Amorphous substance - amorphous substance
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Solid materials are composed of atoms (molecules and ions). A material with a regular arrangement of atoms is called a crystal, whereas a material with a non-regular arrangement and no clear external shape is called an amorphous (non-crystalline or shapeless) material. The original meaning of amorphous is "not showing an external shape." This material can be made by flash-cooling a high-temperature melt (or gas) at an ultra-high speed of 1 million degrees Celsius per second to freeze the atoms into the same random arrangement as in a liquid state. Depending on the type of constituent elements, it is called an amorphous metal (alloy) or an amorphous semiconductor, and amorphous silicon has been put to practical use as a solar cell. Amorphous metals are made by the rotating roll method, in which molten metal is sprayed onto a metal (copper) roll rotating at high speed, or by the submerged spinning method, in which molten metal is sprayed into a refrigerant liquid. Unlike crystals, amorphous metals have no directionality in their physical properties, and are therefore tough, hard, and resistant to corrosion. However, while in the United States it is used as a core material for transformers, in Japan it is mainly used in the magnetic heads of electronic devices, taking advantage of its excellent magnetic properties (soft magnetic properties). For this reason, Allied Chemical, the American company which holds the patent, demanded that the American method be used in Japan through intergovernmental talks, and obtained concessions from the Japanese side. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
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固体物質は原子 (分子・イオン) から構成されており，原子の配列が規則的なものを結晶と呼ぶのに対し，その配列に規則性を欠き，きちんとした外形を呈さないものを，アモルファス (非晶質あるいは無定形) 物質という。アモルファスの元の意味は「外形を示さない」。この物質は，高温融体 (あるいは気体) を1秒間に 100万℃という超高速で瞬間冷却することにより，液体状態と同じばらばらな原子配列に凍結することで作製できる。その構成元素の種類により，アモルファス金属 (合金) ，アモルファス半導体と呼ばれ，アモルファスシリコンは太陽電池として実用化されている。アモルファス金属は，高速回転する金属 (銅) ロールに溶融金属を吹き付ける回転ロール法，冷媒液中に噴出させる液中紡糸法などで作られ，結晶とは異なり，物性に方向性がないので，粘り強い，硬い，腐食に強いなどの特徴がある。しかし，アメリカでは変圧器用の鉄芯 (しん) 材として用いられるのに対し，日本では優れた磁気特性 (軟磁性) を主として電子機器の磁気ヘッドなどに応用している。このため特許を持つアメリカのアライド・ケミカル社は日米政府間協議を通じてアメリカ方式での普及を要求，日本側の譲歩を引き出した。
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