Synthesis and characterization of sol-gel derived continuous spinning alumina based fibers with silica nano-powders

Silica nano-powders were used as the Si source to substitute acidic silica sol in the SiO2-Al2O3 sol mixture for benefiting the sintering of the fibers at 1250 degrees C. With the increase of nano-silica, grain diameter and porosity of the fibers decreased firstly and increased subsequently, a minimum value of 35.86 nm and 0.86% was exhibited at the nano-silica content of 20%. The solid content, linear growth model and homogeneity of the precursor sol were not affected by the presence of nano-silica, although the continuous spinning length became low. NMR Analysis of (27) Al indicated that polymerization degree of the sol was enhanced by nano-silica. The nano-particle contributed to the reduced intermolecular distance of gel, so the appropriate content existed for resulting the reduced grain size and compact structure of the fibers. (C) 2013 Elsevier Ltd. All rights reserved.