粒子軸に垂直な磁気モーメントを有する強磁性針状粒子からなる非希釈コロイド分散系の配向特性とレオロジー特性 : 平均場近似による粒子間相互作用を考慮した解析(流体工学,流体機械)

概要

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We have investigated the particle orientational distribution of a non-dilute colloidal dispersion, which is composed of ferromagnetic rodlike particles with a magnetic moment normal to the particle axis, subject to a simple shear flow. The mean field approximation is applied to take into account the magnetic interaction between rodlike particles. In the present analysis, these spheroidal particles are assumed to suffer from the rotational Brownian motion in a simple shear flow and an external magnetic field. The basic equation of the orientational distribution function has been derived from the balance of the torques and solved numerically. The results obtained here are summarized as follows. For a very strong magnetic field, the magnetic moment of the rodlike particle is significantly restricted in the field direction, so that the particle approximately points to a direction normal to the flow direction (and also to the magnetic field direction). For the case of very strong magnetic interactions between particles, the particle can rotate around the axis of the clusters of the particles, although the magnetic moment nearly points to the field direction. Due to this characteristic motion of the particle, the viscosity for the case of strong particle-particle interactions indicates smaller values than those for the case of weak interactions.
社団法人日本機械学会の論文
2007-01-25