Józefczak A, Hornowski T, Závišová V, Skumiel A, Kubovčíková M, Timko M
Institute of Acoustics, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland.
Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Kosice, Slovakia.
J Nanopart Res. 2014;16(3):2271. doi: 10.1007/s11051-014-2271-z. Epub 2014 Feb 5.
The ultrasonic propagation in the water-based magnetic fluid with doubled layered surfactant shell was studied. The measurements were carried out both in the presence as well as in the absence of the external magnetic field. The thickness of the surfactant shell was evaluated by comparing the mean size of magnetic grain extracted from magnetization curve with the mean hydrodynamic diameter obtained from differential centrifugal sedimentation method. The thickness of surfactant shell was used to estimate volume fraction of the particle aggregates consisted of magnetite grain and surfactant layer. From the ultrasonic velocity measurements in the absence of the applied magnetic field, the adiabatic compressibility of the particle aggregates was determined. In the external magnetic field, the magnetic fluid studied in this article becomes acoustically anisotropic, i.e., velocity and attenuation of the ultrasonic wave depend on the angle between the wave vector and the direction of the magnetic field. The results of the ultrasonic measurements in the external magnetic field were compared with the hydrodynamic theory of Ovchinnikov and Sokolov (velocity) and with the internal chain dynamics model of Shliomis, Mond and Morozov (attenuation).
研究了具有双层表面活性剂壳的水基磁流体中的超声传播。测量是在有和没有外部磁场的情况下进行的。通过比较从磁化曲线提取的磁性颗粒的平均尺寸与通过差示离心沉降法获得的平均流体动力学直径来评估表面活性剂壳的厚度。表面活性剂壳的厚度用于估计由磁铁矿颗粒和表面活性剂层组成的颗粒聚集体的体积分数。根据在没有施加磁场的情况下的超声速度测量，确定了颗粒聚集体的绝热压缩率。在外部磁场中，本文研究的磁流体变为声学各向异性，即超声波的速度和衰减取决于波矢量与磁场方向之间的角度。将外部磁场中超声测量的结果与奥夫钦尼科夫和索科洛夫的流体动力学理论（速度）以及什廖米斯、蒙德和莫罗佐夫的内链动力学模型（衰减）进行了比较。
