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Niobium-tin (Nb3Sn) or triniobium-tin is a metallic chemical compound of niobium (Nb) and tin (Sn), used industrially as a type II superconductor. This intermetallic compound is an A15 phase superconductor. It is more expensive than niobium-titanium (NbTi), but remains superconducting up to a magnetic flux density of 30 teslas (T), compared to a limit of roughly 15 T for NbTi. Nb3Sn was discovered to be a superconductor in 1954. The material's ability to support high currents and magnetic fields was discovered in 1961 and started the era of large-scale applications of superconductivity. The critical temperature is 18.3 kelvins (K). Application temperatures are commonly around 4.2 K, the boiling point of liquid helium at atmospheric pressure. In April 2008 a record non-copper current density was claimed of 2643 A/mm² at 12 T and 4.2 K 〔(【引用サイトリンク】 Record current with powder-in-tube superconductor )〕 ==Practical use== Mechanically, Nb3Sn is extremely brittle and thus can not be easily drawn into a wire, which is necessary for winding superconducting magnets. To overcome this, wire manufacturers typically draw down composite wires containing ductile precursors. The "internal tin" process includes separate alloys of Nb, Cu and Sn. The "bronze" process contains Nb in a copper-tin bronze matrix. With both processes the strand is typically drawn to final size and coiled into a solenoid or cable ''before'' heat treatment. It is only during the heat treatment that the Sn reacts with the Nb to form the brittle, superconducting niobium-tin compound. The powder-in-tube process is also used.〔 The high field section of modern NMR magnets are composed of niobium-tin wire. Some niobium-tin wires can be wound ''after'' heat treatment. 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「Niobium-tin」の詳細全文を読む スポンサード リンク
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