Tantalum-Niobium Ore

Tantalum

Tantalum is a shiny, silvery metal which is soft when is pure. It is almost immune to chemical attack at temperatures below 150 C. Tantalum is virtually resistant to corrosion due to an oxide film on its surface.

The chief tantalum ores are tantalite, which also contains iron, manganese and niobium, and samarskite, which contains seven metals. Another ore which contains tantalum and niobium is pyrochlore. The main mining areas are Thailandia, Australia, Congo, Brazil, Portigal and Canada. The demand of tantalum is about 2300 tonnes a year. No assessment of total reserves of extractable metal have been reliably calculated.

Properties

Tantalum Ta
Atomic number 73
Atomic mass 180.95 g.mol -1
Electronegativity 1.5
Density 16.69 g.cm-3
Melting point 2850 °C
Boiling point 6000 °C
Electronic shell [ Xe ] 4f14 5d3 6s2

Applications

Tantalum finds use in four areas: high-temperature applications, such as aircraft engines; electrical devices, such as capacitors; sirurgical impants and handling corrosive chemicals. It is rarely used as an alloying agent because it tends to make metals brittle. Tantalum resist corrosion and is almost impervious to chemical attack, for this reason it has been employed in chemical industry, e.g. for heat exchanger in boilers where strong acids are vaporized.

Niobium

Niobium is a rare, soft, malleable, ductile, gray-white metal. It has a body-centered cubic crystalline structure and in its physical and chemical properties it resembles tantalum. It must be placed in a protective atmosphere when processed at even moderate temperatures because it tends to react with oxygen, carbon, the halogens, nitrogen, and sulfur. The metal is inert to acids, even to aqua regia at room temperatures, but is attacked by hot, concentrated acids, and especially by alkalis and oxidizing agents.

Niobium was mined chiefly as columbite, and is formerly known as colombium (Cb). Another mined metal is pyrochlore and this is now the most important. The main mining areas are Brazil, which produce more than 85% on the world's niobium, Zaire, Russia, Nigeria and Canada. World production is around 25.000 tonnes per year.

Properties

Niobium Nb
Atomic number 41
Atomic mass 92.91 g.mol -1
Electronegativity unknown
Density 8.4 g.cm-3
Melting point 2410 °C
Boiling point 5100 °C
Electronic shell [ Kr ] 4d4 5s1

Applications

Niobium is used for the production of high-temperature-resistant alloys and special stainless steels. Small amounts of niobium impart greater strength to other metals, especially those that are exposed to low temperatures. Niobium carbide is used in cutting tools. It is used in stainless steel alloys for nuclear reactors, jets, missiles, cutting tools, pipelines, super magnets and welding rods.

Niobium-tin and niobium-titanium alloys are used as wires for superconducting magnets capable of producing exceedingly strong magnetic fields. Niobium is also used its pure form to make superconducting accelerating structures for particle accelerators. Niobium alloys are used in surgical implants because they do not react with human tissue.

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