Enlargement of Grains of Silica Colloidal Crystals by Centrifugation in an Inverted-Triangle Internal-Shaped Container

Abstract

We successfully fabricated large grains of silica colloidal crystals in an inverted-triangle internal-shaped container (inverted-triangle container) by centrifugation. The largest grain in the container was much larger than that in a container which has a flat bottom and constant width (flat-bottomed container). The edged bottom of the inverted-triangle container eliminated the number of the grains, and then the broadened shape of the container effectively widened the grains.

Crystallization of Brownian Particles from Walls Induced by a Uniform External Force

“…During sedimentation by centrifugal force, the hydrodynamic effects [17][18][19][20] may not be neglected. However, since the centrifugal force in the experiment 13) is much weaker than that in other experiments, [21][22][23][24][25] the hydrodynamic effects may be smaller than those in other experiments. Thus, in order to simplify the model, we neglect the hydrodynamic effects and carry out simulation.…”

“…Large domains of ordered particles are formed in bulk, which agrees with experiment. 13) In our simulation, two walls cross orthogonally at an edge. If a {1, 1, 1} face of the fcc structure or a {0, 0, 0, 1} face of the hcp structure are formed on the two walls at a time, the expected faces of crystals formed in two walls cannot cross orthogonally.…”

“…In simulations, 10,11) it is shown that large grains of hard sphere particles without defects are formed by changing the external force during sedimentation, but controlling the force during sedimentation is probably difficult in the experiment. 9) In order to solve the problems in a previous study, 9) recently, Suzuki and co-workers 12,13) used a centrifugation method and succeeded in forming large three-dimensional colloidal crystals. They also pointed out the importance of the relation between the direction of centrifugal force and the grain size: the grain size of the colloidal crystal formed with a tilted force becomes larger than that with the centrifugal force perpendicular to a wall.…”

“…Our aim is to find conditions to form a large colloidal crystal by sedimentation, so that keeping the results of their experiments 12,13) in mind, we carry out Brownian dynamics simulations and study how crystallization of particles depends on the direction and the strength of a uniform external force. In § 2, we introduce the model.…”

Effect of container shape and walls on solidification of Brownian particles in a narrow system

“…One of the methods used to create closepacked colloidal crystals is the centrifugal method. Recently, Hashimoto et al [12] succeeded in creating a large colloidal crystal in a container with an inverted triangular bottom using the centrifugal method. They suggested that the formation of the large grains is caused by suppression of nucleation.…”