Effect of Particle Shape and Charge on Bulk Rheology of Nanoparticle Suspensions

TL;DR

This study uses molecular dynamics simulations to examine how particle shape and charge influence the flow behavior of nanoparticle suspensions, revealing shape-dependent viscosity variations and charge effects on rheology.

Contribution

It provides new insights into how particle shape and charge affect the rheological properties of nanoparticle suspensions through detailed simulation analysis.

Findings

Uncharged systems are in isotropic phase with weak shape dependence on viscosity.

Charged particles increase viscosity, especially for rods and plates.

Particle charge reduces stress relaxation by limiting reorientation.

Abstract

The rheology of nanoparticle suspensions for nanoparticles of various shapes with equal mass is studied using molecular dynamics simulations. The equilibrium structure and the response to imposed shear are analyzed for suspensions of spheres, rods, plates, and jacks in an explicit solvent for both charged and uncharged nanoparticles. For the volume fraction studied, ?$\phi_{vf}=0.075$, the uncharged systems are all in their isotropic phase and the viscosity is only weakly dependent on shape for spheres, rods, and plate whereas for the jacks the viscosity is an order of magnitude larger than for the other three shapes. The introduction of charge increases the viscosity for all four nanoparticle shapes with the increase being the largest for rods and plates. The presence of a repulsive charge between the particles decreases the amount of stress reduction that can be achieved by particle reorientation.