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A synthetic diamond (also known as an artificial diamond, cultured diamond, or cultivated diamond) is diamond produced in an artificial process, as opposed to natural diamonds, which are created by geological processes. Synthetic diamond is also widely known as HPHT diamond or CVD diamond after the two common production methods (referring to the high-pressure high-temperature and chemical vapor deposition crystal formation methods, respectively). While the term ''synthetic'' is associated by consumers with imitation products, artificial diamonds are made of the same material (pure carbon, crystallized in isotropic 3D form). 〔(16 C.F.R. Part 23: Guides For The Jewelry, Precious Metals, and Pewter Industries: Federal Trade Commission Letter Declining To Amend The Guides With Respect To Use Of The Term "Cultured" ), U.S. Federal Trade Commission, July 21, 2008.〕 In the U.S., the Federal Trade Commission has indicated that the alternative terms ''laboratory-grown'', ''laboratory-created'', and ''()-created'' "would more clearly communicate the nature of the stone". Numerous claims of diamond synthesis were documented between 1879 and 1928; most of those attempts were carefully analyzed but none were confirmed. In the 1940s, systematic research began in the United States, Sweden and the Soviet Union to grow diamonds using CVD and HPHT processes. The first reproducible synthesis was reported around 1953. Those two processes still dominate the production of synthetic diamond. A third method, known as detonation synthesis, entered the diamond market in the late 1990s. In this process, nanometer-sized diamond grains are created in a detonation of carbon-containing explosives. A fourth method, treating graphite with high-power ultrasound, has been demonstrated in the laboratory, but currently has no commercial application. The properties of synthetic diamond depend on the details of the manufacturing processes; however, some synthetic diamonds (whether formed by HPHT or CVD) have properties such as hardness, thermal conductivity and electron mobility that are superior to those of most naturally formed diamonds. Synthetic diamond is widely used in abrasives, in cutting and polishing tools and in heat sinks. Electronic applications of synthetic diamond are being developed, including high-power switches at power stations, high-frequency field-effect transistors and light-emitting diodes. Synthetic diamond detectors of ultraviolet (UV) light or high-energy particles are used at high-energy research facilities and are available commercially. Because of its unique combination of thermal and chemical stability, low thermal expansion and high optical transparency in a wide spectral range, synthetic diamond is becoming the most popular material for optical windows in high-power CO2 lasers and gyrotrons. It is estimated that 98% of industrial grade diamond demand is supplied with synthetic diamonds. Both CVD and HPHT diamonds can be cut into gems and various colors can be produced: clear white, yellow, brown, blue, green and orange. The appearance of synthetic gems on the market created major concerns in the diamond trading business, as a result of which special spectroscopic devices and techniques have been developed to distinguish synthetic and natural diamonds. ==History== After the 1797 discovery that diamond was pure carbon,〔 See also: * Lavoisier (1772) ("Premier mémoire sur la destruction du diamant par le feu" ) (First memoir on the destruction of diamond by fire), ''Histoire de l'Académie royale des sciences. Avec les Mémoires de Mathématique & de Physique'' (History of the Royal Academy of Sciences. With the Memoirs of Mathematics and Physics), part 2, 564–591. * Lavoisier (1772) ("Second mémoire sur la destruction du diamant par le feu" ) (Second memoir on the destruction of diamond by fire), ''Histoire de l'Académie royale des sciences. Avec les Mémoires de Mathématique & de Physique'', part 2, 591–616.〕 many attempts were made to convert various cheap forms of carbon into diamond.