Natural and High-Pressure Synthetic Diamond

Unlike graphite and carbon materials, diamond is very rare and, with opal and ruby, considered the most valuable mineral, known the world over as a gemstone of perfect clarity, brilliance, hardness, and permanence. 

Diamond is produced in nature at high pressure etnd temperature in volcanic shafts. The high-pressure synthesis essentially duplicates this natural process and both materials, the natural and the synthetic, have similar properties and are reviewed together in this chapter. 

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Natural and High-Pressure Synthetic Diamond 289 3.4 Shock-Wave Processing... 

NATURAL AND HIGH-PRESSURE SYNTHETIC DIAMOND PRODUCTION... 

CVD-diamond coatings are polycrystsdiine, as opposed to natural and high-pressure synthetic diamond which are normally single crystals. This polycrystalline characteristic has important bearing on the general properties of the coatings as shown in Sec. 4.0. 

The applications of natural and high-pressure synthetic diamond were reviewed in Ch. 12. Although these eipplications have a very large market, particularly in gemstones, they are limited because of the small size and... 

High-pressure synthetic diamond, because of its high purity and uniformity, has taken an increasing share of the industrial diamond market and has replaced natural diamond in many areas. 

Natural diamonds used for jewellery and for industrial purposes have been mined for centuries. The principal diamond mining centres are in Zaire, Russia, The Republic of South Africa, and Botswana. Synthetic diamonds are made by dissolving graphite in metals and crystallising diamonds at high pressure (12-15 GPa) and temperatures in the range 1500-2000 K [6] see section 3. More recently, polycrystalline diamond films have been made at low pressures by... 

Many ceramic applications are high value and small volume, so energy expenditure is high. Ferroelectric magnets, electronic substrates, electrooptics, abrasives such as silicon carbide and diamond, are examples. Diamond is found naturally, and made synthetically by the General Electric Company at high pressure and temperature. Synthetic diamonds for abrasives require less energy to make than the value in Table 4 nevertheless, the market is carefully divided between natural and synthetic diamonds. 

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