Synthesis and characterization of Al2O3 nanopowders by a simple chitosan-polymer complex solution route

Al2O3 nanopowders were synthesized by a simple chitosan-polymer complex solution route. The precursors were calcined at 800-1200 °C for 2 h in air. The prepared samples were characterized by XRD, FTIR and TEM. The results showed that for the precursors prepared with pH 3-9 γ-Al2O3 and δ-Al2O3 are the two main phases formed after calcination at 800-1000 °C. Interestingly, when the precursor prepared with pH 2 was used, α-Al2O3 was formed after calcination at 1000 °C, and pure α-Al2O3 was obtained after calcination at 1200 °C. The crystallite sizes of the prepared powders were found to be in the range of 4-49 nm, as evaluated by the XRD line broadening method. TEM investigation revealed that the Al2O3 nanopowders consisted of rod-like shaped particles and nanospheres with particle sizes in the range of 10-300 nm. The corresponding selected-area electron diffraction (SAED) analysis confirmed the formation of γ- and α-Al2O3 phases in the samples.