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   Nb or Cb

NIOBIUM or COLUMBIUM

( Niobe, daughter of Tantalus) or ( Columbia, name for America)

Nb or Cb  at. wt. 92.906
          at. no. 41 
          m.p.  2468±10°C 
          b.p. 4927°C
          sp. gr. 8.57 (20°C)
          valence  2, 3, 4?, 5.

Niobium or Columbium was discovered in 1801 by Hatchett in an ore sent to England more than a century before by John Winthrop the Younger, first governor of Connecticut. The metal was first prepared in 1864 by Blom- strand, who reduced the chloride by heating it in a hydrogen atmosphere. The name "niobium" was adopted by the International Union of Pure and Applied Chemistry in 1950 after 100 years of controversy. Many leading chemical societies and government organizations refer to it by this name. Most metallurgists, leading metal societies, and all but one of the leading U.S. commercial producers, however, still refer to the metal as "columbium." The element is found in niobite (or columbite), niobite-tantalite, pyrochiore, and euxenite. Large deposits of niobium have been found as- sociated with corbonatites (carbon-silicate rocks), as a con- stituent of pyrochiore. Extensive ore reserves are found in Canada, Brazil, Nigeria, the Congo, and the U.S. The metal can be isolated from tantalum, and prepared in several ways. It is a shiny, white, soft, and ductile metal, and takes on a bluish cast when exposed to air at room temperatures for a long time. The metal starts to oxidize in air at 2000C, and IHE ELE~EI%!Ts+Cntiwed) when processed at even moderate temperatures must be placed in a protective atmosphere. It is used as an alloying agent in carbon and alloy steels and in nonferrous metals. These alloys have improved strength and other desirable properties. The metal has a low capture cross-section for thermal neutrons. It is used in arc-welding rods for stabilized grades of stainless steel. Thousands of pounds of niobium have bten used in advanced air frame systems, sucl( as was used in the Gemini space program. The element has super- conductive properties; superconductive magnets have been made with Nb-Zr wire, which retains its stiperconductivity in strong' magnetic fields. This type of application offers hope of direct large-scale generation of electric power. Twenty- fqur isotopes of niobium are known. Niobium metal (99.5% pure) is priced at about $15/lb.

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