Imaging atoms with electron microscope is Friends of ORNL topic Nov. 8
Larry Allard, principal scientist who helped pioneer the technology of the aberration-corrected electron microscope (ACEM) at Oak Ridge National Laboratory 20 years ago, will speak to Friends of ORNL on Tuesday, on “Heating Experiments in the Electron Microscope: A 60-year ORNL Retrospective.”
Allard, a distinguished research staff member in ORNL’s Materials Science and Technology Division, explained in a brief interview that an ACEM is an advanced electron microscope that enables scientists to “see” single atoms and spacings between atoms in a crystal that are smaller than an atom’s diameter. This ultrahigh-resolution imaging was made possible early this century by the development of the aberration corrector added to the electron microscope, loosely analogous to giving a person with poor eyesight 20-20 vision through corrective lenses.
He added that ORNL’s atomic-level imaging microscopy capabilities have allowed studies of, for example, “single-atom” catalysts, a rapidly developing field that has shown usefulness in many chemical reaction processes and in cleaning up automotive exhausts. Allard also studies aluminum alloys that could be used to improve the efficiency of automotive internal combustion engines, as well as of future electric vehicles.
At the in-person “hybrid” meeting hosted by Friends of ORNL, attendees may bring their own food to eat but are asked to wear a mask when not eating or drinking. To view the virtual noon lecture, click on the talk title on the homepage of the www.fornl.org website and then click on the Zoom link near the top of the page describing the lecture.
Allard will tell the story of how he started his electron microscopy career in 1963 as a sophomore at the University of Michigan, where he earned his B.S.E., M.S.E. and Ph.D. degrees. There he first learned electron microscopy theory and practice as an undergraduate under Wilbur Bigelow, a professor at what is now the university’s Materials Science and Engineering Department. Allard is still collaborating closely with 99-year-old Bigelow, who continues to contribute to the scientific capabilities provided by microscopy researchers at ORNL and other institutions.
Allard will also speak on the accomplishments in the past 15 years that have enabled a remarkable improvement in electron microscopists’ “capability to conduct both heating and gas-reaction experiments inside a transmission electron microscope (TEM) primarily through the introduction of unique heating devices called E-chips.”
These devices are microfabricated on silicon using semiconductor manufacturing methods by companies such as Protochips Inc. in Morrisville, N.C.
“Professor Bigelow and I, in a collaboration with Protochips founders, built the first specimen holder that allowed the E-chips to work in the microscope,” Allard said. “Working with Protochips engineers over the past decade or so, we further contributed to the development of many other specialized holders.
“A remarkable feature of E-chips is that a thin ceramic heating membrane can cycle from room temperature to 1000°C in a millisecond. The E-chips can be combined to form a minicell with a narrow gap that can contain a gas at up to atmospheric pressure in a special holder that allows controlled flow through the cell while the specimen on the chip is being heated. These new capabilities have initiated a resurgence in the field of in situ studies, which first originated in the early 1960s in a few laboratories in the world.”
These early studies included detailed observations at the University of Michigan of the initiation and growth of oxide films and of copper oxide grains in thin single crystals of copper, work that was inspired by research at ORNL.
In his FORNL talk, Allard will address the early days of in situ TEM studies and contrast them with the present-day technology studies enabled by aberration-corrected, atomic-level imaging microscopy capabilities. He will also speak on the applications of ORNL researchers’ findings.
In 2004, Allard’s JEOL 2200FS ACEM at ORNL was one of the first two of the new scanning/transmission electron microscopy (STEM/TEM) instruments with sub-Ångström resolution that were installed in the United States. ORNL now has a half-dozen of these specialized instruments, which are engaged in materials studies. They are housed in the Advanced Microscopy Laboratory (AML), which was constructed to provide the best environment for the instruments. Allard was the principal technical designer for the AML.
Allard has more than 350 scientific publications that have garnered more than 23,000 citations. He is an elected fellow of both the Microscopy Society of America and the Microanalysis Society.
This article originally appeared on Oakridger: Imaging atoms with electron microscope is Friends of ORNL topic Nov. 8
