Microwave-Assisted Acid Digestion Method for Purification of Carbon Nanotubes

The raw carbon nanotubes were obtained by chemical vapor deposition using ethylene as a carbon source and nanocrystalline iron as a catalyst. A microwave-assisted acid digestion method was applied to the purification. Carbon materials directly after the synthesis and treated under air atmosphere were immersed in the Teflon vessel filled with nitric or hydrochloric acid. Then the whole content was placed in the reactor heated with microwaves. Experiments were conducted under pressure in the range from 15 to 30 atm. The removal degree of catalyst particles was estimated using the thermogravimetric method.