Floating catalyst method

Fig. 3. Vapor-grown carbon fibers obtained by substrate method w ith diameter ca. 10 /xrn (a) and those by floating catalyst method (b) (inserted, low magnification).

The preparation is achieved using the floating catalyst method. The precursor of the catalyst (in this case ferrocene or Fe(CO)5 with H2S as cocarbon source (natural gas mainly consisting of methane here). The resulting carbon nanofibers then may be graphitized at about 3(X)0 C. 

A well-known floating catalyst method developed at Rice Uruversity is the so-called HiPCO (high-pressure CO) method. In this case, the growth of SWNTs is realized by disproportionation of CO catalyzed by Fe clusters generated in situ by decomposition of Fe(CO)s in continuously flowing CO at high pressure and elevated temperature (79). A mixture of the Fe precursor and CO is injected into the reactor... 

One of the CVD methods that has been developed is the synthesis of vertically aligned nanofiber bundles for specific applications. The synthesis of VACNF arrays were all carried out in horizontal reactors [37]. All the reported products by vertical floating catalyst method were randomly arranged CNFs. There are few reports on aligned CNF bundles synthesized by floating catalyst procedure in vertical reactors [38]. 

Ci L, Wei J, Wei B, Liang J, Xu C, Wu D. Carbon nanofibers and single-waUed carbon nanotubes prepared by the floating catalyst method. Carhon 2001 39 329-35. 

Ci, L. et al. (2001). Carbon Nanofibers and Single-walled Carbon Nanotubes Prepared by the Floating Catalyst Method. Carbon, 39, 329-335. 

Chenga, J. et al. (2004). Long Bundles of Aligned Carbon Nanofibers Obtained by Vertical Floating Catalyst Method. 241-245. 

SWCNTs, MWCNTs, and CNFs have been synthesized by a floating catalyst method with different tube diameters achieved by controlling the FcH/benzene mole ratio. It is evident that small FcH/C ratios yield SWCNTs, and higher ratios CNFs [35]. SWCNTs were synthesized by the CO disproportionation reaction on Fe catalyst particles formed by FcH vapor decomposition in a laminar flow aerosol (floating catalyst) reactor [31], A mixture of CH4/H2/Ar with added Fe(CO)j was reacted in the presence of a microwave plasma torch for the synthesis of MWCNTs covered by iron oxide nanoparticles (NPs) [33]. 

A floating catalyst method, which has been used for the large-scale production of carbon nanotubes, was applied in the synthesis of double-walled BNNTs by Kim et al." Borazine was chosen as the precursor for BN formation because of its chemical composition (1 1 B/N ratio) and high volatility. In this catalytic chemical vapor deposition (CCVD) technique, a mixture of ammonia and nitrogen gas (in a flow ratio of 100 3 sscm), borazine vapor along with a nickelocene catalyst flowed... 

Fan Y-Y, Kaufmann A, Mukasyan A, Varma A (2006) Single- and multi-wall carbon nanotubes produced using the floating catalyst method synthesis, purification and hydrogen up-take. 

Floating Catalyst Method for Selective Growth of Carbon Nanotube Layers Using Ferrocene as a Catalyst... 

Figure 8.1. Experimental setup (schematic) for CVD of carbon nanotubes onto substrates using the floating catalyst method. The inert gas flow provides oxygen-free atmosphere, and the carbon source/catalyst solution is evaporated from a separate bubbler.

Directed Growth of Carbon Nanotubes by Floating Catalyst Method on 3-D Substrates... 

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