ζ potential of nanoparticle suspensions:: Effect of electrolyte concentration, particle size, and volume fraction

The zeta potentials of three types of alumina particles with median volume diameters 11, 44, and 190 nm have been investigated as a function of particle size, volume fraction, and electrolyte concentration. The magnitude of the zeta potential was found to decrease as both the particle size decreased and as the volume fraction of solids increased. The reduction in zeta potential can be explained by the increase in electrolyte concentration resulting from dissociation of ionizable surface sites on the alumina and soluble species resulting from dissolution of alumina. Both decreasing size and increasing volume fraction increase the total surface area of solid and result in increased solution electrolyte concentration. The results suggest that the electrical double-layer approach will not be successful in producing low-viscosity, high-volume fraction-stable suspensions of nanoparticles suitable for producing advanced ceramic components with nanoscale features. Development of dispersants for high-volume-fraction nanoparticle suspensions based on steric repulsion is advised.