Slip Casting of ZrB2-SiC Composite Aqueous Suspensions

Slip casting of concentrated aqueous suspensions was set up as forming technique for the production of crucibles from ZrB2-SiC composite powder. The dispersion effectiveness and the effect on the final microstructures of two commercial ammonium polyacrylates (Duramax D3005 and Dolapix PC33) used as dispersants were investigated. The first goal was pursued by evaluating the zeta potential of the powders in water at different concentrations of additives, while the second one was assessed by analyzing the microstructure. Duramax D3005 resulted more effective than Dolapix PC33 in electrostatically stabilize the suspensions. Correspondently, almost homogeneous microstructures and lower final porosity of the sintered crucibles were obtained with Duramax D3005, while ZrB2 layers on the vertical surfaces initially in contact with the plaster moulds were observed using Dolapix PC33. Moreover, the use of this latter dispersant did not allow the preparation of thick crucible walls due to the sample rupture during the binders pyrolysis stage.