Effects of glycerol addition on the slurry dispersion and mechanical properties of alumina ceramics prepared by gel-casting process

The addition of glycerin reduced the dielectric constant of the aqueous alumina suspension, increased the zeta potential of the alumina powder, thickened the electric double layer, and improved the dispersibility of an alumina suspension for aqueous gel-casting. The glycerin-added suspension can effectively avoid the agglomeration, so that the green body had a more uniform microstructure and a higher relative density. The simultaneous addition of magnesium nitrate, EDTA and glycerol in aqueous-based alumina slurry can effectively promote the homogeneity of green microstructure and hence obtaining the sintered sample with relative sintered density of 99.7% and the mean grain size and distribution of 1.20 ± 0.44 μm. The (pressure-less sintered) sample Mg + EDTA + Gly exhibited superior Vickers hardness comparable to the samples prepared using HP, HIP, and SPS due to the small grain size (1.2 μm) and high sintered density (99.7%).