In situ studies of a molten metal anode ablation in a nearly atmospheric pressure DC arc

TL;DR

This study employs high-speed pyrometry to measure and analyze the ablation rates of a molten metal anode in a DC arc, revealing how gas composition affects catalyst formation for SWCNT synthesis.

Contribution

It introduces a novel high-speed pyrometry method for in situ molten anode temperature measurement in a DC arc, enabling better control of SWCNT production processes.

Findings

Ablation rates depend on arc and molten pool dynamics.

Reflections significantly affect temperature measurements.

Addition of CH4 alters ablation rates, impacting scale-up.

Abstract

A DC arc with a meltable metal anode in a near-atmospheric pressure hydrocarbon gas is an emerging method for producing single-walled carbon nanotubes (SWCNTs). In these systems, evaporation of the molten metal anode determines the formation of catalyst seed particles needed for SWCNT growth, and therefore, should be monitored, controlled, and optimized. Evaluating the anode ablation rate by weighing the anode before and after a synthesis run is unfeasible due to anode carburization in the hydrocarbon atmosphere. To overcome this, we implemented a high-speed, 2D, 2-color pyrometry for reliable temperature measurements of the molten anode in a DC arc. The obtained temperature fields were used to calculate the anode ablation rates. Results showed the importance of resolving the arc and molten pool dynamics, as well as addressing the issue of reflections. Furthermore, significant changes in ablation rates were revealed upon addition of CH4, which must be considered when scaling up the production of SWCNTs.