Fabrication of Single‐Crystal α‐Al₂O₃ Nanorods by Displacement Reactions

Abstract

Nanometer-sized Al 2 O 3 rods are fabricated by sintering a powder mixture of Al and SiO 2 . The sintered product is leached in HF-HNO 3 solution, followed by rinsing and washing before the nanorods are collected. The yield of the product is about 50 wt%. Transmission electron microscopy reveals that these rods are 1 to 2 m long and have a diameter of 20 to 100 nm, while electron diffraction confirms that these rods are single crystals of ␣-Al 2 O 3 . It is observed that these rods have either round or slightly sharp tips, which is different from those having droplet-like tips that are usually found in products fabricated by catalytic reactions.

Growth mechanism of single-crystal α-Al2O3 nanofibers fabricated by electrospinning techniques

“…The growth of the fibers/whiskers was found to be mostly in the [0 0 1] direction through the VLS mechanism [10][11][12][13][14][15]18 or through a mechanism that is analogous to Ostwald ripening. 16,17 Both of these mechanisms are categorized as tip growth models, resulting in characteristic round droplets or slight sharp curvatures on the tips of the fibers/whiskers. A similar method (basal growth) of growing ␣-Al 2 O 3 whiskers in an aluminum-based MMC has been reported using an internal oxidation reaction between aluminum and molybdenum oxide (MoO 3 ) at 850 • C. 19 The ␣-Al 2 O 3 whiskers obtained were, on average, 1 m in diameter and 10 m in length.…”

Synthesis of ultra thin α-alumina nanobelts from aluminum powder by chemical vapor deposition

“…Currently, nano-alumina have been obtained by catalyst-supported chemical vapor deposition (CVD), [5][6][7] or by the in situ displacement reactions. [8][9][10] In many of these fabrication methods, it is usually not possible to obtain pure products without having impurities. While catalyst-free CVD process like carbothermal synthesis 4 which uses graphite and oxygen, or uses water vapor as oxidizing agent, 3 can produce pure alumina products, a thermal gradient is often needed.…”

Direct Synthesis of Alumina Nanowires on Ceramic Substrates Using Sn Catalysts

“…Deng et al. fabricated single‐crystal α‐Al 2 O 3 nanorods by displacement reactions . Some researchers have also reported the catalyst‐free synthesis of 1D Al 2 O 3 nanostructures .…”