Graphite regime

Chlorination of Fe3C at temperatures of 400°C and above results in the formation of carbon and solid or gaseous iron chlorides. Three temperature regimes have been defined. Amorphous carbon is formed at temperatures of 400 500°C. Flakes and ribbons of nanocrystalline graphite form at 600 -... 

In the presence of liquid HF, graphite is found to be reversibly intercalated by fluorine. First-stage materials have the composition Ci2(HF)F (l < n < 5), and the ultimate salt is the second-stage bifluoride C,2HF2. Extensive studies on these intercalates by Mallouk et al, (1985) have shown conductivities ranging from the metallic to the insulator regime. 

In Section 2 we showed that the properties of amorphous carbon vary over a wide range. Graphite-like thin films are similar to other carbonaceous materials (glassy carbon, and the like) in their electrode behavior. Redox reactions proceed in a quasi-irreversible regime on these films. In particular, the cathodic reduction of nitrate previously studied on crystalline diamond electrodes (see Section 6.4.2) was performed with amorphous carbon films prepared by UHV laser deposition and comprising both sp2- and sp3-carbon [152], Reduction current density as high as 2 mA cur 2 was reached in neutral or alkaline solutions. The use of such electrodes in microgravimetry is discussed [153]. 

The carbon nanotubes up to 10-15 nm in diameter have been produced by the graphite evaporation in water. The resulting structures produced in water do not contain catalysts. This simplifies the process of their purification and reduces the net cost (Fig. 5). Varying the regime of synthesis one can produce both tubular and ribbon structures. 

Different nano-objects can be synthesized under changes of the regime of synthesis and application of catalysts. In the course of synthesis the foamy particles (Fig. 8) are formed during the evaporation of highly dispersed graphite dust. Then-conglomerates range up to 1-5 pm. 

On the Fig. 1 the graphs of the obtained dependencies are shown. One can see that soot, fullerenes and re-crystallized graphite are formed in all cases, and their yields depend on both current value and current type. Re-crystallized graphite is a byproduct of the fullerene synthesis which decreases the fullerene productivity and efficiency. It was established that the optimal regime of fullerene synthesis occurs at 44 kHz AC and 200 A. Under these conditions, a fullerene production rate of 16mg/min at a fullerene yield of 9% was obtained while the yield of re-crystallized graphite (7%) was minimal. 

We have performed X-ray diffraction investigation of the ledges obtained in various regimes of the arc. The X-ray peaks of hexagonal graphite have been only observed in all diffractions. It follows that the spherical particles observed in Fig. 1 mainly consist of graphite. 

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