Pressure-Induced Collapse in Double-Walled Carbon Nanotubes: Chemical and Mechanical Screening Effects

Abstract

The vibrational properties of double-walled carbon nanotubes (DWNTs) is investigated by high-pressure resonance Raman scattering up to 30 GPa in two different pressure-transmitting media (PTM): paraffin oil and NaCl. The protection effect on the outer tube during compression is verified .The collapse of DWNTs is experimentally observed for the first time, showing to be two-step: the onset of the outer 1.56 nm diameter tube collapse at ∼21 GPa is followed by the collapse of the inner 0.86 nm diameter tube at a higher pressure of ∼25 GPa. This observation is supported by calculations. We show that filling a tube with another tube leads to a pressure stabilization against collapse, in strong opposition to what is observed when filling a tube with fullerenes or iodine. The collapse pressure in DWNTs appears to follow a 1/d tav 3 law, where d tav is the average diameter from the inner and outer tubes, in agreement with predictions [ Yang X. Yang X. Appl. Phys. Lett.200689113101]. Contrary to SWNTs and peapods, for DWNTs, the observed collapse pressure is independent of the PTM nature. Those differences are discussed in terms of tube filling homogeneity and of the separate roles of inner and outer tubes: the outer tube offers chemical screening to the inner tube, whereas the inner tube guarantees mechanical support to the outer one. This leads to high collapse pressure independent of the DWNT environnment: a characteristic that makes DWNTs ideal fillers for composite nanomaterials for high load mechanical support.

Raman Spectroscopy in Graphene-Based Systems: Prototypes for Nanoscience and Nanometrology

“…Raman spectroscopy has been broadly used to study effects caused by strain, majorly focusing on the G band behaviour on SWNT bundles [74][75][76][77][78][79][80]. Combination of AFM with confocal Raman spectroscopy was made to follow, in situ, the evolution of the SWNT structure with transversal pressure applied to the tube.…”

Role of the pressure transmitting medium on the pressure effects in DWCNTs

“…It has been demonstrated that the homogeneous filling of the SWCNT cavity with an inner wall, forming what is called a double-walled carbon nanotube (DWCNT), stabilizes the outer tube [8][9][10][11][12][13]. In contrast, filling SWCNTs with C 70 or iodine molecules, which is considered as a case of inhomogeneous filling, leads to the destabilization of the nanotubes [8,10,11,14,15]. This was attributed to the inhomogeneous interaction, i.e., van der Waals forces, between the nanotube wall and the inner filler.…”

Stabilization of carbon nanotubes by filling with inner tubes: An optical spectroscopy study on double-walled carbon nanotubes under hydrostatic pressure

“…High-pressure Raman measurements showed that in the case of double-walled carbon nanotubes (DWCNTs) the inner tube supports the outer one up to high pressure before the collapse. 7,8 On the contrary, iodine and C 70 fillers are supposed to cause a destabilization of the SWCNTs. 6,7 Up to now, the stability of SWCNTs and DWCNTs against hydrostatic pressure has been mainly addressed by Raman spectroscopy, which monitors the vibrational properties.…”

“…Several earlier experimental studies (mostly Raman) reported higher critical pressures for the structural transition of the outer tube in DWCNTs as compared to SWCNTs, and this was attributed to the structural support of the outer tube by the inner tube. 7,30,34 The enhanced structural stability of the outer tube was theoretically predicted by Yang et al 35 : For small-diameter (5,5)(10,10) DWCNT bundles (d inner ≈0.68 nm, d outer ≈1.36 nm) a small discontinuous volume change appears at the critical pressure P d =18 GPa, accompanied by a cross sections' change between two deformed hexagons; the collapse to peanut shaped cross sections, however, happens at higher pressure. In contrast, (7,7)(12,12) DWCNT bundles (d inner ≈0.95 nm, d outer ≈1.63 nm) undergo one structural phase transition and collapse at P d =10.6 GPa.…”