Preparation and properties of gradient Al2O3-ZrO2 ceramic foam by centrifugal slip casting method.

The aim of the present research is to provide a novel technique for preparing gradient Al₂O₃-ZrO₂ ceramic foams. This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al₂O₃ and ZrO₂ particles and high packing density. Aqueous Al₂O₃-20vol.% ZrO₂ slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated. The settling velocity and mass segregation of Al₂O₃ and ZrO₂ particles at different centrifugal accelerations were calculated and studied. The drying behavior, macrostructure, microstructure, compressive property and resistance to thermal shock of the sintered products were also investigated. The results show that the difference of settling velocity of Al₂O₃ and ZrO₂ particles increases and mass segregation becomes acute with an increase in centrifugal acceleration. The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density (99.0% TD) and continuous gradient distribution of Al₂O₃ and ZrO₂ particles. When sintered at 1,550°C for 2 h, the cell size of gradient Al₂O₃-ZrO₂ foam is approximately uniform, about 1.1 mm. With the porosity of gradient Al₂O₃-ZrO₂ ceramic foams increasing from 75.3% to 83.0%, the compressive strength decreases from 4.4 to 2.4 MPa, and the ceramic foams can resist 8-11 repeated thermal shock from 1,100°C to room temperature. [ABSTRACT FROM AUTHOR]