Thermogravimetric analysis (TGA) is widely used to gather data on nanotube chemistry. By monitoring weight loss as a function of temperature, one can determine decomposition kinetics and use this data to closely approximate the distribution of impurities present in a few milligrams of material. Oxidative stability provides an indirect measure of the types of carbons present. The residual mass provides an estimate of the metal fraction, which primarily consists of the catalyst material.
One disadvantage of TGA, however, is the need for relatively large specimen sizes, which is particularly problematic for highly purified materials (where process yields are low). As an alternative to TGA, we developed an elevated temperature quartz crystal microbalance (QCM) technique that interrogates samples on the order of 1 microgram or less. A variety of coating techniques can be used to deposit the nanotube material, including drop casting, spin coating, and spray deposition.