Effect of growth conditions on the structure of two-dimensional latex crystals: modeling |
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Authors: | S Maenosono C D Dushkin Y Yamaguchi K Nagayama Y Tsuji |
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Institution: | (1) Mitsubishi Chemical Corporation Yokohama Research Center Non-Equilibrium Laboratory 1000 Kamoshida-cho, Aoba-ku Yokohama 227-8502, Japan e-mail: dushkin@atlas.rc.m-kagaku.co.jp, JP;(2) National Institute of Physiological Science Department of Molecular Physiology Myodaiji-cho, Okazaki 444-8585, Japan, JP;(3) Osaka University, Department of Mechano–physical Engineering 2-1 Yamadaoka, Suita-shi Osaka 565, Japan, JP |
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Abstract: | Essential experimental features of the nucleation and growth of a 2D colloidal crystal on a solid substrate are modeled.
The crystal, composed of sub-micron-sized latex spheres, is grown by the evaporation of water from the particle suspension
in a circular cell. The calculation of the meniscus profile in the cell allows the prediction of the particle volume fraction
in the suspension surrounding the crystal as a function of time. This quantity enters into a convective-diffusion model for
the crystal growth which calculates the crystal radius as a function of time. Comparison with experimental data for 2D latex
particle crystals shows predominant convective growth over a wide range of evaporation rates set by varying the humidity of
the air. Microscopic parameters of the particle assembly can also be estimated such as the particle velocity, diffusivity,
characteristic time constants, Peclet number, etc. The nucleation is simulated by simultaneously solving the equations of
motion for the ensemble of particles trapped in a thin liquid film using the discrete-element method. These equations account
for the forces which are physically important in the system: contact particle–particle friction, increased viscous resistance
during the particle motion in a wetting film, long-range capillary attraction between two particles screened by the rest of
particles. The final result of the simulation is a particle cluster of hexagonal packing, whose structure resembles very much
the monolayer nucleus of latex particles observed experimentally. The models proposed by us could also be implemented for
the aggregation of species in a variety of practical processes such as coating, texturing, crystal growth from a melt or liquid
solution, or a biological array.
Received: 10 May 1999 Accepted in revised form: 6 July 1999 |
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Keywords: | Two-dimensional crystal Kinetics of crystal growth Nucleation Capillary force Meniscus profile |
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