Glassy carbon

Glassy carbon is a class of non-graphitizing carbon which is widely used as an electrode material in electrochemistry, as well as for high temperature crucibles and as a component of some prosthetic devices. It was first produced by workers at the laboratories of The General Electric Company, UK, in the early 1960s, using cellulose as the starting material. A short time later, Japanese workers produced a similar material from phenolic resin. The preparation of glassy carbon involves subjecting the organic precursors to a series of heat treatments at temperatures up to 3000oC. Unlike many non-graphitizing carbons, they are impermeable to gases and are chemically extremely inert, especially those which have been prepared at very high temperatures. It has been demonstrated that the rates of oxidation of certain glassy carbons in oxygen, carbon dioxide or water vapour are lower than those of any other carbon. They are also highly resistant to attack by acids. Thus, while normal graphite is reduced to a powder by a mixture of concentrated sulphuric and nitric acids at room temperature, glassy carbon is unaffected by such treatment, even after several months.

Related Topics:
Carbon - Electrochemistry - The General Electric Company - Phenolic resin - Graphite

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The structure of glassy carbon has long been a subject of debate. Early structural models for assumed that both sp2 and sp3 -bonded atoms were present, but it is now known that glassy carbon is 100% sp2. A later model was based on the assumption that the molecular orientation of the polymeric precursor material is memorised to some extent after carbonization. Thus, it is assumed that the structure bears some resemblance to that of a polymer, in which the "fibrils" are very narrow curved and twisted ribbons of graphitic carbon. However, more recent research has suggested that glassy carbon has a fullerene-related structure.

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