Effect of pH on the properties of barium titanate slurries with an aniomic dispersant

The colloidal stability of barium titanate (BT) aqueous suspensions with poly(acrylamide/4-carboxylamino-4-oxo-2-butenate) (PAAM/COB) at pH 7, 9, and 12 has been investigated by means of ζ potential, adsorption, sedimentation, and particle size measurements. The isoelectric point of BT powder is at pH 4.6 and the value of ζ potential decreases as the pH of suspensions increases. The adsorption of PAAM/COB onto BT particles follows the Langmuir adsorption isotherm. The saturated amount of adsorbed polymer decreases with increasing pH. In general, BT particles in basic solutions with PAAM/COB are more stabilized, and less agglomerated than those without any dispersant present. As pH is increased, the resulting ζ potential becomes more negative, although lower polymer concentration is required for monolayer coverage of particle surface. Consequently, the resulting suspensions become more stabilized, and contain powder with smaller particle size.