Synthesis and characterization of sol-gel alumina nanofibers

Alumina nanofibers of high aspect ratio with surface area of > 300 m(2) g(-1) has been prepared successfully in bulk quantities by the sol-gel method. The synthesis parameters including the binary water-alcohol solvent system to aluminium isopropoxide ratio, pH, type of solvent and aging temperature affect the uniformity and formation of nanofibers. It is proposed that alumina nanofibers were formed by the curling of the nanosheets upon condensation after the hydrolysis. The phase evolution of alumina nanofibers from pseudoboehmite to alpha phase has been shown by XRD and FTIR. Al-27 NMR investigations show that the Al atoms are six and four coordinated. The morphology of the alumina nanofibers does not change much as the calcination temperature was increased. In addition, the average pore size increases and the BET surface area decreases as a function of calcination temperature. The thermal behavior of alumina nanofibers was investigated by TGA.