Shear Viscosity of Clay-like Colloids in Computer Simulations and Experiments

TL;DR

This study combines simulations and experiments to analyze the shear viscosity and structuring of dense Al2O3 colloidal suspensions, revealing shear thinning behavior and the influence of salt concentration and pH.

Contribution

It introduces a combined MD and SRD simulation approach to study colloidal suspension viscosity and correlates simulation results with experimental data using charge regulation models.

Findings

Viscosity depends on shear rate and salt concentration.

Shear thinning behavior observed in dense suspensions.

Simulation results agree with experimental measurements.

Abstract

Dense suspensions of small strongly interacting particles are complex systems, which are rarely understood on the microscopic level. We investigate properties of dense suspensions and sediments of small spherical Al_2O_3 particles in a shear cell by means of a combined Molecular Dynamics (MD) and Stochastic Rotation Dynamics (SRD) simulation. We study structuring effects and the dependence of the suspension's viscosity on the shear rate and shear thinning for systems of varying salt concentration and pH value. To show the agreement of our results to experimental data, the relation between bulk pH value and surface charge of spherical colloidal particles is modeled by Debye-Hueckel theory in conjunction with a 2pK charge regulation model.