Dielectric response of transformer oil based ferrofluid in low frequency range

Rajňák, Michal; Kurimský, Juraj; Dolník, Bystrík; Marton, K.; Tomčo, L.; Taculescu, Alina; Vékás, L.; Kováč, J.; Vávra, I.; Tóthová, Jana; Kopčanský, P.; Τimko, M.

doi:10.1063/1.4816012

Cited by 46 publications

(17 citation statements)

References 24 publications

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“…The induced anisotropy in real permittivity of a ferrofluid subjected to an external magnetic field can be seen. In the low frequency range (below 1 kHz), we can see the pronounced dielectric dispersion, which is related to a relaxation process [1]. Since the ferrofluids belong to the complex systems, a continuous distribution of relaxation times can be expected.…”

Section: Resultsmentioning

confidence: 92%

“…The study of their dielectric parameters by dielectric spectroscopy can lead to better understand polarization phenomena and improve their properties. The measurements for various concentrations and temperatures showed two main relaxation processes [1,2], the first for high frequencies -the Maxwell-Wagner effect and the second for low frequencies -the Schwarz model [3]. The dielectric behavior of ferrofluid changes with the application of an external magnetic field and with the relative orientation of the electric and magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

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Measurement of Complex Permittivity of Oil-Based Ferrofluid in Magnetic Field

2017

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The changes of dielectric parameters in oil-based ferrofluid have been measured in an external magnetic field. The frequency dependent real permittivity and the dissipation factor were measured within the frequency ranges from 1 mHz to 2 MHz by a capacitance method. These parameters have been studied in combined electric and magnetic field, when fields were parallel and perpendicular. The Cole-Cole model has been used to analyze measured data. When a magnetic field was applied, the interaction between the magnetic field and magnetic moments of nanoparticles led to the aggregation of magnetic nanoparticles to new structures -thick chains which had influence on the value of dielectric permittivity. At constant magnetic field the dependence of real permittivity and tan δ on angle between the electric and magnetic field (anisotropy) were measured, too. The various influences of magnetic field development on the investigated liquid are discussed. IntroductionFerrofluids have specific properties and various technical and biomedical fields of their applications already exist. The study of their dielectric parameters by dielectric spectroscopy can lead to better understand polarization phenomena and improve their properties. The measurements for various concentrations and temperatures showed two main relaxation processes [1,2], the first for high frequencies -the Maxwell-Wagner effect and the second for low frequencies -the Schwarz model [3]. The dielectric behavior of ferrofluid changes with the application of an external magnetic field and with the relative orientation of the electric and magnetic fields. This effect is known as magneto-dielectric anisotropy effect [2,4]. The acoustic spectroscopy is also very useful tool for the study of structure changes of ferrofluids in the magnetic fields [5,6].The complex relative permittivity is one of important dielectric parameter, which is a measure of how much energy from an external electric field is stored in a material and how dissipative a material is to an external field. It can be modeled by the Cole-Cole model plus the addition of dc losses [7] in the form

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Measurement of Complex Permittivity of Oil-Based Ferrofluid in Magnetic Field

2017

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“…To analyze this spectrum we take into account that the transformer oil shows constant permittivity (ε = 2.1) in the whole frequency range. As the known conductivity and permittivity values of the sample constituents determine the appearance of the MaxwellWagner relaxation at much higher frequencies, we associate the low frequency process with the ion impurity polarization taking place on the SNP surfaces [10,11], following the famous Schwarz polarization model.…”

Section: Resultsmentioning

confidence: 99%

Temperature Dependence of a Dielectric Relaxation in Weakly Polar Ferrofluids

et al. 2017

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In this paper, we report on the temperature dependent broadband dielectric response of a ferrofluid based on transformer oil and magnetite nanoparticles covered with oleic acid molecules. For that purpose the method of dielectric spectroscopy has been chosen in the frequency range from 20 Hz up to 100 kHz. The experiments were carried out on thin film ferrofluid samples confined in a glass plate capacitor containing indium tin oxide (ITO) plate electrodes. The obtained complex permittivity spectrum shows a pronounced dielectric dispersion in the low frequency range. Taking into account the ferrofluid composition we associate this relaxation with ion impurity polarization at the nanoparticle-oil interface. The strong temperature dependence of the relaxation process has been found when conducting the experiments in the temperature range from 298 K to 358 K. The relaxation time of the revealed process exhibits a typical Arrhenius behavior. Based on the conducted experiments and analysis, we propose some reasonable practical applications of the studied ferrofluid in the field of electrical engineering.

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“…NPs were obtained by chemical precipitation and stabilized by oleic acid C 18 H 34 O 2 in the carrier fluid [13]. The mean magneticcore diameter d h was 33.28 nm.…”

Section: Methodsmentioning

confidence: 99%

Ultrasound Frequency Analysis of a Magnetic Fluid in Low-Intensity External Magnetic Field

et al. 2017

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This work deals with an interaction of a magnetic fluid of a dielectric nature with a magnetic field by means of ultrasound waves measurements and analysis. Ultrasound analysis is known as a non-destructive inspection tool often used in technical diagnostics, moreover, it has numerous applications in medicine and biology, too. We report the low-frequency ultrasound analysis of a dielectric magnetic fluid in a low-intensity external static magnetic field. The studied magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Experiments were carried out by using an ultrasonic testing cell. The cell was exposed to a magnetic field of 50 mT in both parallel and perpendicular direction to the waves propagation. A through-transmission mode measurement was applied, where two fixed narrow-band transducers with completely shielded crystal for maximum RFI/EMI immunity (Physical Acoustic R15I-AST, the resonant frequency 150 kHz) served as a transmitter and a receiver. In this way we carried out the measurement of the frequency-dependent ultrasonic response to a rectangle calibrating signal of 5 µs pulse width. Digitized signals were recorded for further analysis. We present the frequency domain analysis of the low-frequency ultrasound in magnetic fluid. The frequency spectrum in magnetic fluid colloidal system was calculated by the Fourier transformation method. Results show that there is a frequency shift in the amplitude-frequency spectrum caused by the step-up magnetic field. The higher the magnetic field, the higher the frequency of the peaks. The effect of particle aggregation in magnetic field on the ultrasound wave propagation is discussed in the paper.

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Dielectric response of transformer oil based ferrofluid in low frequency range

Cited by 46 publications

References 24 publications

Measurement of Complex Permittivity of Oil-Based Ferrofluid in Magnetic Field

Measurement of Complex Permittivity of Oil-Based Ferrofluid in Magnetic Field

Temperature Dependence of a Dielectric Relaxation in Weakly Polar Ferrofluids

Ultrasound Frequency Analysis of a Magnetic Fluid in Low-Intensity External Magnetic Field

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