Brownian Dynamics Simulations on the Orientational Distribution and the Rheological Properties of a Suspension Composed of Disk-Like Hematite Particles

We have investigated the orientational distribution and rheological properties of a disk-like hematite particle dispersion by means of Brownian dynamics simulations. The present Brownian dynamics method takes into account the spin Brownian motion about the particle axis in addition to the ordinary translational and rotational Brownian motion [1]. We performed the simulations for the various situations to investigate the influence of the shear rate, the magnetic field strength and the magnetic particle-particle interaction strength on the particle orientational characteristics and the rheological properties. In the situation of a strong applied magnetic field, the particles can freely rotate about the magnetic moment direction together with their magnetic moment aligning along the magnetic field direction, which leads to a linear peak-type orientational distribution. If the shear flow becomes dominant, a single peak-type distribution comes to appear more significantly. This is because column-like clusters come to incline in the direction of the angular velocity vector of a simple shear flow under a strong shear flow situation. Since the magnetic moment is more strongly restricted in the magnetic field direction with increasing field strength, the viscosity due to the magnetic properties of the particles increases more significantly. An increase in the magnetic particle-particle interaction strength leads to a decrease in the viscosity. Unless the regime of aggregation structures changes, the viscosity monotonously decreases with increasing Peclet number.

 

Literature:

1.Satoh, A., 2014, Application of the Brownian Dynamics Method to a Rod-like Hematite Particle Dispersion, Molecular Physics. (in the press; published  online, 20 Aug 2013)