Physical and chemical properties
Tantalum is a metal of gray-steel color with a bluish tint. At ordinary temperatures, it is stable in air. Oxidize begins at t ° 200−300 ° C. The main feature is its ability to absorb oxygen, nitrogen, hydrogen, whose minor impurities affect the mechanical and electrical characteristics. At a low temperature, hydrogen is absorbed slowly, and at a temperature of 500 ° C the maximum absorption rate is observed, not only adsorption but also hydrides begin to occur. Hydrogen absorbs brittleness when absorbed, but during heating above 600 ° C in vacuum, almost all of the H 2 begins to separate and the previous mechanical characteristics are restored.
|Physical properties Ta|
|Atomic (molar) mass g / mol||180.9|
|Degree of oxidation||5|
|Density [g / cm 3 ]||16.65|
|Melting point t ° C||3020 ° С|
|Heat of fusion kJ / mol||24.7|
|Thermal conductivity K [W / (m · K)]||57.5|
|Heat of evaporation kJ / mol||758|
That at 600 ° C absorbs nitrogen, at a higher temperature, nitrite begins to form, which has a melting point of 3087 ° C. Since tantalum is not resistant to alkalis, it is eaten by hot solutions of caustic alkalis and soda. In molten alkalis, it begins to form tantalum acid salts.
|Chemical composition of tantalum|
|copper||0, 0005||0.0005||0, 0005||0, 0005|
|zirconium||0, 0007||0, 0007||0, 0007||0,001|
|aluminum||0, 0005||0.0005||0.0005||0, 0005|
|molybdenum||0, 0005||0, 0005||0.0005||0, 0006|
|sodium||0, 00015||0, 00015||0, 00015||0, 0002|
|hydrogen||0, 0004||0, 0004||0.0004||0, 0005|
|Tantalum, not less than||99.9||99.92||99.96||99.9|
Tantalum was first used in the production of filaments of electric lamps at the turn of the 19th — 20th centuries, but was replaced by tungsten lamps. The use of this metal in the XXI century, is directly related to the development of radio engineering, radar, X-ray technology. The affinity of tantalum for the absorption of gases helps maintain a deep vacuum. Emissivity, as well as the ability to gas adsorption and refractoriness determine its use for the production of parts of vacuum devices.
Tantalum coatings have an attractive appearance, like nickel or chrome. A method of applying tantalum to such large products as pipes, sheets, crucibles, rocket nozzles, etc. An interesting fact is that the Brinell tantalum coating has a strength of 180−200 kg / mm 2, and the strength of technical tantalum in the form of sheets annealed The number of bars is only 50−80 kg / km 2. Tantalum carbide in a mixture with tungsten is a material that does not have an alternative for drilling the strongest rocks with a shock-rotary method, as well as for the machining of tool steels.
It is used in the manufacture of ammunition: as a metal shirt for cumulative armor-piercing shells. Aerospace technology today can not do without tantalum beryllide, because it is resistant to oxidation and very hard. The admixture of TaO 5 to glass is used in experimental physics and nuclear power engineering. This glass delays the gamma rays.
Tantalum is also used to produce high-capacity capacitors and rectifiers. In such condensers, tantalum tablets obtained by powder metallurgy are used, sintered and compressed at high temperatures. The active surface of the porous surface increases by two orders of magnitude, which makes it possible to obtain, with a high capacity, small dimensions of the condenser. Such capacitors are also used for military radio stations, since they can be operated under the most extreme conditions at t ° -80 + 200 ° C. The jewelers have recently begun to show interest in this metal because it is able to form a strong oxide film of different colors on the surface.
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