Seminar 2/27/2013 - Eric Stach, Brookhaven National Lab: Environmental Transmission Microscopy for Catalysis Research: The Example of Carbon Nanotubes
Abstract: Crucial to the application of nano structured materials is control over their nucleation and growth, as these aspects determine their structure and thus properties. I will describe how we can exploit the unique capabilities of in situ environmental cell transmission electron microscopy (ETEM) to observe multiple aspects of these processes. With this approach we can directly visualize how the catalysts that mediate nanotube growth respond to various changes in the growth environment and correlate these changes with the resulting nanotubes structures.
In the first portion of the presentation we will investigate how dynamic changes in catalyst morphology are correlated with the termination of growth in vertically aligned single-walled nanotube arrays. In particular, we have investigated how the processes of catalyst coarsening, Ostwald ripening and diffusion into the catalyst support can lead to growth termination, and I will describe how changes in the growth feedstock - in particular the incorporation of controlled amounts of water vapor - can alter the catalyst evolution.
In the second portion of the presentation, I will describe how altering other aspects of the growth feedstock - in this case the carrier gas, in combination with the water vapor content - can affect not only the catalyst morphological evolution but can also significantly bias the chiral distribution of the resulting nanotubes. Changes in the growth ambient are correlated with a roughening transition, which leads to a change in the rate of Ostwald ripening.
Finally, ongoing developments of the ETEM technique will be presented, focusing on control of gas streams, improvements in data acquisition and correlative studies with x-ray absorption spectroscopy. Extension of the observations of morphological changes in carbon nanotube growth to broader studies in catalysis will be outlined.
Bio: Eric Stach leads the Electron Microscopy Group in the Center for Functional Nanomaterials (CFN) at Brookhaven National Laboratory. He received his Ph.D. in Materials Science and Engineering from the University of Virginia. He has held positions as Staff Scientist and Principal Investigator at the National Center for Electron Microscopy at the Lawrence Berkeley National Laboratory and as Associate then Full Professor at Purdue University, where he retains an Adjunct appointment.
His research interests focus on the development and application of electron microscopy techniques to solve materials problems in nanostructure growth, catalysis, thin film growth and materials deformation. Dr. Stach has received several awards, among them the Microscopy Society of America's Eli F. Burton (Young Scientist) Award, and Purdue University's Faculty Scholar and Early Career Research Excellence Awards. He is the author of over 200 peer-reviewed publications, and has given over 150 invited presentations at conferences and university, corporate and national laboratories.
All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.
Location: Bowen Hall Auditorium
Date/Time: 02/27/13 at 12:00 pm - 02/27/13 at 1:00 pm
Category: PRISM/PCCM Seminar Series