Pressure filtration and slip casting of mixed alumina-zircon suspensions

Mullite-zirconia based ceramics can be obtained from zircon raw material an d alumina. Rheological properties of aqueous 48 vol.% suspensions containin g a mixture of zircon and a-alumina powders were determined to obtain the o ptimum dispersion conditions for colloidal processing of dense mullite-zirc onia composites. Powder compositions with different alumina/zircon (wt.%) r atios in the mixtures were studied. Colloid stability as a function of pH f or zircon and alumina, with and without polyacrylate, was studied by sedime ntation tests. The effect of the chemical composition of the mixed powders and addition of polyacrylate on the viscosity of the suspensions were exami ned. Green density of compacts that were consolidated by slip casting and p ressure filtration at 8 MPa were correlated with theological properties of the suspensions and their compositions. Pressure filtered bodies were sligh tly less dense than the compacts prepared by slip casting and the dried rel ative density increased with increasing the degree of dispersion of the par ticles. After sintering at 1600 degreesC for 2 h, the compacts from well-di spersed suspensions reached high density showing a fine and homogeneous mic rostructure. (C) 2001 Elsevier Science Ltd. All rights reserved.