Study of purification process of single-walled carbon nanotubes by thermoanalytical techniques

The thermal behaviour of commercial Carbolex single-walled carbon nanotubes (SWCNTs) both as-received and after purification by a novel method has been studied by thermogravimetric/derivative thermogravimetric/difference thermal analysis (TG/DTG/DTA). Purification from metal catalysts (Ni and Y) has been successfully obtained using 0.1 M I2 in iso-propanol instead of the usual concentrated HNO3. The final residues of thermal analysis have been characterised by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The gathered results showed that the as-received SWCNTs burns out in a one-step between 573 and 923 K, whereas the SWCNTs treated with HNO3 become highly hygroscopic. The I2-iso-propanol-treated SWCNTs showed three overlapped exothermic peaks between 500 and 973 K in the DTA curve, which allowed separating amorphous carbon from SWCNTs by air-thermal treatment at 573 K. The graphite-like compounds, which are present in both untreated and treated SWCNTs, does not burn up to 1173 K.