2023 年 89 巻 924 号 p. 23-00111
I have addressed a polydisperse suspension composed of cubic hematite particles in thermodynamic equilibrium. From the viewpoint of developing a surface modification technique using cubic hematite particles, I have investigated the local internal structures of cubic particle aggregates in a quasi-two-dimensional (quasi-2D) system. The cubic particles have a full three-dimensional (3D) rotational ability in a quasi-2D system. I have conducted quasi-2D Monte Carlo simulations in the situation of no applied magnetic field to investigate the dependence of the local internal structures of particle aggregates on the magnetic particle-particle interaction strength and the standard deviation in the particle size distribution. The results obtained here are summarized as follows. In a polydisperse system with a small standard deviation, cubic particles tend to aggregate to form closely-packed structures with an aligned face-to-face configuration as the magnetic particle-particle interaction strength is increased. In a polydisperse system with a large standard deviation, they tend to aggregate to form loosely-packed structures with unstable face-to-face contact as the magnetic interaction strength is increased. That is, an increase in the value of standard deviation leads to a decrease in the orientation order of the constituent particles in the aggregates. I understood that the orientation order of the cubic particles decreases sharply within a narrow range of the standard deviation in the particle size distribution.
