diamond

Diamonds are also called diamonds. They are an allotrope of carbon. They are found as octahedral crystals with slightly curved faces. It was thought that it would be difficult to synthesize diamonds from graphite, but in 1954, GE succeeded in synthesizing them under high temperature and pressure (2000 °C, 100,000 atm) using metals such as Mn, Fe, and Co as catalysts. Industrial diamonds are obtained by pyrolysis of carbon-containing gases. They are giant molecules with a cubic diamond structure, in which one carbon atom is surrounded by four carbon atoms in a regular tetrahedral shape and bonded by covalent bonds. They are colorless, but are sometimes colored. They have a diamond-like luster and a high refractive index. 2.4173. When polished, incident light is totally reflected on the inside, increasing its brilliance, so they are used as gemstones. They are the hardest of all substances currently known (Mohs hardness 10, new Mohs hardness 15). Density 3.513 g cm ^-3 . Some types emit strong fluorescence when exposed to ultraviolet light. It is extremely stable and will not burn in air unless it reaches above 800 °C, even when heated with an oxygen torch. It is normally an electrical insulator (resistivity 10 ¹³ Ω cm), but some diamonds exhibit the properties of a p-type semiconductor. In addition to being used as gemstones, it is used in abrasives, cutting tools such as glass cutters, boring awls, and cutters, bearings for specialized precision machinery, and dies for manufacturing wire. All man-made diamonds and the majority of natural diamonds are used for industrial purposes.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

金剛石ともいう．炭素の同素体の一つ．多少湾曲した面をもつ八面体の結晶として産出する．黒鉛からの合成は困難視されていたが，1954年，アメリカGE社で，Mn，Fe，Coなどの金属を触媒として高温，高圧(2000 ℃，10万atm)下での合成に成功した．工業用ダイヤモンドは炭素含有気体の熱分解によって得られる．1個の炭素原子の周囲を，4個の炭素原子が正四面体型に取り囲んで共有結合で結合している立方晶系ダイヤモンド構造の巨大分子．無色．ときには着色したものもある．ダイヤモンド光沢をもち，屈折率も高い．2.4173．研磨すると入射光が内面で全反射を起こし輝きが増すので，宝石として用いられる．硬さは現在知られている物質中では最高(モース硬度10，新モース硬度15)．密度3.513 g cm^－3．紫外線により強い蛍光を発するものもある．きわめて安定で，空気中では酸素トーチで加熱しても800 ℃ 以上でなければ燃焼しない．普通は電気の絶縁体(比抵抗 10¹³ Ω cm)であるが，p型半導体の特性を示すものもある．宝石として使用される以外に，研磨剤，ガラス切り，ボーリング用錐(きり)，カッターなどの切削工具，特殊精密機械用ベアリング，針金製造用ダイスなどに用いられる．人工ダイヤモンドすべてと，天然ダイヤモンドの大半は工業用に使用される．

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