Chain Formation and Phase Separation in Ferrofluids: The Influence on Viscous Properties

Abstract

Ferrofluids have attracted considerable interest from researchers and engineers due to their rich set of unique physical properties that are valuable for many industrial and biomedical applications. Many phenomena and features of ferrofluids’ behavior are determined by internal structural transformations in the ensembles of particles, which occur due to the magnetic interaction between the particles. An applied magnetic field induces formations, such as linear chains and bulk columns, that become elongated along the field. In turn, these structures dramatically change the rheological and other physical properties of these fluids. A deep and clear understanding of the main features and laws of the transformations is necessary for the understanding and explanation of the macroscopic properties and behavior of ferrofluids. In this paper, we present an overview of experimental and theoretical works on the internal transformations in these systems, as well as on the effect of the internal structures on the rheological effects in the fluids.

Magnetoviscosity of a Magnetic Fluid Based on Barium Hexaferrite Nanoplates

“…Qualitatively, observed behaviour also correlates with the model of formation and destruction of particles aggregates, which could be chain- or droplike ones [ 4 ]. In particular, this behaviour corresponds with the mechanism for breaking down the nanoparticles domain overlapping the walls of the measuring cell [ 32 ].…”

“…These particle aggregates are oriented along the applied magnetic field on the one hand, while on the other hand, shear flow deflects the aggregates from this direction or separates them into smaller structures or individual particles. As a result, the MVE is a product of the competition between magnetic field strength and shear flow both qualitatively and quantitatively [ 4 ]. As a criterion for evaluating the ability of particles to form structures under the influence of a magnetic field, the so-called interaction parameter is used [ 24 ].…”

“…This topic has been intensively explored in the past from both experimental and theoretical viewpoints. Recent reviews on this subject have been presented, e.g., in [ 2 , 3 , 4 ]. Various technical and biomedical applications of ferrofluids have been considered in [ 5 , 6 , 7 , 8 ].…”

Optothermal grid activation of microflow with magnetic nanoparticle thermophoresis for microfluidics

“…To retain the stability of the colloid in magnetic field, the attractive energy of dipole–dipole interaction between magnetic nanoparticles should be weak [34–36]. The estimate shows that for larger particles the dipolar coupling parameter βU=false(1/kBTfalse)false(μ0μ2/4πDh3false)≈1.4.…”

Investigation of the Rheological Properties of Zn-Ferrite/Perfluoropolyether Oil-Based Ferrofluids

“…The magnetoviscous effects of the ferrofluids are related to the content of large particles [ 22 ]. The influence of large particles on the macroscopic dynamic properties of ferrofluids is related to the formation of internal heterogeneous structures as a result of their magnetic dipole interations with one another [ 23 ]. It is shown that an increase in the concentration of small particles leads, on the one hand, to a rise in phase transition temperature and, on the other hand, to an increase in the threshold concentration of large particles [ 24 ].…”