Preparation of Al 2O 3 and Al 2O 3–ZrO 2 ceramic foams with adjustable cell structure by centrifugal slip casting

Abstract

Al 2O 3 and Al 2O 3–ZrO 2 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 Al 2O 3 and ZrO 2 particles with suspension pH was measured. The rheological characteristic of Al 2O 3 and Al 2O 3–ZrO 2 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 Al 2O 3 and Al 2O 3–ZrO 2 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 Al 2O 3 and Al 2O 3–ZrO 2 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 Al 2O 3 and the Al 2O 3–ZrO 2 foams decreases from 3.20 MPa to 1.78 MPa and from 3.80 MPa to 2.07 MPa, respectively.