Crystallization Kinetics and Morphology in Phase Separating and Sedimenting Mixtures of Colloidal Spheres and Rods

• Published in: The journal of physical chemistry. B Vol. 108; no. 47; pp. 18158 - 18163
• Main Authors: Oversteegen, S. M, Wijnhoven, J. G. E. J, Vonk, C, Lekkerkerker, H. N. W
• Format: Journal Article
• Language: English
• Published: American Chemical Society 25.11.2004
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp0491515

The crystallization of sedimentating silica spheres in the presence of silica-coated boehmite rods in low-salt dimethylformamide is studied by means of confocal scanning laser microscopy. As expected, addition of rods gives rise to a net attraction due to the depletion effect. Upon increasing rod volume fractions, below a predicted equilibrium binodal, crystalline ordering of the spheres takes place faster but gives cause for more grain boundaries. Addition of rods at volume fractions in the theoretically predicted two-phase region gives rise to aggregation and glasslike sediments. We explain these results on the basis of the different gravitational lengths and sedimentation rate of both species:  higher rod concentrations drive the system quicker into the two-phase region of the predicted phase-diagram.