Selection of suitable dispersants for aqueous suspensions of zirconia and titania powders using acoustophoresis

Acoustophoresis was used to study the effect of adding various commercially available dispersants onto aqueous suspensions of two zirconia and two tit ania powders. These powders were characterised for elemental composition by X-ray fluorescence (XRF) spectroscopy and for surface area by BET single p oint nitrogen adsorption. From the maximum value of the zeta potential, it was possible to select the most promising dispersants. From the shape of th e curve the minimum amount of dispersant required to stabilise the powder p articles was noted. The iso electric point (i.e.p) of the powders was also identified. Several dispersants can be recommended for the first titania po wder, whilst none can be recommended for the second titania as the final ze ta potentials on addition of the dispersants were low. The two powders had different surface chemistries which was reflected in a large difference in their i.e.p; the first at pH 7.5 and the second at pH 6.1. This was due to different coatings on the powder surfaces; alumina and an organic material respectively. Removal of this organic coating by calcinatian then enabled t he dispersants to fully adsorb. Similarly dispersants for the first zirconi a powder could be identified and the i.e.p identified at pH 5.4. However, n o dispersants can be recommended for the second zirconia powder as yttria d issolves out of the powder under the naturally occurring weakly acidic cond itions. The i.e.p was estimated to be pH(i.e.p) 7-7.5. (C) 1999 Elsevier Sc ience Limited. All rights reserved.