Preparation of Al2O3 and Al2O3–ZrO2 ceramic foams with adjustable cell structure by centrifugal slip casting

Al2O3 and Al2O3–ZrO2 ceramic foams with dense cell struts and uniform cell structure were fabricated by centrifugal slip casting using pre-arrayed epispastic polystyrene (EPS) templates. The variation of Zeta potential for Al2O3 and ZrO2 particles with suspension pH was measured. The rheological characteristic of Al2O3 and Al2O3–ZrO2 slurries with up to 50 vol.% solid content was investigated. Centrifugal slip casting was performed at various centrifugal accelerations varying from 1118 G to 2860 G. Segregation phenomenon during centrifugal process was studied and found negligible for highly stable slurry with 50 vol.% solid content. Cell struts of the Al2O3 and Al2O3–ZrO2 compacts have high green densities of 63.4% TD and 61.5% TD, respectively. After sintering at 1500 °C and 1550 °C for 2 h, respectively, sintered densities of the struts of the Al2O3 and Al2O3–ZrO2 foams are 98.8% TD and 99.1% TD. Porosity of the ceramic foams can be adjusted by changing the load applied on the EPS spheres during packing. With the increase of porosity from 75.6% to 83.2%, compressive strength of the Al2O3 and the Al2O3–ZrO2 foams decreases from 3.20 MPa to 1.78 MPa and from 3.80 MPa to 2.07 MPa, respectively.