Morphology of Colloidal Aggregates

Colloidal aggregates may be formed by different mechanisms. For instance, particles surrounded by an electrical double layer coagulate either in the primary or secondary minimum by the addition of salt. Polymer-coated particles may flocculate by polymer bridging or by changing the composition of the medium such that the polymer coats become insoluble. 

FIGURE 16.13 Fractal aggregates illustrating self-similarity. 

Gels may expel or take up solvent. These phenomena, known as syneresis and imbibition, are briefly described in Section 12.7. 

FIGURE 16.14 Particle gel showing (from left to right) progressive ageing stages. 

2 Using advanced equipment, the interaction force/between two flat, molecu- 

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In contrast, the three- or two-dimensional morphologies of colloidal aggregates via Brownian particle trajectories show a fractal-like structure. One of the most prominent features of the surface deposits formed by the diffusion-limited aggregation mechanism is the formation of isolated treelike clusters (9). In our experiments, the surface morphology of the silica-coated polyethylene composite prepared by... 

The morphology obtained by crystallizing an undiluted polymer can be considerably more complicated. The simplest model proposed consists of a system in which small crystallites exist, with amorphous chains attached to them like fringes on a colloidal aggregate. Such a system is called a micelle. This model is probably too simple except for a few polymers which form relatively few, very small crystallites. 

Schudel, M. et al., Absolute aggregation rate constants of hematite particles in aqueous suspensions A comparison of two different surface morphologies, J. Colloid Inteif. Sci., 196, 241, 1997. 

Sorensen, C.M., Light scattering from fractal aggregates. A review. Aerosol Sci. Tech., 35, 241, 2001. Cai, J., Ln, N., and Sorensen, C.M., Analysis of fractal clnster morphology parameters stmctnral coefficient and density antocorrelation function cutoff, J. Colloid Interface Sci., 171, 470, 1995. Sorensen, C.M. and Feke, G.D., The morphology of macroscopic soot. Aerosol Sci. Tech., 25, 328, 1996. 

The behavior of colloidal silica is based on its morphology and structure and on the chemistry of its surface. To fully characterize colloidal silicas one must pleasure not only the particle size, particle size distribution, surface area, and degree of aggregation, but also the structural and surface properties. 

We examined the morphology of our gold colloidal films on glass with atomic force microscopy and found that the gold nanoparticles form close-packed monolayer with a small amount of aggregates. To cover the gold film with... 

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