Abstract
A series of Fe and Fe/Mo catalysts, supported on alumina, were examined for Single-Walled Nanotube (SWNT) growth by Chemical Vapor Deposition (CVD) in methane. Molybdenum (20 wt %) was found to provide a clear synergistic benefit, lowering the growth temperature and eliminating the need for catalyst activation in hydrogen. The dependence of the carbon mass yield and sample quality on the CVD growth conditions is discussed. Catalyst activity in both the oxide and reduced (metallic) form were investigated under low methane flow (40 cm3/min) and in the temperature range 600 < T < 900°C. We found that the Fe/Mo oxide catalyst was active at temperatures as low as 680°C. Under these "soft" conditions (680°C, 40 cm3/min methane), the Fe-oxide catalyst (without Mo) was not active for tube growth, but it could be activated by an in situ reduction to metal in flowing He/(10% H2). Tube diameters in the range 0.7 to 1.7 nm were produced under most of the growth conditions studied, as determined by Raman scattering. In most cases, the SWNTs were produced in bundles ∼10 nm in diameter, as observed by transmission electron microscopy. No evidence for coproduction of multiwalled tubes was found.
Original language | English |
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Pages (from-to) | 525-530 |
Number of pages | 6 |
Journal | Nano Letters |
Volume | 2 |
Issue number | 5 |
DOIs | |
State | Published - May 2002 |