〔As early as 1828, investigators claimed to have synthesized diamonds: * Procès-verbaux des séances de l'Académie (Académie des sciences) , November 3, 1828, volume 9, (page 137: ) ''"Il est donné lecture d'une lettre de M. Gannal qui communique quelques recherches sur l'action du phosphore mis en contact avec le carbure de soufre pur, et sur le produit des ses espériences qui ont offert des propriétés semblables à celles de particules de diamant."'' (There was given a reading of a letter from Mr. Gannal, who communicated some investigations into the action of phosphorus placed in contact with pure carbon disulfide, and into the product of his experiments, which have presented properties similar to those of particles of diamond.) * ("Artificial production of real diamonds," ) ''Mechanics' Magazine'' … , 10 (278): 300–301 (December 6, 1828). * Procès-verbaux des séances de l'Académie (Académie des sciences), November 10, 1828, volume 9, (page 140: ) ''"M. Arago communique une note de M. Cagniard de Latour, par laquelle ce physician déclare qu'il a de son côté réussi à faire cristalliser le carbone par des méthodes différentes de celles de M. Gannal, et qu'un paquet cacheté qu'il a déposé au Secrétariat en 1824 contient le détail de ses premiers procédés. M. Arago annonce qu'il connaît une autre personne qui est arrivée à des résultats semblables, et M. Gay-Lussac fait connaître que M. Gannal lui avait parlé depuis plus de huit ans de ses tentatives."'' (Mr. Arago communicated a note from Mr. Cagniard de Latour, in which this physicist states that he has, on his part, succeeded in making carbon crystallize by methods different from those of Mr. Gannal, and that a sealed packet which he deposited with the Secretary in 1824 contains the details of his initial procedures. Mr. Arago announced that he knew another person who had arrived at similar results, and Mr. Gay-Lussac announced that Mr. Ganal had spoken to him eight years ago about his attempts.) * Procès-verbaux des séances de l'Académie (Académie des sciences), December 1, 1828, volume 9, (page 151: ) ''"M. Thenard donne lecture du procès verbal des expériences faites le 26 Novembre 1828 sur la Poudre présentée comme diamant artificiel, par M. Cagniard de Latour."'' (Mr. Thenard gave a reading of the minutes of experiments made on November 26, 1828 on the powder presented as artificial diamond by Mr. Cagniard de Latour.)〕 The earliest successes were reported by James Ballantyne Hannay in 1879 and by Ferdinand Frédéric Henri Moissan in 1893. Their method involved heating charcoal at up to 3500 °C with iron inside a carbon crucible in a furnace. Whereas Hannay used a flame-heated tube, Moissan applied his newly developed electric arc furnace, in which an electric arc was struck between carbon rods inside blocks of lime. The molten iron was then rapidly cooled by immersion in water. The contraction generated by the cooling supposedly produced the high pressure required to transform graphite into diamond. Moissan published his work in a series of articles in the 1890s. Many other scientists tried to replicate his experiments. Sir William Crookes claimed success in 1909. Otto Ruff claimed in 1917 to have produced diamonds up to 7 mm in diameter, but later retracted his statement. In 1926, Dr. J Willard Hershey of McPherson College replicated Moissan's and Ruff's experiments, producing a synthetic diamond; that specimen is on display at the McPherson Museum in Kansas. Despite the claims of Moissan, Ruff, and Hershey, other experimenters were unable to reproduce their synthesis.〔O'Donoghue, p. 473〕 The most definitive replication attempts were performed by Sir Charles Algernon Parsons. A prominent scientist and engineer known for his invention of the steam turbine, he spent about 40 years (1882–1922) and a considerable part of his fortune trying to reproduce the experiments of Moissan and Hannay, but also adapted processes of his own. Parsons was known for his painstakingly accurate approach and methodical record keeping; all his resulting samples were preserved for further analysis by an independent party.〔Barnard, pp. 6–7〕 He wrote a number of articles—some of the earliest on HPHT diamond—in which he claimed to have produced small diamonds. However, in 1928, he authorized Dr. C.H. Desch to publish an article in which he stated his belief that no synthetic diamonds (including those of Moissan and others) had been produced up to that date. He suggested that most diamonds that had been produced up to that point were likely synthetic spinel.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Synthetic diamond」の詳細全文を読む スポンサード リンク
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