Rajnak Michal, Kurimsky Juraj, Dolnik Bystrik, Kopcansky Peter, Tomasovicova Natalia, Taculescu-Moaca Elena Alina, Timko Milan
Institute of Experimental Physics SAS, Watsonova 47, 04001 Košice, Slovakia.
Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice, Slovakia.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Sep;90(3):032310. doi: 10.1103/PhysRevE.90.032310. Epub 2014 Sep 26.
An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field.
本文介绍了在基于变压器油的铁磁流体中，由外部电场诱导磁性胶体颗粒团簇形成的实验研究。利用频域等温介电谱，我们研究了测试池电极间距对低频弛豫过程的影响。我们认为弛豫过程与颗粒表面发生的双电层极化有关。研究发现，在电极间距较大的测试池中进行测量时，弛豫最大值显著向低频方向移动。由于电场强度始终保持恒定值，我们认为外部交流电场诱导的颗粒团簇形成是导致该现象的原因。弛豫时间的增加符合双电层极化的施瓦茨理论。此外，我们分析了直流偏置电压产生的静电场对弛豫最大值位置类似移动的影响。为进行滞后测量而改变直流电场，有助于理解颗粒团簇的形成及其衰减过程。根据我们的研究结果强调了介电谱作为一种简单的补充方法，用于检测和研究由外部电场诱导的胶体颗粒团簇的实用性。
