The Transformation of Core/Shell Aluminium/Alumina Nanoparticles into Nanowires

Core/shell nanowires of Al/Al2O3 are obtained by decomposition of tert-butoxyalane on metal, silicon or glass substrates heated up to 650 °C without use of a noble metal seed. These biphasic nanowires are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and high-resolution TEM. They have uniform diameters of about 20–30 nm, are composed of an inner aluminium wire, wrapped up by aluminium oxide at a constant molar ratio, and have lengths of several micrometers. As the temperatures approach the melting point of Al (660.4 °C), we propose a growth mechanism for the nanowires which resembles to vapour-liquid-solid (VLS) growth of ceramic nanowires with a liquid metal phase catalyst seed which in this case is aluminium. The biphasic nature of the wires is due to the disproportionation of aluminium in the transient “AlO” and to Ostwald ripening.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)