Aqueous slip casting of MgAl2O4 spinel powder

A stoichiometric MgAl2O4 spinel (MAS) powder was synthesized by calcining a compacted mixture of alpha-Al2O3 and calcined caustic MgO at 1400 degrees C for 1 h and was surface treated against hydrolysis using an ethanol solution of H3PO4 and Al(H2PO4)(3) after fine grinding. Aqueous suspensions with 41-45 vol.% treated powder were prepared using tetra methyl ammonium hydroxide (TMAH) and an ammonium salt of polyacrylic acid (Duramax D-3005) as dispersing agents. These stable suspensions were consolidated in plaster moulds by slip casting (SC) route for the first time. For comparison purposes, the treated powder was also compacted by die-pressing technique after converting into freeze-dried granules and sintered along with slip cast samples at 1550-1650 degrees C for 1-2 h. The MAS ceramics fabricated by slip casting and die-pressing exhibited comparable properties.