Metallic alloy surfaces

A definite theoretical explanation of this behavior is not available. It is important to realize that the preference of a metal for 3C as opposed to 2C complexes or for 5C as opposed to 3C complexes may be either intrinsic or induced by adsorption of less reactive carbonaceous fragments and carbon (for simplicity, we shall refer to both of these as carbon ) on the metal (alloy) surface. Also, the choice of the reaction conditions (apparent contact time, poisoning or self-poisoning of the catalyst, etc.) influences the temperature range in which the catalysts can be tested, and since the selectivity in various complex formations is also temperature dependent, one must always analyze which aspects of the product distributions are intrinsic properties of a metal and which are induced by often unavoidable side reactions. 

Direct and indirect channels to molecular dissociation at metal and metal alloy surfaces... 

Ordered metal alloy systems might expose profound different surface characteristics even though consisting of the same elemental composition in the bulk. Intermixing or phase separation is correlated with the surface composition and structure. Differences appear associated by the influence of the free surface energy with segregation and surface ordering. Some prospects have been illustrated at specific metal alloy surfaces. 

Gauthier Y (2001) Pt-metal alloy surfaces systematic trends. Surf Rev Lett 3 1663... 

Studies of single-crystal surfaces under UHV conditions have allowed us to quantify fundamental interactions at surfaces, and the majority of surface-science studies have been conducted in this manner. Utilization of XPD and LEIS techniques require the studies to be conducted under high vacuum, and studies of clean surfaces or precisely controlled adsorbate layers require UHV conditions. Here we discuss a few examples of the use of these two techniques in studies of single-crystal surfaces, illustrating their power and limitations. The surfaces discussed are metal surfaces that contain controlled amounts of adsorbates, ultrathin metal films, two-component metal alloy surfaces, and oxide surfaces. 

A Retry stand is designed to sample a flat surface spectroscopically. This design is especially useful to study metal or metal alloy surfaces. The counter electrode usually is a sharp, pointed graphite or carbon rod and spark excitation is most common. Some Retry stands have a motor-driven turntable so the flat sample can be rotated during excitation. The system also may include provision to flow a gas across the analytical gap. Retry stands are also constructed so they may be mounted in the electrode holder jaws of an arc-spark stand. 

Adzic et al. [102] developed a new approach for designing and synthesizing electrocatalysts that can dramatically reduce the required Pt content while affording possibilities to enhance their catalytic performance. These electrocatalysts consist of a monolayer (one-atom thick) of Pt on extended or supported nanoparticle metal or metal-alloy surfaces. The Pt-monolayer (PIml) approach has several attractive... 

Di Maggio, R., Rossi, S., Fedrizzi, L., Scardi P. (1997). Zr02-Ce02 films as protective coatings against dry and wet corrosion of metallic alloys. Surface and Coatings Technology, Vol. 89,No. 3, pp.292-298, ISSN 0257-8972. 

This is the case when the exposed metal/alloy surface area is entirely corroded in an environment such as a liquid electrolyte (chemical solution, liquid metal), gaseous electrolyte (air, CO2. SO2, etc.), or a hybrid electrolyte (solid and water, biological organisms, etc.). Some types of general corrosion and their description are given below [8]. 

Liu Z, Chong PH, Skeldon P, Hilton PA, Spencer JT, Quayle B, (2006), Fundamental understanding of the corrosion performance of laser-melted metallic alloys . Surface... 

The redox reactions associated with corrosion are invariably linked with local changes in pH, with metal oxidation reactions leading to a decrease in pH (since metal ions in aqueous solution are Lewis acids and undergo hydrolysis) and cathodic reactions leading to an increase in pH (e.g ff, H2O, and/or O2 reduction reactions). Thus, for localized corrosion where anodic and cathodic reactions occur at different sites on a metal surface, measurement of the pH distribution across the surface provides useful details about corrosion mechanisms. Variations in local pH often correlate with the heterogeneous microstructure of a metal alloy surface, since such microstructure influences the location of local anodes and cathodes on the surface. 

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