Microstructure and permeability of porous YSZ ceramics with aligned and gradient pore channels fabricated by freeze casting

Abstract

Porous yttria-stabilized zirconia (YSZ) ceramics with aligned and gradient pore channels were fabricated by the unidirectional freezing of aqueous suspensions with distinct solid loadings under different sintering temperatures. The results indicate that the microstructure and response properties could be tailored by adjusting the solid loading and sintering temperature. The pore channel size increased with the increase of solid loading or the decrease of sintering temperature, regardless of microstructure changes in an individual sample. With increasing the solid loading and sintering temperature, the compressive strength (7.18–30.76 MPa) increased owing to the lower porosity of individual samples. The fabricated samples had increasing Darcian and non-Darcian constants along the freezing direction due to the enhanced pore size and open porosity. The Darcian and non-Darcian constants in this paper were in the range of 7.06 × 10−13 to 5.92 × 10−12 m2 and 1.66 × 10−7 to 8.83 × 10−7 m, respectively. These results are of practical value for the fabrication and optimization of porous ceramics in the applications of filters and membrane supports.