Thermodynamics Theoretically predicted phase diagram of carbon The alpha form can be converted to the beta form through mechanical treatment and the beta form reverts to the alpha form when it is heated above 1300 ☌. They differ in terms of the stacking of the graphene layers: stacking in alpha graphite is ABA, as opposed to ABC stacking in energetically less stable and less common beta graphite. The two forms of graphite are called alpha ( hexagonal) and beta ( rhombohedral). Įlectrical conductivity perpendicular to the layers is consequently about 1000 times lower. Bonding between layers is relatively weak van der Waals bonds and are often occupied by gases, which allows the graphene-like layers to be easily separated and to glide past each other. In each layer, the carbon atoms are arranged in a honeycomb lattice with a bond length of 0.142 nm, and the distance between planes is 0.335 nm. The individual layers are called graphene. Graphite consists of sheets of trigonal planar carbon. Graphite may be the second or third oldest mineral in the Universe. These minerals were formed in the ejecta when supernovae exploded or low to intermediate-sized stars expelled their outer envelopes late in their lives. They are one of about 12 known types of minerals that predate the Solar System and have also been detected in molecular clouds. Some microscopic grains have distinctive isotopic compositions, indicating that they were formed before the Solar System. Small graphitic crystals in meteoritic iron are called cliftonite. In meteorites, graphite occurs with troilite and silicate minerals. The principal export sources of mined graphite are in order of tonnage: China, Mexico, Canada, Brazil, and Madagascar. Minerals associated with graphite include quartz, calcite, micas and tourmaline. It also occurs in igneous rocks and in meteorites. Graphite occurs in metamorphic rocks as a result of the reduction of sedimentary carbon compounds during metamorphism. Synthetic graphite is a material consisting of graphitic carbon which has been obtained by graphitizing of non-graphitic carbon, by CVD from hydrocarbons at temperatures above 2500 K, by decomposition of thermally unstable carbides or by crystallizing from metal melts supersaturated with carbon. The name "graphite fiber" is sometimes used to refer to carbon fibers or carbon fiber-reinforced polymer.Highly ordered pyrolytic graphite refers to graphite with an angular spread between the graphite sheets of less than 1°.Lump graphite (or vein graphite) occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin.Amorphous graphite: very fine flake graphite is sometimes called amorphous.When broken the edges can be irregular or angular Crystalline small flakes of graphite (or flake graphite) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken.The principal types of natural graphite, each occurring in different types of ore deposits, are It is a good (but not excellent) conductor of both heat and electricity. Under high pressures and temperatures it converts to diamond. Synthetic and natural graphite are consumed on large scale (300 kton/year, in 1989) for uses in pencils, lubricants, and electrodes. Graphite occurs naturally and is the most stable form of carbon under standard conditions. It consists of stacked layers of graphene. Graphite ( / ˈ ɡ r æ f aɪ t/) is a crystalline form of the element carbon. ![]() Strongly anisotropic, conducts electricity, greasy feel, readily marks Soluble in molten nickel, warm chlorosulfuric acid Opaque, transparent only in extremely thin flakes Tabular, six-sided foliated masses, granular to compacted massesįlaky, otherwise rough when not on cleavage Iron-black to steel-gray deep blue in transmitted light
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