Fabrication of ultrahigh density ZnO-Al2O3 ceramic composites by slip casting

The conditions of ZnO-Al2O3 aqueous suspensions and slip casting were optimized to obtain dense green compacts and further to obtain high density ZnO-Al2O3 ceramic composites. The Zeta potential of raw powders was measured. ZnO and Al2O3 powders have lower Zeta potential than −45 mV commonly at pH 8-10.3 with polyacrylic acid (PAA) added. The influence of pH and the mass fraction of the additives on the stability and fluidity of the suspensions added with PAA and polyethylene glycol (PEG) was investigated by experiments of viscosity and sedimentation. The suspensions have the lowest viscosity and the best stability at pH 9 with 0.2% PAA (mass fraction). The maximum density of green compacts is 66.6% of theoretical density (TD) with compacting and homogeneous green particles. An ultrahigh density sintered compact (>99.6% TD) could be obtained after pressureless sintering at 1 400 °C for 2 h.