Measurements of near-ultimate strength for multiwalled carbon nanotubes and irradiation-induced crosslinking improvements.
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.
Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3111, USA.
Bei
B
Peng
Mark
M
Locascio
Peter
P
Zapol
Shuyou
S
Li
Steven L
SL
Mielke
George C
GC
Schatz
Horacio D
HD
Espinosa
D003460:Crystallization / Q000379:methods; D055119:Elastic Modulus / Q000528:radiation effects; D055664:Electrochemical Techniques / Q000379:methods; D004581:Electronics / Q000295:instrumentation / Q000379:methods; D004583:Electrons; D008422:Materials Testing / Q000379:methods*; D055617:Micro-Electrical-Mechanical Systems / Q000379:methods; D046529:Microscopy, Electron, Transmission / Q000379:methods; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000528:radiation effects*; D011827:Radiation; D013718:Tensile Strength / Q000528:radiation effects
D037742:Nanotubes, Carbon