Synthesis of onion-like carbon using 3-phase plasma reactor

Abstract

Since the discovery of fullerenes in 1985, synthesizing nano-materials such as fullerene, onion like carbon (OLC), nanotube etc. has been widely researched. One of the most used techniques in synthesizing nanocarbons is the high temperature plasma method. The plasma method, in this case a 3-phase arc plasma, provides efficiency, low environmental impact, scalability, and greater purity. While the 3-phase plasma method has been studied in fullerene and nanotube production, utilizing the 3-phase plasma in the synthesis of OLC has yet to be investigated. The OLCs can be defined as giant molecules synthesized from carbon into the form of multilayered graphite. The OLC can be considered a hybrid nano-carbon with a structure between that of fullerene and graphene. The traditional methods of OLC production are batch based, expensive, and non-uniform, thereby limiting market use. This research studies 3-phase plasma synthesis of OLC. A 3-phase plasma reactor was modelled, designed, constructed, and operated at conditions required for OLC formation. A previously developed quasi-2D model using convection-diffusion in finite volume was utilized to monitor the key parameters: gas flow rate, residence time, and power. After heat treating an amorphous carbon feedstock by the plasma, the products were characterized by 3 different characterization methods: thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), and Raman spectroscopy. The results were then compared to the data gathered from the original feedstock and a reference OLC to determine conversion ratios. In addition, the energy efficiency of the plasma method was compared to conventional furnace annealing.