Solid-phase low temperature steam-assisted synthesis of thermal stable alumina nanowires

A simple steam-assisted solid phase synthesis method was developed for synthesis of boehmite nanowires in the presence of TEAOH surfactant. The boehmite nanowires had uniform diameters (12-16 nm) and length up to 1-2 microm. The morphology of the nanostructured wires was well preserved after being converted to pure gamma-Al2O3 by thermal treatment at 600 degrees C for 5 h. The nanowires of Al2O3 exhibited excellent thermal stability by retarding the phase transformation and maintaining the wires-like nanostructure after being aged up to 1300 degrees C by preventing sintering between particles at high temperatures. The surface areas of Al2O3 nanowires could be maintained as high as 68 m2/g at 1300 degrees C while the surface areas of Al2O3 micropowder shrank to 0.89 m2/g after same thermal treatment. Both in-situ XRD and 27Al NMR results indicated that the crystal structure of gamma-Al2O3 nanowires was not transformed to alpha-Al2O3 at 1300 degrees C whereas micropowder Al2O3 was fully converted to alpha-Al2O3 at 1100 degrees C.