Researchers in the Material Measurment Laboratory (MML) have developed a thermogravimetric analysis (TGA) technique to monitor the composition of as manufactured samples that contain carbon nanotubes (CNTs). The constituents of the sample can be measured using their thermal stability; because of the relative simplicity of the technique, it has recently become a preferred method for determining the quality of carbon nanotube materials in an industrial setting. Results obtained from TGA analysis are the residual mass at a given temperature and the oxidation temperature. The residual mass provides a measure of the metallic content of the CNT sample, while oxidation temperature is a measure of the thermal stability of the nanotubes in an oxidative environment. Oxidation temperature can be influenced by a number of factors, including defects, length and diameter of the nanotubes, and metallic impurities. This research was presented as part of a paper just published in Metrologia where nine different methods to characterize single-walled carbon nanotube (SWCNT) materials are detailed in a collaborative effort between NIST, the National Research Council in Canada, and the National Physical Laboratory in the UK.
MML researchers using the TGA technique were further able to demonstrate how CNT chemistry can have a dramatic effect on thermal stability of the material. Through the use of NIST-length sorted SWCNTs, researchers were able to show for the first time that the length of the carbon nanotubes impacts oxidation temperatures. Changes in oxidation temperature were also observed for nanotubes of different diameters. These results were published in "Application of thermogravimetric analysis in quality control of single-walled carbon nanotubes." E. Mansfield, A. Kar, S. Hooker., Anal. Bioanal. Chem., 396(3), 1071-1077, 2010.