The effect of acids and bases on the dispersion and stabilization of ceramic particles in ethanol

The dispersion and stability of alumina, titania, and silicon carbide powders in ethanolic medium have been investigated. An operational pH-scale, pH*, based on an ethanol-based reference electrode, was used to systematize the suspension properties. The electrokinetic behavior was determined as a function of pH*. The isoelectric points in ethanol — pH∗iep(SiC)=7.5; pH∗iep(Al2O3)=4.4 and pH∗iep(TiO2)=4.2 — were discussed in relation to the dissociation constants of the charge determining reactions at the powder surfaces. We have evaluated the long-term stability of the ethanolic dispersions through settling studies which showed that the primary particle size could be retained for extended times providing that the surface potential and ionic strength were optimized.