Dependence on the temperature of the activation energy in the dielectric relaxation processes for ferrofluids in low-frequency field

Mălăescu, I.; Marin, C.N.

doi:10.1016/s0304-8853(02)00663-7

Cited by 20 publications

(10 citation statements)

References 5 publications

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“…Several previous studies mostly focused on the polarization and relaxation process of ferrofluids in low-frequency field. [11][12][13] However, the magnetic nanoparticles added into the oil are greatly influenced by the magnetic field, which is unsuitable for the improvement of electrical performance and practical application of transformer oil. In this paper, the AC breakdown characteristic of the TNFs loaded with different concentrations of nanoparticles was investigated.…”

Section: Introductionmentioning

confidence: 99%

Insight into the dielectric response of transformer oil-based nanofluids

et al. 2017

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The oil-based nanofluids with greater dielectric strength have attracted much attention as a crucial insulating materials in high-voltage oil-immersed power equipment. In fact, the different microstructures of the transformer oil-based nanofluids (TNFs) would result in different dielectric properties. In this work, the broadband dielectric spectroscopy measurement was used to establish the linkage between the electric double layer (EDL) and dielectric response properties of TNFs which was performed at 298K temperature and with frequency range from 10-2Hz∼106Hz. The modified Havriliak-Negami (HN) model function was used to analyze the measured results. The results demonstrate that both the real and imaginary parts of dielectric spectra of two kinds of oil are composed of the conductivity and polarization process. Compared with pure oil, two polarization process could be observed for the TNFs, explained by the EDL structure reasonably. The introduction of the EDL structure provides an idea to account for the insulating strength improvement of TNFs for the first time.

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Section: Introductionmentioning

confidence: 99%

Insight into the dielectric response of transformer oil-based nanofluids

et al. 2017

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“…Given a prolate ellipsoid of axes a and b, of volume V ¼ p=6ab 2 and eccentricity e 2 ¼ 1 À a 2 =b 2 ; the anisotropic electric susceptibility per particle can be used to compute the differential anisotropic modulus amplitude in both parallel and perpendicular configurations for a collection of identical particles at volume fraction F as: M II À hMi ¼ À 6 5 e 2 f; M ? À hMi ¼ 3 5 e 2 f: That is, a parallel alignment decreases the potential, while an anti-parallel alignment will increase it in a constant charge capacitor.…”

Section: Discussionmentioning

confidence: 99%

“…Complex dielectric response or impedance spectroscopy techniques have been applied to the study of ferrofluids by many authors [1][2][3][4][5][6]. Different mechanisms have been invoked in order to interpret the observed dielectric response including particle orientation or other generic relaxation processes, low-frequency activation of counter-ion atmosphere, polaron hopping and highfrequency vibrational modes of chained dipoles.…”

Section: Introductionmentioning

confidence: 99%

Non-linear dielectric response of ferrofluids under magnetic field

Licínio

Teixeira

Figueiredo

2005

Journal of Magnetism and Magnetic Materials

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“…Becoming negatively charged, each magnetite particle is surrounded by NH + 4 ions, forming an electric double layer [4], a fact experimentally proved by electrophoresis [9]. Consequently, the dielectric polarization of magnetic uids in a low frequency eld may be aected by the electric conductivity due to the ions from the surface of particles and/or due to the free ions in the carrier liquid.…”

Section: Introductionmentioning

confidence: 97%

“…They are magneto--dielectric materials and represent a convenient model system to investigate fundamental properties of nanoparticle systems. Thus, many authors have performed research on dielectric properties of magnetic uids such as: the magneto-dielectric eect [2,3], the experimental dependence on temperature of the complex dielectric permittivity [4,5], the low frequency dependence of the dielectric permittivity at room temperature [6], the dielectric behaviour in the microwave range [7].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Low Frequency Polarization Mechanisms in Magnetic Fluids

2013

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The dielectric behaviour of a magnetic uid with magnetite particles dispersed in kerosene was analyzed. Therefore, the frequency (f ) and temperature (T ) dependences of the complex dielectric permittivity, ε(f, T ), over the ranges 4 kHz to 2 MHz and 25• C to 90• C were measured. Based on the experimental results of ε(f, T ) and using the ClausiusMossotti equation, we have determined the temperature dependence of the real part of the total polarizability α , of a magnetic uid. The computations have taken into account that the magnetic uid consists of three components, namely magnetite particles, surfactant, and carrier liquid. The results show that at a given frequency, α increases with temperature in the low frequency range (4 kHz to 100 kHz) and decreases with temperature above 100 kHz. This behaviour demonstrates that in low frequency range the polarization mechanism related to the deformation of the counter ions atmosphere around each particle is predominant and above 100 kHz the orientation of the dipole moments is the main polarization mechanism of the magnetic uid. These measurements enabled the evaluation of the eective dipole moment of the magnetic uid, in order of 1.21 × 10 −30 C m.

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Dependence on the temperature of the activation energy in the dielectric relaxation processes for ferrofluids in low-frequency field

Cited by 20 publications

References 5 publications

Insight into the dielectric response of transformer oil-based nanofluids

Insight into the dielectric response of transformer oil-based nanofluids

Non-linear dielectric response of ferrofluids under magnetic field

Investigation of the Low Frequency Polarization Mechanisms in Magnetic Fluids

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