Repulsion, interactions between suspensions

This value of kn is actually low by an order of magnitude for dilute suspensions of charged spheres of radius Rg. This is due to the neglect of interchain correlations for c < c in the structure factor used in the derivation of Eqs. (295)-(298). If the repulsive interaction between polyelectrolyte chains dominates, as expected in salt-free solutions, the virial expansion for viscosity may be valid over considerable range of concentrations where the average distance between chains scales as. This virial series may be approxi-... 

Figure 5 shows the calculated potential energy of interaction Vt of AI2O3 particles (t/ = 0.25 pm, A = 4.5 x 10 J, and 0.01 M ionic strength) as a function of the surface-to-surface distance of separation for various conditions of potential in an aqueous suspension. Note that the height of the potential energy barrier increases quite sharply as the potential becomes larger than a certain critical value ( 30 mV in Fig. 5). Therefore, the potential is a very good index of the magnitude of the repulsive interaction between colloid particles. Because of this, measurements of potential are most commonly used to assess the stability of a given colloidal sol.

The impact of HHb (pH([EP] 6.8, plateau adsorption onto flne sihca with bet 200 va lg is 2 h [Gun ko et al. 2009a]) on the stability of the aqueous suspension of nanosilica is the most typical among the studied proteins, as the ADj values decreases with pH (except pH=2 with a maximum of ADi(Cp)) (Figure 6.42f) that corresponds to enhancement of the stability of the HHb/A-300 suspension with increasing pH values and shows the importance of electrostatic contribution to repulsive interaction between protein molecules and silica surface both negatively charged (Gun ko et al. 2003a,c). 

The zeta potential is the potential at the surface between a stationary solution and a moving charged colloid particle. This surface defines the plane of shear. Its definition is somewhat imprecise because the moving charged particle will have a certain number of counterions attached to it (for example ions in the Stern layer, plus some bound solvent molecules), the combined flowing object being termed the electrokinetic unit. The stability of colloidal suspensions is often interpreted in terms of the zeta potential, because, as we shall see, it is more readily accessible than the surface potential (Eq. 3.7), which describes the repulsive interaction between electric double layers. 

Here we consider the total interaction between two charged particles in suspension, surrounded by tlieir counterions and added electrolyte. This is tire celebrated DLVO tlieory, derived independently by Derjaguin and Landau and by Verwey and Overbeek [44]. By combining tlie van der Waals interaction (equation (02.6.4)) witli tlie repulsion due to the electric double layers (equation (C2.6.lOI), we obtain... 

Comprehension of the interactions among microstructures composed of tethered chains is central to the understanding of many of their important properties. Their ability to impart stability against flocculation to suspensions of colloidal particles [52, 124, 125] or to induce repulsions that lead to colloidal crystallization [126] are examples of practical properties arising from interactions among tethered chains many more are conceivable but not yet realized, such as effects on adhesion, entanglement or on the assembly of new block copolymer microstructures. We will be rather brief in our treatment of interactions between tethered chains since a comprehensive review has been published recently of direct force measurements on interacting layers of tethered chains [127]. 

Suspension Model of Interaction of Asphaltene and Oil This model is based upon the concept that asphaltenes exist as particles suspended in oil. Their suspension is assisted by resins (heavy and mostly aromatic molecules) adsorbed to the surface of asphaltenes and keeping them afloat because of the repulsive forces between resin molecules in the solution and the adsorbed resins on the asphaltene surface (see Figure 4). Stability of such a suspension is considered to be a function of the concentration of resins in solution, the fraction of asphaltene surface sites occupied by resin molecules, and the equilibrium conditions between the resins in solution and on the asphaltene surface. Utilization of this model requires the following (12) 1. Resin chemical potential calculation based on the statistical mechanical theory of polymer solutions. 2. Studies regarding resin adsorption on asphaltene particle surface and... 

Impregnating a basic colloidal suspension (pH = 12) on alumina does not induce proton liberation, thus the pH is constant (Fig. 13.25b). The system keeps its initial properties, i.e. negative charges for alumina support and PdO particles. Repulsive interactions are created between the alumina surface and the PdO particles so that the particles deposited on the support are redispersed, and finally isolated from each other. 

Colloidal suspensions are often stabilized by the adsorption of polymers that are expected to exert additional configurational-steric repulsive forces. The additional, potentially significant van der Waals interactions between polymer coatings... 

In addition, if one considers a concentrated suspension, one cannot describe its behavior in terms of the interactions between two particles only, but in terms of the collective interactions among all the particles. let us consider an ensemble of particles in which each pair interacts via the attractive interaction potential U, and within that ensemble, consider two adjacent particles I and 2, Ihe first located on the left and the second on the right. The attraction which particle I experiences from the other particles except particle 2 can be dominated by the particles on its left. As a result, particle 1 can be pushed to the left. For the same reason, particle 2 can be pushed to the right. These attractions to the left of particle I and to Ihe righl of particle 2 generate an effective repulsion between particles 1 and 2 which may contribute to the stability of the system. Of course, this effect should be superimposed on the attraction between the two particles. Similarly, if the interaction potential is repulsive, an effective attraction can be generated superimposed on the repulsion between the two particles. These complexities must be accounted for in a more satisfactory treatment of concentrated dispersions. 

Figure 7 illustrates the total interparticle potential, E, for colloidally stable systems and flocculated systems, where d is the particle diameter and r is the distance between the centers of two approaching particles. A colloidally stable suspension is characterized by a repulsive interaction (positive potential) when two particles approach each other (Figure 7a). Such a repulsion varies with distance, and hence it is termed soft repulsion. In the extreme, owing to the short range of the repulsive...

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