Direct coagulation casting of nano-8YSZ powder suspensions using nano-MgO as coagulating agent

Abstract New colloidal techniques such as direct coagulation casting (DCC) arise to manufacture dense, homogeneous and nanocrystalline advanced ceramics. In this work, it was possible to obtain a high solid content (72 wt%) aqueous suspension from nano-8YSZ (15–50 nm) using a suitable PAA-NH 4 dispersant. Moreover, coagulation was reached by increasing ionic strength mechanism, with an optimized amount of 0.25 wt% nano-MgO (~20 nm) maintaining a low initial viscosity (~60 mPa s at 100 s −1 ), which corresponds to a suitable rheological behavior for direct casting. An attenuated coagulation rate was found, along a 30-min window process, due to the nanosized MgO particles. The nanosuspension was then successfully cast into a non-porous PVC mould at 25 °C producing a dense structure without cracks after 6 h. High density (~96% T.D.) samples were obtained at 1350 °C/5 h with mean grain sizes of ~800 nm and a cubic phase corresponding to 8 mol% Y 2 O 3 according to XRD analysis.