Lamellae interfaces

Figure 5.21 shows the results of an analysis trace made across the primary lamellae/ secondary lamellae interface shown in Figure 5.20 as the line X-X. 

For increased flow rates, however, the CFD simulations show more and more deviations from an ideal SAR multi-lamination pattern [7]. Since inertial forces come into play, a secondary flow pattern is superposed on the SAR velocity profile of the creeping flow regime. Streamlines seeded at the initial lamellae interface in top view for various Reynolds numbers. The lamellae pattern right at the outlet for the same set of Reynolds numbers were also given. Further simulations showed that for Re above -15 the center lamellae are thinned out until they detach from the top and bottom walls for Re 30 (see center image of Figure 1.128). 

Good descriptions of practical experimental techniques in conventional electrophoresis can be found in Refs. [81,253,259]. For the most part, these techniques are applied to suspensions and emulsions, rather than foams. Even for foams, an indirect way to obtain information about the potential at foam lamella interfaces is by bubble electrophoresis. In bubble microelectrophoresis the dispersed bubbles are viewed under a microscope and their electrophoretic velocity is measured taking the horizontal component of motion, since bubbles rapidly float upwards in the electrophoresis cells [260,261]. A variation on this technique is the spinning cylinder method, in which a bubble is held in a cylindrical cell that is spinning about its long axis (see [262] and p.163 in Ref. [44]). Other electrokinetic techniques, such as the measurement of sedimentation potential [263] have also been used. 

An indirect way to obtain information about the potential at foam lamella interfaces is by bubble electrophoresis, in which an electric field is applied to a sample causing charged bubbles to move toward an oppositely charged electrode. The electrophoretic mobility is the measured electrophoretic velocity divided by the electric field gradient at the location where the velocity was measured. These results can be interpreted in terms of the electric potential at the plane of shear, also known as the zeta potential, using well-known equations available in the literature (29—31). Because the exact location of the shear plane is generally not known, the zeta potential is usually taken to be approximately equal to the potential at the Stem plane (Figure 11) ... 

Figure 1.8 Semiorystalline polymer (PE) with arrangement of crystalline lamellae (clearly visible as bright bands in edge-on position) and interlamellar amorphous regions and lamellae interfaces (dark), and gray bands represent lamellae in a tilted or flat-on position (chemically stained UDS, TEM)...

There are two primary types of lamellar interfaces in multiphase TlAl TlAl/TlAl interfaces between two twin-related lamellae with LIq structures, and TlAl/TiaAl interfaces between lamellae with Llo and DOig structures, respectively. In the former case the interfacial planes are (111) and (l 10) vectors in adjacent lamellae are parallel. In the latter caseJnterfacial planes are (111) in TlAl and (0001) in TigAl and (l lO) and 1120) vectors in adjacent lamellae are parallel. 

While the c/a ratio deviates only by about 2% from one, it is not ideal and this has significant consequences for the pseudotwin and 120° rotational fault. It results in a misfit at these interface which is compensated by a network of misfit dislocations (Kad and H2izzledine 1992). In contrast, the non-ideal c/a ratio does not invoke any misfit at ordered twins. However, the misfit dislocations present at interfaces are about fifty lattice spacings apart and thus there are large areas between them where the matching of the lamellae is coherent. The structures and... 

Experimentally, the stretching of block copolymer chains has been addressed in two ways by measuring L as a function of N, and by measuring the components of Rg of the block chains both parallel and perpendicular to the interface. The domain dimensions have been studied most extensively for styrene-isoprene and styrene-butadiene block copolymers X-ray and neutron scattering are the methods of choice. The predicted SSL scaling of L N2/3 has been reported for spheres, cylinders and lamellae [99,102-106], but not in all cases. For example, Bates et al. found N0 37 for styrene-butadiene spheres [100], and Hadziioannou and Skoulios observed N0 79 for styrene-isoprene lamellae [107], In the sphere case, kinetic limitations to equilibration were felt to be an important factor [100],... 

One of the major themes of boundary lubrication is to transfer the shear stress at the interface of direct solid contact to somewhere inside the lubricating layer, to achieve low friction and high wear resistance. In this sense, materials with low shear strength, such as liquid films, soft metals, and lamella solids, can be employed as candidate lubricants. 

In some species, onion (2), tomato, and sugar beet (13), the interface regions between cells, ie the middle lamella and the cell corners, are rich in relatively unesterified pectins which may function in cell-cell adhesion and play an important structural role in tissue integrity. Cell corners, in particular, may act as joists in the scaffolding function of the wall, bearing much of the mechanical load of the tissue (Jeronomidis, pers. comm.). In Zinnia leaves, although all of the cell-walls contain methyl-esterified pectin. 

The decay of liquid lamellae of circular cross-section at rest was studied in a 2-D model using the VOF method without subcellular tracking of the interface (in the following denoted basic VOF method ) in combination with a correction algorithm... 

OS 43] [R 14] [P 32] Using a three-liquid layer (water/oil/water) flow instead of a two-liquid layer flow at constant channel dimensions decreases the liquid lamellae width and doubles the absolute value of the organic/aqueous interface. As a consequence, mass transport is facilitated compared with the two-flow configuration. Hence it was found that a much higher yield was obtained for the three-liquid layer flow when performing experiments of both flow configurations imder the same experimental conditions (210 s, 0.2 pi min room temperature, 300 W, > 300 nm... 

Figure 5.21 shows that the analysis of the fine lamellae included both the W-rich and W-poor phases, and does not reveal any deviation from the original W-composition of the alloy. There is an abrupt change of solute concentration at the interface, consistent with the discontinuous mechanism of transformation. 

The role of various surfactant association structures such as micelles and lyotropic liquid crystals (372), adsorption-desorption kinetics at liquid-gas interfaces (373) and interfacial rheology (373) and capillary pressure (374) on foam lamellae stability has been studied. Microvisual studies in model porous media indicate... 

For DCE in water, the Cl-C-C-Cl torsional angle was taken as the reaction coordinate. For the transfer of FMet across the water-hexane interface, was defined as the z component of the distance between the centers of mass of the solute and the hexane lamella. 

The best-known and simplest class of block copolymers are linear diblock copolymers (AB). Being composed of two immiscible blocks, A and B, they can adopt the following equilibrium microphase morphologies, basically as a function of composition spheres (S), cylinders (C or Hex), double gyroid (G or Gyr), lamellae (L or Lam), cf. Fig. 1 and the inverse structures. With the exception of the double gyroid, all morphologies are ideally characterized by a constant mean curvature of the interface between the different microdomains. 

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