Electroviscous effects tertiary

The electroviscous effect present with solid particles suspended in ionic liquids, to increase the viscosity over that of the bulk liquid. The primary effect caused by the shear field distorting the electrical double layer surrounding the solid particles in suspension. The secondary effect results from the overlap of the electrical double layers of neighboring particles. The tertiary effect arises from changes in size and shape of the particles caused by the shear field. The primary electroviscous effect has been the subject of much study and has been shown to depend on (a) the size of the Debye length of the electrical double layer compared to the size of the suspended particle (b) the potential at the slipping plane between the particle and the bulk fluid (c) the Peclet number, i.e., diffusive to hydrodynamic forces (d) the Hartmarm number, i.e. electrical to hydrodynamic forces and (e) variations in the Stern layer around the particle (Garcia-Salinas et al. 2000). 

For poly electrolyte solutions with added salt, prior experimental studies found that the intrinsic viscosity decreases with increasing salt concentration. This can be explained by the tertiary electroviscous effect. As more salts are added, the intrachain electrostatic repulsion is weakened by the stronger screening effect of small ions. As a result, the polyelectrolytes are more compact and flexible, leading to a smaller resistance to fluid flow and thus a lower viscosity. For a wormlike-chain model by incorporating the tertiary effect on the chain... 

Figure 3.23 The tertiary electroviscous effect observed for particles of polystyrene latex with a copolymer of polyacrylic acid at the outer surface. The experimental points were obtained at pH 3 and 10. The dry particle radius was 75 nm and Ka 25...

The term tertiary electroviscous effect is applied to the changes in the conformation of poly electrolytes that are caused by //t/ramolecular double-layer interactions. It is customary to extend this definition to include all effects in which the geometry of the system is altered as a result of double-layer interactions. 

As mentioned in Section 4.7c, the tertiary electroviscous effect is at least partly due to the expansion and contraction of particles arising from the conformational changes of the polyelectrolytes (adsorbed or chemically bound to the surface of the particles) with changes in... 

Electroviscous Effect Any influence of electric double layer(s) on the flow properties of a fluid. The primary electroviscous effect refers to an increase in apparent viscosity when a dispersion of charged colloidal species is sheared. The secondary electroviscous effect refers to the increase in viscosity of a dispersion of charged colloidal species that is caused by their mutual electrostatic repulsion (overlapping of electric double layers). An example of the tertiary electroviscous effect would be for polyelectrolytes in solution where changes in polyelectrolyte molecule conformations and their associated effect on solution apparent viscosity occur. 

Figure 8.10 Origin of electroviscous effects (a) electrical double layer round a particle at rest, (b) distortion of the electrical double layer in a shear field, leading to the primary electroviscous effect, (c) trajectories of repelling particles caused by double-layer repulsion, leading to the secondary electroviscous effect, (d) effect of ionic strength (or pH) on the extension of a charged adsorbed poly electrolyte, causing a change of the effective diameter of the particle, and the tertiary electroviscous effect.

Additionally, a tertiary electroviscous effect exists, which is related to the dependence of the interfacial geometry on the parameters of the EDL. This can be, e.g., observed for adsorbed polyelectrolytes, whose conformation on the particle surface (stretched, random etc.) is determined by surface charge and ionic strength (Hunter 1988, pp. 200-204). 

A systematic review on the primary, secondary and tertiary electroviscous effect has been presented by Conway and Dobry-Duclaux [IJ in 1960. A brief review on some of those cITccts has been given by Dukhin [50] and Saville [51], and a more unified review has been presented by Hunter [4], In a dilute suspension, the apparent viscosity will increase with the particle volume fraction and the surface charge of the particle. A viscosity equation first published by Smoluchowski without proof [52] for describing such a system is... 

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