Large-scale synthesis of multi-walled carbonnanotubes by microwave CVD

Abstract

Carbon nanotubes (CNTs) are an interesting class ofnanostructures which can be thought of as arising from thefolding of a layer of graphite (a graphene sheet) to form ahollow cylinder composed of carbon hexagons. However, practicalapplications are still limited by the intricate process of synthesis and the inability of present day methods to provide large-scale production of CNTs. Moreover, high-qualitynanotubes with functionalization capability with polymers aredesired for polymermicroelectromechanical systems (MEMS), nanodvices and BioMEMS. In thispaper, an innovative CVD approach using microwave energy wasdeveloped for the large-scale production of multi-wall carbonnanotubes (MWNTs). Straight and helical CNTs were obtained when acetylene created by a microwave field was decomposed over the cobalt catalyst at700 °C. Scanning electronmicroscopy of microwave-driven MWNTs revealed theirhomogenous nature. High-resolution electron microscopyshowed that typically the MWNT has 26 layers. The average diameterof the tubes observed was 20-30 nm. Electron microscope observations showed a higher yield of nanotubes obtained frommicrowave CVD than the thermal filament CVD method.