Surface segregation phenomenon

Statistical thermodynamic descriptions of these transitions in substitutional alloys have been developed for the cases of both binary and ternary alloys , using a simple nearest neighbor bond model of the surface segregation phenomenon (including strain energy effects). Results of the model have been evaluated here using model parameters appropriate for a Pb-5at%Bi-0.04at%Ni alloy for which experimental results will be provided below. However, the model can be applied in principle to the computation of equilibrium surface composition of any ternary solution. 

Nohr, R.S. and Macdonald, J.G. 1994. New biomaterials through surface segregation phenomenon New quaternary ammonium compounds as antibacterial agents. J Biomater Sci Polym Ed. 5 607-619. 

In our early work with bimetallic systems, we noticed that, depending on the preparation procedure in UHV, different surface compositions could be produced over the same bulk material owing to the phenomenon of surface segregation [Stamenkovic et al., 2002]. It was essential, then, to establish a methodology for transferring a well-defined bimetallic system into an electrochemical environment for further electrochemical characterization. 

Segregation of the mix This mix can occur when larger doses of the admixture are added to offset the lack of initial fluidizing of the concrete or to reinstate workability. The segregation phenomenon is always related to a superplasticizer overdose, beyond the saturation point. In some instances the surface of the hardened concrete is covered with a white layer composed... 

The quantitative study of polymer surfaces and interfaces is about ten years old and so is a relatively recent subject. It is therefore not surprising that there are many possibilities for future research. Many of the phenomena that occur at polymer interfaces are related to self-assembly. Even the simplest example, that of surface segregation of one component of a polymer blend to an interface is self-assembly. This is because where we initially had a homogeneous film, we now have one with two layers, a bulk layer and a surface segregated layer. We have shown how even such a well-studied phenomenon as surface segregation can have a future because with it one can generate a surface which could provide an excellent precursor to an interface. 

The Existence of an Unusual Reversible Deactivation Phenomenon Associated with Preferential Surface Segregation in Bimetallic Systems... 

A significant problem in alloys is the difference in the composition of their surfaces with respect to their bulk. The enrichment of one element with respect to the other on the surface compared to the bulk is called surface segregation and is a widespread phenomenon in bimetallic compounds. The most important property that has to be determined in an alloy is its exact composition at the surface and in the bulk, in relative number of atoms per unit area. 

With Pt-Ni catalysts, under reducing atmosphere, clean surfaces of bulk alloys are enriched with platinum when oxygen treatments show that the surface is then enriched with nickel (2). On Pt-Ni/A O catalyst with only 0.2wt% Pt - 1.5wt% Ni, the crystallites may be small enough to prevent any segregation phenomenon. 

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