Upcoming Lectures
April 4, 2024
12:20 p.m. - 1:10 p.m.
N-205 Millennium Science Complex
University Park, PA
Frontiers in Glassy Materials: Spatial and Temporal Complexity at the Nanoscale Revealed by Electron Microscopy
Paul Voyles
Professor of Materials Science and Engineering,
Harvey D. Spangler Professor of Engineering
University of Wisconsin-Madison
Abstract:
Much of our day-to-day lives is spent interacting with some form of glassy material: looking through a silicate glass windshield while driving, drinking from a polycarbonate glass cup, or watching a display powered by organic glass light emitting diodes. However, the ubiquity and apparent featurelessness of glasses masks deep complexity associated with structural disorder, cooperative, spatially non-uniform atomic motions, and metastable thermodynamics. Electron nanodiffraction with a coherent probe is well-suited to measuring these phenomena experimentally. This talk will provide an introduction to the thermodynamics, kinetics, and structures common to the glassy state of materials, then discuss applications of time-resolved electron nanodiffraction and four-dimensional scanning transmission electron microscopy to the study of glasses. These applications include: (1) The first real-space images of nanometer-scale spatially heterogeneous dynamics near the glass transition temperature. (2) Momentum-resolved diffraction measurements of the decoupling of atomic mobilities for different elements in a multicomponent liquid at deep undercooling. (3) High-speed, low-dose imaging of orientation domains in organic glasses with liquid-crystal-like global molecular anisotropy.
Orientation domains measured with 4D STEM in glassy thin film of the organic semiconductor phenanthroperylene ester with quenched-in discotic liquid-crystalline order.
Short Bio:
Paul Voyles is Professor of Materials Science and Engineering and Harvey D. Spangler Professor of Engineering at the University of Wisconsin-Madison. He earned degrees in physics from Oberlin College and the University of Illinois, Urbana-Champaign, then worked as a post-doctoral member of technical staff at Bell Labs in Murray Hill NJ. He joined the UW-Madison in 2002 as an Assistant Professor. His research specialty is the structure of materials, investigated primarily with electron microscopy, supplemented by simulations and data science. He has worked on metallic and other glasses and on materials for microelectronics, spintronics, and superconductors. He was Chair of the Materials Science and Engineering Department from 2016 to 2018 and is currently director of the NSF-funded Wisconsin Materials Research Science and Engineering Center. He has published over 220 journal articles, book chapters, and conference proceedings.