Abstract: The effect of a dispersant on the electrokinetics and rheology of silicon nitride aqueous suspension with solids loading of
50wt% was investigated. The results indicated that the isoelectric point (IEP) of the silicon nitride powders is at the pH value of 4.2, and the
value of zeta potential is up to its maximum near pH value of 11. The IEP of the silicon nitride powders decreases with the addition of the dispersant and
the shift dependents on the amount of the dispersant. The suspension is a non-Newtonian time-dependent fluid. The optimum amount of the
dispersant is at the ranges from 0.8 to 1.2wt%, in which the suspension is near Bingham fluid. Beyond that range, the suspension
exhibits thixotropic behavior, or the suspension is an anti-thixotropy.

Key words: dispersant, silicon nitride, electrokinetics, rheology