Transport properties of ferrofluids

Abstract

Long-time self-diffusion coefficients of ferrofluid suspensions are derived from an effective Langevin equation approach. The dependences of these transport properties on the volume fraction of particles and the strength of interparticle interaction are investigated. Strong reduction of the rotational and the translational Brownian motion of the particles is manifested upon increase of particle-particle interaction or ferrofluid concentration.

Diffusion microrheology of ferrofluids

“…with the single time dependent relaxation function [36]. The first term on the right hand side of (28) was first derived by Nägele et al [43] for spherically symmetric interacting particles and the second term in the present manuscript.…”

“…The Langevin equations of the translational and rotational Brownian motion of the probe particle that interacts with the others in the suspension are the stochastic Eqs. [36] M…”

Equilibrium Structures and Stationary Patterns on Magnetic Colloidal Fluids

“…Moreover, they ignore the molecular degrees of freedom of position and orientation coordinates and momenta. They are coupled to the thermally driven solvent random forces f 0 and torques t 0 by fluctuationdissipation theorems [32][33][34]. The total force and torque F, T on the tracer by the rest of the colloidal particles, which are at the concentration nr…”

“…The measured structure factor provides the microscopic arrangements of particles accurately. Here, we provide a Langevin stochastic approach that allows the determination of the translational and rotational diffusion of the particles in ferrofluids [32,33]. These dynamic properties, in turn, allow quantifying the viscoelastic and dielectric moduli of the structural evolution of the fluid toward their equilibrium states [34].…”

“…Explicit statistical mechanics derivations for the dynamical collective correlation functions (intermediate scattering function) have been given that fit well Brownian dynamics simulations just at long wave numbers but fail at intermediate and short k values. In Refs [32][33][34],. we proposed a Langevin equation theory for a tracer ferroparticle whose motion is coupled to the cloud of the other colloidal magnetic particles with which it interacts.…”