STRUCTURE AND PROPERTIES OF VITREOUS CARBON

This random structure, characteristic of vitreous carbon, is believed to have the form of an extensive and stable network of graphitic ribbons, shown in the simplified schematic of Fig. 6.5.( i These ribbon-like tangled aromatic molecules are cross-linked by carbon-carbon covalent bonds with varying bond energies. Some of these bonds may be highly strained.l l 

It has been suggested that the structure of vitreous carbon includes, in addition to the graphitic sp (trigonal) bonds, some sp (tetragonaQ bonds which are characteristic of diamond bonding. This would possibly contribute to the isotropy, the high strength, and the hardness of the material (see Ch. 2, Sec. 3.0).i ii The presence of the diamond structure in a similar material, diamond-like carbon, is well established (see Ch. 14). 

These two factors, ribbon network and sp bonds, would prevent further ordering of the structure, regardless of the graphitization temperature. 

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