Dielectric anisotropy in ferrofluids

Cotae, C.

doi:10.1016/0304-8853(83)90405-5

Cited by 22 publications

(6 citation statements)

References 6 publications

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“…In magnetic liquids with spherically shaped particles, there exist critical frequencies above which the magnetodielectric effect appears [4]. The critical frequency of transformer oil based magnetic liquid with spherically shaped magnetite particles coated with oleic acid (specific density of sample is 1470 kg m −3 and magnetization at H = 8 × 10 4 A m −1 is M = 25.2 × 10 3 A m −1 ) reaches a value of 55 Hz and the critical frequency of kerosene based magnetic liquid is lower at lower specific density [4] therefore we suppose that the critical frequency of our magnetic liquid (specific density is 919 kg m −3 , magnetization at H = 8 × 10 4 A m −1 is M = 4.1 × 10 3 A m −1 ) is lower than the used frequency of 50 Hz. As shown in figures 8-10 the loss factor slowly increased at = 0.0019 and decreased with increasing electric field intensity at the higher volume concentrations of magnetic particles.…”

Section: Resultsmentioning

confidence: 99%

“…They are oriented in the direction of the magnetic field. Magnetic field applied perpendicular to electric field decreases the permittivity of a magnetic liquid but magnetic field applied parallel to electric field increases the permittivity of a magnetic liquid [4]. It is known that also high electric fields initiate cluster formation [5].…”

Section: Introductionmentioning

confidence: 99%

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Breakdown and partial discharges in magnetic liquids

Herchl

Marton

Tomčo

et al. 2008

J. Phys.: Condens. Matter

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The dielectric properties (permittivity, loss factor, dielectric breakdown strength) of magnetic liquids were investigated. The magnetic liquids were composed of magnetite particles coated with oleic acid as surfactant and dispersed in transformer oil. To determine their dielectric properties they were subjected to a uniform magnetic field at high alternating electric fields up to 14 MV m(-1). Nearly constant permittivity of magnetic liquid with particle volume concentration Φ = 0.0019 as a function of electric field was observed. Magnetic liquids with concentrations Φ = 0.019 and 0.032 showed significant changes of permittivity and loss factor dependent on electric and magnetic fields. The best concentration of magnetic fluid was found at which partial current impulse magnitudes were the lowest. The breakdown strength distribution of the magnetic liquid with Φ = 0.0025 was fitted with the Duxbury-Leath, Weibull and Gauss distribution functions.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Breakdown and partial discharges in magnetic liquids

Herchl

Marton

Tomčo

et al. 2008

J. Phys.: Condens. Matter

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“…Magneto-optical properties of the colloids were used to analyse the aggregation process [6]. Furthermore, MDA for concentrated colloids was also studied [9], but limited to low values of the applied magnetic field.…”

Section: = M O L ( P )mentioning

confidence: 99%

Magnetically induced dielectric anisotropy in concentrated ferrofluids

Espurz

Alameda

Espurz-Nieto

1989

J. Phys. D: Appl. Phys.

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Magnetically induced dielectric anisotropy (MDA) has been studied in concentrated suspensions of magnetite in paraffin (n-hexadecane). The volumetric fraction was phi =0.3. The maximum value for the applied magnetic field was 48 kA m-1. A clear trend to the saturation in MDA was found for applied fields larger than 32 kA m-1. In this case, the dielectric anisotropy is up to 15% of the dielectric constant at zero field. A constant value for g=1.23 was found for magnetic fields higher than 12 kA m-1 (g=( epsilon /sub ///- epsilon (0))/( epsilon (0)- epsilon perpendicular to ) where epsilon (0) is the dielectric constant at null field). Below this field, a transition to g=1 was attained at 4 kA m-1. These results disagree with the value g=2 theoretically deduced for ideally monodispersive suspensions in the overall field range. The present results are tentatively explained qualitatively and quantitatively taking into account the mechanism of particle aggregation.

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“…The increase in permittivity absented in the liquid with Φ = 0.0019. The decrease (in the case of B ⊥ E) and increase (in the case of B E) in permittivity in the applied magnetic field was observed that is known as magnetodielectric effect [3]. As it is shown in Fig.…”

Section: Resultsmentioning

confidence: 76%

“…It is known that the permittivity of magnetic liquids is dependent on the presence of magnetic field, that is called magnetodielectric effect. This effect is caused by the reorientation of magnetic particles and the formation of the chain-like clusters of magnetic particles [3]. We suppose that the creation of clusters is also caused by the influence of high electric fields.…”

Section: Introductionmentioning

confidence: 94%

Dielectric Properties of Magnetic Liquids in High Electric Fields

et al. 2008

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In this work, dielectric properties of magnetic fluids composed of magnetite particles dispersed in transformer oil and subjected to a uniform magnetic field were investigated at the high alternating electric field intensities in the range of 0.5-2.5 MV/m. Dielectric stability of the magnetic fluid with the particle volume concentration Φ = 0.0019 was observed. The magnetic fluid with the concentration Φ = 0.019 showed the significant changes of permittivity and dielectric losses, too.

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Dielectric anisotropy in ferrofluids

Cited by 22 publications

References 6 publications

Breakdown and partial discharges in magnetic liquids

Breakdown and partial discharges in magnetic liquids

Magnetically induced dielectric anisotropy in concentrated ferrofluids

Dielectric Properties of Magnetic Liquids in High Electric Fields

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