A modified diffusion-limited cluster aggregation model for accurate prediction of the coagulation and fragmentation process in nanoparticle suspension

Abstract

Traditionally, the coagulation and fragmentation process in colloid or nanofluid has been estimated by diffusion-limited cluster aggregation (DLCA) or the population balance model. However, both models fail to give a clear physical meaning when considering the cluster fragmentation. In our present work, we developed a modified DLCA model by adding a new breaking mechanism with a clear physical meaning, which is elucidated by the stress concentration concept in materials science. When an impact (such as a collision) acts on the aggregate, one can compare whether the energy of the impact is larger than its binding energy. If the former is larger, the breaking of aggregates will happen. Otherwise, aggregates cannot be broken. A 2D experiment has been conducted to validate our model. The modeling results showed that Df (the fractal dimension of the clusters) is around 1.34 for the DLCA model, while it is estimated to be 1.43 by our modified model, which is in good agreement with the experimental value of Df = 1.44 ± 0.08. Clearly, our model is more accurate than the DLCA model. The relationship between Df and initial particle size and particle concentration have also been investigated. Our work is expected to add new insight into the evaluation of aggregate morphology and size distribution in various nanoparticle suspension systems.