Effect of catalysis on coal to nanotube in thermal plasma

Abstract

Arc/graphite, laser ablation and CVD are three main methods for the production of carbon nanotubes (CNTs). A free coal-based or graphite electrodes method was explored in our lab. In this method, coal powder was directly injected into arc plasma jet instead of arc evaporation of coal-based electrodes, so we called it coal/arc-jet process. It is found that the Cu nano-particles sputtered from copper electrodes played an important role of catalyst for the synthesis of CNTs. Three metal particles (Fe, Co, Cu) with grain size of 120 mesh were mixed into coal powder and injected into plasma jet, respectively. It is found that the yield of CNTs was improved evidently. The difference of their effectiveness of catalysis was discussed. Under the condition of thermal plasma jet with initial temperature of 3700 K, coal was cracked into aromatic fragments, carbon free radicals and light hydrocarbons. Meanwhile, metallic particles were vaporized and then condense to nano-droplet that was the active site for CNTs growth. The generation of carbon precursor and “preparation” of metallic nano-particles was finished within one stage.