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Continuous Hot Wire Chemical Vapor Deposition of High-Density Carbon Multiwall Nanotubes

“…Figure a displays Raman spectra for MWNTs produced with optimal synthesis conditions before and after purification. In both spectra, features at ∼1590 and 1355 cm -1 are consistent, respectively, with the in-plane carbon stretching mode (G-band) and a disorder-induced vibrational mode (D-band) associated with either MWNT finite size effects and structural defects or the presence of nanocrystalline graphite impurities. , The D-band/G-band intensity (D/G) ratio in the spectrum of the as-produced HWCVD nanotubes is ∼0.40, indicating that these MWNTs are more completely graphitized and/or contain fewer carbon impurities than other CVD-generated MWNTs where the D/G ratio is ≥1. ,,,,, However, a similar 14,16,17,20 and slightly smaller D/G ratio than that observed here has also been previously reported for unpurified CVD-generated MWNTs.…”

“…Chemical vapor deposition (CVD) techniques employing benzene pyrolosis, and the decomposition of ethylene and acetylene on supported metal catalysts were also demonstrated as viable large-scale production methods. Recently, MWNTs have been grown on supported metal particles or films via CVD, − plasma enhanced CVD, − hot wire chemical vapor deposition (HWCVD), , and plasma enhanced HWCVD methods. , Also, one HWCVD report employed evaporation of the Fe−Cr filament to supply a gas-phase catalyst, resulting in MWNTs with a high density of structural defects and significant carbon impurities . Although more research is necessary, this particular HWCVD method has potential for large-scale production since it is not substrate dependent.…”

Vertically Aligned Carbon Nanotube Membranes: Water Purification and Beyond

“…Microwave plasma-enhanced chemical vapor deposition (MPECVD) is a well-known technique that generates high electron density from the collision of electrons with gaseous ions and molecules. By using microwave frequencies, higher quality VACNTs ( > 95% purity) with reasonably high yields were produced as a result of the higher concentration of H radicals activated in the carbonaceous feed gas [42,43]. Bower et al suggested that the primary growth mechanism of VACNTs by MPECVD is caused by the electrical self-bias imposed on the surface of the substrate by the microwave plasma [44].…”

Carbon Nanotubes and Carbon Nanotubes/Metal Oxide Heterostructures: Synthesis, Characterization and Electrochemical Property

“…CVD techniques employing benzene pyrolosis [52] and the decomposition of ethylene [53] and acetylene [54] on supported metal catalysts have been demonstrated as viable large-scale production methods. MWCNTs have also been grown on supported metal particles or films via CVD [55][56][57][58][59], plasma-enhanced CVD [60][61][62][63][64][65][66][67][68][69][70], hot-wire chemical vapor deposition [71,72], and plasmawww.intechopen.com Carbon Nanotubes -Growth and Applications 8 enhanced HWCVD methods [73,74]. One HWCVD report employed evaporation of the Fe-Cr filament to supply a gas-phase catalyst, resulting in MWCNTs with a high density of structural defects and significant carbon impurities [75].…”