Date/Time
Date(s) - 08/04/2018
1:30 pm - 2:30 pm
Location
Rhines Hall 125
Categories
Intelligent, Multiscale Microscopy: We Really CAN Have It All
It is an exciting time not only for electron microscopy, but also for x-ray and neutron-based characterization methods; recent technique developments have allowed us to define how we can link length and time scales with multiple beams/tools. Transmission electron microscopy (or TEM), remains at the heart of these efforts. In situ transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) are powerful tools for the observation of real-time materials processes. Specifically, in situ TEM is a reliable source for probing dynamic phenomena in order to gain a predictive understanding of myriad materials and use this knowledge to tailor future, improved systems.
The development of radiation hard direct detection (DD) electron sensors has enabled improvements in the quality of in situ data for TEM imaging, and recently, we have demonstrated that DD provides far-reaching benefits for EELS. Specifically, the sharper point spread function and reduced pixel size of DD provides a significant improvement in combined energy resolution and field of view (FOV). Using the combined energy resolution and FOV and increased spectrum SNR offered by the DD EELS system, critical issues in both physical and biological sciences can be addressed. Additionally, dynamic ionic or defect-dependent phenomena can be quantified with the combination of in situ methods and the DD EELS system.
This talk reviews some of our group’s recent work with DD EELS in a wide variety of systems, including in situ investigation of chemistry-property relationships in a rapidly emerging family of 2D materials, MXenes, that show for energy storage and electromagnetic interference shielding; scattering and local structure of high entropy and other candidate metallic systems under radiation damage; dynamic semiconducting device failure, and finally, cervical tissue remodeling. These experiments enable new understanding of complex materials systems, including the first direct correlation of MXene surface terminations and conductivity, providing a predictive understanding of MXene properties for device development, as well as improved sensitivity in EFTEM imaging of biological tissues and the promise for low dose studies necessary for biological and soft matter applications. Additionally, with the ability to characterize materials behavior with high temporal and spatial resolution, we are now able to fill in gaps in the current understanding interfacial and defect-driven phenomena. Results will be presented from systematic studies of absorption processes at characteristic interfaces, or sinks will be using in situ and ex situ TEM imaging coupled with quantitative techniques, such as precession electron diffraction and strain mapping. Even with fixed macroscopic degrees of freedom, it is clear that the microscopic degrees of freedom are instrumental in controlling the efficiency of grain boundaries with respect to interstitial absorption. The results provide a platform from which a new model of sink efficiency can be obtained, and have implications in developing thermally stable, radiation tolerant materials.
In closing, an outlook on emerging time resolved studies and key challenges for “big data” will be presented. In particular, high-throughput data analysis and artificial intelligence methodologies with next generation detection systems yielding more data at faster rates (over 400 frame/second acquisition) will be discussed.
ABOUT Dr. Mitra Taheri
Hoeganaes Professor of Metallurgy
Drexel University
Mitra Taheri is the Hoeganaes Professor of Metallurgy in the Department of Materials Science & Engineering at Drexel University. At Drexel, she runs the “Dynamic Characterization Group,” which focuses primarily on the development and use of cutting edge in situ microscopy to develop and characterize materials for a wide variety of applications, ranging from energy to health. While at Drexel, she has received both the NSF and DOE Early Career awards, an ONR Summer Faculty Fellowship, and has been a visiting scholar at the Politecnico di Milano, in Milan, Italy. Her research has been featured in high profile publications such as Science, Nature Communications, ACS Nano, and Nanoletters, and has garnered over 120 invited presentations and seminars across the world.
Taheri received her PhD in Materials Science & Engineering (MSE) from Carnegie Mellon University. As a PhD student, she received a US Steel Graduate Scholarship, a Materials Research Society Graduate Student Award, a full member to Sigma Xi, and was a visiting scholar at RWTH Aachen University in Germany, the National Center for Electron Microscopy (LBL), and the Northwestern University’s Center for Atom Probe Tomography. Following her doctoral studies, Taheri was an NRC Postdoctoral Fellow at the Naval Research Laboratory (NRL) and a Director’s Postdoctoral Fellow at Lawrence Livermore National Laboratory (LLNL), where she and her group at LLNL won an R&D 100 award, a Nano-50, and the Microscopy Society of America’s Microscopy Innovation Award.
Taheri has brought in nearly 13 million dollars in research funds, produced 11 patents or patents-pending, graduated over 25 graduate students, and has held various administrative positions, including Assistant Dean of Research and Graduate Education, Provost’s Fellow, and currently founding Director of the Drexel Additive Manufacturing Collaborative Center. She serves on the editorial board for the Journal of Materials Research and Scientific Reports (a Nature family journal), and on external advisory boards for various universities and national laboratories in the United States.
A native of Washington, D.C., she resides in Center City, Philadelphia with her husband and two children.