Chemical vapor deposition CNTs synthesis

P. Coquay, E. Flahaut, E. de Grave, A. Peigney, R.E. Vandenberghe, and C. Laurent, Fe/Co alloys for the catalytic chemical vapor deposition synthesis of single- and double-walled carbon nanotubes (CNTs). 2. The CNT-Fe/Co-MgAl204 system. J. Phys. Chem. B 109, 17825-17830 (2005). 

For large scale production of carbon nanotubes and nanofibers chemical vapor deposition (CVD) method is most effective. Acetylene, ethylene, propylene, methane, natural gas (consisting predominantly of propane), carbon monoxide were used as a source of carbon [ 1 -8] (in view of large number of publications on CNT synthesis these references are selected arbitrary). Ethylene and possibly propylene are most convenient carbon sources for mass synthesis of high quality multiwall CNT (MWNT). 

CNTs can be obtained by electric arc discharge, laser ablation, high-pressure carbon monoxide, and catalyzed chemical vapor deposition. The multiple synthesis methods for CNTs are outside the scope of this chapter and had been extensively reviewed elsewhere [26-28]. The first three methods produce a large amount of by-products such as graphitic debris, metallic NPs, and fullerenes. On the contrary, CNTs obtained by chemical vapor deposition are highly crystalline and have low defect densities, although a minimal amount of amorphous content and NPs is present [27]. 

The pyrolysis or chemical vapor deposition of a metal precursor, a volatile complex such as FeCp2, CoCp2, or NiCp2, and a carbon source, such as acetylene, toluene, dichlorobenzene, or Cgo, also permits the simultaneous synthesis of CNTs and confined metal nanowires. Encapsulated nanowires of Fe [56,178-181], FeCo [69], and FeNi [182] within CNTs were synthesized using elevated temperatures. When [Co(CO)3NO] was used both as catalyst and the source for CNT growth, the nanowires and the filling yields were poor [183]. 

Synthesis of CNT over oxides supports by Catalytic Chemical Vapor Deposition (CCVD) is one of the most important techniques for mass production of non-aligned CNT. It could be useful for the production of composite materials, field emission sources, fuel cells, supercapacitors among others technological applications. The CCVD method consists on the decomposition of a gas or a liquid precursor, which supplies carbon to the surface of the catalytic particles (e.g. Fe) in a tube furnace at temperatures around 900 °C. This technique is scalable for mass production at lower temperatures and could be adapted for continuous production. 

Several methods have been developed for synthesizing the M-N4 macrocycle modified CNTs. The method most widely employed is the impregnation method [129, 134-142, 144], in which the Me-N4 macrocyclic complexes are first impregnated into CNTs in a solution and subsequently the M-N4 macrocycle modified CNT composites are obtained by evaporation of solvent. In some smdies, the acquired composites are further heat-treated in inert gas atmosphere [138, 141, 144]. The other synthesis methods to produce the M-N4 macrocycle modified CNTs include electrochemical deposition [128, 133] direct deposition [131, 132] and chemical vapor deposition [130]. 

Generally, the synthesis methods of CNTs are arc discharge, laser ablation and chemical vapor deposition (CVD). While first two methods use high-energy input to release the carbon atoms from carbon-containing precursor molecules, CVD relies on caibon atomization via catalytic decomposition of carbon precursors on... 

In Part Two, Chapter 4 describes a general fabrication-characterization route of electrospinning PLA poly(s-caprolactone) (PCL)/HNT composite fibers. The effects of HNTs with or without the modifier 3-aminopropyltriethoxysilane on fiber diameter, morphological structure, thermal properties, crystalline stmctures, and degree of crys-talhnity, as well as the intermolecular interaction of electrospun nanocomposite fibers, are thoroughly studied to provide the appropriate guidance to the controlled drug release associated with fibrous structures. Chapter 5 deals with the synthesis and characterization of CNT hybrid fillers via chemical vapor deposition (CVD) technique for polymer nanocomposites. Optimized synthesis parameters are presented and comparative studies are also conducted between chemical hybrid-filled and physical hybrid-fiUed polymer nanocomposites in terms of their typical applications. 

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