Double layer hydrodynamic slipping plane

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). 

Zeta-potential (or electrokinetic potential) electric potential at the shear (or slip) plane within an electric double layer (EDL) the zeta-potential can be measured in case of a relative motion between the charged surface (and Stem layer) and the bulk liquid (including the difluse layer)—e.g. by application of an electric field or due to sedimentation the concept of a slip plane assumes a sharp transition between a stagnant liquid layer attached to the smface and a hydrodynamically mobile liquid phase which is located very close to the outer Helmholtz plane (OHP) the zeta-potential is, therefore, equal or lower in magnitude than the diffuse layer potential at the OHP (cf Sect. 3.1.5.1). 

Measuring electrokinetic potentials before and after polymer adsorption, that is, the Stern potential of the bare quartz surface ij/i and C potential, which reflect a shift in the position of slipping plane, it becomes in principle possible to assess the hydrodynamic thickness 5 of an adsorbed polymer layer. Assuming that presence of polymer does not change significantly the exponential distribution of local potential values il/(x) in the electrical double layer, the hydrodynamic thickness may be calculated from the Gouy equation... 

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