Rapid thermal processing of inorganic membranes

Rapid thermal processing (RTP) methods can be used to majorly reduce the processing time of thin supported inorganic membrane layers. The methods result in a finer, more homogeneous membrane microstructure and can be used to form membrane layers requiring high-temperature processing on supports with limited thermal stability. The short processing time of RTP reduces fabrication cost price, helps improve process optimization, and also encourages exploration of other multi-layer structures. The work in this paper demonstrates the use of RTP for thin defect-free supported mesoporous γ-alumina membranes that have a thickness of ∼400 nm. Conventionally thermal processed (CTP) and RTP γ-alumina membranes were characterized by ellipsometry, microscopy, aqueous ion rejection and permporometry. CTP and RTP membranes showed an aqueous ion rejection of >95% and >97%, respectively for a solution of 1 mol/m3 calcium chloride dihydrate with 0.01 mol/m3 aluminum chloride. According to ellipsometry analysis, the porosity of the RTP and CTP membranes are approximately 43 and 50%, respectively. Permporometry provides RTP and CTP membrane pore size, Øp of 3.4 + 2t and 4.3 + 2t nm, respectively where t ≈ 0.35 nm.

Research highlights▶ Rapid thermal processing (RTP) greatly reduces thermal treatment time of thin inorganic membranes. ▶ RTP results in finer microstructures and more densification. ▶ RTP does not adversely affect membrane integrity. ▶ RTP of supported γ-alumina membranes resulted in similar or better nanofiltration properties.