Amorphization of graphite

One useful classification of graphite depends on the mode of formation that leads to three physically distinct common varieties dake, lump, and amorphous. The term dake is self-explanatory dake forms occur disseminated in rock. Lump graphite occurs in fissure-filled veins in pegmatite dikes, also associated with chip and the rarer needle forms. Amorphous graphite occurs in beds that were once coal, but fine-grained, easily ground vein graphite is also classified as amorphous. 

In addition to diamond and amorphous films, nanostructural forms of carbon may also be formed from the vapour phase. Here, stabilisation is achieved by the formation of closed shell structures that obviate the need for surface heteroatoms to stabilise danghng bonds, as is the case for bulk crystals of diamond and graphite. The now-classical example of closed-shell stabilisation of carbon nanostructures is the formation of C o molecules and other Fullerenes by electric arc evaporation of graphite [38] (Section 2.4). 

Fig. 7. TEM picture of iron nanocrystals collected from the chamber soot nanocrystals are embedded in amorphous carbon globules. On the surface of some core crystals, a few fringes with 0.34-0.35 nm spacing suggesting the presence of graphitic layers are observed, as indicated by arrows.

These batteries incorporate a polyacenic semiconductor (PAS) for the active material of the positive electrode, lithium for that of the negative electrode and an organic solvent for the electrolyte. PAS is essentially amorphous with a rather loose structure of molecular-size order with an interlayer distance of 4.0 A, which is larger than the 3.35 A of graphite [56, 57]. 

The crystal structure of graphite and amorphous carbon is illustrated by the schematic representations given in Fig. 1. 

There are more than a million known carbon compounds, of which thousands are vital to life processes. The carbon atom s unique and characteristic ability to form long stable chains makes carbon-based life possible. Elemental carbon is found free in nature in three allotropic forms amorphous carbon, graphite, and diamond. Graphite is a very soft material, whereas diamond is well known for its hardness. Curiosities in nature, the amounts of elemental carbon on Earth are insignificant in a treatment of the... 

Fig. 5 shows typical Raman spectrum for SWNTs, the Raman spectra of SWNTs have fingerprint features, which is quite different fi om those of graphite, MWNTk and amorphous carbon. 

Also presented were data on carbon-coating of graphite powder using a propylene gas thermal decomposition processes. High weight percent amorphous carbon-coatings are possible with this method, and the process appears uniquely suited to materials that are reductively stable to 700°C. The coated materials work better in the 30% PC electrolyte solutions, thus showing better resistance to solvent co-intercalation problems versus uncoated types. 

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