentation, the nanoscale oxidation mechanisms and kinetics for a model ß-NiAl system were characterized using an in situ STEM-based closed-cell gas reaction (CCGR) system, which permits the direct visualization of dynamic structural and chemical changes during high-temperature oxidation at high spatial resolution. This system is composed of a MEMS-based gas-cell with microfabricated heater devices and a controlled gas delivery system. Using this approach, site-specific oxidation initiation sites were identified, Al₂O₃ oxidation kinetics were measured, and chemical changes were spatially resolved using analytical electron microscopy techniques. In addition to dry gas environments, there is interest in understanding the role of water vapor on high-temperature corrosion mechanisms. Thermal barrier coatings (TBC) for example are used to protect turbine blades from high-temperature degradation; however, TBC lifetimes can be substantially decreased in the presence of water vapor and combustion gas. The methods and protocols, as well as the many challenges associated with introducing and quantifying water vapor in MEMS-based closed-cell reactor systems, will be discussed with comparison to conventional high-temperature laboratory-scale testing.

Bio

Kinga Unocic is a R&D Staff Scientist in the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory. She received her M.S. degree in Metallurgical Engineering from AGH University of Science and Technology in Krakow Poland and her Ph.D. in Materials Science and Engineering from the Ohio State University in 2008. Her current research focuses on developing and applying analytical and in situ/operando electron microscopy techniques to investigate environmental effects on material properties and behaviour with an emphasis on innovative materials processing, alloy development, mechanical behaviour, radiation effects, high temperature oxidation, corrosion, and catalysis. She is active in professional societies with leadership roles in the TMS Young Leaders Program (secretary, vice-chair, and chair), the TMS Diversity committee (vice-chair and chair), TMS Corrosion and Environmental Effects Committee (vice-chair and current chair), the TMS High Temperature Alloys Committee, Additive Manufacturing Bridge Committee and in conference symposia organization for TMS, M&M, MS&T, ICMCTF and NACE. She has received several notable recognitions: 2019 ORNL finalist in the YWCA Tribute to Women, the 2017 TMS-JIM Young Leaders International Scholar award, and the 2010 TMS Young Leader Professional Development Award.

Zoom option:

https://osu.zoom.us/j/99691734565?pwd=eTJyS0ZPaHh3SkRRQU1oTFV1ZEc0dz09

Meeting ID: 996 9173 4565

Password: 340635

Dr. Unocic's presentation is not part of the graded 7895 course.