Microgravity experiments on colloidal crystallization of silica spheres in the presence of sodium chloride |
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Authors: | A Tsuchida K Taguchi E Takyo H Yoshimi S Kiriyama T Okubo M Ishikawa |
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Institution: | (1) Department of Applied Chemistry Faculty of Engineering Gifu University, Yanagido 1-1 Gifu 501-1193, Japan e-mail: okubotsu@apchem.gifu-u.ac.jp Fax: +81-58-2932628, JP;(2) Mitsubishi Research Institute Inc 2-3-6 Otemachi, Chiyoda-ku Tokyo 100-0004, Japan, JP |
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Abstract: | Rate coefficients (k) in the colloidal crystallization of monodispersed silica spheres in the presence of sodium chloride are studied in microgravity
achieved by parabolic flights of an aircraft. Time-resolved reflection spectroscopy is made with a continuous circulating-type
stopped-flow cell system. The k values decrease as the salt concentration increases both at 0 and 1 G and those in microgravity are smaller than those in
normal gravity by 16% (maximum), especially in water and in the presence of a small amount of the salt lower than 2 × 10−6 mol/l. The rates in flight at 1 G are larger by 15% (maximum) compared with those at 1 G on the ground. The k values obtained at 0 G, 1 G in flight and 1 G on the ground agree excellently with each other for the suspensions with 3 × 10−6 and 4 × 10−6 mol/l sodium chloride. Disappearance of the downward diffusion of spheres and no convection of the suspensions are important
for retardation in microgravity.
Received: 20 January 2000 Accepted: 9 March 2000 |
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Keywords: | Colloidal crystallization kinetics Microgravity experiments Salt effect Reflection spectroscopy |
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