Table 1 Summary and comparison of three representative methods of CNT production

Arc discharge method

Under high current, carbon vaporizes and forms a hot plasma between two graphite rods spaced a few millimeters apart

< 30%

Relatively simple and inexpensive

Large quantities of CNTs can be produced at once

Produce a lot of impurities substantial; purification is needed and the SWCNTs have structural defects

Short tubes with diameters of 0.6–1.4 nm

Short tubes with inner diameter of 1–3 nm and outer diameter of approximately 10 nm

[48,49,50]

Laser ablation

Intense laser pulses cause graphite to evaporate and form CNTs

70%

Produce high-quality, single-walled CNTs with a narrow size distribution

Expensive equipment and specialized operating knowledge

Energy-intensive and may require the use of hazardous gases

Long bundles of tubes (5–20 microns), with individual diameter from 1 to 2 nm

Not very much interest in this technique, as it is too expensive, but MWCNT synthesis is possible synthesis is possible

[50, 51]

Chemical vapor deposition

Heated up to 1000 °C in an oven with/without a substrate, carbon-bearing gas such as methane decomposes on a catalyst into CNTs

95%–99%

Commercially the most developed method, easiest to scale up, good yield and quality control, high-purity SWCNTs

MWCNTs are often riddled with defects compared with SWCNTs, for which the quality is better controlled

Long tubes with diameters ranging from 0.6 to 4 nm

Long tubes with diameters ranging from 10 to 240 nm

[50, 52, 53]