Effective Condition for Purification of Multi-walled Carbon Nanotubes by Nitric Acid

The multi-walled carbon nanotubes were synthesized on Fe-Ni bimetallic catalysts supported by MgO using thermal chemical vapor deposition. A comparative study on the effect of nitric acid molarity and time duration of acid treatment on purification of multi-walled nanotubes was done. The studies revealed that for finding a suitable condition for purification of multi-walled carbon nanotubes, it is necessary to determine suitable molarity of acid and immersion time of the carbon nanotubes. It was found that 5 M of boiling nitric acid at 3 h leads to the highest removal of the impurities with the least destructive effect. Various analytical techniques such as: scanning electron microscopy (SEM), high resolution transition electron microscopy (HRTEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and Raman spectroscopy techniques were employed to investigate the morphology, graphitization and quality of the carbon nanotubes.