Carbon nanotube catalytically grown

Bando and co-workers271 have prepared BN nanolubes by the reaction of MgO, FeO and B in the presence of NH, at 1400 °C. Reaction of boric acid or B20, with N2 or NH, at high temperatures in the presence of carbon or catalytic metal particles has been employed in the preparation of BN nanotubes.2 2 Boron nitride nanotubes can be grown directly on substrates at 873 K by a plasma-enhanced laser-deposition technique.172 Recently, GaN nanotube brushes have been prepared using amorphous carbon nanotubes templates obtained using AAO membranes.274... 

Figure 11.1. Crystallinity of PVA-nanotubes composites versus carbon nanotube volume fraction, for various types of nanotubes (DWNT= double-walled nanotubes, OHMWNT= hydroxyled MWNTs, NMWNT= catalytic Nanocyl S.A. MWNTs, OMWNT=catalytic MWNTs from Orleans, AMWNT=Arc grown MWNTs produced in the author s laboratory. Reprinted with permission from reference (23)).

Various carbon nanotubes including aligned arrays have been catalytically grown on metal substrates and alumina-supported catalyst with carbon monoxide as a carbon source at 500 °C under assistance of non-equilibrium plasma generated at atmospheric pressure. 

An article by lijima showed that carbon nanotubes are formed during arc-discharge synthesis of C, and other fullerenes also triggered an outburst of the interest in carbon nanofibers and nanotubes. These nanotubes may be even single walled whereas, low-temperature, catalytically grown... 

Figure 9.4. Growth modes of catalytically formed carbon nanotubes. Fe, Co, and Ni are the catalysts and hydrocarbons, and CO are the carbon precursors. SWNTs are grown on particles < 40-50 A, whereas MWNTs are grown on larger particles. The outside tube diameter is the...

The purification of nanotubes has been studied. It is relatively easier to purify the catalytically grown nanotubes than that from graphite vaporization. The metal catalysts and the inorganic support can be removed with HCl and HF solution. The transition metals can be dissolved in HNO3 solution. The amorphous carbon can be removed with HNO3 solution, and also by permanganate solution. Oxidation with air at mild temperatures is also effective in removing the amorphous carbon. 

Dense, vertically aligned double-walled carbon nanotubes (DWNTs) were grown on the surface of a sihcon tip by catalytic chemical vapor deposition (Step... 

Lukic, B., J. W. Seo, R. R. Bacsa, S. Delpeux, F. Beguin, G. Bister, A. Fonseca et al. 2005. Catalytically grown carbon nanotubes of small diameter have a high Young s modulus. Nano Lett 5(10) 2074-7. 

Figure 5, Transmission electron micrograph of catalytically grown multiple-wall carbon nanotubes with less impurities, but with a higher defect density and strongly entangled.

Figure 6. Scanning electron micrograph of catalytically grown multiple-wall carbon nanotubes. The cotton-like appearance is due to the manufacturing CVD process, where CNT grow onto a catalyst-covered substrate plate and, in addition to the strong entanglement, a generally parallel orientation of the tubes can be achieved. ...

Y. Zhang, Y. Li, W. Kim, D. Wang and H. Dai. Imaging as-grown single-walled carbon nanotubes originated from isolated catalytic nanoparticles. Appl. Phys. Mater. Sci. Pwcess. 74, 2002, 325-328. 

It occurs catalytically on the surface of Fe nanoparticles grown from Fe(CO)5. Also, the conventional synthesis of nanotubes by catalytic CVD from acetylene or methane can be formally considered as redox reaction. Nevertheless, the electrochemical model of carbonization (Sections 4.1.1 and 4.1.2) is hardly applicable for CVD and HiPco, since the nanotubes grow on the catalyst particle by apposition from the gas phase, and not from the barrier film (Figure 4.1). The yield and quality of electrochemically made nanotubes are usually not competitive to those of catalytic processes in carbon arc, laser ablation, CVD and HiPco. However, this methodology demonstrated that nanotubes (and also fullerenes and onions (Section 4.3)) can be prepared by soft chemistry" at room or sub-room temperatures [4,5,101]. Secondly, some electrochemical syntheses of nanotubes do not require a catalyst [4,5,95-98,100,101]. This might be attractive if high-purity, metal-free tubes are required. 

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