Tantalum

History

(Gr. Tantalos: mythological character, father of Niobe) Discovered in 1802 by Ekeberg, but many chemists thought niobium and tantalum were identical elements until Rowe in 1844, and Marignac, in 1866, showed that niobic and tantalic acids were two different acids. The early investigators only isolated the impure metal. The first relatively pure ductile tantalum was produced by von Bolton in 1903.

Properties

Tantalum is a gray, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire. Tantalum is almost completely immune to chemical attack at temperatures below 150oC, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulfur trioxide. Alkalis attack it only slowly. At high temperatures, tantalum becomes much more reactive. The element has a melting point exceeded only by tungsten and rhenium. Tantalum has a good "gettering" ability at high temperatures, and tantalum oxide films are stable and have good rectifying and dielectric properties.

Tantalum is used to make a variety of alloys with desirable properties such as high melting point, high strength, good ductility, etc. Scientists at Los Alamos National Laboratory have made a tantalum carbide graphite composite material that is one of the hardest materials made. The compound has a melting point of 3738oC.

Sources

Tantalum occurs principally in the mineral columbite-tantalite. Tantalum ores are found in Australia, Brazil, Mozambique, Thailand, Portugal, Nigeria, Zaire, and Canada.

Separation of tantalum from niobium requires several complicated steps. Several methods are used to commercially produce the element, including electrolysis of molten potassium fluorotantalate, reduction of potassium fluorotantalate with sodium, or reacting tantalum carbide with tantalum oxide.

Uses

Tantalum is used to make electrolytic capacitors and vacuum furnace parts, which account for about 60% of its use. The final uses for tantalum capacitors is in telephones, pagers, personal computer, and automotive electronics. Tantalum is also used to produce a variety of alloys that have high melting points, are strong and have good ductility. Alloyed with other metals, it is also used in making carbide tools for metalworking equipment and in the production of super alloys for jet engine components, chemical process equipment, nuclear reactors, and missile parts. It is ductile and can be drawn into fine wire, which is used as a filament for evaporating metals such as aluminum.

Tantalum is completely immune to body liquids and is a nonirritating material. It has, therefore, found wide use in making surgical appliances. Tantalum oxide is used to make special glass with high index of refraction for camera lenses. The metal has many other uses.

Isotopes

Hazards