Metal substrates, restructuring

Adsorbate-induced Restructuring of Metal Substrates 17 Lt/irecotts/riic/ed sur/aoex- f/xO... 

Note finally that, as mentioned in the Introduction, the corrosion of the substrate may also damage irreversibly a microstructured device under the severe conditions of fuel processing reactions. For example, under water vapor pressure, many detrimental effects can occur, such as surface migration of Ni in stainless-steel alloys, surface oxidation of metals (Fe to Fe203), surface enrichment with trace elements able to alloy/react with the coated catalyst (Sn, Pb, Cl ions) and poison it or surface substrate restructuring. 

G. A. Somorjai and Y. Borodko, Adsorbate (substrate)-induced restructuring of active transition metal sites of heterogeneous and enzyme catalysts, Catal. Lett., 1999, 59, 89. 

In a second set of experiments, overlapping thin films of nickel and titania were heated to 1100 K in the presence of hydrogen in a controlled atmosphere scanning transmission electron microscope (STEM). During reaction the metal film was observed to restructure into discrete particles which eventually moved and attacked the titania substrate. We believe that this behavior provides direct evidence that both the mobility of reduced titania and metal species are involved in the initiation of strong metal-support interactions. 

A more dramatic type of restructuring occurs with the adsorption of alkali metals onto certain fee metal surfaces [39] In this case, multilayer composite surfaces are formed in which the alkali and metal atoms are intermixed in an ordered structure. These structures involve the substitution of alkali atoms into substrate sites, and the details of the structures are found to be coverage-dependent. The structures are influenced by the repulsion between the dipoles formed by neighbouring alkali adsorbates and by the interactions of the alkalis with the substrate itself [40]. 

Ordered Monolayers and the Reasons for Ordering Adsorbate-Induced Restructuring Atomic Adsorption and Penetration into Substrates Metals on Metals Epitaxial Growth Growth Modes at Metal Surfaces Molecular Adsorption... 

Ethylidyne restructures the Rh(l 11) crystal face [30], sulfur restructures the Fe(l 10) face [7], and carbon restructures the Ni(lOO) face [6, 46]. The surface metal atoms move into new equilibrium p>ositions upon chemisorption in different ways, and there is evidence of restructuring even in the second substrate layer under the surface. Review the available data and point out the important electronic and structural parameters that influence the nature and magnitude of chemisorption-induced surface restructuring. 

The incommensurate, hexagonal monolayers are compressed compared to the bulk metal and they are rotated from the substrate by several degrees. From the results, the monolayer compressibility could be calculated. The restructuring (i.e. surface reconstruction) of top layers of single crystal metal surfaces as a function of solution composition and electrode potential has been studied [73]. The induced charge density was found to be the critical parameter [74]. Structural changes during... 

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