Graphite - Graphite

Also called graphite. An allotrope of carbon. Although natural graphite is called scaly graphite or earthy graphite depending on the occurrence, most graphite is artificial, obtained by heating amorphous carbon to 2400-3000 °C (graphitization). Heating to 3000 °C or higher is necessary to obtain a complete graphite structure. A hexagonal crystal with a layered structure in which layers of six carbon rings are stacked in two dimensions. The interatomic distance CC within a layer is 0.142 nm, and the layer spacing is 0.335 nm. The layers are bonded by van der Waals forces. It is usually obtained as a scaly, granular, lumpy, earthy, or other aggregate crystal. It is completely cleaved at the basal surface. It is black to steel gray, opaque, and has a metallic luster. Density 2.26 g cm ^-3 (single crystal, 20 °C). Hardness 1-2. It has a melting point of 3550 °C and sublimes at 4800 °C. Its structure shows a remarkable anisotropy. For example, its electrical resistance is 0.40 μΩ m in the direction of the single crystal layer, but several orders of magnitude larger in the perpendicular direction. Therefore, there is a remarkable difference in physical properties between single crystals and polycrystalline aggregates or powders. Differences also occur due to structural imperfections. In particular, in man-made products, differences in physical properties occur due to differences in the degree of graphitization caused by the raw materials and processing methods. It is highly heat-resistant, resistant to thermal shock, and corrosion. It is a good conductor of electricity and heat and has a lubricating property. It is a chemically stable substance and is not easily attacked by ordinary reagents. Atoms, molecules, or ions that react with the π electrons enter between the layers and form intercalation compounds. Its ignition temperature in air is 500-600 °C or higher. When the powder is treated with concentrated sulfuric acid and a strong oxidizing agent, graphite acid and other substances of unknown structure are produced. It is used in various electrodes, especially for lithium-ion batteries, brushes for electric motors and generators, resistance heating elements, crucibles, refractories, antifriction agents, pencils, etc. High purity is especially required for those used as moderators for nuclear reactors and reflective materials. Fibrous material is used as a resin reinforcement material in aerospace equipment, fishing, golf and tennis equipment, etc. [CAS 7782-42-5][See other terms] Diamond

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

石墨，グラファイトともいう．炭素の同素体の一つ．天然にも，産状によってうろこ状黒鉛，土状黒鉛などとよばれるものが産出するが，無定形炭素を2400～3000 ℃ に加熱(黒鉛化)すると得られる人造黒鉛がおもである．完全な黒鉛構造にするためには3000 ℃ 以上の加熱が必要である．六炭素環が二次元的に連なった層が積み重なった層状構造をもつ六方晶系の結晶．層内の原子間距離C-C 0.142 nm，層間隔0.335 nm．層と層との結合はファンデルワールス力による．普通，うろこ状，粒状，塊状，土状などの集合晶として得られる．へき開は底面に完全．黒～鋼灰色，不透明，金属光沢をもつ．密度2.26 g cm^－3(単結晶，20 ℃)．硬さ1～2．融点3550 ℃，4800 ℃ で昇華する．構造上いちじるしい異方性を示す．たとえば，電気抵抗は，単結晶層方向で0.40 μΩ m であるが，垂直方向では数けた大きい．したがって，単結晶と多結晶集合体，あるいは粉末との間にはいちじるしい物性の差がある．また，構造の不完全さによっても差を生じる．とくに人造品では，原料および処理方法による黒鉛化度の差による物性上の差も生じる．耐熱性，耐熱衝撃性，耐食性に富む．電気，熱の良導体で滑性がある．化学的に安定な物質で，通常の試薬には侵されにくい．π電子と反応する原子，分子またはイオンは層間に入り込み層間化合物をつくる．空気中での着火温度は500～600 ℃ 以上．粉末を濃硫酸と強酸化剤で処理すると，石墨酸などの構造不明の物質を生じる．各種の電極，とくにリチウムイオン電池用，電動機や発電機などのブラシ，抵抗発熱体，るつぼ，耐火物，減摩剤，鉛筆などに用いられる．原子炉用減速材，反射材として利用するものは，とくに高純度が要求される．繊維状のものは樹脂補強用強化材として，航空宇宙機器，釣り，ゴルフ，テニス用具などに用いられる．[CAS 7782-42-5][別用語参照]ダイヤモンド

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