Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 55: Poster Session III - MA 141/144 (Methods: Atomic and Electronic Structure; Particles and Clusters; Heterogeneous Catalysis; Semiconductor Substrates: Epitaxy and Growth+Adsorption+Clean Surfaces+Solid-Liquid Interfaces; Oxides and Insulators: Solid-Liquid Interfaces+Epitaxy and Growth; Phase Transitions; Metal Substrates: Adsorption of Inorganic Molecules+Epitaxy and Growth; Surface Chemical Reactions; Bimetallic Nanosystems: Tuning Physical and Chemical Properties; Oxides and insulators: Adsorption; Organic, polymeric, biomolecular films; etc.)
O 55.52: Poster
Mittwoch, 27. Februar 2008, 18:30–19:30, Poster F
Adsorption, Dissociation and Desorption of Acetylene on Steel — •Andreas Bayer1, Jürgen Rossa1, Reinhard Denecke2, and Hans-Peter Steinrück1 — 1Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen — 2Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstr. 2, 04103 Leipzig
One way to improve the hardness and wear resistance of crude steel is low-pressure carburisation. In this process, the surface near region of steel is enriched with carbon, produced in-situ by dissociative adsorption of hydrocarbons followed by diffusion of carbon atoms into the bulk. In order to gain a detailed understanding of this process, adsorption, dissociation and desorption of acetylene (C2H2) on steel at temperatures between 500 and 1200 K were studied by mass spectrometry and Auger electron spectroscopy utilising molecular beam techniques. At low temperatures (T<700 K), the sticking probability for C2H2, measured by the technique of King and Wells, is very small. Nevertheless, an increase in surface carbon coverage can be seen at 500 K, indicating a slow diffusion rate at this temperature. Upon raising temperature, the sticking coefficient reaches a maximum of 0.3 at 1000-1050 K. For even higher temperatures, the sticking probability decreases again due to nitrogen, segregating to the surface and blocking the adsorption of C2H2. Increasing the kinetic energy of C2H2 molecules by seeding with helium leads to smaller sticking coefficients at all temperatures, proposing a non-activated adsorption process.
This work was supported by BMBF (03X2506C).