Influence of Gravity on Perikinetic Coagulation

Summary

Experimentally, a difference was found in coagulation rates of polystyrene, quartz and silica particles in aqueous solutions, when comparing microgravity conditions (sounding rocket), lg-conditions and high-g conditions (centrifuge). In microgravity, coagulation was faster than at 1g; at lg, coagulation was faster than at high g. The coagulation rate was determined by measuring light transmission as a function of time. This dependence of coagulation rate on gravity seems not to coincide with theoretical expectations. However, at lg the coagulation rate of neutrally buoyant dispersions was also higher than that of dispersions with a density difference between disperse and continuous phases. In order to explain these unexpected results, we discuss a number of relevant phenomena involved in the perikinetic coagulation process: hydrodynamics, interaction potentials, surface roughness, double layer characteristics during flow, and convection