Gel Transition in Adhesive Hard-Sphere Colloidal Dispersions: The Role of Gravitational Effects.

The role of gravity in gelation of adhesive hard spheres is studied and a critical criterion developed for homogeneous gelation within the gas-liquid binodal. We hypothesize that gelation by Brownian diffusion competes with phase separation enhanced by gravitational settling. This competition is characterized by the gravitational Péclet number Peg, which is a function of particle size, volume fraction, and gravitational acceleration. Through a systematic variation of the parameters, we observe the critical Peg of ~0.01 can predict the stability of gels composed of adhesive hard spheres. [ABSTRACT FROM AUTHOR]