COLLOIDAL FRACTAL AGGREGATES OR A GEL

A theoretical criterion is proposed to predict whether aggregates or a gel will be formed in a dilute colloidal system characterized by rapid particle coagulation and the formation of nonequilibrium aggregates with a fractal structure. The prediction is made on the basis of parameters of the system. Examined as an alternative is a variant in which the aggregates fill a small fraction of the system volume and have mean dimensions which are either constant or change slowly over time due to compensation for aggregation by aggregate fragmentation (steady-state variant). The time required to reach the steady state is estimated and the dependence of the dimensions and other characteristics of fractal aggregates in the steady state are determined as a function of the concentration of colloidal particles in the system, the energy of the lyophobic bonds between particles, and the viscosity of the dispersion medium. The problem is solved for the case of the absence of rings in the structure of the fractal aggregates. The more general case of aggregates with rings will be examined in the next article.