Chemical vapor deposition nanofibers

The multiwalled nanotubes as well as the herringbone type carbon nanofibers were synthesized in-house in a quartz glass fluidized bed reactor via chemical vapor deposition (CVD). The method is described in detail elsewhere.19 The platelet nanofibers, in contrast, were purchased from the company FutureCarbon GmbH (Bayreuth, Germany). 

Che, G., Lakshmi, B.B., Martin, C.R., and Fisher, E.R. Chemical vapor deposition based synthesis of carbon nanotubes and nanofibers using a template method. Chem. Mater. 10, 1998 260-267. 

Keywords Carbon nanotubes, Carbon nanofibers, Chemical vapor deposition, Catalyst, Activation. 

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). 

Che G, Lakshmi B, Maifin C, Fisher E, Ruoff R (1998) Chemical vapor deposition based syntliesis of carbon nanotubes and nanofibers usmg a template metliod. Chem Mater 10 260—267. 

Chemical vapor deposition on carbon nanoflbers/tubes was described by Liang et al. [84]. Oxidized carbon nanoflbers were loaded in a fixed-bed reactor, and [Pd(allyl)Cp] was sublimed onto the fibers at 353 K. After reduction the final catalyst was obtained. The loading of Pd depended on the number of functional groups introduced by an HNO3 treatment. Unfunctionalized carbon nanofibers did not show any Pd uptake. Pt loadings of 2 to 4 wt% were typically obtained with Pd particle sizes of 2 to 4 nm. 

Figure 14.2 Some representative sp carbon materials (a) graphite (b) Ceo (c) single-walled carbon nano tubes (d) multi walled carbon nanotube (e) carbon nanofibers grown by plasma-enhanced chemical vapor deposition.

The catalytic decomposition of carbon-contaming compounds is an extensively investigated method, also known as catalytic chemical vapor deposition (CCVD). One of the advantages of this method is the potential for large-scale production at a lower energy consumption and overall cost than with other methods. The CCVD method is essentially the same as that used for a long time in the synthesis of other filamentous forms of carbon, such as nanofibers or fibrils. The CCVD method involves the catalytic decomposition of hydrocarbons or carbon monoxide on transition metal particles. The major difference with those processes that produce nanofibers is in the structure of the catalyst. To produce SWNT, the size of the metal cluster needs to be very small. Therefore, the success of a CCVD method lies in the design of the catalyst. 

The catalysts can be prepared by coelectrospinning of poly(amido amine) dendrimers and poly(ethylene oxide). These nanofibers can be coated with poly(/ -xylylene) by chemical vapor deposition. 

Carbon nanofibers [42] Thermal chemical vapor deposition... 

Carbon nanofibers or vapor-grown carbon nanofibers are sp hybridized one-dimensional carbon nanostructures. Three types of carbon nanofiber structures classified based on the angle of graphene sheets are stacked, cup-stacked, and nanotubular [10]. The diameter of carbon nanofibers lies in between carbon nanotubes (100 nm) and carbon fibers (1000 nm). The synthesis procedures used for carbon nanofibers include chemical vapor deposition (CVD). 

Matthews K, Gruden BA, Chen B, Meyyappan M, Delzeit L. Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers. J Nanosci Nanotechnol 2002 2 475-80. 

Verplanck et al. [62] made superhydrophobic silicon (Si) nanofiber surfaces of vertically aligned posts, shown in Fig. 10a, using a process based on chemical vapor deposition of silicon catalyzed by the metal particles. First a thin (4 nm) layer... 

As we discuss there are various methods to produce carbon nanofibers or carbon nanotubes, for example, vapor growth [89], arc dischaige, laser ablation and chemical vapor deposition [28, 89]. However, these are very expensive processes owing to the low product yield and expensive equipment. Preparation carbon nanofiber by electrospinning of proper precursors is preferred because of its lower cost and more output [90]. 

Figure 4.11.25 Energy-dispersive X-ray image of herringbone-carbon nanofibers synthesized by catalytic chemical vapor deposition in a fluidized bed reactor (Department of Chemical Engineering, University of Bayreuth) from an ethylene-nitrogen mixture ( ung, 2005).

---