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MSE Seminar: A Tale of Two "High Entropy" Ceramics
Speaker: Elizabeth J. Opila, Rolls Royce Commonwealth Professor, Materials Science and Engineering
Title: A Tale of Two "High Entropy" Ceramics
“High entropy” ceramics, more aptly termed multi-principal element ceramics, provide opportunities for new property achievements. In the first story, oxidation resistance of high entropy ultra-high ceramics such as refractory metal (Ti,Zr,Hf,Nb,Ta,Mo,W) carbides and borides exposed at temperatures between 1500C to 1800C will be described. Preferential oxidation, complex oxide formation and eutectic liquid formation was observed. In this case, the high entropy concept, while beneficial for mechanical properties, resulted in decreased oxidation resistance. In a second story, the design of high entropy rare earth silicates for thermal/environmental barrier coatings to co-optimize the thermochemical stability, thermomechanical behavior, and thermal properties will be described. Preliminary results demonstrating successful property co-optimization through mixing rare earth cations within silicate phases will be presented. These two tales provide counter-examples of the challenges and opportunities of utilizing the high entropy approach for materials design.
Elizabeth Opila is the Rolls-Royce Commonwealth Professor of Materials Science and Engineering and Director of the Rolls-Royce University Technology Center for Advanced Materials Systems at the University of Virginia in Charlottesville, where she has been since 2010. Prior to that she held the position of Materials Research Engineer at the NASA Glenn Research Center in Cleveland, OH for 19 years where she worked primarily on ceramics for applications in turbine engines, rocket engines, hot structures for thermal protections systems, and other power and propulsion applications. Her current research focus includes understanding thermodynamic and kinetic mechanisms for material degradation in extreme environments, development of life prediction methodology based on understanding of fundamental high temperature chemical reaction mechanisms, and materials development for protection of materials from extreme environments. Prof. Opila received her BS in Ceramic Engineering from the University of Illinois, her MS in Materials Science from the University of California Berkeley, and her PhD in Materials Science from the Massachusetts Institute of Technology. She is Fellow of the American Ceramic Society and the Electrochemical Society and recipient of the 2021 American Ceramic Society’s Arthur L. Friedberg Award. She has over 130 publications, is editor of 10 proceedings volumes, and coinventor on six patents.
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