Effect of additives on the pore evolution of zirconia based ceramic foams after sintering

A new superplasticity foaming method was used to form zirconia-based ceramic foams. Silica and alumina were chosen as additives because they facilitate the 2D superplastic deformation. The effects of these additives on macroscopic pore evolution were examined after heat treatment for up to 40 h. The addition of silica or alumina also enhanced the 3D deformation during superplasticity foaming. The total porosity of mono-foams made from 3 mol% yttria-stabilised zirconia without additives increased with heat treatment for up to 24 h, and then levelled off. The porosity of silica-dispersed foam was greater than that without additives and continued to increase for up to 40 h. Conversely, the porosity of alumina-dispersed ceramic foam reached saturation within 8 h. Consequently, the porosity of alumina-dispersed foam was greater than that without additives after heating for 8 h, while the latter exceeded the former with prolonged heating for more than 16 h. The detailed effects of alumina dispersion on the foam development behaviour were examined in connection with the microstructure.