磁性液体中非磁性小球与磁性纳米颗粒的相互作用及磁组装

Interaction and assembly of non-magnetic spheres and magnetic nanoparticles dispersed in magnetic fluid

利用磁性液体与聚苯乙烯小球溶液混合得到的复合磁性液体,研究了聚苯乙烯小球和磁性纳米颗粒在外加磁场作用下的动力学过程.实验结果表明,当外加磁场的方向平行于样品平面时,聚苯乙烯小球在沿着磁场的方向上表现出相互吸引而形成链状结构,其动力学过程可分为聚苯乙烯小球被反磁化产生相互吸引而形成短链的快过程以及短链间相互吸引形成长链的慢过程;当外加磁场的方向垂直于样品平面时,相邻聚苯乙烯小球表现出排斥的相互作用而形成短程有序的二维结构,当磁场强度增加到一定的阈值时,聚苯乙烯小球和磁性纳米颗粒形成的团簇会产生相互吸引而组装成复合式的花瓣结构.

In this paper, we systematically investigate the dynamics of non-magnetic spheres （polystyrene spheres） and magnetic nanopar- ticles dispersed in Fe304 magnetic colloid under an externally applied magnetic field. It is found that the polystyrene spheres form chain-like structures when the direction of magnetic field is parallel to the sample cell. The whole dynamic process of polystyrene spheres in the magnetic field can be characterized by a fast interaction between polystyrene spheres and magnetic nanoparticles and a slow interaction among polystyrene chain-like structures respectively. When a magnetic field is applied in the direction perpendicular to the sample cell, polystyrene spheres can be assembled into a short-range ordered two-dimensional structure due to the repulsive interaction among polystyrene spheres. Once the applied magnetic field excesses a critical level, a flower-shaped complex structure can be formed due to the attractive interaction between the polystyrene sphere and the magnetic cluster.