Rotational diffusion of anisotropic-shaped colloidal particles in microgravity as studied by free-fall experiments

• Published in: Colloid and polymer science Vol. 277; no. 6; pp. 601 - 606
• Main Authors: OKUBO, T, TSUCHIDA, A, YOSHIMI, H, MAEDA, H
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.06.1999; Springer Nature B.V
• Subjects: Anisotropy; Atoms & subatomic particles; Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Colloids; Constraining; Diffusion; Diffusion coefficient; Exact sciences and technology; General and physical chemistry; Microgravity; Relaxation time; Rotational; Slopes; Colloidal suspension; Anisotropic material; Spherical particle; Aqueous solution; Diffusion coefficient; Microgravity; Rotational relaxation
• ISSN: 0303-402X; 1435-1536
• DOI: 10.1007/s003960050432

Rotational relaxation times (τ) and diffusion coefficients of ellipsoidal colloids of tungstic acid are studied in aqueous suspension in microgravity by free-fall experiments. τ values are evaluated from the relaxation traces of the optical transmittance of the suspension using the stopped-flow technique. Experimental errors at 0 G are small compared with those at 1 G, which is ascribed to lack of the movement of impurities in suspension such as quite small dust and bubbles and the convection of the suspension in microgravity. The limiting slopes of the relaxation curves in the plots of the transmittance against time at 1G depend on the flow direction of the suspension in the flow cell, whereas those at 0 G remain zero irrespective of the flow direction. For more reliable diffusion coefficients are obtained in microgravity; however, the diffusion coefficients themselves are quite insensitive to gravity.[PUBLICATION ABSTRACT]