PARTICLE-SIZE AND SOLVENT EFFECTS IN THE PROCESSING OF SILICON

A dispersibility model previously developed for silicon powder that do es not possess surface charge in non-aqueous media is extended to pred ict the behavior when surface charge exists, for instance as a result of surface oxidation. The role of particle size is also examined. In t he absence of surface charge, a critical particle size exists below wh ich silicon susPensions are colloidally stable and above which they ar e not. This value depends on the dielectric permittivity of the liquid medium and becomes infinite if it matches that of silicon. In the pre sence of surface charge, the critical size also depends on the electro static 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, st able suspensions and those that promote extensive agglomeration of sil icon are developed.