Carbon Nanotube | Purity | Evaluation of Purity and Heat Resistance

Evaluation of Purity and Heat Resistance

When carbon nanotubes (CNTs) are heated in air, their mass reduces due to combustion. This mass reduction can be used to evaluate the purity of CNTs. The decomposition temperature can also be used to evaluate the heat resistance of CNTs, and this is applied to investigating the conditions of CNT formation.
Thermogravimetric analyzers offer qualitative and quantitative measurements of thermal decomposition and dehydration of various samples. Using a simultaneous thermogravimetric/differential thermal analyzer (TG/DTA), differential thermal analysis can be simultaneously conducted.

The DTG-60 Thermal Analyzer simultaneously performs measurements of changes in mass and DTA measurements of the exothermic peak temperatures and calorific values, which allows detailed determination of the ratio of amorphous carbon and CNTs.
Fig. 1 shows the thermogravimetric (TG) curve and differential thermal analysis (DTA) curve of single-walled carbon nanotubes (SWNTs) created by arc discharge. The largest exothermic peak in the DTA curve is near 683 ºC, which indicates the combustion of SWNTs. As the 322 ºC peak in the DTA curve is thought to be the combustion of amorphous carbon, the content ratio of SWNTs and amorphous carbon can be determined from their mass loss ratios in the TG curve.

Fig. 2 shows the results of thermogravimetric analysis (using a TGA-50 thermogravimetric analyzer) of SWNTs produced by the HiPco method. The TGA-50 is a dedicated thermogravimetric instrument that uses a highly sensitive vibration-resistant, suspension-type balance to achieve high-sensitivity measurements of less than 1 mg CNT samples. It offers good repeatability, even with less than 0.5 mg samples.