Comprehensive Study of Morphological Modification of Dual-Layer Hollow Fiber Membrane

The NiO–YSZ/LSCF–YSZ dual-layer hollow fiber membrane receives increasing attention which is due liable to quick changes in properties during co-extrusion followed by the co-sintering method. The effect of mixed bore liquid of water + ethanol + n-methyl-2-pyrrolidone and co-sintering temperature on physical and chemical characteristics of the obtained membrane was systematically explored in this study. Here, the characterization of the membrane was inspected using scanning electron microscope–energy-dispersive X-ray, three-point bending, mercury porosimetry, X-ray diffraction and nitrogen tightness tests as well as the oxygen permeation test. Results indicated that membrane prepared using 100% water as a bore liquid produced a sandwich structure. On the contrary, by employing 40:10:50% of water/ethanol/NMP as a mixed bore liquid and sintering for 8 h at 1300 °C, an open-channel structure in the microstructure gives a good porosity as tested using mercury porosimetry, mechanical properties and nitrogen permeability with no secondary phases. In addition, the co-sintering effect was examined by increasing temperature to 1400 and 1500 °C. However, an impurity phase of LaZr₂O₇ was formed which is due to the chemical reaction of La and Sr into YSZ structure. Oxygen permeate concentration through the dual-layer membrane was found to be slightly different as compared to the single-layer hollow fiber membrane. The results further suggest that the outer layer should be tighter and thinner to enhance the oxygen ion diffusion.