Superior carbon nanotube stability by molecular filling:a single-chirality study at extreme pressures

Abstract

Carbon nanotubes have extraordinary mechanical properties, but modifications of their structure tend to weaken them. Here, we have studied by experiments and modelling the one-dimensional filling of single chirality (6,5) carbon nanotubes with iodine and water. We show that iodine-filling can enhance the pressure of radial collapse of these nanotubes by a factor 2 compared to the empty (6,5) tubes. For water filling, this enhancement factor reduces to 1.4. Our single-chirality study allows correlating the different Raman signatures of the radial collapsing process, which was not possible in samples with mixed chiralities. A clear spectroscopic signature of the collapse pressure can thus be given: it is the pressure at which the G-band frequency evolution with pressure softens while the radial breathing mode intensity vanishes. These new criteria for the detection of radial collapse allow correcting some existing discrepancies in the literature. Finally, we discuss the impact of molecular filling on the radial mechanical stability as a function of the tube diameter. It results that molecular filling allows for a superior stability effect than filling with tubes (i.e. multi-wall carbon nanotubes). The stability enhancement tends to grow with the tube diameter and depends strongly on the nature of the filling molecules.

Effect of extreme mechanical densification on the electrical properties of carbon nanotube micro-yarns

“…In particular, it is not clear what role the radial collapse of CNTs may have. In the effort to optimize mechanical densification to improve the electrical conductivity of the CNT yarns we suggest the following: (i) improving the specific properties of the MWCNTs produced by HF-CVD [28]; (ii) applying hydrostatic conditions at higher pressures; (iii) if radial collapse appears as a limiting factor, pushing forward the collapse pressure by molecular filling of CNTs [55] or using different kinds/sizes of CNTs to avoid CNT collapse at relatively low pressure. The development of high conductivity CNT yarns through pressure may also benefit from the combined use of other physico-chemical parameters such as doping or variation of the MWCNT's processing temperature.…”

Manipulating the interlayer thermal conductivity in circular/collapsed carbon nanotube clusters

“…The temperature is maintained at 1.0 K to eliminate thermal fluctuations. Note that previous high-pressure experiment suggests that the occurrence of symmetry-breaking transitions at critical pressures is around 1.5 ∼ 2.1 GPa for CNT with a diameter of 1.54 nm [32], while a smaller CNT diameter of 0.75 nm results in a higher critical pressure of 9.0 GPa [33]. In this work, the CNT diameters ranging from 3.66 ∼ 5.153 nm are chosen.…”

Carbon nanowires under compression and their vibrational anomalies

“…This buckling depends on the diameter of the CNT and the number of walls 22,23 and is affected by the presence of chain lling. 24,25 Here we consider the case in which the CNTs remain straight. Where the carbon chain is conned in a CNT (Fig.…”