RANDOM-WALK AGGREGATION PHENOMENA IN SOLID BIMODAL LIQUID DISPERSIONS- TRANSITION TO NONDETERMINISM FROM SI3N4 TO SI3N4+AL2O3 AQUEOUS SYSTEMS

This paper, which is based on another recent work, (Mezzasalma, S. A., Phys. Rev. E 55(4), (1997)) deals with experiments and theory concern ing an aqueous dispersed system formed from silicon nitride (Si3N4), a lumina (Al2O3), and mixed silicon nitride + alumina (Si3N4 + Al2O3) so lid agglomerates. From titration data applied to a thermodynamic equil ibrium condition, the minimum number of each agglomerate species and t heir maximal average dimensions have been derived as functions of the aqueous solution pH. These parameters are of the order of, respectivel y, (1-2) mu m for Si3N4 and Al2O3 agglomerates and (20-50) mu m for th e mixed agglomerates. The numbers of solid particles of all species ar e poorly correlated with changes in pH of the liquid phase. This behav ior has been interpreted as intrinsically related to the complexity of the system which, due to the many interactions among the different sp ecies, probably becomes non-deterministic. In order to describe such b ehavior a probabilistic approach has been developed. The probability o f finding a given solid agglomerate number within a scatter band varie s with the suspension pH. Furthermore, the scatter band amplitude beco mes negligible near the isoelectric point. Accordingly, only the numbe rs of aggregates derived in the neighborhood of the isoelectric point are predictable. (C) 1997 Academic Press.