title: Direct observation of the initial process of Ostwald ripening using spherical aberration-corrected transmission electron microscopy.
abstract: We study in situ behavior of platinum single atoms on amorphous carbon (a-carbon) using a spherical aberration-corrected transmission electron microscope (AC-TEM). Diffusion of single atoms, bi-atoms, clusters (<1 nm) and nanoparticles (<3 nm) was recorded in the same image with a time resolution of 1 s, and such diffusion matches the expected mechanism of Ostwald ripening, which was seen on these samples. In situ AC-TEM shows promise for dynamical observation of single atom diffusion, which is important for understanding nanosized catalysts and ceramic sintering processes. We apply in situ AC-TEM to image platinum (Pt) nanoparticles on a-carbon, which is a model catalyst system for the real Pt electrode catalysts using alloys and core-shell structures supported on carbon/oxide composite materials in the proton exchange membrane fuel cell.
authors.affiliation: Nanostructures Research Laboratory,  Japan Fine Ceramics Center, Atsuta-ku, Nagoya 456-8587,  Japan.
authors.forename: Kenta
authors.initials: K
authors.lastname: Yoshida
authors.forename: Alexander
authors.initials: A
authors.lastname: Bright
authors.forename: Nobuo
authors.initials: N
authors.lastname: Tanaka