Effects of proton irradiation on thermal stability of single-walled carbon nanotubes mat

We report effects of proton irradiation on thermal oxidation of single-walled carbon nanotubes (SWNTs). Following 400 keV proton irradiation to doses of 10(13)-10(17) cm(-2), thermal oxidation of SWNTs was conducted at temperatures 200-700 degrees C. The mass of SWNTs during oxidation was monitored with thermogravimetric analysis (TGA) and ion-beam-induced structural modifications in nanotubes were characterized with Raman spectroscopy. Proton irradiation leads to enhanced thermal stability of nanotubes, as indicated by increased values of the temperature (T-max) for maximum oxidation rate, e.g. T-max similar to 495 degrees C for pristine SWNTs and T-max similar to 525 degrees C for SWNTs irradiated to the dose of 1 x 10(15) cm(-2). The activation energy for oxidation increases gradually from 1.13 +/- 0.01 eV for pristine SWNTs, to similar to 1.25 +/- 0.02 eV for the largest dose of 5 x 10(16) cm-(2). Based on the correlation between TGA and Raman data, we discuss possible mechanisms for the observed effects of proton irradiation on SWNT thermal oxidation. (c) 2005 Elsevier B.V. All rights reserved.