Structure and viscosity of a transformer oil-based ferrofluid under an external electric field

Rajňák, Michal; Τimko, M.; Kopčanský, P.; Paulovičová, K.; Tóthová, Jana; Kurimský, Juraj; Dolník, Bystrík; Cimbala, Roman; Авдеев, М. В.; Петренко, В. И.; Feoktystov, Artem

doi:10.1016/j.jmmm.2016.10.008

Cited by 32 publications

(14 citation statements)

References 13 publications

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“…In the context of structural relaxation of magnetic nanoparticle aggregates, the potential of a rotating sample in a static magnetic field instead of using a rotating magnetic field was demonstrated for the investigation of the q-dependent diffusion time τ q , applicable to relaxation times of 3 − 300 ms (Wandersman et al, 2009). An analogous electroviscous effect was reported upon application of DC or AC electric fields, where changes in the viscosity were related to aggregate formation in transformer-oilbased ferrofluids (Kurimský et al, 2017;Rajnak et al, 2017Rajnak et al, , 2015.…”

Section: Interparticle Correlationsmentioning

confidence: 98%

Magnetic small-angle neutron scattering

et al. 2019

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Small-angle neutron scattering (SANS) is one of the most important techniques for microstructure determination, being utilized in a wide range of scientific disciplines, such as materials science, physics, chemistry, and biology. The reason for its great significance is that conventional SANS is probably the only method capable of probing structural inhomogeneities in the bulk of materials on a mesoscopic real-space length scale, from roughly 1 − 300 nm. Moreover, the exploitation of the spin degree of freedom of the neutron provides SANS with a unique sensitivity to study magnetism and magnetic materials at the nanoscale. As such, magnetic SANS ideally complements more real-space and surface-sensitive magnetic imaging techniques, e.g., Lorentz transmission electron microscopy, electron holography, magnetic force microscopy, Kerr microscopy, or spinpolarized scanning tunneling microscopy. In this review article we summarize the recent applications of the SANS method to study magnetism and magnetic materials. This includes a wide range of materials classes, from nanomagnetic systems such as soft magnetic Fe-based nanocomposites, hard magnetic Nd−Fe−B-based permanent magnets, magnetic steels, ferrofluids, nanoparticles, and magnetic oxides, to more fundamental open issues in contemporary condensed matter physics such as skyrmion crystals, noncollinar magnetic structures in noncentrosymmetric compounds, magnetic/electronic phase separation, and vortex lattices in type-II superconductors. Special attention is paid not only to the vast variety of magnetic materials and problems where SANS has provided direct insight, but also to the enormous progress made regarding the micromagnetic simulation of magnetic neutron scattering.

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Section: Interparticle Correlationsmentioning

confidence: 98%

Magnetic small-angle neutron scattering

et al. 2019

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“…Due to the increasing demand of high voltage rate and small size for transformers, the development of transformer oils with favorable dielectric and thermal characteristics are extensively required. Ferrofluids, the well-known and prominent term nowadays in the dielectric society, have been the subject of huge research work over the past decade [1,2]. A liquid with nanosized superparamagnetic particles homogeneously suspended in a nonmagnetic carrier liquid at just a few weight percentage (wt%) is called a ferrofluid (FF) or a magnetic * corresponding author; e-mail: paulovic@saske.sk fluids.…”

Section: Introductionmentioning

confidence: 99%

“…These nanofluids are a kind of smart materials (also called active materials), whose physical properties can be controlled and by external magnetic or electric field. In consequence of the magnetic dipolar-dipolar interaction between the magnetic particles, the magnetic fluids demonstrate typical magnetorheological (MR) effects, as their viscosity could change reversibly and rapidly by tuning the external magnetic field (MF) [2][3][4]. Thus, magnetic particles play the key role in determining the MR effect for the magnetic fluid.…”

Section: Introductionmentioning

confidence: 99%

Rheological and Thermal Transport Characteristics of a Transformer Oil Based Ferrofluid

et al. 2018

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Ferrofluids based on insulating liquids are intensively studied as a potential substitute of liquid dielectric in high voltage technologies. In this work we focus on the experimental investigation of flow and thermal transport characteristics of a ferrofluid based on transformer oil (Mogul) and iron oxide nanoparticles. The magneto-rheological behavior of the ferrofluid was studied by a rotational rheometer in the shear rate range from 1 to 1000 s ¡1 and magnetic field up to 1 T. By means of a thermal constants analyzer and a transient plane source method we obtained the thermal conductivity, specific heat and thermal diffusivity values for the studied oil and the ferrofluid. It is shown that the Newtonian character of the ferrofluid changes to a non-Newtonian with application of the magnetic field. The notable magneto-viscous effect has been observed especially at low shear rates. We found that the doping of the transformer oil by 3 wt% of the nanoparticles results in a thermal conductivity enhancement by about 3.2%.

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“…Influence of the several surfactants in the colloidal stability, particle size distribution and thermal conductivity of water-based a-Fe 2 O 3 nanofluids have been investigated by Gayadhthri et al [10]. The structural changes of the oil-based ferrofluids were investigated under external magnetic fields by Rajnak et al [11]. The magnetoviscous effect in the oil-based ferrofluids containing superparamagnetic oxide (Fe, Ni) in the presence of magnetic field was investigated by Katiyar et al [12].…”

Section: Introductionmentioning

confidence: 99%