Fabrication and characterization of alumina and zirconia-toughened alumina porous structures

In the present study, alumina (Al2O3) and zirconia-toughened alumina (ZTA) porous structures (foams) were manufactured using the space holder technique. Al2O3 and ZTA foams with varying porosities from 20% to 69% were fabricated by adding different sizes (10, 20, and 40 μm) and different volume % of polystyrene beads (space holders) to Al2O3 and ZTA powders. All the fabricated foams were investigated under static conditions to assess the compressive behavior. It is observed that the compressive strength of these foams strongly depends on porosity, pore size, pore size distribution and pore wall thickness. Among all fabricated foams, Al2O3 foams with 20 vol% beads of 10 μm size showed a higher compressive strength of 700 MPa with low porosity (21%) and a higher pore wall thickness (2.8 μm). It is also observed that the pore wall thickness decreased with the increase in beads size and the volume % of the beads, resulting in a low compressive strength value of 8 MPa with a lower pore wall thickness of 1.75 μm at 80 vol% of 40 μm beads. All the foams, irrespective of pore size, showed a typical ceramic failure phenomenon up to 70 vol% of beads; after that, the failure behavior changed to complete open-cell fracture.