title: Understanding catalyst behavior during in situ heating through simultaneous secondary and transmitted electron imaging.
abstract: By coupling techniques of simultaneous secondary (SE) and transmitted electron (TE) imaging at high resolution in a modern scanning transmission electron microscope (STEM), with the ability to heat specimens using a highly stable MEMS-based heating platform, we obtained synergistic information to clarify the behavior of catalysts during in situ thermal treatments. Au/iron oxide catalyst 'leached' to remove surface Au was heated to temperatures as high as 700°C. The Fe2O3 support particle structure tended to reduce to Fe3O4 and formed surface terraces; the formation, coalescence, and mobility of 1- to 2-nm particles on the terraces were characterized in SE, STEM-ADF, and TEM-BF modes. If combined with simultaneous nanoprobe spectroscopy, this approach will open the door to a new way of studying the kinetics of nano-scaled phenomena.
authors.affiliation: Physical Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Rd, TN 37831 Oak Ridge, USA ; Hitachi High-Technologies Canada Inc, 89 Galaxy Blvd, Toronto, ON M9W 6A4, Canada.
authors.forename: Jane Y
authors.initials: JY
authors.lastname: Howe
authors.affiliation: Physical Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Rd, TN 37831 Oak Ridge, USA.
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Allard
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, 1221 Beal Avenue, Ann Arbor, MI 48104, USA.
authors.forename: Wilbur C
authors.initials: WC
authors.lastname: Bigelow
authors.affiliation: Department of Mining and Materials Engineering, McGill University, 845 Rue Sherbrooke Ouest, Montreal, QC H3A 2B2, Canada.
authors.forename: Hendrix
authors.initials: H
authors.lastname: Demers
authors.affiliation: Physical Sciences Directorate, Oak Ridge National Laboratory, 1 Bethel Valley Rd, TN 37831 Oak Ridge, USA.
authors.forename: Steven H
authors.initials: SH
authors.lastname: Overbury
keywords: Catalyst; In situ characterization; Phase transformation; Scanning electron microscopy; Scanning transmission electron microscopy