World Library  
Flag as Inappropriate
Email this Article

Pyrolytic carbon

Article Id: WHEBN0001953299
Reproduction Date:

Title: Pyrolytic carbon  
Author: World Heritage Encyclopedia
Language: English
Subject: Diamagnetism, Pebble-bed reactor, Magnetic levitation, Artificial heart valve, Neutron moderator
Collection: Carbon Forms, Magnetic Levitation, Refractory Materials
Publisher: World Heritage Encyclopedia

Pyrolytic carbon

Sheets of pyrolytic carbon

Pyrolytic carbon is a material similar to graphite, but with some covalent bonding between its graphene sheets as a result of imperfections in its production.

Pyrolytic carbon is man-made and not found in nature.[1] Generally it is produced by heating a hydrocarbon nearly to its decomposition temperature, and permitting the graphite to crystallise (pyrolysis). One method is to heat synthetic fibers in a vacuum. Another method is to place seeds or a plate in the very hot gas to collect the graphite coating.


  • Physical properties 1
  • Magnetic levitation 2
  • Applications 3
    • Biomedical applications 3.1
  • Footnotes 4
  • External links 5
    • Biomedical applications 5.1

Physical properties

Pyrolytic carbon samples usually have a single cleavage plane, similar to mica, because the graphene sheets crystallize in a planar order, as opposed to graphite, which forms microscopic randomly oriented zones. Because of this, pyrolytic carbon exhibits several unusual anisotropic properties. It is more thermally conductive along the cleavage plane than graphite, making it one of the best planar thermal conductors available.

Pyrolitic graphite forms mosaic crystals with controlled mosaicities up to a few degrees.

It is also more diamagnetic (-400x10−6) against the cleavage plane, exhibiting the greatest diamagnetism (by weight) of any room-temperature diamagnet.

Magnetic levitation

Pyrolytic carbon levitating over permanent magnets

Few materials can be made to magnetically levitate stably above the magnetic field from a permanent magnet. Although magnetic repulsion is obviously and easily achieved between any two magnets, the shape of the field causes the upper magnet to push off sideways, rather than remaining supported, rendering stable levitation impossible for magnetic objects (see Earnshaw's Theorem). Strongly diamagnetic materials, however, can levitate above powerful magnets.

With the easy availability of rare earth permanent magnets in recent years, the strong diamagnetism of pyrolytic carbon makes it a convenient demonstration material for this effect.

A recent discovery in Japan shows that pyrolytic carbon can respond to laser light or sufficiently powerful natural sunlight by spinning or moving in the direction of the field gradient.[2] The carbon's magnetic susceptibility changes upon illumination, leading to an unbalanced magnetization of the material and thus a sideways force.


Biomedical applications

Because blood clots do not easily form on it, it is often advisable to line a blood-contacting prosthesis with this material in order to reduce the risk of thrombosis. For example, it finds use in artificial hearts and artificial heart valves. Blood vessel stents, by contrast, are often lined with a polymer that has heparin as a pendant group, relying on drug action to prevent clotting. This is at least partly because of pyrolytic carbon's brittleness and the large amount of permanent deformation which a stent undergoes during expansion.

Pyrolytic carbon is also in medical use to coat anatomically correct orthopaedic implants, a.k.a. replacement joints. In this application it is currently marketed under the name "PyroCarbon". These implants have been approved by the U.S. Food and Drug Administration for use in the hand for metacarpophalangeal (knuckle) replacements. They are produced by two companies: Tornier (BioProfile) and Ascension Orthopedics.[3] (On September 23, 2011, Integra LifeSciences acquired Ascension Orthopedics.) The FDA has also approved PyroCarbon interphalangeal joint replacements under the Humanitarian Device Exemption.[4]


  1. ^ Ratner, Buddy D. (2004). Pyrolytic carbon. In Biomaterials science: an introduction to materials in medicine. Academic Press. p. 171-180. ISBN 0-12-582463-7. Google Book Search. Retrieved 7 July 2011.
  2. ^ Phillip Broadwith (4 January 2013). "Laser guided maglev graphite air hockey". Chemistry World ( 
  3. ^ Cook, Stephen D.; Beckenbaugh, Robert D.; Redondo, Jacqueline; Popich, Laura S.; Klawitter, Jerome J.; Linscheid, Ronald L. (1999). "Long-Term Follow-up of Pyrolytic Carbon Metacarpophalangeal Implants". The Journal of Bone and Joint Surgery 81 (5): 635–48.  
  4. ^ "Ascension PIP: Summary of Safety and Probable Benefit HDE # H010005" (PDF). Food and Drug Administration. 22 March 2002. Retrieved 7 July 2011. 

External links

Biomedical applications

  • Ascension Orthopedics
  • Pyrolytic Carbon Manufacturing
  • Pyrolytic Carbon for Biomedical Applications
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.