Simulations of heteroaggregation in a suspension of alumina and silica particles: effect of dilution.

The influence of dilution on the aggregation process of suspensions composed of two kinds of oxide particles (alumina positively charged particles d(1)=400 nm and silica negatively charged particles d(2)=250 nm) has been studied by computer simulations. Two kinds of simulations have been performed: Brownian dynamics simulations to study the aggregation process and its kinetics and global minimization searches to find the most stable configurations of aggregates. We show that the rate of dilution has a strong influence on the structure and on the shape of aggregates in Brownian dynamics simulations. By confronting these aggregates with the stable aggregates found by global minimization, we demonstrate that they are metastable and their shape is explained by the competition between the kinetics of aggregate coalescence and the kinetics of aggregate reorganization into more stable configurations.