Ceramics-Silikáty 44, (1) 1 - 8 (2000)

A stable, agglomerate-free suspension with almost Newtonian flow behavior is one of the basic requirements when slip casting is to be used as a shaping process for bioceramic materials. In this work suspensions of three commercial zirconia powders with different alumina admixtures (Tosoh TZ-3Y, TZ-3YE, TZ-3Y20A) are investigated. The rheological behavior is determined by rotational viscometry, the particle size distribution by low-angle laser light scattering. For the powder types studied the alkali-free polyelectrolyte Dolapix CE64 turned out to be the most effective deflocculant. The optimum deflocculant concentration is approx. 0.6 wt.% in all cases. It has been found that peptization alone is not sufficient for destroying the agglomerates, mechanical dispersion (ball-milling) is also necessary. The concentrational changes during the evacuation step are in the order of several percent and lead to non-negligible viscosity changes.