Simulation of particle motion and stability in concentrated dispersions

Systems of DLVO-type particles have been simulated by the Brownian dynamics technique. The rate of dissociation of a pair of flocculated particles of radii 0.5 and 1.0 µm is reported as a function of electrolyte concentration, doublet orientation and sedimenting field strength. Using a simple cluster model, which includes and allowance for hydrodynamic screening, the kinetics of fast coagulation in a concentrated dispersion of particles of radii 0.25 µm has been followed as a function of electrolyte concentration and the range of the hydrodynamic interactions. A preliminary study on the influence of a sedimenting field on motion in stable and unstable systems is reported. A time-averaged screening function obtained by simulation is used to correct the theoretical self-diffusion coefficient for the effect of non-additivity of pair hydrodynamics. The concept of a single characteristic screening length is discussed.