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首页> 外文期刊>The Journal of Chemical Physics >Electrode polarization and unusual magnetodielectric effect in a transformer oil-based magnetic nanofluid thin layer
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Electrode polarization and unusual magnetodielectric effect in a transformer oil-based magnetic nanofluid thin layer

机译：变压器油基磁性纳米流体薄层中的电极偏振和异常磁电效应

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摘要

In the present paper, we provide low-frequency dielectric spectra for a thin layer of a nanofluid based on transformer oil and iron oxide nanoparticles stabilized by oleic acid. The complex dielectric permittivity measured in the frequency range from 1 mHz to 200 kHz shows an obvious electrode polarization effect and a Debye-like dielectric relaxation process. Both effects stem from the presence of space charge in the oil due to impurity ions, and in the nanofluid represented predominantly by a residual surfactant and uncompensated particle surface charge. It is shown that the spectra, which were measured in the temperature range from 298 K to 358 K, can be well represented by a fitting function consisted of one Havriliak-Negami term and the Jonscher's power law. In the investigated magnetic nanofluid layer, we found that the onset of the electrode polarization is suppressed to lower frequencies by the application of an external magnetic field (300 mT). This phenomenon is explained by a slowed-down migration of the space charge due to the Lorentz force and by a hindering effect of the formed magnetic nanoparticle aggregates. Surprisingly, a moderate decrease in the whole permittivity spectrum was observed for both parallel and perpendicular orientations of the electric and magnetic fields. This is in contradiction with the usual magnetodielectric anisotropy effect. Based on our qualitative analysis, we discuss potential reasons accountable for the observed effect. Published by AIP Publishing.
机译：在本文中，基于由油酸稳定的变压器油和氧化铁纳米颗粒提供纳米流体的薄层的低频介电光谱。在1MHz至200 kHz的频率范围内测量的复杂介电介电常数示出了明显的电极偏振效果和类似于脱模的介电松弛工艺。由于杂质离子，两种效应源于油中的空间电荷，并且在纳米流体中主要由残留的表面活性剂和未补偿的颗粒表面电荷表示。结果表明，在298k至358k的温度范围内测量的光谱可以通过拟合函数提供优质的函数，包括一个havriliak-negami术语和jonscher的权力法。在所研究的磁性纳米流体层中，我们发现通过施加外部磁场（300mt）来抑制电极偏振的发作到较低的频率。由于洛伦兹力引起的空间电荷减慢迁移并通过形成的磁性纳米粒子聚集体的阻碍效果来解释这种现象。令人惊讶的是，对于电场的平行和垂直取向，观察到整个渗透光谱的中等减少。这与通常的磁电极各向异性效应相矛盾。基于我们的定性分析，我们讨论了对观察到的效果负责的潜在原因。通过AIP发布发布。

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