Morphological change of multiwalled carbon nanotubes through high-energy (MeV) ion irradiation

Multiwalled carbon nanotubes (MWCNTs) were expanded by 2.5 times in diameter through high-energy (MeV) ion irradiation. Pristine MWCNTs were synthesized onto SiO2 substrate by chemical vapor deposition. The 4MeV Cl2+ ions with a dose of 3×1016ions∕cm2 were irradiated on MWCNTs. From high-resolution transmission electron microscopy (HR-TEM) images, the average diameter of the high-energy-ion-irradiated MWCNTs was ∼180nm, while that of the pristine MWCNTs was ∼70nm. The wall thickness of the pristine and the high-energy-ion-irradiated MWCNT samples was ∼20nm and 40–50nm, respectively. We observed the clear formation of nanocompartments with bamboolike structure inside the tubes after ion irradiation. The amorphous carbon structure in the ion-irradiated MWCNT shells was observed from Raman spectra. Based on the results of HR-TEM and Raman spectra, the expansion of the systems represents morphological transition from crystalline graphite structure to amorphous carbon or finite sized graphite structure due to ...