摘要
A modified freeze-drying strategy for asymmetric SiC ceramic membranes was proposed. • The membrane realized synergistic balance of high permeance, strength and filtration precision. • Key parameters precisely regulated the microstructure and comprehensive performance of the membrane. • The membrane showed ultra-high filtration efficiency for PM 0.3 and coal-fired fly ash at 300 °C. Unidirectional freeze-drying technique can boost the gas permeance of the ceramic membranes for gas filtration. However, the conventional unidirectional freeze-drying technique typically generates a highly uniform structure, which compromises the green body quality and the mechanical strength of the final ceramic membranes. Accordingly, this work proposed a modified unidirectional freeze-drying technique to fabricate asymmetric silicon carbide membranes (ASCM) by introducing a cross-linking and sedimentation pretreatment step prior to freezing. The ASCM membranes featured a distinct asymmetric gradient structure, with a dense fine-pore layer at the bottom and a lamellar porous structure at the top. Porosity exhibited a gradually increasing gradient from the bottom to the top surface. It was demonstrated that by adjusting cross-linking and sedimentation time, freezing temperature, and solid content, the ASCM membranes exhibited a tunable pore size distribution of 2.2–11.8 μm, porosity of 62.3%–72.1%, gas permeance of 113.9–595.9 m 3 m −2 h −1 kPa −1 and bending strength of 2.0–9.3 MPa. Additionally, the ASCM membranes exhibited outstanding high-temperature filtration performance for both standard PM 0.3 and real coal-fired fly ash, with a removal efficiency higher than 99.99%. This work provides a novel and feasible route for high-performance SiC ceramic membranes, enabling their engineering application in high-temperature gas-solid filtration. Download: Download high-res image (387KB) Download: Download full-size image
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