Segregated surfaces

Discuss the role of the surface free-energy in phenomena such as alloy segregation, surface reconstruction, faceting and sintering of small particles. How does a gas environment (air, vacuum) affect the surface composition of alloys ... 

Although bulk- and surface-decorated samples agree broadly in terms of optimal Pt Ru surface ratios for MeOH oxidation, there is less agreement with practical PtRu catalysts, although the data are sparse. This would suggest that PtRu particles show Pt-segregated surfaces as predicted by theoretical calculations. 

All substrates prepared according to our new procedure yielded the same roughness value of 2.4 0.1 A, which is also the value determined on the Ca-segregated surfaces. Because the relaxation and rumpling are both very small, slightly different values were found on the different substrates. The average values of p = (-0.56 0.35) %, and e = (1.07 0.5) % are thus given, with the error bar estimated from the uncertainties of each fit, and from the different values obtained. 

The author discusses selected examples of Auger electron spectroscopy applications to the study of the role played by sulfur adsorption in the field of heterogeneous catalysis and its implication for the metallurgical problems of segregation, surface self-diffusion and temper embrittlement. 

Fig. 10 Possible model for depth dependence of Tg as a function of Mn, showing the mobility gradient in the surface region. Within the depth region in which chain ends are segregated, the mobility gradient should be strongly dependent on M. This would be not the case far beyond the segregated surface layer of chain ends...

Surface segregation Surface/interfacial energy Layered segregation Nanometer Block copolymer segregation from blends afford nano-structured interfaces [4, 142, 143]... 

Nowotny and Wagner reexamined a large number of kinetic studies reported in the literature, arriving at the conclusion that in mar cases the data from relaxation measrtrement studies actually appear to exhibit mixed control, i.e., the overall kinetics is determined both by surface exchange and by bulk diffusion. The authors proposed a model in which the transport of lattice defects toward the surface, and vice versa, is affected by the electrical barrier generated across the jimction between the crystalline birlk and a qrrasi-isolated segregated surface layer. (See also Chapter 4 of this handbook). 

Zheng, R., Liu, G., and Yan, X. (2005) Polymer nano- and microspheres with bumpy and chain-segregated surfaces. 

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