Effect of nanoparticle polarization on relative permittivity of transformer oil-based nanofluids

Jiang, Miao; Dong, Ming; Ren, Ming; Wu, Xuezhou; Shen, Lu; Wang, Hao

doi:10.1063/1.4807297

Cited by 95 publications

(49 citation statements)

References 9 publications

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“…Although the presences of the hydroxyl group on the surface of particles or the impurities, such as polar species, can affect the polarization, it can be minimized by pre-heat treatment during sample preparation [25,26]. Therefore, the apparent polarization in this study is the summation of the polarization of the base oil, inner polarization of nanoparticles and orientation polarization of charged nanoparticles as polar molecules due to Miao et al [27]. Since the electrical properties of iron oxide are more conductive than titanium dioxide, it can be more easily charged and polarized than titanium dioxide when being dispersed in natural ester.…”

Section: Frequency Dielectric Response (Fds) Resultsmentioning

confidence: 99%

Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

et al. 2018

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Nowadays, studies of alternative liquid insulation in high voltage apparatus have become increasingly important due to higher concerns regarding safety, sustainable resources and environmentally friendly issues. To fulfil this demand, natural ester has been extensively studied and it can become a potential product to replace mineral oil in power transformers. In addition, the incorporation of nanoparticles has been remarkable in producing improved characteristics of insulating oil. Although much extensive research has been carried out, there is no general agreement on the influence on the dielectric response of base oil due to the addition of different amounts and conductivity types of nanoparticle concentrations. Therefore, in this work, a natural ester-based nanofluid was prepared by a two-step method using iron oxide (Fe 2 O 3 ) and titanium dioxide (TiO 2 ) as the conductive and semi-conductive nanoparticles, respectively. The concentration amount of each nanoparticle types was varied at 0.01, 0.1 and 1.0 g/L. The nanofluid samples were characterised by visual inspection, morphology and the dynamic light scattering (DLS) method before the dielectric response measurement was carried out for frequency-dependent spectroscopy (FDS), current-voltage (I-V), and dielectric breakdown (BD) strength. The results show that the dielectric spectra and I-V curves of nanofluid-based iron oxide increases with the increase of iron oxide nanoparticle loading, while for titanium dioxide, it exhibits a decreasing response. The dielectric BD strength is enhanced for both types of nanoparticles at 0.01 g/L concentration. However, the increasing amount of nanoparticles at 0.1 and 1.0 g/L led to a contrary dielectric BD response. Thus, the results indicate that the augmentation of conductive nanoparticles in the suspension can lead to overlapping mechanisms. Consequently, this reduces the BD strength compared to pristine materials during electron injection in high electric fields.

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Section: Frequency Dielectric Response (Fds) Resultsmentioning

confidence: 99%

Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

et al. 2018

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“…For the low frequency relaxation process, the best fitting value for α was close to 1, which gives the well-known Debye relaxation law. From calculated parameters we consider that the relaxation maximum is associated with a single relaxation process which can stem from a polarization of electric double layer observed in the magnetic particles [9] The Schwarz model of electric double layer polarization can be used to explain the low frequency relaxation maximum. The dependence of the real permittivity and the dissipation factor of ferrofluid on the magnetic field show a hysteresis effect (Figs.…”

Section: Resultsmentioning

confidence: 99%

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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“…The study of the electrical properties of nanouids describes only a few papers at the moment, which focused mainly on the electrical conductivity of waterbased nanouids [611], even fewer papers describing permittivity of nanosuspensions [10,12]. There is a several ways to measuring electrical properties of nanouids.…”

Section: C55mentioning

confidence: 99%