Stability of silicon nitride-yttrium oxide mixed aqueous suspensions in solutions of electrolytes and poly(ethyleneoxide)

The aggregation stability of mixed suspensions of the powders of silicon ni tride prepared by low-temperature plasma synthesis and yttrium oxide prepar ed by the thermal degradation of its basic carbonate in aqueous solutions o f electrolytes and poly(ethyleneoxide) (PEO) is studied. It is shown that h eterocoagulation proceeds in a neutral medium, where the particles of dispe rsed phases carry dissimilar charges. Under the conditions in which the par ticles of dispersed phases carry similar charges, the aggregation stable mi xed suspensions are formed only in the cases where individual suspensions a re stable (an alkaline medium). Upon adding indifferent electrolytes, both the aggregation of the particles of each phase and their heterocoagulation are possible. The results obtained correlate with the data on the calculati on of the energy of the interparticle interaction in these systems. The ads orption of a nonionic polymer (PEO) at the particle surface of one of the d ispersed phases (silicon nitride) does not protect systems from heterocoagu lation when the phases have opposite charges. The adsorption of PEO at the silicon nitride particles in the presence of hydrochloric acid stabilizes t he individual suspension and enhances the aggregation stability of mixed di spersions.