Fractal aggregates.

In recent years it has been shown that the structures of a wide variety of colloidal aggregates can be described in terms of the concepts of fractal geometry. The purpose of this review is to discuss some of the evidence for fractal geometry in experimental systems and indicate how fractal geometry can be used to develop a better understanding of their aggregation kinetics and physical properties. At the present time much of our understanding of the structure and properties of fractal aggregates has come from computer simulations. Consequently, a major part of this paper is concerned with the role played by simple computer models in understanding the origins of fractal aggregates as well as their physical and chemical properties. The main emphasis is on models for colloidal aggregation but a brief description of a few other models for non-equilibrium growth and aggregation processes which have been of particular interest during the past few years has been included.