A Review of Carbon Nanotube Synthesis via Fluidized-Bed Chemical Vapor Deposition

Abstract

Carbon nanotubes (CNTs) are crystalline, tubular, carbon structures with extraordinary mechanical, chemical, optical, and electrical properties. These unique properties make CNTs potentially valuable in a wide range of end-use applications. Currently, research into nanotubes and their applications is hampered by the lack of a suitable technique for manufacturing them in large quantities, which we define here as 10 000 tons per plant per year. Consequently, research into large-scale manufacturing techniques is ongoing. There are three established methods of CNT synthesis: (i) arc discharge, (ii) laser ablation, and (iii) chemical vapor deposition (CVD). Of these, CVD techniques show the greatest promise for economically viable, large-scale synthesis, based upon yields reported in the literature and the inherent scalability of similar technologies, e.g., fluidized catalytic cracking. In particular, the fluidized-bed CVD (FBCVD) technique (where the CVD reaction occurs within a fluidized bed of catalyst particles) has the potential to produce high-quality CNTs, inexpensively in large quantities. In this work, we review the existing literature on CNT synthesis via FBCVD and demonstrate that no systematic study of the key parameters has been undertaken. We demonstrate that there is no clear understanding of the influence of key variables (e.g., temperature, pressure, and carbon source) on CNT properties (e.g., CNT diameter, length, and morphology), which shows that further research is necessary to optimize this process and, ultimately, understand the science behind CNT growth using this technique. We also highlight the assessment of CNT quality as being an issue for further research. CNT quality is usually characterized visually (e.g., from TEM images), and a standard CNT characterization protocol has yet to be elucidated. The successful scale-up of any process requires detailed understanding of key process parameters and their interactions. Hence, further research to optimize the purity, yield, and selectivity of the synthesized CNTs is required before the potential of this technique can be realized.

Synthesis of Carbon Nanomaterials in a Swirled Floating Catalytic Chemical Vapour Deposition Reactor for Continuous and Large Scale Production

“…Carbon saturation in the metal occurs either by reaching the carbon solubility limit in the metal at a given temperature or by lowering the solubility limit via temperature decrease (Moisala et al, 2003). Supersaturation of the saturated solution then results in precipitation of solid carbon from the metal surface (Moisala et al, 2003;See and Harris, 2007). In summary, the mechanism of the catalytic growth of CNT or carbon nanofibre (CNF) is generally accepted as consisting of three steps (de Jong and Geus, 2000): The first step is the decomposition of carbon containing gases on the metal surface, with carbon atoms deposited on the surface.…”

Microstructural analysis of carbon nanomaterials produced from pyrolysis/combustion of Styrene-Butadiene-Rubber (SBR)

“…To generate carbon nanomaterials carbon bearing gases are needed at an elevated temperature environment. Such gases can be generated by high temperature pyrolysis and/or combustion of hydrocarbon-based feedstocks 12 . In prior work, it was found that carbon bearing gases can be provided from other types of solid waste fuels, such as plastics 13 and biomass 14 .…”

A review of the large-scale production of carbon nanotubes: The practice of nanoscale process engineering

“…Many other articles have reviewed the growth of singleand multi-walled carbon nanotubes, using either arc discharge, laser ablation, or catalytic CVD techniques [4][5][6][7][8][9][10][11][12][13][14][15][16].…”