After a somewhat complicated history of discovery, the Swedish chemist Christian Wilhelm Blomstrand finally isolated metallic niobium in 1864. It is formally named for the Greek mythological figure Niobe, although its original name, columbium, is still occasionally used.
Niobium is a soft, grey, lustrous, ductile transition metal. As niobium oxidizes at temperatures above 400 °C, a protective coating is necessary for these applications to prevent the metal from becoming brittle. It takes on a bluish tinge when exposed to air at room temperature for extended periods. It also has a low density in comparison to other refractory metals. Furthermore, it is corrosion resistant and exhibits superconductivity properties; both properties however being strongly dependent on the purity of the niobium metal.
It was not until the early 20th century that niobium was first used commercially as a filament in light bulbs. Ultimately, it was replaced by tungsten.
Niobium is primarily obtained from the mineral pyrochlore, most of which is mined and processed in Brazil and to a lesser extent in Canada. Other mineral sources include the tantalum bearing mineral columbo-tantalite, or what is called "Coltan" in Africa. Most of the pyrochlore that is mined is converted to a niobium-iron alloy known as ferro-niobium and serves as the start point for most of its applications.
APPLICATIONS OF NIOBIUM
Steel production: Niobium is an effective microalloying element for steel that improves the grain refining and precipitation hardening of the steel, thereby increasing the toughness, strength, formability, and weldability. Microalloyed stainless steels have a niobium content of less than 0.1%. These high strength low alloy (HSLA) steels are widely used as structural components in modern automobiles and pipeline construction.
Superalloys: Niobium is used in nickel-, cobalt-, and iron-based superalloys for applications in jet engine components, gas turbines, rocket subassemblies, and heat resisting and combustion equipment. These alloys contain up to 6.5% niobium; an example of which, Inconel 718, is a nickel-based niobium-containing superalloy used in advanced air frame systems. Another alloy, C103, is comprised of 89% niobium, 10% hafnium and 1% titanium and is used for liquid rocket thruster nozzles.
Electronics: Niobium has a high dielectric constant and is thus able to hold and store electrical charges. The most effective capacitors are those made of tantalum, but high tantalum prices have lead to the substitution of niobium in many non-critical applications where ambient temperatures are low.
Superconducting Magnets: Niobium becomes a superconductor at very low, or cryogenic temperatures. Niobium also has the largest magnetic penetration depth of any element. As such, niobium-tin and niobium-titanium alloys are used as wires for superconducting magnets capable of producing exceedingly strong magnetic fields. These superconducting magnets are used in magnetic resonance imaging (MRI) and nuclear magnetic resonance instruments. They are also used in the construction of particle accelerators such as the Large Hadron Collider which uses 600 metric tons of superconducting wire strands. The International Thermonuclear (Fusion) Experimental Reactor is estimated to use 600 metric tonnes of Nb3Sn strands and 250 metric tonnes of NbTi strands.
Numismatics: Niobium is used as a precious metal in commemorative coins and jewellery, often with silver or gold. The colour in these coins, ranges from blue, green, brown, purple, violet, or yellow, and is created by diffraction of light through a thin oxide layer produced by anodizing of the niobium surface.
Other Uses: Niobium is used in medical devices such as pacemakers as niobium is physiologically inert and thus hypoallergenic. Niobium-doped glass has a high refractive index; a property of use to the optical industry in making thinner corrective glasses. It is also used in nuclear components as it has low capture cross-section for thermal neutrons. Niobium is also used in arc welding rods for some stabilized grades of stainless steel and in the arc-tube seals of high pressure sodium vapor lamps.
LINKS: For chemical and physical properties: www.webelements.com or http://education.jlab.org/itselemental/ele041.html
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