EXPERIMENTAL-STUDY OF COLLOIDAL AGGREGATION IN 2 DIMENSIONS .2. KINETIC ASPECTS

The kinetics of aggregation of colloidal particles at an air-water interface have been investigated. The cluster size distribution and its various moments exhibited scaling with time and cluster size in accord with simulations in which the sticking probability for clusters of size i and j was proportional to (ij)sigma. Modification of the growth conditions caused systematic variation of the scaling exponents, due to changes in the sticking probability exponent-sigma. The various scaling exponents satisfied a constraint derived from the critical nature of the nonequilibrium aggregation process. Under all experimental conditions the observed kinetics exhibited a crossover from slow to rapid growth, as expected for reaction-limited cluster-cluster aggregation. This implies that the probability of irreversible particle-particle reaction was always very small.