Tantalum (element)

Tantalum was discovered in 1802 by the Swedish chemist A. G. Ekeberg in two minerals found in Finland and Sweden . However, in its pure form it was not possible to isolate it. Due to the difficulty of obtaining this element was named after the hero of ancient Greek mythology Tantalus .

Subsequently, tantalum and "Colombia" ( niobium ) were considered identical. Only in 1844, the German chemist Heinrich Roze proved that the mineral columbite-tantalite contains two different elements - niobium and tantalum.

Plastic metal tantalum was first obtained by the German scientist in 1903.

The first industrial headquarters of tantalum was obtained in 1922, while it did not exceed the size of a match head. Then the element began to be used in rectifiers and radio tubes. Active production of tantalum was launched at the very end of World War II.

Tantalum is a rare metal, in the earth's crust it accounts for 0,0002%. About 20 of its own tantalum minerals are known - a series of columbite-tantalite , vginite , loparite , manganotantalite and others, as well as more than 60 minerals containing tantalum. All of them are associated with endogenous mineral formation . In minerals, tantalum is always found together with niobium due to the similarity of their physical and chemical properties. Tantalum is a typically dispersed element, as it is isomorphic with many chemical elements. Tantalum deposits are confined to granite pegmatites, carbonatites and alkaline stratified intrusions.

Deposits

The largest deposits of tantalum ores are located in France , Egypt , Thailand ^[4] , and China . Tantalum ore deposits are also found in Mozambique , Australia , Nigeria , Canada , Brazil , the CIS , DRC , and Malaysia ^[4] .

The world's largest tantalum ore deposit, Greenbushes , is located in Australia in Western Australia , 250 km south of Perth ^[5] .

Tantalum has a high melting point - 3290 K ( 3017 ° C ); boils at 5731 K ( 5458 ° C ) ^[3] . The density of tantalum is 16.65 g / cm³ ^[3] . Despite its hardness, it is plastic as gold . Pure tantalum lends itself well to mechanical processing, is easily stamped, rolled into wire and the thinnest sheets with a thickness of a hundredth of a millimeter. Tantalum is an excellent getter (getter), at 800 ° C it is able to absorb 740 volumes of gas. The crystal lattice is cubic, body-centered ^[4] . It has paramagnetic properties ^[4] .

At temperatures below 4.45 K, it transforms into a superconducting state ^[4] .

Isotopes

Tantalum isotopes with mass numbers from 155 to 190 (the number of protons 73, neutrons from 82 to 117), and more than 30 nuclear isomers are known .

Natural tantalum consists of a mixture of a stable isotope and a stable isomer: ¹⁸¹ Ta (99.9877%) and ^180m Ta (0.0123%). The latter is an extremely stable isomer (excited state) of the ¹⁸⁰ Ta isotope, whose half-life is just over 8 hours ^[6] .

Under normal conditions, tantalum is inactive, it oxidizes in air only at temperatures above 280 ° C , covered with an oxide film of Ta ₂ O ₅ ; reacts with halogens at temperatures above 250 ° C. When heated, reacts with C, B, Si, P, Se, Te, H ₂ O, CO, CO ₂ , NO, HCl, H ₂ S.

Chemically pure tantalum is extremely resistant to liquid alkali metals , most inorganic and organic acids, as well as many other aggressive environments (with the exception of molten alkalis).

In terms of chemical resistance to reagents, tantalum is similar to glass. Tantalum is insoluble in acids and their mixtures, except for a mixture of hydrofluoric and nitric acids; even aqua regia does not dissolve it. The reaction with hydrofluoric acid occurs only with metal dust and is accompanied by an explosion . It is very resistant to sulfuric acid of any concentration and temperature (at 200 ° C the metal corrodes in acid by only 0.006 millimeters per year) ^[7] , it is stable in deoxygenated molten alkali metals and their superheated vapors (lithium, sodium, potassium, rubidium, cesium )

MPC 5 mg / m³ .

The average tantalum content (by weight):

• in the earth's crust 2.5⋅10 ⁻⁴ % ^[4]
• in ultrabasic rocks 1⋅10 ⁻⁶ %
• in basic rocks 4.8 410 ⁻⁵ %
• in acid rocks 3,5⋅10 ⁻⁴ %
• in semi-acidic rocks 7⋅10 ⁻⁴ %

The main raw materials for the production of tantalum and its alloys are tantalite and loparite concentrates containing about 8% Ta ₂ O ₅ , as well as 60% or more Nb ₂ O ₅ . Concentrates decompose with acids or alkalis, loparite - chlorinate. Separation of Ta and Nb is carried out by extraction . Tantalum metal is usually obtained by reduction of Ta ₂ O ₅ with carbon , or electrochemically from melts. Compact metal is produced by vacuum arc, plasma smelting or powder metallurgy .

To obtain 1 ton of tantalum concentrate, it is necessary to process up to 3000 tons of ore.

The cost of tantalum is about 530 dollars per 1 kg (July 2013) ^[8] . Particularly pure tantalum (from 99.985%) has a price of about $ 4,500 per 1 kg ^[9] .

Originally used for the manufacture of wire for incandescent lamps. Today, tantalum and its alloys are made:

• heat resistant and corrosion resistant alloys;
• corrosion-resistant equipment for the chemical industry, spunbond plates , laboratory glassware and crucibles for the production, smelting, and casting of rare-earth elements, as well as yttrium and scandium ;
• heat exchangers for nuclear power systems (tantalum is the most stable of all metals in superheated melts and cesium vapors);
• in surgery, sheets, foil and tantalum wire are used to bond tissues, nerves, sutures, and prostheses to replace damaged parts of bones (due to biological compatibility);
• tantalum wire is used in cryotrons - superconducting elements installed in computer technology;
• in the production of ammunition, tantalum is used to make metal cladding of promising cumulative charges, which improves armor penetration ;
• tantalum and niobium are used for the production of electrolytic capacitors (better than aluminum electrolytic capacitors, but designed for lower voltage);
• tantalum has been used in recent years as a jewelry metal, due to its ability to form durable oxide films of beautiful rainbow colors on the surface;
• The tantalum-180m2 nuclear isomer, which accumulates in the structural materials of nuclear reactors, can, along with hafnium-178m2, serve as a source of gamma rays and energy in the development of weapons and special vehicles.
• The US Bureau of Standards and the International Bureau of Weights and Measures of France use tantalum instead of platinum to produce high-precision standard analytical weights;
• Tantalum beryllide is extremely solid and resistant to oxidation in air up to 1650 ° C ; it is used in aerospace engineering;
• Tantalum carbide (melting point 3880 ° C , hardness is close to diamond hardness) is used in the production of hard alloys - a mixture of tungsten carbides and tantalum (grades with TT index), for the most difficult conditions of metal working and rotary impact drilling of the toughest materials (stone, composites), and also applied to nozzles, nozzles of missiles;
• Tantalum oxide (V) is used in nuclear technology to make glass that absorbs gamma radiation . One of the most widely used compositions of such glass: silicon dioxide - 2%, lead monoxide (lead) - 82%, boron oxide - 14%, tantalum pentoxide - 2%;
• In numismatics. Since 2006, the National Bank of Kazakhstan has been issuing commemorative bimetallic coins of 100 and 500 tenge from silver and tantalum.

• Columbite tantalite

• Tantalum in the Popular Library of Chemical Elements