Nanocrystalline graphitic carbon

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 -... 

RS) of as-carbonized samples showed a strong double band in range of 1000-1600 cm 1 that is inherent to amorphous/nanocrystalline graphite-like carbon clusters. After carbonization the samples were oxidized at atmospheric pressure in flow of wet Ar(0.9 1/min) or dry Ar(0.9 l/min)/O2(0.3 1/min) mixture for 3 h at 650 °C, 800 °C and 950 °C. 

Healing of diamond as found in the case of nanocrystalline diamond can be explained by redeposition of carbon from the hydrothermal fluid, which also explains the increasing formation of graphitic carbon with increasing temperature observed in these experiments. It was reported that hydrothermal treatment in the presence of a catalyst at 900°C and 1 GPa enhanced the graphitization of amorphous carbon [41]. 

According to the characterizations by TEM and XRD, the sample prepared from a CH4/H2 plasma was composed of nanocrystalline diamond and disordered microcrystalline graphite. Then nondiamond carbon was effectively removed with an increase in [CO]. It is therefore concluded that the VDOS of the nanocrystalline diamond and DEC films extracted from the HREELS data is in qualitative agreement with the characterizations of TEM and XRD. Although the HREELS probes only the region near the surface, the agreement suggests that the surface dynamics do not differ dramatically from those of the bulk. 

Many methods have been reported for production of nanodiamonds (NDs) such as laser ablation, " plasma-assisted chemical vapor deposition," autoclave synthesis from supercritical fluids, ion irradiation of graphite, chlorination of carbides, electron irradiation of carbon onions, and ultrasound cavitation. Smaller NDs can be prepared by detonation processes that yield aggregates of NDs with sizes of 4-5 nm embedded in a detonation soot composed of other carbon allotropes and impurities. An explosive mixture having an overall negative oxygen balance provides a source of both carbon and energy for the conversion. Because of their small size (2-10 nm) detonation NDs have also been referred to as ultradispersed, nanocrystalline... 

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