Synthesis of Carbon Nanotubes via Plasma Arc Discharge Method

1. Introduction

Carbon nanotubes possess extensive chemical, mechanical, optical, and thermal properties listed in Table 1. They are broadly classified as SWCNTs, MWCNTs, and DWCNTs. Moreover, SWCNTs are divided into three kinds, namely arm-chair, zigzag, and chiral carbon nanotubes. CNTs can show metallic or semiconducting behavior, depending on the nature of the structure or chirality. While armchair carbon nanotubes are always metallic with indices m=n=3q, others can be metallic or semiconductors. The indices n and m identify the electronic structure and q be the integer. In arm-chair carbon nanotubes, there is no band-gap between the valence and the conduction band but in the case of zig-zag and chiral carbon nanotubes, a narrow bandgap exists which is the nature of the semiconductor materials.

Researchers devised different ways to synthesize CNTs via various precursors. The most popular synthesis methods are arc discharge, laser ablation, and chemical vapor deposition (Chau et al., 2020). Hydro-thermal, ball milling and electrolysis have also been used to synthesize CNTs. CNTs were synthesized by lijima via the arc discharge method (Bahgat et al., 2011). While the literature has no more comprehensive research on the formation mechanism of CNTs. There is a need of an elevated correlation between parameters and growth conditions of nano-tubes. Yoshinori et al. (Yoshinori, 2010) presented the chronological feature of CNTs under hydrogen atmosphere. Tessonnier (Tessonnier & Su, 2011) revealed the growth and nucleation process during production. Journet et al. (Journet et al., 2012) explained medium and low-temperature routes to synthesized CNTs. In this literature, the growth mechanism of CNTs formation has been extensively explained.