Stability Characteristics of Nanoparticles in a Laminar Linear Shear Flow in the Presence of DLVO and Non-DLVO Forces.

Abstract

Stability characteristics of colloids in a laminar flow have been studied by solving the Fokker-Plank equation for the pair probability density function. This was done by simultaneously incorporating, for the first time, the effects of (i) Brownian motion, (ii) fluid convection, (iii) the van der Waals force, and (iv) double-layer repulsion. Furthermore, this work, for the first time, studies the effects of solvation and steric repulsion on a colloid's stability. This work interestingly finds that the stability of colloids initially increases with an increase in particle size followed by a decrease. In contrast to that, stability is observed to increase in an accelerating manner with an increase in surface potential. Similarly, it is found that stability shows a relatively stronger dependence on the solvation potential pre-exponential coefficient as compared to that found with the solvation potential decay length or surface potential. In the case of the coating thickness, though stability shows increasing behavior, the rate of increase is decelerating. The coating density is found to be the single most important parameter in controlling stability as observed by even higher self-accelerating rate of increase of stability as compared to that observed with particle size or the surface or solvation potential. Importantly, analysis reveals that stability to secondary minimum coagulation is not affected by either solvation or steric potential.