Abstract:

In the past 15 years or so, electron microscopists have seen a remarkable improvement in the capability to conduct both heating and gas-reaction experiments in situ...inside the transmission electron microscope (TEM) due primarily to the introduction of unique heating devices called “E-chips.”  These devices are “MEMS-based” elements (microelectromechanical systems) that are fabricated using semiconductor manufacturing methods and have the remarkable feature 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 thru 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, that first originated in the early ‘60s in a few laboratories in the world, including the new electron microscopy facility in the Department of Chemical and Metallurgical Engineering at the University of Michigan, headed by Prof. Wilbur Bigelow.  One of the microscopes was equipped with a cine camera that allowed 16-mm film recording of dynamic changes in samples during observations.  Prof. Bigelow and his thesis advisor Michigan Chemistry Prof. Lawrence Brockway built a gas-handling system and a special furnace for the specimen holder, to study the initiation and growth of copper oxide grains in thin Cu single crystals beginning in the summer of 1965...and this study was inspired by earlier work that Prof. Brockway was familiar with, as a consultant at ORNL.  The ORNL work, led by Dr. John Cathcart, involved the oxidation of highly polished Cu spheres studied at the optical microscope level; when he was appraised of that work on a visit to ORNL, Prof. Brockway had the inspiration that the early details of the development of oxide films might be revealed by in situ single crystal thin film studies.  I was at the time (1963) just beginning to learn electron microscopy from Prof. Bigelow (still active today at age 99!), and I became the principal microscopist on the project.  The work was actually funded by the microscopy group at the Oak Ridge K-25 plant, who were interested in adapting our methods to the study of oxidation of Ni single crystal films, giving a second connection to Oak Ridge.  The talk today will span the history of those “early days” of in situ TEM studies and contrast them to the present-day technology with examples of studies of catalysts (e.g., for treating automotive exhausts) and aluminum alloys for automotive applications that are possible with today’s aberration-corrected, atomic-level imaging capabilities.