A Contact Model for the Discrete Element Simulations of Aggregated Nanoparticle Films

This chapter presents the development of a Discrete Element Method (DEM) contact model for aggregated nanoparticles. Particle synthesis from the gas phase often results in nanoparticles with a primary particle diameter smaller than 20 nm. These particles interact via sinter bridges (aggregates) or weaker adhesion forces such as capillary and solvation forces (agglomerates). Here, we present a set of five DEM contact model components to compute non-covalent adhesion forces (capillary and solvation forces), normal and tangential contact, rolling torque and stiff sinter bridges between nanoparticles with a diameter smaller than 20 nm. This model can represent nanoparticle films comprised of hundreds of thousands of primary particles under mechanical load. Validation against atomic force microscopy (AFM) force distance curves and mechanical compaction up to 3.4 MPa reproduced experiments with striking agreement. The DEM simulations allow us to gain insight into the structure and the restructuring of nanoparticle films that is impossible to obtain from experiments. This can help tailor particle films and coatings in a wide range of applications including catalysis, gas sensing and energy storage.