From Modeling of Particle-Packing Dynamics to Forming of Functionally Graded Ceramic Membrane Filters

摘要

The time-dependent particle packing processes during colloidal powder forming have been modelled by using the discrete element method (DEM). Hereby the long-range potential interactions according to the DLVO theory have been implemented into the DEM simulation program. This DEM simulation method has been used to study the mechanics for the pore-gradient formation via centrifugal casting. The simulation results show that pore-gradient membranes can be formed by using stabilised Al_2O_3 suspensions with a suspension height of 70 mm and a solid density of ≤ 10 % under a centrifugal acceleration of greater than 40 g. Using commercial Al_2O_3 powders, flat membranes with a graded pore-size distribution from 40 to 250 nm across a membrane thickness of about 5mm were fabricated by centrifugal casting. The graded microstructure of the pore-gradient membrane has been analysed by scanning electron microscope and mercury porosimetry. The experimental results have been correlated with the simulation results.