Towards single step production of multi-layer inorganic hollow fibers

In this work we propose a generic synthesis route for the single step production of multi-layer inorganic hollow fibers, based on polymer wet spinning combined with a heat treatment. With this new method, membranes with a high surface area per unit volume ratio can be produced, while production time and costs are dramatically reduced. The proof-of-principle of the concept will be demonstrated with the production of double layer α-alumina hollow fibers. Although various problems were anticipated at the interface of the layers, the adhesion between the two layers is surprisingly good, both in the precursor and the sintered fiber. Produced fibers show an asymmetric structure with a porosity between 37 and 45%. The macrostructure of the sintered fiber is largely determined by the macrostructure of the precursor fiber, while differences in microstructure disappear during the heat treatment step. The proposed method is not limited to α-alumina membranes; in principle many ceramic or metallic powders may be used. This means that this method can open up the way for a new generation of membranes.