Stability of colloidal silicon nitride suspension with poly-electrolyte

Abstract

This investigation aimed at elucidating the polymer conformation of NH 4 + salt of poly(acrylic acid) (PAA–NH 4) and relating it to the stability of colloidal silicon nitride suspension as a function of pH values. Conformation of PAA–NH 4 on silicon nitride particle was monitored along with electrokinetic and stability responses at different PAA–NH 4 concentration. The conformation of PAA–NH 4 has been identified by the use of titration experiments, from which the values of α and their corresponding pH can be roughly characterized by four stability regions. The stability properties indicate that conformation of the PAA–NH 4 chain along with the electrostatic interactions is shown to be a major controlling factor in determining the stability of the slurries considered here. At the acidic pH range, polymer adsorption in the coiled form is demonstrated to have a positive contribution to the dispersion. Nevertheless, the residual polymer in the stretched form is detrimental to the stability properties in the alkaline pH range. ©