Forum Schedule Spring 2020

Fridays 3:45pm - 4:45pm BPB-217

Date Speaker Topic (click down-arrow to see abstract)
Jan 24

Jan 31

Feb 7 Miaofang Chi
Oak Ridge National Laboratory host: Qiang Zhu
Understanding interfaces via probing ions and electrons in a STEM

In spite of various physical and chemical properties, materials’ function is defined at the level of electrons and atoms. Electron microscopy has experienced significant technical developments in the past decades and now is powerful in revealing the atomic arrangements and identify chemical species of single atoms. This capability is especially crucial in studying and designing functional nanofeatures, such as interfaces, grain boundaries and point defects in energy and quantum materials, where these nanofeatures often introduce exotic chemical and physical properties that are inaccessible in their bulk counterparts. Very recently, new microscopy techniques, especially four-dimensional scanning transmission electron microscopy (4D-STEM) imaging, has opened a new era of characterizations in a STEM where not only single atoms can be imaged, but also the electron distributions at the sub-Å scale in real space. In this talk, I will first demonstrate the applications of the state-of-art and in situ STEM imaging for battery materials, by giving couple of examples on revealing ion transport and stability at the interfaces of solid electrolytes; then I will introduce 4D-STEM and differential phase contrast (DPC) imaging techniques, focusing on their capabilities in revealing electron distributions in materials. Examples of imaging electron distributions in electrides will be given.

Miaofang Chi is a senior staff scientist at the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL). She received her Ph.D. in Materials Science and Engineering from University of California, Davis in 2008. Her primary research interest lies in the advancements and applications of novel electron microscopy techniques in energy and nanotechnology research, especially in the understanding of interfacial charge transfer behavior in energy storage and nanoelectronics systems. She was awarded the Burton Metal by the Microscopy Society of America (2016). She received the ORNL Director’s Award for Outstanding Individual Accomplishment in Science and Technology (2015) and the ORNL’s Early Career Research Award (2015). Miaofang is the author and co-author of more than 150 peer-reviewed journal articles. She was named to the Clarivate’s 2018 list of Highly Cited Researchers.

Feb 14 Gregory Herczeg
The Kavli Institute for Astronomy
and Astrophysics, Peking University
host: Zhaohuan Zhu
From protostars to adolescence: A tour of young stellar systems

While the stages in the formation of stellar systems are now well charted, uncertainties in the initial conditions and evolution lead to stellar systems with a diverse array of architectures. In this talk I will discuss the major stages in the evolution of young stellar objects, starting from the young protostars and ending in stars that have dispersed all circumstellar material. At each step I will describe insights into some of the relevant processes that are being obtained from ongoing observational programs. For protostars, we are pursuing the first long-term monitoring program in the sub-mm to establish the role of accretion variability during the main phase of stellar growth. The next stage, protoplanetary disks, is now being revolutionized by exquisite ALMA images of substructures, which point to the presence of hidden planets. Finally, Gaia observations of young stars that have shed their disk promise to reveal the recent star formation in our local neighborhood, although this will require improved measurements of stellar properties.

Feb 21 Erin Kara
host: Daniel Proga
Reverberation mapping black hole accretion discs

Accreting supermassive black holes can produce more electromagnetic and kinetic luminosities than the combined stellar luminosity of an entire galaxy. Most of the power output from an Active Galactic Nucleus is released close to the black hole, and therefore studying the inner accretion flow is essential for understanding how black holes grow and how they affect their surrounding environments. In this talk, I will present a new way of probing these environments, through X-ray reverberation mapping, which allows us to map the gas falling on to black holes on microparsec scales and measure the effects of strongly curved spacetime close to the event horizon. I will give an overview of the field and present new results from the NICER observatory of unprecedented reverberation measurements in accreting black hole X-ray binaries.

Feb 28

Mar 6

Mar 13 Gary Ferland
University of Kentucky
host: Daniel Proga

Mar 20 Spring Break

Mar 27

Apr 3

Apr 10 Brian Metzger
Columbia University
host: Bing Zhang

Apr 17

Apr 24 Joshua Pepper
Lehigh University
host: Jason Steffen

May 1 Ilse Cleeves
University of Virginia
host: Zhaohuan Zhu

May 8 Study Week

May 15 Finals Week

Future forums: Fall 2020 

Past forums: Fall 2019  Spring 2019  Fall 2018   Spring 2018  Fall 2017  Spring 2017  Fall 2016  Spring 2016  Fall 2015   Spring 2015   Fall '14   Spring '14   Fall '13   Spring '13   Fall '12 Spring '12   Fall '11   Spring '11   Fall '10   Spring '10   Fall '09   Spring '09   Fall '08