Surface characteristics and aqueous dispersibility of commercial silicon nitride powders: Effects of acid leaching, surface hydrolysis, and thermal oxidation

Four types of commercial silicon nitride (Si3N4) powders with poor dispersibilities have been studied, and influences of acid leaching, surface hydrolysis, and thermal oxidation on the aqueous dispersibilities for the powders have been investigated systematically, in conjunction with their DRIFT spectra and soluble counterions. Soluble counterions (especially high-valency counterions) and particle surface groups have proved to be the two crucial factors that determine the aqueous dispersibility of Si3N4 powders. A universal modification method involving surface hydrolysis and subsequent thermal oxidation gives the different Si3N4 powders similar, and excellent, dispersibilities.