Alumina nanowire growth by water decomposition and the peritectic reaction of decagonal Al65Cu15Co20 quasicrystals

• Hexagonal alumina nanowires are grown at 1050 °C through the VLS process.
• Alumina nanowires are obtained by the decomposition of decagonal quasicrystalline phase.
• The decagonal phase decomposition follows a peritectic reaction at 1030 °C.
• Nanoparticles are obtained by hydrogen embrittlement mechanism.
• The nanoparticles catalyze the water decomposition to form wires

In this paper, the results of the Al2O3 nanowires' growth through a chemical reaction between Al and water vapor at 1050 °C are presented. Our approach is based on two primary considerations. First, at room temperature, the Al65Cu15Co20 alloy is affected by the following mechanism: 2Al (s) + 3H2O (g) → Al2O3 (s) + H2 (g). In this reaction, the released hydrogen induces cleavage fracture of the material to form small particles. Second, the Al65Cu15Co20 quasicrystalline phase is transformed on heating to liquid + Al (Cu, Co) cubic phase through a peritectic reaction at 1050 °C. The Al-rich liquid then reacts with water vapor, forming Al2O3 nanowires. X-ray diffraction (XRD) analysis shows that the formed nanowires have a hexagonal structure, and infrared analysis further confirms the presence of α-Al2O3 phase in the final products. Transmission electron microscopy observations show that nanoparticles are present at the end of nanowires, suggesting the VLS growth mechanism. Elemental analysis by energy dispersive spectroscopy (EDS) indicates that the particles at the tip of the nanowires are mainly formed by Co and Cu alloying elements and small amounts of Al. Electron microscopy observations showed nanowires with diameters ranging from 20 to 70 nm; the average diameter was 37 nm and the nanowire lengths were up to several micrometers.

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