Tantalum is a metal steel-gray color with a bluish tint, with surface oxides, element number 73 in the periodic table of the chemical. elements, denoted by Ta. The Swedish chemist A. G. Ekeberg in 1802, from the two minerals that were found in Finland and Sweden, have isolated a new metal, and then it turned out that in its composition contains 2 different elements. Only after 40 years, the chemist rose was able to figure out that the mineral columbite in its composition contains niobium and tantalum. Because of the difficulties of obtaining tantalum in pure form he was given the name after the Greek hero Tantalus.
The richest tantalum deposits are France, Egypt, Australia, Thailand and China. Stable tantalum-181 has a slight impurity in ores (1:1000) of radioactive tantalum 180 with a half-life of thousands of billions of years.
Properties of tantalum
Tantalum is a metal steel-gray color with a bluish tint. At normal temperatures, tantalum is stable in air. Its oxidation starts at a temperature of 200−300°C. the Main feature of tantalum is its ability to absorb gases hydrogen, oxygen, nitrogen, whose slight impurities affect the mechanical and electrical characteristics. At lower temperatures the hydrogen is absorbed very slowly, at a temperature of 500 °C has a maximum absorption rate thus starts to occur not only adsorption, but also to form hydrides.
The gas in the absorption transfers to the metal fragility, but in the process of heating over a temperature of 600 °C in vacuum almost the entire H2 starts to separate and the restoration of the former mechanical characteristics. Tantalum at a temperature of 600 °C absorbs nitrogen at a higher temperature, begins to form nitrite which has a melting temperature of 3087 °C. Since tantalum is practically not resistant to alkalis, it is being eroded by hot solutions of caustic alkali and soda. In the molten alkali it starts to form a salt of tantalic acid.
|Physical quality Ta|
|Atomic (molar) mass, g/mol||180,9|
|The degree of oxidation||5|
|The melting temperature t°C||3020°C|
|The heat of fusion kJ/mol||24,7|
|The thermal conductivity K [W/(m·K)]||57,5|
|Heat of evaporation kJ/mol||758|
Tantalum was first used in the production of filament bulbs in 1900−1903, he was later replaced by tungsten. The use of this metal in the XXI century, is directly connected with the development of radio, radar and x-ray equipment. The uniqueness of tantalum to absorb gases helps to maintain a deep vacuum in the vacuum technique.
High emission ability, and the ability to gas adsorption and the refractoriness of tantalum to determine its use in the manufacture of parts for electrical vacuum devices. Tantalum coatings are attractive as Nickel and chromium and is not only external. Developed a method of applying tantalum to large items such as pipes, sheets, crucibles, rocket nozzles, etc. Interesting fact — the strength of the tantalum coating Brinell составляет180−200 kg/mm2, and technical strength of tantalum in the form of sheets, annealed bars is only 50−80 kg/кмм2. tantalum carbide mixed with tungsten is a material having no alternative for drilling of strong breeds percussive-rotary method, and the metal working tool steels.
Tantalum is used in the manufacture of ammunition as the metal shirts for cumulative armor-piercing shells. In aerospace engineering the most in demand was beryllide tantalum, because it is resistant to oxidation and is very solid. The admixture of tantalum pentoxide glass used in experimental physics and nuclear energy for the melting of glass which will filter out the gamma rays. It is also used in electrical engineering in the production of high-capacity capacitors, and rectifiers. These capacitors use a tantalum pellet obtained by powder metallurgy, sintered and compacted under high temperatures. Active surface of the porous tantalum of the pill increases a hundred times, which gives the possibility to obtain high capacity at small dimensions of the capacitor. Tantalum capacitors are also used in military radios because they can operate in very extreme conditions at a temperature of -80 +200°C. the tantalum in recent years began to manifest interest and jewelers, as it is able to form a solid oxide film of different colors on the surface.
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