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Niobium, formerly columbium, is a chemical element with symbol Nb (formerly Cb) and atomic number 41. It is a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite. The name comes from Greek mythology: ''Niobe'', daughter of ''Tantalus'' since it is so similar to tantalum.〔Knapp, Brian. ''Francium to Polonium''. Atlantic Europe Publishing Company, 2002, p. 40.〕 Niobium has physical and chemical properties similar to those of the element tantalum, and the two are therefore difficult to distinguish. The English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The German chemist Heinrich Rose determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949, but the name columbium remains in current use in metallurgy in the United States. It was not until the early 20th century that niobium was first used commercially. Brazil is the leading producer of niobium and ferroniobium, an alloy of niobium and iron. Niobium is used mostly in alloys, the largest part in special steel such as that used in gas pipelines. Although these alloys contain a maximum of 0.1%, the small percentage of niobium enhances the strength of the steel. The temperature stability of niobium-containing superalloys is important for its use in jet and rocket engines. Niobium is used in various superconducting materials. These superconducting alloys, also containing titanium and tin, are widely used in the superconducting magnets of MRI scanners. Other applications of niobium include its use in welding, nuclear industries, electronics, optics, numismatics, and jewelry. In the last two applications, niobium's low toxicity and ability to be colored by anodization are particular advantages. ==History== Niobium was discovered by the English chemist Charles Hatchett in 1801.〔See: * Charles Hatchett (1802) ("An analysis of a mineral substance from North America, containing a metal hitherto unknown" ), ''Philosophical Transactions of the Royal Society of London'', 92 : 49–66. * 〕 He found a new element in a mineral sample that had been sent to England from Massachusetts, United States in 1734 by John Winthrop F.R.S. (grandson of John Winthrop the Younger) and named the mineral ''columbite'' and the new element ''columbium'' after ''Columbia'', the poetical name for the United States.〔 The ''columbium'' discovered by Hatchett was probably a mixture of the new element with tantalum. Subsequently, there was considerable confusion over the difference between columbium (niobium) and the closely related tantalum. In 1809, the English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm3, and tantalum—tantalite, with a density over 8 g/cm3, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum.〔 This conclusion was disputed in 1846 by the German chemist Heinrich Rose, who argued that there were two different elements in the tantalite sample, and named them after children of Tantalus: ''niobium'' (from Niobe), and ''pelopium'' (from Pelops). This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements ''pelopium'', ''ilmenium'' and ''dianium'' were in fact identical to niobium or mixtures of niobium and tantalum.〔 The differences between tantalum and niobium were unequivocally demonstrated in 1864 by Christian Wilhelm Blomstrand,〔 and Henri Etienne Sainte-Claire Deville, as well as Louis J. Troost, who determined the formulas of some of the compounds in 1865〔 and finally by the Swiss chemist Jean Charles Galissard de Marignac in 1866, who all proved that there were only two elements. Articles on ''ilmenium'' continued to appear until 1871. De Marignac was the first to prepare the metal in 1864, when he reduced niobium chloride by heating it in an atmosphere of hydrogen.〔(【引用サイトリンク】Niobium )〕 Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was first used commercially, in incandescent lamp filaments.〔 This use quickly became obsolete through the replacement of niobium with tungsten, which has a higher melting point and thus is preferable for use in incandescent lamps. The discovery that niobium improves the strength of steel was made in the 1920s, and this application remains its predominant use.〔 In 1961 the American physicist Eugene Kunzler and coworkers at Bell Labs discovered that niobium-tin continues to exhibit superconductivity in the presence of strong electric currents and magnetic fields,〔Geballe ''et al.'' (1993) gives a critical point at currents of 150 kiloamperes and magnetic fields of 8.8 tesla.〕 making it the first material to support the high currents and fields necessary for useful high-power magnets and electrically powered machinery. This discovery would allow — two decades later — the production of long multi-strand cables that could be wound into coils to create large, powerful electromagnets for rotating machinery, particle accelerators, or particle detectors. 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」の詳細全文を読む スポンサード リンク
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