Influence of sintering temperature on the morphology of ceramic hollow fibers prepared from niobium pentoxide

Ceramic hollow fibers were prepared by the phase inversion and sintering method using niobium pentoxide (Nb2O5) as an innovative starting material. X-ray diffraction and Raman analyses revealed the same monoclinic crystalline phase for the ceramic material, H-Nb2O5, at all the evaluated sintering temperatures. According to SEM images, the starting material was composed of polydisperse particles of irregular size and shape with sizes ranging from 12.5 to 89.7 mu m. The increase in the sintering temperature caused particles agglomeration. In the hollow fiber precursor (without sintering), Nb2O5 grains were surrounded by the coagulated polymer. The polymeric phase was eliminated when the fibers were sintered at temperatures above 600 degrees C. When sintered at 1350 degrees C, the outer surface of the fiber presented elongated crystals of well-defined shape, while agglomerated round shape grains were observed at the inner surface of the fiber. Formation of these elongated crystals was probable due to the material sintering at high temperatures (up to 1350 degrees C) for more than 300 minutes. This study demonstrated the potential for general applicability of niobium pentoxide to fabricate ceramic hollow fiber membranes.