What is Glassy carbon?

Glassy carbon, also called vitreous carbon, is a non-graphitizing carbon which combines glassy and ceramic properties with those of graphite. The most important properties are high temperature resistance, hardness (7 Mohs), low density, low electrical resistance, low friction, low thermal resistance, extreme resistance to chemical attack and impermeability to gases and liquids. Glassy carbon is widely used as an electrode material in electrochemistry, as well as for high temperature crucibles and as a component of some prosthetic devices, and can be fabricated as different shapes, sizes and sections.
The structure of glassy carbon has long been a subject of debate. Early structural models assumed that both sp2- and sp3-bonded atoms were present, but it is now known that glassy carbon is 100% sp2. However, more recent research has suggested that glassy carbon has a fullerene-related structure.
Note that Glassy carbon should not be confused with amorphous carbon. This from IUPAC: 'Glass-like carbon cannot be described as amorphous carbon because it consists of two-dimensional structural elements and does not exhibit ‘dangling’ bonds.'
It exhibits a conchoidal fracture.
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