Experimental study on contribution of clustering structure to surface tension change of magnetic fluid under magnetic field

Abstract

When a magnetic field is applied to a magnetic fluid for long time, inner magnetic particles form clustering structure, and this clustering structure grows from time by time. The surface tension of magnetic fluid is possible to change with the influence of this growth of clustering structure. For long time use of magnetic fluid application, it is important to clarify the contribution of clustering structure to surface tension change of magnetic fluid after application of magnetic field. In this study, the surface tension of water-based and kerosene-based magnetic fluid was measured by maximum bubble pressure method, and we attempted to detect the contribution of the clustering structure to the surface tension change of the magnetic fluid after the application of magnetic field. To investigate the contribution of the clustering structure, magnetic field is applied for certain time to magnetic fluid for the growth of the clustering structure in magnetic fluid before the surface tension measurement. We defined this time as the cluster growing time in this study, and the cluster growing time was set to 2, 60 and 120 min. The magnetic field intensity was 68 mT by using permanent magnets. The result shows that we detected the contribution of the clustering structure to the surface tension change by applying magnetic field in only the case of the diluted water-based magnetic fluid. In contrast, because the clustering structure is difficult to form in kerosene-based magnetic fluid due to the difference of the surfactant structure around magnetic particle, the surface tension change by applying magnetic fluid is hardly different with the cluster growing time.