Fabrication of alumina nanofibers by precipitation reaction combined with heterogeneous azeotropic distillation process

γ-Alumina nanofibers have been prepared from a precipitation reaction between aluminum ammonium sulfate and Baker's salt solutions followed by a heterogeneous azeotropic distillation process with N-butanol and calcination at 1173 K. Experimental results indicate that the terminal pH value of the reaction mixture should be kept at 7.00-8.00 in order to obtain γ-Al₂O₃ nanofibers. The resulting spherical aluminum hydrate precipitates are evolved into two-dimensional crystallized pseudoboehmite lamellae after the heterogeneous azeotropic distillation and then transformed into γ-Al₂O₃ nanofibers with ca. 3-5 nm thick and 50-150 nm long after further calcination at 1173 K. The formation of γ-Al₂O₃ nanofibers can attribute to the preferential growth along the longitudinal axis due to the inherent instability of the planar structure of the pseudoboehmite during the calcination process.