Tantalum - refractory metal

Tantalum (Ta) - chemical elements of the V group of the periodic system, atomic number 73, atomic weight 180,94. A glossy silver-white refractory metal. Density - 16,65 g/cm³, melting temperature t_melt. = 3017 °С, boiling temperature t_boil. = 5458 °С. It has a high durability, hardness and at the same time is rather plastic.

The described chemical element belongs to rare metal. Its content in the earth core is approximately 0.0002%. In ores it is always paired with niobium. Main minerals are columbite-tantalite and loparite.

Tantalum was discovered in 1802 by Swedish chemist A. G. Ekeberg. But it was not purified. By 1844 Ta and Nb had been considered to be the same element. In 1903 German scientist W. Bolton was the first to receive plastic tantalum and the first commercial billet was produced in 1922. Active industrial Ta production has begun since the end of WWII.

Physical properties

Property	Value
Atomic number	73
Atomic weight, amu	180,94
Atomic radius, pm	149
Density, g/cm³	16,65
Molecular heat capacity, J/(K·mole)	25,39
Heat conductivity, W/(m·K)	57,5
Melting temperature, °С	3017
Boiling temperature, °С	5458
Melting heat, kJ/mole	24,7
Vaporization heat, kJ/mole	758
Molecular volume, cm³/mole	10,9
Group of metals	Refractory metal

Chemical properties

Property	Value
Covalent radius, pm	134
Ionic radius, pm	(+5e) 68
Electronegativity (Pauling)	1,5
Electrolytic potential, V	0
Степени окисления	5

In most cases the material is supplied in pure form, but sometimes it is alloyed with other metals.

• TVCh - high-purity tantalum, Ta content is 99.9%.
• Т - pure tantalum with 99.37% of Ta and 0.5% of Nb.
• ТW - Ta-W alloy.

Advantages:
• has a high melting temperature;
• has good mechanical and technological properties - a hard, durable and plastic metal;
• corrosive-resistant in many chemically aggressive environments;
• has good gas-absorption properties;
• has good compatibility with human tissues.

Drawbacks:
• low content in the earth core;
• very high cost.

This metal is used in the following spheres:

• vacuum-tube equipment;
• electronics;
• medicine;
• chemical and nuclear industry;
• metallurgy.

The main properties used for producing components of vacuum-tube devices are high melting temperature and good gas-absorption properties. Among the components made of tantalum, the following can be mentioned: springs, grids of powerful oscillator tubes, directly- and indirectly-heated cathodes, anodes.

Ta ability to form a stable oxide film during anodic oxidation is used for creating electronic components. Such tantalum property allows using this material in chemical capacitors.

Due to Ta compatibility with human tissues, it is widely used in medicine.

Tantalum corrosive stability, durability and refractoriness determine its use in chemical and nuclear machine engineering as a construction material.

Very high Ta hardness allows using this metal for producing hard alloys. Replacing TiС with TaС significantly improves the mechanical properties of this hard alloy.

There is a huge variety of commercial blanks made of this refractory material. The most common flat products include tantalum foil and strip, sheets and flat bars; rolled products include tantalum pipes, wire и filament, rods and round bars. Tantalum powder is also an important commercial product.