液中分散微粒子の構造体形成過程の解析 二成分粒子系の構造体形成に関するシミュレーション

Abstract

Network formation process by particle settling in binary dispersion is simulated, where the formation mechanism is essentially attributed to collisions of dispersed particles and hence the difference in their settling velocities. It is demonstrated that two-dimensional particle settling model satisfactorily expresses the dependency of network structure morphology on the mixing ratio in binary dispersion, and enables us to understand the essentials of network formation mechanism qualitatively. The packing fraction of network structure formed in binary dispersion is shown to be lower than that formed from monodisperse particles. The binary dispersion which results in the network structure with a minimum packing fraction contains a small number of large particles, and shows an indication of phase subsidence during the particle settling process, suggesting that the mixing ratio strongly influences the morphology of network structure. In the region where free settling of large particles is dominant, particle collisions lead to particle aggregates from the bottom and form dendrites. As the growth of aggregate becomes dominant, the network structure tends to show a morphology with loose packing of clusters. It is also shown that the network structure formed in binary dispersions with any mixing ratio has no directional change in packing fraction.