Stability of colloidal silicon nitride suspension with poly-electrolyte

This investigation aimed at elucidating the polymer conformation of NH4+ salt of poly(acrylic acid) (PAA-NH4) and relating it to the stability of colloidal silicon nitride suspension as a function of pH values. Conformation of PAA-NH4 on silicon nitride particle was monitored along with electrokinetic and stability responses at different PAA-NH4 concentration. The conformation of PAA-NH4 has been identified by the use of titration experiments, from which the values of alpha and their corresponding pH can be roughly characterized by four stability regions. The stability properties indicate that conformation of the PAA-NH4 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. (C) 1999 Elsevier Science Ltd and Techna S.r.l. All rights reserved.