Chemisorption of Sulfur on Iron and Its Influence on Iron-Gas Reactions, Surface Self Diffusion and Sintering of Iron
Segregation equilibria of sulfur on iron single crystals are studied at elevated temperatures, 600–900°C, in an UHV apparatus using LEED for the observation of chemisorption structures and AES for the determination of surface concentrations. Even at very low sulfur activities, as established by the concentration of dissolved sulfur (10 and 27 ppm), the surface is covered with an ordered layer of chemisorbed sulfur.
In other experiments, the sulfur activity was established by the H2S/H2 ratio in a flowing gas phase at atmospheric pressure. The carburization of iron in CH4-H2 and the nitrogenation in N2 or NH3-H2 are strongly retarded by chemisorbed sulfur. The surface self diffusion coefficient of iron is increased by the presence of chemisorbed sulfur.
KeywordsGroove Width Iron Foil LEED Pattern Segregation Equilibrium Iron Single Crystal
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