Surface excess structure

The Surface Excess Structure in 1,4-Polyisoprene-Polyacetylene Copolymer Solutions... 

For a porous adsorbent, the amount adsorbed in the pore structure per unit mass of adsorbent, based on surface excess, is obtained by the difference... 

In this example, we have focused on the surface excess charge term in (5.18) and (5.19) the next example wUl show that the potential is able to modify not only the electrode structure, but also its composition. 

We have also discussed two applications of the extended ab initio atomistic thermodynamics approach. The first example is the potential-induced lifting of Au(lOO) surface reconstmction, where we have focused on the electronic effects arising from the potential-dependent surface excess charge. We have found that these are already sufficient to cause lifting of the Au(lOO) surface reconstruction, but contributions from specific electrolyte ion adsorption might also play a role. With the second example, the electro-oxidation of a platinum electrode, we have discussed a system where specific adsorption on the surface changes the surface structure and composition as the electrode potential is varied. 

Surface-enhanced resonance Raman scattering (SERRS), 21 327-328 advantage of, 21 329 Surface Evolver software, 12 11 Surface excess, 24 135, 136 Surface extended X-ray absorption fine structure (SEXAFS), 19 179 24 72 Surface filtration, 11 322-323 Surface finish(es). See also Electroplating in electrochemical machining, 9 591 fatigue performance and, 13 486-487 Surface finishing agents, 12 33 Surface force apparatus, 1 517 Surface force-pore flow (SFPF) model,... 

It has been shown (Friberg, 2003 Birdi, 2002, 2008) that there exists a correlation between foam stability and the elasticity [E] of the film (i.e., the monolayer). In order for E to be large, surface excess must be large. Maximum foam stability has been reported in systems with fatty acid and alcohol concentrations well below the minimum in y. Similar conclusions have been observed with -C12H25S04Na [SDS] + -C12H25OH systems that give minimum in y versus concentration with maximum foam at the minimum point (Chattoraj and Birdi, 1984). Because of mixed mono-layer formation it has been found that SDS + C12H25OH (and some other additives) make liquid-crystalline structures at the surface. This leads to a stable foam (and liq-... 

The surface tension was stated (Section 6.4.5), on general grounds, to be related to the surface excess of species in the interphase. The surface excess in turn represents in some way the structure of the interface. It follows therefore that electrocapillaiy curves must contain many interesting messages about the double layer at the electrode/ electrolyte interface. To understand such messages, one must learn to decode the electrocapillary data. It is necessary to derive quantitative relations among surface tension, excess charge on the metal, cell potential, surface excess, and solution composition. 

Stockholm convention 60 stoichiometric number 42 stokes 112 strain 12 bulk 12 linear 12 shear 12 volume 12 stress 12, 72 Strouhal number 65 structural formula 45 structure factor 36 sublimation 51 substance concentration 5 substitution structure distance 24 sum over states 39 surface amount 63 surface charge density 14, 59 surface chemistry 63 surface concentration 42 surface coverage 63 surface density 12 surface electric potential 59 surface excess 63 surface excess concentration 63 surface pressure 63 surface properties 64 surface tension 12, 48, 63 susceptance 15 svedberg 111 symbols 5... 

There is an excess energy at a surface, measurable as a surface tension(8.). This causes the surface layer of a curing polymer to react farther and faster than the bulk. In the case of polyimide, it also promotes some surface layer structural rearrangement (-8%) to isoimide( ), causing changes in both mechanical(10) and electrical ( ll I properties. Further, a recent IR study (12) demonstrated that the polyimide structure obtained on curing depended on the cure schedule. 

Since the reduced and relative surface excess isotherms convey composite information on the adsorption of the two components, there is a strong incentive to determine the individual (or separate ) isotherms, i.e. the adsorbed amount n (or ) versus concentration, mole fraction or mass fraction. It will be recalled that this implies some assumptions about the thickness, composition and structure of the adsorbed layer, and therefore is not to be recommended for reporting adsorption from solution data in a standard form. Indeed, this second step is already part of the theoretical interpretation of the adsorption mechanisms. 

Other macroscopic properties that in principle can be measured are the excess density and the excess compressibility of the interfacial liquid. These excess quantities can be positive or negative and follow from a comparison of the corresponding quantities in systems with the liquid and solid separated. Alternatively, liquid behaviour in pores can be studied. An example of this kind has been given by Derjaguin ) who claims that water in narrow pores of silica gel or Aerosil does not exhibit the typical thermal expansion minimum at 4 C because of structural changes near the surface. Ldring and Findenegg ) studied surface excesses dilatometrically. 

If the temperature dependence of the surface tension is known, it is possible to obtain additional structured information by thermodynamic means. In principle, by differentiation of the surface tension with respect to the temperature we can obtain the surface excess entropy, which carries such information. However, the required analysis demcmds some scrutiny. Consider (4.2.71, which is rigorous (at given pressure) and contains S°, the excess entropy per unit cirea with reference to the surface entropy that a reference system with mole fractions (1 - x) and x would have up to the surface. From (4.2.7] we eliminated one of the chemiccd potentials using the Gibbs-Duhem rule as (1 - x)d/ij + xdp = 0. However, if the temperature becomes variable, the Gibbs-Duhem rule must be extended to... 

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