Ferrofluid Structure and Rheology

Chirikov

2013

Abstract-A theoretical model is proposed to describe experimental data on the magnetorheological prop erties of magnetic fluids containing clustered particles consisting of single domain ferromagnetic nanoparti cles distributed in a polymeric shell 80-100 nm in diameter. These fluids combine the sedimentation stability typical of nanodisperse ferrofluids with the high sensitivity of rheological parameters to magnetic fields. The developed model explains the experimentally found long term rheological relaxation and residual stress that is retained after the medium ceases to flow. DOI: 10.1134/S1061933X13050190 D d

Section: Introductionmentioning

confidence: 52%

Magnetorheological properties of ferrofluids containing clustered particles

Chirikov

2013

“…Formula (4) in [8] corresponds to this approximation. The sec ond, more awkward, approximation allowed for time variations in R (formula (11) in [8]). …”

Section: Analytical Model Of Chain Growthmentioning

confidence: 99%

“…In this approximation, the hydrody namic mobility of an aggregate composed of number n of strongly interacting particles is proportional to 1/n. This approximation is frequently used in computer models of magnetic suspensions (see, e.g., [9][10][11]). In particular, it was applied in our previous calculations [8].…”

mentioning

confidence: 99%

On the theory of structuring magnetic suspensions

Kostenko

2013

Abstract-The results of the three dimensional computer and analytical simulation are presented for the kinetics of chain shaped aggregate growth in suspensions of magnetizable non Brownian particles. The results of the computer experiment show that, when the volume fraction of particles is no larger than 2-3%, chain shaped aggregates are formed in the suspensions under the action of a field. The dependence of average number of particles in a chain on time t is adequately described by the power law = Ct k . The exper iment indicates that, in contract to the common power approximations, in which exponent k is considered to be a universal constant parameter, it depends on the concentration of particles and their interactions with walls bounding a suspension. At concentrations noticeably exceeding 2-3%, dense bulk aggregates are formed in suspensions. The kinetics of their growth depends on the sizes of a suspension containing vessel.

“…It is known [10,11] that the presence of the aggre gates strongly affects the dynamic and, in particular, rheological properties of ferrofluids. It is reasonable to assume that aggregates also affect the transport prop erties, in particular, diffusion and magnetophoretic phenomena, in these systems.…”

Section: Introductionmentioning

confidence: 99%

“…These systems include, e.g., ferrofluids based on cobalt nanoparticles [11] and ferrofluids containing clustered particles composed of standard ferromagnetic nano particles bonded by polymeric shells [12,13]. Due to the presence of a large number of single domain par ticles in a cluster, the clusters strongly interact with one another and unite into aggregates.…”

Section: Introductionmentioning

confidence: 99%

Diffusion and magnetotransport in ferrofluids containing chain-shaped aggregates

2013

Abstract-The effect of chain structures on particle diffusion in nanodisperse ferrofluids subjected to exter nal magnetic fields is studied. It is shown that the chain formation imparts very strong anisotropy to the dif fusion properties of ferrofluids: the diffusion coefficient along a field appears to be approximately two orders of magnitude higher than that in the transverse direction. The presence of the chains changes the particle magnetophoresis coefficient significantly.