Ultra-High Oxidation Resistance of Suspended Single-Wall Carbon Nanotube Bundles Grown by an "All-Laser" Process
Abstract:Single-wall carbon nanotubes (SWCNTs) were laterally grown on SiO2/Si substrates by means of an "all-laser" growth process. Our "all-laser" process stands out by its exclusive use of the same pulsed UV laser, first, to deposit the CoNi nanocatalyst and, second, to grow SWCNTs through the laser ablation of a pure graphite target. The "all-laser" grown SWCNTs generally self-assemble into bundles (5–15 nm-diam.) sprouting from the CoNi nanocatalyst and laterally bridging the 2 m gap separating adjacent catalysed electrodes (in either "suspended" or "on-substrate" geometries). A comparative study of the oxidation resistance of both suspended and on-substrate SWCNTs was achieved. The "all-laser" grown SWCNTs were subjected to annealing under flowing oxygen at temperatures ranging from 200 to 1100 °C. Systematic scanning electron microscopy observations combined with micro-Raman analyses revealed that more than 20% of suspended nanotubes were still stable at temperatures as high as 900 °C under flowing O2 while the on-substrate counter-part were completely burnt out at this temperature. Accordingly, the activation energy, as deduced from the Arrhenius plot, of the suspended SWCNTs is found to be as high as ∼180 kJ mol−1 (∼9 times higher than that of the on-substrate ones). The high quality (almost defect-free) of the nanotubes synthesized by the "all-laser" approach, their protected tips into the embedded CoNi catalyst nanolayer together with their suspended geometry are thought to be responsible for their unprecedented ultra-high oxidation resistance. This opens up new prospects for the use of these suspended nanotubes into nanodevices that have to operate under highly oxidizing environments.
Document Type: Research Article
Publication date: October 1, 2007
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- Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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