Evolution of the fractal-like aggregate system in colloids

Abstract

The evolution of a colloidal fractal-like aggregate system is studied theoretically with account for the reduction of the single-particle concentration in the space between these growing aggregates. Two different mechanisms of the initial aggregate formation are considered. They are heterogeneous aggregation, when the initial aggregates appear on foreign nuclei (the biggest particles, pollution, etc.), and homogeneous nucleation, when the initial clusters appear due to a random meeting and combination of single Brownian particles. The principles of colloid supersaturation decrease and the aggregate distribution in size are obtained in both cases as well as the internal structure of the clusters. Unlike the usual condensation-type phase transition, the system of discrete clusters is formed at the final stage of the aggregation process. The internal particle distribution in these clusters does not obey the universal scaling power law, which differs from the model case of separate cluster growth in an infinite colloidal medium with permanent concentration of free particles.