A computational study on synthesis of carbon nanotubes in a sooty inverse diffusion flame

• Published in: International journal of environmental science and technology (Tehran) Vol. 20; no. 3; pp. 1 - 10
• Main Authors: Safaei, B., How, H. C., Scribano, G.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2023
• Subjects: Aquatic Pollution; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Science and Engineering; Original Paper; Soil Science & Conservation; Waste Water Technology; Water Management; Water Pollution Control; Carbon nanotube; Flame synthesis; Computational fluid dynamics; Diffusion flame; Soot
• ISSN: 1735-1472; 1735-2630
• DOI: 10.1007/s13762-022-04143-6

Hydrocarbon-flame synthesis is one of the simplest methods of carbon nanotubes production. During catalytic growth of carbon nanotubes in this method, soot formation poses a major issue as it can contaminate the carbon nanotube. In this study, a numerical simulation is conducted to investigate the competition between growth of carbon nanotubes and soot particles inside a laminar inverse diffusion flame. The flame simulated replicates an experimental inverse diffusion flame which has been studied for synthesis of carbon nanotubes on nickel catalyst. The growth of carbon nanotubes in the flame is computed based on a model developed for chemical vapour deposition of diamond. As a modification to this model, bulk and surface diffusivities of carbon in the catalyst nanoparticle are treated as temperature-dependent variables. Through comparison of simulation results with experimental data, it was discovered that the rate of carbon bulk diffusion is not sufficient on its own to predict the carbon nanotube growth regions in the flame due to the presence of soot contamination. Instead, the ratio of carbon bulk diffusion rate to soot nucleation rate is supposedly a more appropriate indicator as it qualitatively measures the dominance of carbon nanotube growth to soot formation. The flame temperature profile was also found to be critical for identifying carbon nanotube growth regions as too high a temperature can result in melting of the substrate, while at low temperatures of less than 600–700 K no appreciable amounts of carbon nanotubes can be produced due to negligibly small carbon diffusion rates.