一様磁場での磁性流体の凝集構造解析 : ミクロスコピック系からの検討(流体工学, 流体機械)

抄録

Ferrofluids show a magnetic field response. Magnetic particles in ferrofluids make aggregations by the own magnetic moment. Magnetic particles in ferrofluids are usually covered with surfactants, and dispersion ability of ferrofluids is high. Therefore, the aggregation does not become a problem under no magnetic fields. However, the aggregation cannot be disregarded in the strong magnetic field because the magnetic moment of magnetic particles is orientated in the direction of magnetic field. Therefore, the rheological characteristics also show complex behavior in the magnetic field. In this research, the aggregate structure in the state of equilibrium under the uniform magnetic field is analyzed. And we do a research on the aggregate structure from the view point of the "microscopic system." Results obtained are as follows. (1) A cylindrical structure in a strong magnetic field is shown when the saturation magnetization of particles is small. And, a plate structure is shown when the saturation magnetization is large in a strong magnetic field. (2) The particles in the cylindrical aggregation move violently in comparison with particles in the plate aggregation. (3) The aggregation does not move as pulsing and the translational velocity of the particle is constant when the system considered is the state of equilibrium in spite of microscopic system. (4) There exists a metastable area in the aggregation of ferrofluids.