Influence of diameter on the degradation profile of multiwall carbon nanotubes

Ten multiwall carbon nanotubes purchased from two companies with diameters ranging from 7 to 100 nm with tapped bulk densities from 57 to 250 kg m(-3) and with similar lengths and powder sizes were analyzed by thermogravimetric analysis in dynamic and isothermal mode to investigate the importance of the diameter size and tapped bulk density on the degradation behavior of carbon nanotubes. In the case where mass/heat transfer effects were eliminated, results showed that the oxidation temperature depends on diameter only at sufficiently small diameters. The number of surface defects as measured from the I-D/I-G ratio obtained from Raman spectroscopy was not correlated with degradation stability. The tapped bulk density, on the other hand, dominated the pattern of degradation at high enough heating rates where mass/heat transfer effects become appreciable. As found in previous work which examined nanotubes with roughly constant diameter, tapped bulk density linearly correlated with the ending oxidation temperature at sufficiently high heating rates.