'''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 °|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 typically hard, low density materials. Non-graphitizing carbons includeare otherwise known as ''chars'', porous''hard carbons'' or, more colloquially, [[charcoal]] and certain coals. [[Glassy carbon]] is also an example of a non-graphitizing carbon material.
The precursors for graphitizing carbons pass through a fluid or liquid stage during their pyrolysis (followed by [[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>
Non-graphitizing carbons generally do not pass through a liquidfluid stage during carbonization. However, glassy (glass-like) carbon is an exception to this, which features an atomically flat surface owing to a rubbery or semi-solid phase that occurs during its carbonization. Since the time of Rosalind Franklin, researchers have put forward a number of models for their microstructurestructure. Oberlin and colleagues emphasised the role of basic structural units (BSU), made of planar aromatic structures consisting of less than 10–20 rings, with four layers or fewer. Cross-linking between the BSUs in non-graphitizing carbons prevents [[graphitization]].<ref>{{cite journal|author= A. Oberlin |title= Carbonization and graphitization |journal= Carbon|volume=22|pages=521–541 |year=1984|issue= 6 |doi = 10.1016/0008-6223(84)90086-1}}</ref> More recently, some have put forward models that incorporate pentagons and other non-six-membered carbon rings.<ref>{{cite journal|author= P.J.F. Harris |title= Fullerene-like models for microporous carbon |journal= Journal of Materials Science |volume=48|pages=565–577|year=2013 |issue= 2 |doi= 10.1007/s10853-012-6788-1|bibcode= 2013JMatS..48..565H |s2cid= 14903411 |url= http://centaur.reading.ac.uk/28956/1/Revised%20JMS%2031%20July%20For%20Centaur.pdf }}</ref> In 2022, the presence of Buckminsterfullerene was confirmed in non-graphitizing carbon, which exist along with curved and flat graphene sheets in the material. <ref>{{cite journal|author= S. Sharma, S. Zorzi, V. Cristiglio, R. Schweins, C. Mondelli |title= Quantification of Buckminsterfullerene (C60) in non-graphitizing carbon and a microstructural comparison of graphitizing and non-graphitizing carbon via Small Angle Neutron Scattering |journal= Carbon|volume=189|pages=362-368 |year=2022|issue= |doi = 10.1016/j.carbon.2021.12.062}}</ref> The research on graphitizing and non-graphitizing carbon, their microstructure and formation mechanism is an active area of research.
