Viscoelastic behavior of ceramic suspensions with carrageenan

Aqueous gelcasting of ceramic suspensions with carrageenan is one of the novel ceramic shaping techniques that have received considerable attention during the last few years. The ability of carrageenans to form cold-setting reversible gels in aqueous media is responsible for the body formation step. In this work the rheology and viscoelastic behavior of these systems is studied. Zirconia (TZ-3YE) suspensions with a solids loading of 67 wt.% (i.e. approximately 25 vol.%) and three different carrageenan concentrations (0.7, 1.0 and 1.3 wt.%, related to the free water content in the suspension) were prepared. The temperature dependence of the dynamic storage and loss moduli is determined by oscillatory shear rheometry. The concentration dependence of melting and cooling cycles (ranges 50–63 and 29–37 °C, respectively) is considered and analyzed. The results are interpreted in terms of linear viscoelasticity and the gelation step is discussed in relation to the mechanism of body formation.