Modeling hetero-agglomeration in two-component systems

When nanoparticles are made from different materials, the precise control over the mixing process determines the number of hetero-contacts between the components which is one of the key characteristics that determines the quality of the final product. In this study, we develop a model in the context of a population balance modelling approach that captures the statistics of hetero-contact formation in a two-component system as a function of agglomerate size, agglomerate composition, space and time. The two components are characterized by varying primary particle diameters and current simulations include diameter size ratios between 1 and 6. Langevin Dynamics simulations, where every single primary particle is tracked, aid the model development and provide a database for validation. The new method accurately predicts both, the total number of hetero-contacts in the system and the size-specific average number of hetero-contacts. The model is valid in the entire transition regime from the free molecular to the continuum regime, and correctly captures increased mixing quality for higher gas Knudsen numbers, i.e. smaller primary particle sizes.