Interfaces depletion zones

Finally, in this section we consider the case where Xs = 0 i.e. where no adsorption takes place. There is then a depletion of segments in the region near the interface (figure 5). It is useful to define an effective depletion zone of thickness, <5, defined such that the two shaded areas are equal, and given by,... 

Fig. 16 Schematic representation of an interface-induced segregation scenario. As long as the viscosity of the crosslinking system is low enough, segregation of epoxy resin and curing agent may occur, driven by the polar surface of the Cu component. Conservation of mass requires a depletion zone close to the zone of enrichment. Via the network structure the concentration profile is reflected by the local mechanical properties of the cured epoxy system...

Dill, 1985). However, there are important properties of water that are not considered in this model. Recent theoretical and experimental studies have demonstrated a depletion (drying) of water at the hydrophobic surface-water interface (Ball, 2003). This depleted zone extends 2 to 5 nm from the hydrophobic surface. The water molecules in this zone are 85 to 90% less dense than that of the bulk water zone (Schwendel et al., 2003 Steitz et al.,... 

Fig. 7.52 Interface profile of intergranular corrosion when solute-depleted zone is anodic to precipitate and undepleted matrix, (a) Intergranular attack when precipitateand solute-depleted zone iscontinuous. (b) Intergranular attack when precipitate and depleted zones are discontinuous...

Figure 1-7. The Raman spectral stackplot shows the spectra obtained from a vertical transect through the surface crust, the biological hyaline layer, algal layer, depletion zone and basal rock, from the top. Endolithic colonisation of Beacon Sandstone, Mars Oasis, Antarctica, showing zonation. The lower interface of the algal zone dominated by cyanobacteria occurs 8 nun below the upper surface of the rock...

The P-N junction. The Fermi level of a p-type semiconductor is lower in energy than that of an z-type semiconductor. When p- and zz-type semiconductors are joined, a common Fermi level is created by the combination of holes and electrons at the interface. No carriers are present in this depletion zone at the junction. When a positive voltage is applied to the p-type side of the p-zz junction and a negative voltage to the zz-type side, current can flow since the positive voltage pushes the holes toward the... 

Another example of the depletion zone relates to the core-shell effects in the synthesis of latexes (63). Consider a partly polymerized latex. The remaining monomer may be the same or different from the already formed polymer. Many such systems have most of the polymer in the interior, and most of the monomer near the surface, because the polymer avoids the aqueous interface. A requirement is that the latex particle be larger than the end-to-end distance of the polymer chains already formed. This requirement is usually met. This has two consequences ... 

Polymeric amphiphiles, even when they are not adsorbed to the droplet interfaces, provide an entropic effect that can expressed as a change in viscosity. Depletion flocculation occurs because the center of mass of the depleting agent (the polymers) will not approach the droplet more closely than its effective radius (as mentioned before). Hence there is an area around the droplet that is not accessible to the polymer because of its reduced entropy. If the total depletion volume of the droplets is reduced by the overlap of their depletion zones, the excluded volume is decreased, and the volume accessible to the polymer is increased, increasing its entropy. The attractive force that appears... 

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