Dispersion mechanisms dependence

Extraparticle Transport and Dispersion Mechanisms Extraparticle mechanisms are affecded by the design of the contacting device and depend on the hydrodynamic conditions outside the particles. 

We note that Dr may or may not equal the molecular diffusion coefficient D, depending on the absence or presence of extraneous random dispersion mechanisms as discussed in Chapter 5. For simplicity, we relate DT to D by... 

In 1930s, London [39,40] introduced the dispersive force depending on the deformation polarizability, ao. The first ionization potential, /, of molecules, on the basis of the quantum mechanics gives out energy, E, for the system... 

Effects of Capillary Number, Capillary Pressure, and the Porous Medium. Since the mechanisms of leave-behind, snap-off, lamella division and coalescence have been observed in several types of porous media, it may be supposed that they all play roles in the various combinations of oil-bearing rocks and types of dispersion-based mobility control (35,37,39-41). However, the relative importance of these mechanisms depends on the porous medium and other physico-chemical conditions. Hence, it is important to understand quantitatively how the various mechanisms depend on capillary number, capillary pressure, interfacial properties, and other parameters. 

In summary, the formation, stability, and mechanical properties of food dispersed systems depend on the way in which the constituent particles and macromolecules adsorb and interact at fluid-fluid interfaces (Figure 14.1). Thus, the optimum use of emulsifiers depends on our knowledge of their interfacial physico-chemical characteristics — such as surface activity, structure, stability, superficial viscosity, etc. — and the kinetics of film formation at fluid-fluid interfaces. 

As discussed above, the plausibility of this gravitational capture mechanism depends upon whether a sufficient mass of the Earth accretes prior to dispersal of nebular gases, and further work is required to determine if dispersal of the nebula can extend over such time periods. 

This study demonstrated that the HIPS-TPP/clay blend properties (flammability, combustion, thermal, rheological, and mechanical) depend on the dispersion and distribution of the particles into the polymer matrix. Three extrusion processes were considered to produce different degrees of... 

It is appropriate to consider first the influences of long-range flocculation or collision mechanisms. Depending on the size and movement of dispersed droplets, different mechanisms will play different roles in the collision process. In a compact electrostatic coalescer (CEC), Brownian motion, sedimentation, laminar shear, turbulent shear, or turbulent inertia may play a role in droplet movement owing to hydrodynamic effects. Additionally, electrophoretic and dielectrophoretic forces, arising from the apphed electric field, may act on dispersed droplets. 

The electrical properties of nail resemble those of SC and hair. However, note that the low-frequency susceptance plateau in Figure 4.24 represents a deviation from a simple model with a distribution of relaxation times for a single dispersion mechanism (cf. Section 9.2), and it must be due to another dispersion mechanism such as, for example, electrode polarization, skin layers, etc. The admittance of nail is also logarithmically dependent on water content, as shown in Figure 4.25 (Martinsen et al., 1997c). 

Fink synthesized a series of siUcone-based surfactants [39] and used these to examine the emulsion polymerization of vinyl pyrrolidone (VP) in CO2. These monomers are liquids under ambient conditions, and hence phase behavior in CO2 was measured to determine under what conditions one could operate in an emulsion polymerization mode (Fig. 7.7). As is the case with NVF, the phase behavior of 1-vinyl-2-pyrrolidone offers the possibility for distinct polymerization regimes. Above pressures of ca. 28 MPa at 338 K, VP is miscible with carbon dioxide in all proportions. Below 28 MPa, VP and CO2 will either phase split into monomer-rich and C02-rich phases, or exist as a single phase, depending upon the initial VP concentration and system pressure. Consequently, a polymerization can be conducted initially in the single phase regime above 28 MPa, leading to a purely dispersion mechanism, or initially within the two-phase dome in P-x space, leading to an inverse emulsion polymerization. Finally, a polymerization can be conducted where pressure and composition are chosen to initially... 

Apart from pinch-offs detachment, fiow may also speed up the pull-out of copolymers from the interface and their subsequent dispersion as micelles in the continuous blend phase. This pull-out mechanism depends on the frictional shear force exerted on the interfacial copolymer chains, which is determined by the thermodynamical interaction of the interfacial copolymer chain with the blend chains at each phase and by the molecular weight and structure of the copolymer chains [77[. The experimental studies of Inoue et al. [77-79] corroborate the frictional theory and show that the pull-out tendency depends on the structure of the interfacial copolymer, on its molecular weight, and on the intensity of shear stress during fiow ... 

Finally, the book deals with the dispersion of colloidal suspensions and considers their microscopic stability (Chap. 5). Apart from a brief review on dispersion mechanisms and dispersion techniques, the chapter examines empirical scaling laws for the dispersion of p3Togenic powders and discusses aspects of monitoring dispersion processes. The dispersion of colloidal suspensions is usually accompanied by measures to stabilise the colloidal particles. The suspension stabUily depends on the interaction forces between the particles and can even be predicted under certain conditions. Nonetheless, the suspension stabUily has to be evaluated on a basis of measurements. Aspects of the comparability and extrapolation of such measurements... 

Bainite, a plate- or spearhead-shaped product consisting of a ferrite matrix in which carbide particles are dispersed. The bainitic transformation mechanism depends sensitively on alloy composition and the temperature of transformation, yielding essentially two microstructural variants. A somewhat coarser transformation product formed at about 450 is called upper bainite and a finer transformation product formed at about 350 °C is termed lower bainite. 

---