Measurements of near-ultimate strength for multiwalled carbon nanotubes and irradiation-induced crosslinking improvements

Abstract

The excellent mechanical properties of carbon nanotubes are being exploited in a growing number of applications from ballistic armour to nanoelectronics. However, measurements of these properties have not achieved the values predicted by theory due to a combination of artifacts introduced during sample preparation and inadequate measurements. Here we report multiwalled carbon nanotubes with a mean fracture strength >100 GPa, which exceeds earlier observations by a factor of approximately three. These results are in excellent agreement with quantum-mechanical estimates for nanotubes containing only an occasional vacancy defect, and are approximately 80% of the values expected for defect-free tubes. This performance is made possible by omitting chemical treatments from the sample preparation process, thus avoiding the formation of defects. High-resolution imaging was used to directly determine the number of fractured shells and the chirality of the outer shell. Electron irradiation at 200 keV for 10, 100 and 1,800 s led to improvements in the maximum sustainable loads by factors of 2.4, 7.9 and 11.6 compared with non-irradiated samples of similar diameter. This effect is attributed to crosslinking between the shells. Computer simulations also illustrate the effects of various irradiation-induced crosslinking defects on load sharing between the shells.

Fabrication of high strength PVA/SWCNT composite fibers by gel spinning

“…It was reported that defects introduced by oxidative pitting during composite preparation markedly reduce fracture strength, and extensive pitting leads to lower modulus [22,23]. Moreover, the other potential source of large defects of nanotubes was found by the use of sonication that caused strength underperformance [11]. In the present study, the direct physical homogenizing process in the presence of The dispersion state of SWCNTs in PVA matrix was directly observed by TEM.…”

“…This analysis gives effective nanotube strength of 175 GPa, which is relatively comparable to the highest measured strength of carbon nanotubes (ca. 110 GPa) [11].…”

“…Dispersion of SWCNTs by sonication is possible [11][12][13], but it requires long treatment time and is also reported to be destructive for SWCNTs, decreasing its strength [14]. Thus a damage-free dispersion of SWCNTs without sonication is desirable.…”

High-strength carbon nanotube fibre-like ribbon with high ductility and high electrical conductivity

“…To narrow the gap further, the structural parameters such as length, diameter and alignment of CNTs should be better controlled. For strength improvement, the intertube load transfer may be manipulated by already reported methods such as electron irradiation 31,32 , chemical treatment 33 and polymer impregnation [34][35][36] , forming primary bonds between CNTs, which are much stronger than Van der Waals interactions. For conductivity improvement, tube chirality should be particularly tailored 37 , and iodine doping 13,38 and metal coating 39,40 may be imposed.…”

Observation of the intrinsic bandgap behaviour in as-grown epitaxial twisted graphene

“…The sp 3 C-C interlayer bonding has been experimentally observed in graphite and carbon nanotubes modified by electron irradiation 28 , femtosecond laser excitation 29 and thermal treatment 30 without chemical functionalization. In addition, quantum molecular dynamics calculation have evidenced the existence of interlayer sp 3 C-C bonding between graphene layers contained defects such as vacancies and interstitials 31 .…”