Fabrication of high permeability SiC ceramic membrane with gradient pore structure by one-step freeze-casting process

Abstract

A highly permeable porous SiC ceramic membrane with multilayered unidirectional gradient pore microstructure was prepared by one-step freeze-casting process. The multilayer microstructures, mechanical properties and filtering performances of freeze-casting SiC ceramic membranes were controlled by optimizing the preparation process. It was found that with the increase of solid content from 30 vol% to 40 vol%, the directional pore channels gradually narrowed by about 50% and the mechanical properties increased from 0.47 MPa to 5.44 MPa. In addition, the increase of coarse particle content not only thickened the separation layer and the transition layer, but also widened the directional pore channel, which is beneficial to improve the permeability efficiency. When the coarse particle content of SiC ceramic membranes was 90%, the average pore size of separation layer, transition layer and lamellar structure was 5.52 μm, 7.63 μm and 36.09 μm, respectively. The maximum water permeability of S35C90 ceramic membrane reached up to 5.67 × 105 L/m2 h bar, and the rejection rate for ground calcium carbonate was 96.1%, confirming the superior perviousness and separation efficiency of freeze-casting ceramic membranes in the field of filtration.