niobium

/nuy oh"bee euhm/, n. Chem.
a steel-gray metallic element resembling tantalum in its chemical properties; becomes a superconductor below 9 K; used chiefly in alloy steels. Symbol: Nb; at. no.: 41; at. wt.: 92.906; sp. gr.: 8.4 at 20°C.
[1835-45; < NL; see NIOBE, -IUM]

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 chemical element, refractory metal of Group 5 (Vb) of the periodic table, used in alloys, tools and dies, and superconductive magnets. Niobium is closely associated with tantalum in ores and in properties.

      Due to the great chemical similarity of niobium and tantalum, the establishment of the individual identities of the two elements was very difficult. Niobium was first discovered (1801) in an ore sample from Connecticut by the English chemist Charles Hatchett (Hatchett, Charles), who called the element columbium in honour of the country of its origin, Columbia being a synonym for the United States. In 1844 a German chemist, Heinrich Rose, discovered what he considered to be a new element occurring along with tantalum and named it niobium after Niobe, the mythological goddess who was the daughter of Tantalus. After considerable controversy it was decided that columbium and niobium were the same element. Eventually international agreement (about 1950) was reached to adopt the name niobium, though columbium persisted in the U.S. metallurgical industry.

      Niobium is roughly 10 times more abundant in the crust of the Earth than is tantalum. Niobium, more plentiful than lead and less abundant than copper in the Earth's crust, occurs dispersed except for relatively few minerals. Of these minerals, the columbite–tantalite series, in which columbite (FeNb2O6) and tantalite (FeTa2O6) occur in highly variable ratios, is the main commercial source. Pyrochlore, a calcium sodium niobate, is also the principal commercial source. Natural niobium occurs entirely as the stable isotope niobium-93.

      The production procedures for niobium are complex, the major problem being its separation from tantalum. Separation from tantalum, when necessary, is effected by solvent extraction in a liquid-liquid process; the niobium is then precipitated and roasted to niobium pentoxide, which is reduced to niobium powder through metallothermic and hydriding processes. The powder is consolidated and purified further by electron-beam melting. Vacuum sintering of powder is also used for consolidation. Niobium can also be obtained by either electrolysis of fused salts or reduction of fluoro complexes with a very reactive metal such as sodium. (For information on the mining, recovery, and applications of niobium, see niobium processing.)

      The pure metal is soft and ductile; it looks like steel or, when polished, like platinum. Although it has excellent corrosion resistance, niobium is susceptible to oxidation above about 400° C (750° F). Niobium can best be dissolved in a mixture of nitric and hydrofluoric acids. Completely miscible with iron, it is added in the form of ferroniobium to some stainless steels to give stability on welding or heating. Niobium is used as a major alloying element in nickel-based superalloys and as a minor but important additive to high-strength, low-alloy steels. Because of its compatibility with uranium, resistance to corrosion by molten alkali-metal coolants, and low thermal-neutron cross section, it has been used alone or alloyed with zirconium in claddings for nuclear reactor cores. Cemented carbides used as hot-pressing dies and cutting tools are made harder and more resistant to shock and erosion by the presence of niobium. Niobium is useful in constructing cryogenic (low temperature) electronic devices of low power consumption. Niobium-tin (Nb3Sn) is a superconductor below 18.45 Kelvins (K), and niobium metal itself, below 9.15 K.

      Compounds of niobium are of relatively minor importance. Those found in nature have the +5 oxidation state, but compounds of lower oxidation states (+2 to +4) have been prepared. Quadruply charged niobium, for example, in the form of the carbide, NbC, is used for making cemented carbides.

atomic number
41
atomic weight
92.906
melting point
2,468° C (4,474° F)
boiling point
4,927° C (8,901° F)
specific gravity
8.57 (20° C)
oxidation states
+2, +3, +4, +5
electronic config.
[Kr]4d45s1

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Universalium. 2010.

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  • niobium — [ njɔbjɔm ] n. m. • 1854; all. 1844; de Niobé n. pr. gr., fille de Tantale ♦ Chim. Corps simple (Nb; no at. 41; m. at. 92,91), métal blanc brillant, rare et toujours associé avec le tantale dans ses minerais (d où le nom du métal). ● niobium nom… …   Encyclopédie Universelle

  • niobium — i*o bi*um, n. [NL., fr. L. & E. {Niobe}.] (Chem.) The chemical element of atomic number 41. Chemical symbol Nb. Atomic weight 92.91. Previously called {columbium}. See also {Columbium}. [1913 Webster] …   The Collaborative International Dictionary of English

  • Niobium — Niobium, Atomgewicht 48,9 (H = 1), 611,25 (O = 100), chemisches Zeichen Nb, eins der seltensten Metalle, wurde von Rose im Tantalit (Niobit, Columbit) von Bodenmais in Baiern entdeckt. Das N. ist ein schwarzes Pulver, welches an der Luft unter… …   Pierer's Universal-Lexikon

  • Niobĭum — (Niob) Nb, Metall, findet sich häufig in Begleitung von Tantal im Columbit, Pyrochlor und gehört zu den seltensten Elementen. Es ist glänzend stahlgrau, vom spez. Gew. 7,06, Atomgewicht 94, oxydiert sich beim Erhitzen an der Luft zu farblosem… …   Meyers Großes Konversations-Lexikon

  • Niobium [1] — Niobium (Niob) Nb, Atomgew. 94, spez. Gew. 7,06, stahlgraues, neben Tantal in den Erzen Kolumbit, Tantalit, Pyrochlor, Euxenit u.a. vorkommendes, seltenes Metall; es verbrennt, an der Luft erhitzt, zu Niobpentoxyd Nb2O5 und zeigt in seinem… …   Lexikon der gesamten Technik

  • Niobium [2] — Niobium (Niob), Nb, Atomgew. 93,5, Schmelzpunkt 1950°. Ziemlich duktiles Metall. Moye …   Lexikon der gesamten Technik

  • Niobium — Niobĭum (chem. Zeichen Nb), sehr selten vorkommendes Element vom Atomgewicht 94; findet sich immer mit Tantal zusammen (im Kolumbit und Pyrochlor) …   Kleines Konversations-Lexikon

  • Niobium — Niobium, von H. Rost entdecktes Metall, findet sich immer mit dem Tantal in Columbit, Pyrochlor etc. in sehr geringer Masse …   Herders Conversations-Lexikon

  • niobium — Symbol: Nb Atomic number: 41 Atomic weight: 92.906 Soft, ductile grey blue metallic transition element. Used in special steels and in welded joints to increase strength. Combines with halogens and oxidizes in air at 200 degrees celsius.… …   Elements of periodic system

  • niobium — named by German scientist Heinrich Rose, who discovered it in 1844 in the mineral tantalum; so called because in Greek mythology NIOBE (Cf. Niobe) was the daughter of Tantalus …   Etymology dictionary

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