Editing Graphite (section)

===Other properties===
[[File:Graphite-pV.svg|thumb|upright=1.15|Molar volume against pressure at room temperature]]
The [[Acoustics|acoustic]] and [[Heat|thermal]] properties of graphite are highly [[anisotropic]], since [[phonons]] propagate quickly along the tightly bound planes, but are slower to travel from one plane to another. Graphite's high thermal stability and electrical and thermal conductivity facilitate its widespread use as electrodes and refractories in high temperature material processing applications. However, in oxygen-containing atmospheres graphite readily oxidizes to form [[carbon dioxide]] at temperatures of 700&nbsp;°C and above.<ref>{{cite journal |last1=Hanaor |first1=Dorian |last2=Michelazzi |first2=Marco |last3=Chenu |first3=Jeremy |last4=Leonelli |first4=Cristina |last5=Sorrell |first5=Charles C. |title=The effects of firing conditions on the properties of electrophoretically deposited titanium dioxide films on graphite substrates |journal=Journal of the European Ceramic Society |date=December 2011 |volume=31 |issue=15 |pages=2877–2885 |doi=10.1016/j.jeurceramsoc.2011.07.007 |arxiv=1303.2757 }}</ref>

Graphite is an [[electrical conductor]], hence useful in such applications as [[arc lamp]] [[electrode]]s. It can conduct electricity due to the vast [[electron]] [[delocalization]] within the carbon layers (a phenomenon called [[aromaticity]]). These valence electrons are free to move, so are able to conduct electricity. However, the electricity is primarily conducted within the plane of the layers. The conductive properties of powdered graphite<ref>{{cite journal |last1=Deprez |first1=N. |last2=McLachlan |first2=D. S. |year=1988 |title=The analysis of the electrical conductivity of graphite conductivity of graphite powders during compaction |journal=[[Journal of Physics D: Applied Physics]] |volume=21 |issue=1 |pages=101–107 |doi=10.1088/0022-3727/21/1/015 |bibcode=1988JPhD...21..101D |s2cid=250886376 }}</ref> allow its use as pressure sensor in [[carbon microphone]]s.

Graphite and graphite powder are valued in industrial applications for their self-lubricating and dry [[lubricant|lubricating]] properties. However, the use of graphite is limited by its tendency to facilitate [[pitting corrosion]] in some [[stainless steel]],<ref>[http://steel.keytometals.com/Articles/Art160.htm Galvanic Corrosion] {{Webarchive |url=https://web.archive.org/web/20090310033053/http://steel.keytometals.com/Articles/Art160.htm |date=2009-03-10 }}. keytometals.com</ref><ref>{{cite web |url= http://metals.lincdigital.com.au/files/ASM_Tech_Notes/TN7-0506-Galvanic%20Corrosion.pdf |archive-url= https://web.archive.org/web/20090227143601/http://metals.lincdigital.com.au/files/ASM_Tech_Notes/TN7-0506-Galvanic%20Corrosion.pdf |archive-date= 2009-02-27 |title= ASM Tech Notes – TN7-0506 – Galvanic Corrosion |work= Atlas Specialty Metals}}</ref> and to promote [[galvanic corrosion]] between dissimilar metals (due to its electrical conductivity). It is also corrosive to aluminium in the presence of moisture. For this reason, the [[US Air Force]] banned its use as a lubricant in aluminium aircraft,<ref>Jones, Rick (USAF-Retired) [http://www.graflex.org/speed-graphic/lubricants.html Better Lubricants than Graphite]. graflex.org</ref> and discouraged its use in aluminium-containing automatic weapons.<ref>{{cite web |url = http://gojackarmy.blogspot.com/2005/09/weapons-lubricant-in-desert.html  |archive-url = https://web.archive.org/web/20071015045426/http://gojackarmy.blogspot.com/2005/09/weapons-lubricant-in-desert.html |archive-date = 2007-10-15 |date = September 16, 2005 |title = Weapons Lubricant in the Desert |access-date = 2009-06-06}}</ref> Even graphite [[pencil]] marks on aluminium parts may facilitate corrosion.<ref>{{cite web |url = http://7faq.com/owbase/ow.asp?GoodEngineeringPractice%2FCorrosion |title = Good Engineering Practice/Corrosion |publisher = Lotus Seven Club |date = 9 April 2003 |archive-url = https://web.archive.org/web/20090916035828/http://7faq.com/owbase/ow.asp?GoodEngineeringPractice%2FCorrosion |archive-date = 16 September 2009}}</ref> Another high-temperature lubricant, [[boron nitride|hexagonal boron nitride]], has the same molecular structure as graphite. It is sometimes called ''white graphite'', due to its similar properties.

