What are the uses of graphite

graphite

Along with diamond and the fullerenes, graphite is one of the modifications of carbon. Its formula is C.

View: Start the Jsmol visualization by clicking the link under the graphite crystal. Look at the crystal from the front to see the layered structure, and look at it from above, across the layers, to see the two-dimensional network of hexagons of carbon atoms.

Structure and properties

Graphite has a layer structure. In one layer, each carbon atom is bonded to 3 other carbon atoms, so that a two-dimensional network of hexagons of carbon atoms results. For these (covalent) bonds, each carbon atom gives off 3 of its 4 valence electrons. The “fourth” valence electrons build up a delocalized (aromatic) pi-electron system that extends over the entire layer. These electrons can move freely within the layer, so that graphite is electrically conductive parallel to the carbon layers.

Each carbon atom in one layer is linked to a carbon atom in the adjacent layer. At 335 pm, these bonds are more than twice as long as the bonds within a layer (142 pm). This makes them very weak and graphite can easily be split parallel to the layers.

Occurrence - extraction - use

natural graphite: the most important deposits are in China, Korea and India. It is mined there in large quantities (approx. 600,000 tons per year) both in opencast mines and underground. Graphite is not only used for pencil leads. Wherever oil cannot be used (e.g. because it gums), graphite is the right lubricant. Other applications are brake linings (here it is used instead of asbestos) and refractory crucibles.

Artificial graphite is obtained by pyrolysis of coal and petroleum. Several million tons per year are mainly used as electrodes.

Soot, coke, and charcoal have a structure similar to graphite. The layers, however, are no longer ordered, but shifted or twisted against each other at random.

Conversions

At room temperature and normal pressure, graphite is the thermodynamically stable modification of carbon.

At very high pressure (over 50,000 bar) and high temperatures (around 2000 °), graphite quickly transforms into diamond, which is thermodynamically more stable under these conditions.

Physical Properties

  • Sublimation point: 3825 ° C
  • Density at 20 ° C: 2.26 g / cm3
  • Mohs hardness: 0.5
  • CAS no. : 7440-44-0

more about the properties of graphite

more information about graphite

 

 

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