CHARACTERIZATION AND STABILIZATION OF SI3N4 SUSPENSIONS

Two commercial Si3N4 powders were mixed with Al2O3 and Y2O3 through coprecipitation of the oxides from solutions of nitrates. The samples were characterized by XPS spectroscopy and electrophoretic mobility determinations on the suspensions. Sedimentation tests indicated that an oxylignin-based polyelectrolyte proved effective in the dispersion of the powders. The adsorption of the deflocculant followed Langmuir type isotherms characterized by values of the standard free energy of adsorption in the range typical of physisorption processes. The results of the different characterizations are discussed point by point, and different localizations of the dispersant in the interfacial region of the different samples are proposed.