The effect of membrane thickness on the co-sintering process of bi-layer ZrO₂/Al₂O₃ membrane

As a method for fabrication of multilayer structures, co-sintering process has attracted increasing attention due to its promising advantages. In this study, co-sintering process was applied to fabricate bi-layer ZrO₂/Al₂O₃ membranes supported by rigid Al₂O₃ substrates. Following our previous work, this paper focused on the effect of membrane thickness on the co-sintering process. Experimental results showed that thinner sub-layer membrane without defects was favorable to achieve good bonding between the membrane layers and the support after co-sintering. The thickness of the top-layer membrane should be not very thin. Otherwise the compressive stress caused by fast shrinkage of the top-layer membrane would be insufficient to promote the sintering of the sub-layer membrane during the co-sintering process. The suitable thicknesses for the sub-layer and the top-layer membranes have been determined, which were about 15 and 10 μm, respectively. The bi-layer ZrO₂/Al₂O₃ membrane co-sintered at 1200 °C had the average pore size of about 0.28 μm and the pure water flux through the membrane was about 2.82 × 10^-2 L m^-2 h^-1 Pa^-1 (2.82 × 10³ L m^-2 h^-1 bar^-1). The bi-layer ZrO₂/Al₂O₃ membranes prepared by co-sintering process showed good performance in an oil-water separation.