三次元流れ場中にある強磁性棒状粒子からなる非希釈コロイド分散系の粒子間相互作用が粒子配向に及ぼす影響

摘要

We have analyzed the time-dependent behaviors of the orientational distributions of a nondilute colloidal dispersion composed of the ferromagnetic spherocylinder particles influenced by the external magnetic field. In order to understand the effects of the magnetic interactions between the particles, we have derived a series of basic equations for the orientational distributions of the particles in steady three dimensional flow by applying the mean-field theory and the perturbation expansion method. Exact solutions of the basic equations are obtained theoretically. By using the solution, the mean-field, which is derived from the self-consistent condition, is analytically calculated. The magnetic interactions between the particles restrict the particle directions and make the particle incline to the direction of the chainlike cluster. The strength of the restriction decreases with the larger aspect ratio of the particle. Compared with a dilute system, in the nondilute system, the existence of the particle-particle interactions provides the increased stability of the particle orientation and the swift response to the external magnetic field.%強磁性コロイド粒子として，球状ではなく，一端 に正，他端に負の磁荷をもつ棒状の粒子は，大きな磁 気粘性効果が得られるなどの種々の効果が期待され， 活発に研究が進められている．このような強磁 性棒状粒子からなるコロイド分散系の解析としては， 近年，定常状態での特性が詳しく調べられ,単純せん 断流中の粒子の配向分布とレオロジー特性に及ぼす印 加磁場の影響が定性的に明らかにされている．