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  • How the graphite into diamond
  • [2013-04-18]
  • The chemical composition of diamond and graphite are carbon (C), the scientists call "polymorph like variant" also known as "allotrope". From this call can know that they have the same "quality", "form" or "sex" is different, and there is a world of difference, diamond is the hardest substance, graphite is one of the softest material. We all know that pencil lead is made of graphite powder and clay ratio, graphite powder and more soft, with a "B" means clay mixed with more hard, with the "H". Mineralogist Mohs hardness relative hardness, diamond, graphite Mohs hardness of only 1. Their hardness big difference lies in their internal structure is very different.
    The carbon atoms of the graphite inside the layered arrangement, one of the carbon atoms around only three carbon atoms connected thereto, carbon and carbon to form a hexagonal ring, a layer of an infinite number of hexagons. Between the layers, the contact force is very weak, and the three carbon atoms in the layer is very firmly contact force, it is easy to slide the interlayer, which is very soft graphite can write.
    The intra-diamond carbon atoms Movement "skeleton"-shaped three-dimensional spatial arrangement, one carbon atom is surrounded by four carbon atoms connected in three-dimensional space is formed of a skeleton-like, such a structure contact force evenly in all directions, the coupling force is strong, Therefore, the diamond has a high hardness characteristics.
    Graphite and diamond hardness vary so much, but people still want to get the diamond can be synthetic methods, because the graphite (carbon) in the nature reserves is very rich. Make graphite carbon into diamond arranged as carbon, is not so easy. The late eighteenth century, people began to look for the biosynthetic pathway, until the middle of this century. 1938 scholars Rossini thermodynamic calculation, laid the theoretical foundation of the synthetic diamond is calculated to make the graphite into diamond, at least 15,000 atm, 1500 degrees Celsius under high temperature conditions, built in the 1950s and 1960s Instrument able to achieve the above conditions. Graphite in the 5-6 million atmospheres ((5-6) × 103MPa) and a temperature of 1000 to 2000 degrees Celsius, and then make the catalyst metal of iron, cobalt, nickel, etc., enables the graphite into diamond.
    There are more than a dozen countries in the world (including China) are synthesized diamond. However, this diamond as very fine particles, the main purpose is to do abrasives, cutting and geology, petroleum drilling with drill. This world diamond consumption, 80% of synthetic diamond is used in industry, its output is also far more than natural diamond production.

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