Observation of association in a ferromagnetic colloid

2013

Colloid J

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.

Section: Introductionmentioning

confidence: 61%

“…At the same time, it is well known that, when the energy of the magnetic interparticle interactions in ferrofluids markedly exceeds thermal energy kT, the particles can form linear chains or dense bulk droplet shaped aggregates (see, e.g., [5][6][7][8][9]). …”

Section: Introductionmentioning

confidence: 99%

Diffusion and magnetotransport in ferrofluids containing chain-shaped aggregates

2013

Colloid J

“…The values of dimensionless energies ε c, T will be estimated in what follows. The terms with logarithms in formulas (1) correspond to the entropy of the ideal gas of chains, Y forks, and network nodes, respectively. The adopted order of summation over i, j, and k eliminates multiple counting of identical configurations for forks and the network [27].…”

Section: Main Assumptions and Statistical Modelmentioning

confidence: 99%

“…Numerous experiments have shown that particles in ferrofluids are capable of forming various heteroge neous structures such as linear chains, closed rings, Y like forks, and dense droplets [1][2][3][4][5][6]. These struc tures have a typical size of several microns, and they can be readily observed with common optical micro scopes.…”

Section: Introductionmentioning

confidence: 99%

Structurization of ferrofluids in the absence of an external magnetic field

Iskakova

2013

J. Exp. Theor. Phys.

Abstract-Structural transformations in a model ferrofluid in the absence of an external magnetic field have been theoretically studied. The results agree with well known laboratory experiments and computer simula tions in showing that, if the concentration of particles and their magnetic interaction energy are below certain critical values, most particles form separate linear chains. If these parameters exceed the critical values, most particles concentrate so as to form branched network structures. The passage from chains to network has a continuous character rather than represents a discontinuous first order phase transition.

“…It is well known (see, for example, refs. [11][12][13][14][15][16][17]) that magnetic field stimulates the phase condensation in ferrofluids, although only the biggest particles of polydisperse ferrofluid interact strongly enough to undergo the phase condensation.…”

Section: Theoretical Modelmentioning

confidence: 99%

Microdynamics of Magnetic Particles Dispersed in Complex Media

Bossis

López–López

Electro-Rheological Fluids and Magneto-Rheological Suspensions

2011

The aggregation of magnetic particles in the presence of a magnetic field is the basic phenomenon which underlies all the physics of magnetorheological (MR) fluids. Although these interactions are well understood when the suspending fluid is a simple liquid, new MR fluids based on dispersion of magnetic microparticles in a ferrofluid or MR elastomers based on dispersion of magnetic particles in a rubber matrix, present some unusual properties which are not well described by conventional theories. We analyze in this work the motion of magnetic particles dispersed in a ferrofluid and submitted to a magnetic field and discuss the possible applications.