COLL 473 |
| Lani M. Sanders, Department of Chemical Engineering/Materials Chemistry Department, University of New Mexico/Sandia National Laboratories, PO Box 5800, MS 1349, Albuquerque, NM 87185, Abhaya, K. Datye, Department of Chemical and Nuclear Engineering, University of New Mexico, Farris Engineering Center, Room 203, Albuquerque, NM 87131, Allen G. Sault, Scientific and Computing Systems Department, Sandia National Laboratories, PO Box 5800, MS 0807, Albuquerque, NM 87185, and Brian S. Swartzentruber, Surface and Interface Science Department, Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185. |
| In contrast to earlier approaches utilizing size distributions, we identify the crucial role of particle mobility in determining the mechanism for sintering heterogeneous catalysts. We have developed a three-dimensional Monte Carlo model simulating diffusion, vapor phase transport, and particle faceting. We report power law scaling relations between diffusion coefficient and particle size, as well as unique Arrhenius results for evaporation-condensation and periphery diffusion mechanisms, where the simulation data provide a good fit to the Gibbs-Thomson framework and perimeter scaling analyses, respectively. We measure diffusing Pd nanoparticles on titania with an atom-tracking scanning tunneling microscope capable of following a particle (or atom) with time resolution ~1 ms. This system exhibits Volmer-Weber growth we accurately simulate with our Monte Carlo model. Work supported by National Science Foundation, Grant CTS-99-11174, and U.S. Department of Energy under contract DE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the USDOE. |
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Mechanistic Surface Chemistry
Division of Colloid and Surface Chemistry |