Magneto-dielectric anisotropy in magnetic fluids determined from magneto-optical measurements

Yusuf, N.A.; Shobaki, J.; Abu-Safia, H.; Abu‐Aljarayesh, I.

doi:10.1016/0304-8853(95)00059-3

Cited by 22 publications

(9 citation statements)

References 22 publications

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“…The transformer oil-based ferrofluids possess many performance advantages as compared to transformer oils and are summarized as follows [9][10][11][12][13][21][22][23][24][30][31][32][33][40][41][42][43][44]:…”

Section: Advantages Of Transformer Oil-based Ferrofluidsmentioning

confidence: 99%

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Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

Rafiq

et al. 2017

Energies

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Abstract:Research on the transformer oil-based nanofluids (NFs) has been raised expeditiously over the past decade. Although, there is discrepancy in the stated results and inadequate understanding of the mechanisms of improvement of dielectric nanofluids, these nanofluids have emerged as a potential substitute of mineral oils as insulating and heat removal fluids for high voltage equipment. The transformer oil (TO) based magnetic fluids (ferrofluids) may be regarded as the posterity insulation fluids as they propose inspiring unique prospectus to improve dielectric breakdown strength, as well as heat transfer efficiency, as compared to pure transformer oils. In this work, transformer oil-based magnetic nanofluids (MNFs) are prepared by dispersal of Fe 3 O 4 nanoparticles (MNPs) into mineral oil as base oil, with various NPs loading from 5 to 80% w/v. The lightning impulse breakdown voltages (BDV) measurement was conducted in accordance with IEC 60897 by using needle to sphere electrodes geometry. The test results showed that dispersion of magnetic NPs may improve the insulation strength of MO. With the increment of NPs concentrations, the positive lightning impulse (LI) breakdown strength of TO is first raised, up to the highest value at 40% loading, and then tends to decrease at higher concentrations. The outcomes of negative LI breakdown showed that BDV of MNFs, with numerous loadings, were inferior to the breakdown strength of pure MO. The 40% concentration of nanoparticles (optimum concentration) was selected, and positive and negative LI breakdown strength was also further studied at different sizes (10 nm, 20 nm, 30 nm and 40 nm) of NPs and different electrode gap distances. Augmentation in the BDV of the ferrofluids (FFs) is primarily because of dielectric and magnetic features of Fe 3 O 4 nanoaprticles, which act as electron scavengers and decrease the rate of free electrons produced in the ionization process. Research challenges and technical difficulties associated with ferrofluids for practical applications are mentioned. The advantages and disadvantages linked with magnetic fluids are also presented.

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Section: Advantages Of Transformer Oil-based Ferrofluidsmentioning

confidence: 99%

“…This phenomenon is called the magnetodielectric effect [9,21,22]. The first magnetic colloid with the aim of liquid insulation was produced to improve the heat transfer from the transformer windings by imposing the magnetic interplay between the field formed by the windings and fluid [23]. [20].…”

Section: Introductionmentioning

confidence: 99%

Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

Rafiq

et al. 2017

Energies

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“…Magnetodielectric effect in magnetic fluids have been investigated by many workers [1][2][3][4][5][6][7][8][9][10][11][12] both experimentally and theoretically. The experimental investigations were based on impedance measurement techniques where the magnetic fluid is placed in a capacitor.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8] It is known that impedance measurement techniques suffer some serious disadvantages such as electrode effects, parasitic impedances, skin depth, and accuracy related problems. Very recently Yusuf et al 9 have determined the magnetodielectric effect from magnetooptical measurements where the disadvantages suffered by conventional impedance measurement techniques are avoided.…”

Section: Introductionmentioning

confidence: 99%

Numerical calculation of the magnetodielectric anisotropy effect in magnetic fluids

et al. 1996

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The magnetodielectric anisotropy effect in Fe 3 O 4 particle magnetic fluid has been numerically calculated. Our results, in agreement with previously reported results, show that the dielectric constant in the direction parallel to the field increases with the applied field, while that normal to the field decreases. The results also, in agreement with previous results, show that the dielectric constant in the field direction increases with temperature above a given temperature T s reaching a maximum at T m then decreases for higher temperatures; while in the direction normal to the field it decreases with temperature for temperatures above T s reaching a minimum at T m then increases for higher temperatures. Furthermore, our results show the important role that dimensionality plays on the magnetodielectric anisotropy effect.

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“…In FFs based on a mineral oil, a magnetodielectric effect has been studied extensively [1]. Although there is high number of papers published on the topic of FFs, the interaction with an electrical field has not received sufficient attention yet from both experimental and theoretical approach [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Generation of Fe ₃O ₄ Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field

et al. 2017

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In the paper the experimental study of magnetic nanoparticle aggregation in a transformer oil based ferrofluid driven by an external electric field is reported. The studied ferrofluid was composed of the magnetite nanoparticles, oleic acid surfactant, and transformer oil. Generally, it is considered that superparamagnetic nanoparticles do not interact in the absence of external magnetic field. In the paper we present an experimental observation of the particle assembly formation in a direct current external electric field by optical microscopy. During the observation no external magnetic field was applied. A diluted low-polarity ferrofluid drop on a glass surface was exposed to the external static inhomogeneous electric field. It is assumed that induced dipole-dipole interaction and subsequent dielectrophoretic motion give rise to the electrohydrodynamic flow in the fluid after a certain time period. As a result, a visible particle chain was formed at the drop electrical equator. This demonstration is expected to contribute to the understanding of the streamer formation and electrical breakdown in transformer oil based ferrofluids.

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Magneto-dielectric anisotropy in magnetic fluids determined from magneto-optical measurements

Cited by 22 publications

References 22 publications

Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

Numerical calculation of the magnetodielectric anisotropy effect in magnetic fluids

Generation of Fe ₃O ₄ Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field

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Magneto-dielectric anisotropy in magnetic fluids determined from magneto-optical measurements

Cited by 22 publications

References 22 publications

Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

Numerical calculation of the magnetodielectric anisotropy effect in magnetic fluids

Generation of Fe 3O 4 Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field

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Generation of Fe ₃O ₄ Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field