Colloidal dispersions fractals

Rouw P W and de Kruif C G 1989 Adhesive hard-sphere colloidal dispersions fractal structures and fractal growth in silica dispersions Phys. Rev. A 39 5399-408... 

A more modern approach to colloidal dispersions is based on fractal geometry. The fractal approach, as explained later, provides a new basis for the definition and characterization of colloidal systems. 

This chapter describes some of the simulation and theoretical models used to investigate aggregation processes. The models depend upon whether the problem under consideration is defined at a microscopic or mesoscopic level and on the appropriate degree of complexity and rigour that is required to solve real practical problems of interest. Several techniques and examples will be described that are applicable to coagulation/fiocculation processes in colloidal dispersions. Owing to the fact that such processes are now recognized to lead to the formation of fractal objects, fractal concepts will be discussed. 

It is clear that more accurate calculations of collision efficiencies are still required to better understand aggregate formation, structures and fractal dimensions. This is critical, as the number of available parameters to describe colloidal dispersions is continuously increasing with the development of new characterization techniques. In summary, much improvement in our understanding of aggregation can still be acquired, especially with respect to the kinetics of the process, the structure of the aggregated phase, and the transport of the aggregate via sedimentation processes. 

Monodisperse particles correspond to PD < 0.02, and PD between 0.02 and 0.08 represents a narrow distribution. Notice that features of aggregation (aggregation rates) of the particles and aggregate fractality depend strongly on initial PD of particles, and preparation of monodisperse uniform inorganic colloid dispersions has a great practical importance. 

Potanin A. A., Russel W.B. Fractal model of consolidation of weakly aggregated colloidal dispersions. Phys. Rev. E. 1996 53(4) 3702-3709... 

Fig. 8.2. A liquid containing fractals. Represented are two linear polymers, a branched polymer and a colloidal aggregate. Each has been trimmed to fit into a spherical pervaded volume of radius R, shown as shaded regions. For comparison a cloud of dispersed monomers from one of the polymers is also shown...

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