When a large number of crystallographic defects bind its planes together, graphite loses its lubrication properties and becomes what is known as [[pyrolytic graphite]]. It is also highly anisotropic, and [[diamagnetic]], thus it will float in mid-air above a strong magnet. (If it is made in a fluidized bed at 1000–1300&nbsp;°C then it is isotropic turbostratic, and is used in blood-contacting devices like mechanical heart valves and is called [[pyrolytic carbon]], and is not diamagnetic. Pyrolytic graphite and pyrolytic carbon are often confused but are very different materials.<ref>{{cite book |last1=Marsh |first1=Harry |last2=Reinoso |first2=Francisco Rodríguez |title=Activated carbon |date=2007 |publisher=Elsevier |isbn=9780080455969 |pages=497–498 |edition=1st}}</ref>)

For a long time graphite has been considered to be hydrophobic. However, recent studies using highly ordered pyrolytic graphite have shown that freshly clean graphite is hydrophilic ([[contact angle]] of 70° approximately), and it becomes hydrophobic (contact angle of 95° approximately) due to airborne pollutants (hydrocarbons) present in the atmosphere.<ref name=":1">{{cite journal |last1=Martinez-Martin |first1=David |last2=Longuinhos |first2=Raphael |last3=Izquierdo |first3=Jesus G. |last4=Marele |first4=Antonela |last5=Alexandre |first5=Simone S. |last6=Jaafar |first6=Miriam |last7=Gómez-Rodríguez |first7=Jose M. |last8=Bañares |first8=Luis |last9=Soler |first9=Jose M. |last10=Gomez-Herrero |first10=Julio |title=Atmospheric contaminants on graphitic surfaces |journal=Carbon |date=September 2013 |volume=61 |pages=33–39 |doi=10.1016/j.carbon.2013.04.056 |bibcode=2013Carbo..61...33M }}</ref><ref>{{cite journal |last1=Li |first1=Zhiting |last2=Wang |first2=Yongjin |last3=Kozbial |first3=Andrew |last4=Shenoy |first4=Ganesh |last5=Zhou |first5=Feng |last6=McGinley |first6=Rebecca |last7=Ireland |first7=Patrick |last8=Morganstein |first8=Brittni |last9=Kunkel |first9=Alyssa |last10=Surwade |first10=Sumedh P. |last11=Li |first11=Lei |last12=Liu |first12=Haitao |title=Effect of airborne contaminants on the wettability of supported graphene and graphite |journal=Nature Materials |date=October 2013 |volume=12 |issue=10 |pages=925–931 |doi=10.1038/nmat3709 |pmid=23872731 |bibcode=2013NatMa..12..925L }}</ref> Those contaminants also alter the electric equipotential surface of graphite by creating domains with potential differences of up to 200 mV as measured with [[Kelvin probe force microscope|kelvin probe force microscopy]].<ref name=":1" /> Such contaminants can be desorbed by increasing the temperature of graphite to approximately 50&nbsp;°C or higher.<ref name=":1" />

Natural and crystalline graphites are not often used in pure form as structural materials, due to their shear-planes, brittleness, and inconsistent mechanical properties.