Catalyst-free synthesis of multiwalled carbon nanotubes via microwave-induced processing of biomass

Carbon nanotubes (CNTs) have been the focus of research in the past two decades due to their fascinating properties and significant potential for a range of applications, from electronics to high performance polymers. In this research, multiwalled CNTs with a diameter of 50 nm and a wall thickness around 5 nm were successfully prepared via microwave-induced pyrolysis of gumwood at 500 °C. The mechanism for the growth of such CNTs is under microwave irradiation. Volatiles were released from the biomass and left behind char particles. These char particles then acted as substrates, mineral matter in char particles (originating from biomass) acted as the catalyst, and the volatiles released acted as the carbon source gas. The volatiles were then undergoing thermal and/or catalytic cracking on the surface of char, forming the amorphous carbon nanospheres; the carbon nanospheres then subsequently self-assembled into multiwalled CNTs under the effects of microwave irradiation.