Random-Walk Aggregation Phenomena in Solid Bimodal Liquid Dispersions: Transition to Nondeterminism from Si3 N4 to...

This paper, which is based on another recent work, (Mezzasalma, S. A., Phys. Rev. E 55 (4), (1997)) deals with experiments and theory concerning an aqueous dispersed system formed from silicon nitride (Si3 N4 ), alumina (Al2 O3 ), and mixed silicon nitride + alumina (Si3 N4 + Al2 O3 ) solid agglomerates. From titration data applied to a thermodynamic equilibrium condition, the minimum number of each agglomerate species and their maximal average dimensions have been derived as functions of the aqueous solution pH. These parameters are of the order of, respectively, (1-2) &mgr;m for Si3 N4 and Al2 O3 agglomerates and (20-50) &mgr;m for the mixed agglomerates. The numbers of solid particles of all species are poorly correlated with changes in pH of the liquid phase. This behavior has been interpreted as intrinsically related to the complexity of the system which, due to the many interactions among the different species, probably becomes nondeterministic. In order to describe such behavior a probabilistic approach has been developed. The probability of finding a given solid agglomerate number within a scatter band varies with the suspension pH. Furthermore, the scatter band amplitude becomes negligible near the isoelectric point. Accordingly, only the numbers of aggregates derived in the neighborhood of the isoelectric point are predictable.