Transient Oxidation Stages of Metals

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9902863YangThe goal is to gain new understanding of the stages of oxidation where metal surface conditions and impurities are highly controlled. A coordinated series of in-situ TEM experiments on copper and aluminum address open issues in transient oxidation, including the kinetics of initial oxide formation. Sample preparation, initial ex-situ characterization and oxidation experiments, as well as data analysis and modeling, are conducted at University of Pittsburgh. The initial stages of oxidation are followed by in-situ ultrahigh-vacuum transmission electron microscopy performed at the Materials Research Laboratory, University of Illinois at Urbana-Champaign (UIUC). Close interaction with the Corrosion Science and Technology (CS&T) Group at Oak Ridge National Laboratory (ORNL) is integral to this program. At present the behavior of oxygen atoms on metal surfaces are observed by surface techniques such as low energy electron diffraction (LEED) and ultra-high vacuum-scanning tunneling microscopy (UHV-STM), where the surfaces are highly controlled, or by studies of macroscopic oxide growth occurring at high and low temperatures, where surface cleanliness at the atomic level is extremely challenging to achieve. The planned experiments provide essential information that bridges the gap between these two extremes.%%%Surface oxidation processes play critical roles in environmental stability, high temperature corrosion, electrochemistry, certain catalytic reactions and thin film growth as well as extreme fuel reactions. Much is known about oxygen interaction with metal surfaces and about the macroscopic growth of thermodynamically stable oxides. At present, however, the transient stages of oxidation, from the nucleation of the metal oxide to the formation of the thermodynamically stable oxide, represent a scientifically challenging and technologically important area.***