Particle size and solvent effects in the processing of silicon

Abstract

A dispersibility model previously developed for silicon powder that does not possess surface charge in non-aqueous media is extended to predict the behavior when surface charge exists, for instance as a result of surface oxidation. The role of particle size is also examined. In the absence of surface charge, a critical particle size exists below which silicon suspensions are colloidally stable and above which they are not. This value depends on the dielectric permittivity of the liquid medium and becomes infinite if it matches that of silicon. In the presence of surface charge, the critical size also depends on the electrostatic potential at the particle—liquid interface. Steric dispersants that stabilize suspensions may affect the critical size also. Diagrams which show the transitions between conditions that lead to useful, stable suspensions and those that promote extensive agglomeration of silicon are developed.