New concept for simulating particle packing in colloidal forming processes

A new simulation concept based on the discrete element method (DEM) has been developed for studying particle-packing dynamics during colloidal forming processes, Long-range potential interactions, medium influences, solid-body contact, and adhesion are considered. DEM regards each particle as an individual element and enables the observation of the spatially and temporally resolved microscopic details. The importance of different competitive interaction forces is compared. The electrostatic repulsion constrains the Brownian motion for all particle sizes. The simultaneous, competitive influences of the colloidal chemical and process parameters on the particle-packing structure during pressure filtration and centrifugal casting have been simulated and analyzed. In the pressure filtration test, the well-stabilized monomodal particles form a close-packed hexagonal structure, and this regularity is strongly dependent on the filtration rate. The higher the filtration rate, the more packing defects are formed, Although well-stabilized suspensions with high zeta-potential tend to form particle chains, suspensions with low zeta-potential form agglomerate structures. The limitations of the long-range interaction functions derived from the Hamaker theory and from the electrostatic Poisson-Boltzmann equation are discussed.