Abstract
High temperature heat treatment (HTT) of bundled single-walled carbon nanotubes (SWNTs) in vacuum (∼10 -5 Torr) has been found to lead to the formation of two types of graphitic nanoribbons (GNRs), as observed by high-resolution transmission electron microscopy. Purified SWNT bundles were first found to follow two evolutionary steps, as reported previously, that is, tube coalescence (HTT ≈ 1400°C) and then massive bond rearrangement (HTT ≈ 1600°C), leading to the formation of bundled multiwall nanotubes (MWNTs) with 3-12 shells. At HTT > 1800°C, we find that these MWNTs collapse into multishell GNRs. zThe first type of GNR we observed is driven by the collapse of diameter-doubled single-wall nanotubes, and their production is terminated at HTT ≈ 1600°C when the MWNTs also start to form. We propose that the collapse is driven by van der Waals forces between adjacent tubes in the same bundle. For HTT > 2000°C, the heat-treated material is found to be almost completely in the multishell GNR form.
Original language | English |
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Pages (from-to) | 2195-2201 |
Number of pages | 7 |
Journal | Nano Letters |
Volume | 5 |
Issue number | 11 |
DOIs | |
State | Published - Nov 2005 |