Graphitizing and non-graphitizing carbons: Difference between revisions

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{{Short description|Categories of carbon}}

'''Graphitizing''' and '''non-graphitizing''' carbons (alternatively graphitizable and non-graphitizable carbon) are the two categories of [[carbon]] produced by [[pyrolysis]] of organic materials. [[Rosalind Franklin]] first identified them in a 1951 paper in ''[[Proceedings of the Royal Society]]''.<ref>{{cite journal|author= R.E. Franklin |title= Crystallite growth in graphitizing and non-graphitizing carbons |journal= Proceedings of the Royal Society A|volume=209|pages=196–218 |year=1951 |issue= 1097 | authorlink = Rosalind Franklin| doi = 10.1098/rspa.1951.0197|bibcode= 1951RSPSA.209..196F |s2cid= 4126286 }}</ref> In this paper, she defined graphitizing carbons as those that can transform into crystalline graphite by being heated to {{cvt|3000&nbsp;°|C|K F}}, while non-graphitizing carbons do not transform into graphite at any temperature. [[Precursor (chemistry)|Precursors]] that produce graphitizing carbon include [[polyvinyl chloride]] (PVC) and petroleum coke. [[Polyvinylidene chloride]] (PVDC) and [[sucrose]] produce non-graphitizing carbon. Physical properties of the two classes of carbons are quite different. Graphitizing carbons are soft and non-porous, while non-graphitizing carbons are hard, low density materials. Non-graphitizing carbons are otherwise known as ''chars'', ''hard carbons'' or, more colloquially, [[charcoal]]. [[Glassy carbon]] is also an example of a non-graphitizing carbon material.

The precursors for graphitizing carbons pass through a fluid stage during pyrolysis ([[carbonization]]). This fluidity facilitates the molecular mobility of the aromatic molecules, resulting in intermolecular dehydrogenative polymerization reactions to create aromatic, lamellar (disc-like) molecules. These "associate" to create a new liquid crystal phase, the so-called mesophase. A fluid phase is the dominant requirement for production of graphitizable carbons.<ref name= Mesophase >H. Marsh and M.A. Diez (1994) " Mesophase of Graphitizable Carbons" In: Shibaev V.P., Lam L. (eds) Liquid Crystalline and Mesomorphic Polymers. Springer, New York, NY {{doi| 10.1007/978-1-4613-8333-8_7 }}</ref>