Settling suspensions of colloidal silica: observations and X-ray measurements

Abstract

Suspensions of colloidal particles execute Brownian motion and thus exhibit thermodynamic properties analogous to those of molecular systems. Hard-sphere colloidal silica suspensions undergo a disorder-rder transition, i.e. freezing or crystallization, at high volume fractions. In suspensions of small particles the slow sedimentation permits the transition to occur at the bottom where the bulk of the crystalline sediment is formed by one-dimensional crystallization, as illustrated with photographs and scanning electron microscopy. X-Ray tomography measurements reveal a volume fraction discontinuity coincident with the observed crystal boundary occurring between the sediment and hindered settling region of the Kynch theory. Larger particles, however, form amorphous sediments because their rate of accumulation at the bottom exceeds the maximum crystal growth rate, in accord with classical kinetic theory. This theory is paired with Kynch's kinematic theory using an experimental sedimentation coefficient to interpret observations of settling suspensions.

Optical properties of nanostructured metal films

“…57 A popular approach is to use gravity sedimentation from a dispersion of the colloid in a suitable solvent. [58][59][60][61] This yields centimetre-scale pieces of polycrystalline material but with numerous defects in the crystal lattice (stacking faults, dislocations, grain boundaries and vacancies). In addition, during gravity sedimentation it is difficult to control film thickness.…”

Surface enhanced raman scattering of aromatic thiols adsorbed on nanostructured gold surfaces

“…Several methods, e.g. gravity sedimentation [4][5][6] and capillary force at a meniscus between a substrate and the spheres colloidal solution [7][8][9][10][11], were used for assembling the spheres into templates. After the formation of the templates, the interstitials spaces are then impregnated with the desired precursors.…”

Sedimentation in flocculating colloidal suspensions

“…Simultaneous treatment of sedimentation and flocculation has, for all of its practical importance, been reported much less frequently. 2 ' 7 ' 19 Auzerais et al 2 ' 20 for example, studied sedimentation in an idealized flocculating suspension (that is, with a hardsphere or nearly hard-sphere interparticle potential), both experimentally and theoretically. Buscall 21 has compiled a bibliography and review of the theoretical aspects of this area.…”