Physical properties. Tantalum

Tantalum. Chemical element, symbol Ta (Latin Tantalum, English Tantalum, French Tantale, German Tantal). Has a serial number 73, atomic weight 180.948, density 16.60 g/cm 3, melting point 3015° C, boiling point 5300°C.

Tantalum is a steel-gray metal with a slightly bluish tint. At ordinary temperatures, tantalum is stable in air. The onset of oxidation is observed upon heating to 200-300°C. Above 500° rapid oxidation occurs to form oxide Ta 2 O 5 .

Characteristic property tantalum - the ability to absorb gases: hydrogen, nitrogen and oxygen. Small impurities of these elements greatly affect the mechanical and electrical properties metal At low temperatures, hydrogen is absorbed slowly, at a temperature of approximately 500° Hydrogen is absorbed at maximum speed, and not only adsorption occurs, but also the formation chemical compounds- hydrides (TaH). Absorbed hydrogen makes the metal brittle, but when heated in a vacuum it is higher 600° Almost all the hydrogen is released and the samemechanical properties are being restored.

Tantalum absorbs nitrogen already at 600° C, at higher temperatures nitride is formed TaN , which melts at 3087° N.

Carbon and carbon-containing gases (CH 4 , CO) at high temperatures in 1200-1400° C interact with the metal to form hard and refractory carbide TaC (melts at 3880° C).

With boron and silicon, tantalum forms a refractory and solid boride and silicide: TaB 2 (melts at 3000 °C) and NaSi 2 (melts at 3500 °C).

Tantalum is resistant to action hydrochloric, sulfuric, nitrogen , phosphoric and organic acids of any concentration in the cold and at 100-150° C. According to durability in hot salt and sulfur tantalum is superior to acids niobium . Tantalum dissolves in hydrofluoric acid and especially intensely - in a mixture of fluoride and nitric acids.

Tantalum is less stable in alkalis. Hot solutions of caustic alkalis noticeably corrode metal in molten alkalis and soda it quickly oxidizes to form the sodium salt of tantalic acid.

Tantalum was first used in 1900-1903 gg. for the manufacture of incandescent filaments in electric lamps, but later, in 1909-1910 gg., it was replaced tungsten

The widespread use of tantalum was associated with the development of electrovacuum technology, which included the production of radio engineering, radar and X-ray equipment.

Tantalum has a combination of valuable properties (high melting point, high emissivity and the ability to absorb gases) that make it possible to use it for the manufacture of parts for electric vacuum equipment. The ability to absorb gases is used to maintain a deep vacuum in radio tubes and other electric vacuum devices.

They are made from tantalum sheets and bars« hot fittings» (heated parts) - anodes, grids, indirectly heated cathodes and other parts of electronic tubes, especially powerful generator tubes.

In addition to pure metals, tantalonium-bium alloys are used for the same purposes.

Late 50s - early 60s In the 1980s, the use of tantalum for the manufacture of electrolytic capacitors and current rectifiers became important. Here, the ability of tantalum to form a stable oxide film during anodic oxidation is used. The oxide film is stable in acidic electrolytes and passes current only in the direction from the electrolyte to the metal. Specific electrical resistivity of the film Ta 2 O 5 in a direction that does not conduct current, very high ( 7, 5. 10 12 ohm. cm), dielectric constant of the film 11, 6.

Tantalum capacitors with solid electrolyte are characterized by high capacity with small dimensions, high insulation resistance (in 2-3 times higher than aluminum capacitors ), film durability. The positive plate of these capacitors is made in the form of a tablet, pressed from tantalum powder and sintered in a neutral environment at high temperature. The effective surface of such a porous tablet is 50-100 times larger than the geometric one, which makes it possible to obtain very small dimensions capacitor with a relatively large capacity. The positive plate is placed in a housing filled with electrolyte, which serves as a negative plate connected to the housing. Capacitors of the ETO type were produced in four types: ETO- 1 (THIS-C), THIS- 2, THIS- 3, THIS- 4. Capacitors of the type ETO- 1, intended for use in especially critical equipment are designated ETO-S. There are also capacitors of the ET and ETN types: electrolytic tantalum and electrolytic tantalum non-polar. Capacitors can be used in a wide temperature range from - 80 to +200° C. Tantalum capacitors are widely used in radio stations, various military equipment and other devices.

The corrosion resistance of tantalum in acids and other environments, combined with high thermal conductivity and ductility, makes it a valuable structural material for equipment in chemical and metallurgical industries. Tantalum serves as a material for dies (instead of platinum ) for the formation of fibers in the production of rayon.

Tantalum is included in various heat-resistant alloys for gas turbines jet engines. Tantalum alloying molybdenum, titanium,

Tantalum in the form of wire and sheets is used in medicine - in bone and plastic surgery (bonding,"patches" in case of damage to the skull, suturing, etc.). The metal does not irritate living tissue at all and does not harm the vital functions of the body.

In organic synthesis, some tantalum compounds (fluoride complex salts, oxides) are used as catalysts.

The knowledge-intensive and strategic industries of the world's leading countries are continuously growing. The dynamics of this growth are explained by two interrelated reasons. The first is the need to improve the quality characteristics of high-tech products for civilian and military purposes. The second is that tantalum is best suited for solving the first problem, since it has an impressive list most valuable properties, among which:

• exceptional corrosion resistance;
• unique resistance to chemical attack by gases and acids;
• high density(16.6 g/cm 3) and specific electrical capacity;
• superhardness and ductility;
• good manufacturability (machinability, weldability);
• heat resistance and heat resistance (melting point 3000°C);
• the ability to absorb gases (hundreds of times more than its own volume);
• high heat transfer coefficient;
• unique biological compatibility and much more.

Forms of tantalum release

For the production of high-tech products, tantalum is used both in pure form and in the form of alloys. Its wide range of applications is due to big choice tantalum and tantalum-containing semi-finished products. For further processing Tantalum rod and strip, plates, disks, and ingots are produced (grades ELP-1, ELP-2, ELP-3). The most in demand are tantalum wire and sheets, as well as foil (TVCh and TVCh-1 grades) and capacitor grade metal powder. The powder accounts for about 60% of the world's tantalum production, which is consumed by the radio-electronics industry to create the elemental base of modern “smart” technology. About 25% of the market is occupied by tantalum sheet and wire, plus foil.

Figure 1. Tantalum products.

Areas of application of tantalum

• production of electric vacuum devices;
• electrical and Electronics;
• telecommunications and communications;
• aerospace industry;
• chemical engineering;
• nuclear industry;
• metallurgy of hard alloys;
• medicine, etc.

Tantalum in vacuum devices

Working space electric vacuum devices are filled with a special gas or vacuum, in which there are two (anode and cathode) or more electrodes that form an emission current in space. Such devices include electrovacuum microwave devices of the magnetron type, devices for radar, navigation and hydroacoustic stations, oscilloscopes, counters elementary particles, electrovacuum photocells, X-ray equipment, electron tubes and much more. In a number of electric vacuum devices, tantalum serves as a material for getters - gas absorbers that maintain a state of deep vacuum in the chambers. In some devices, the electrodes heat up very quickly and strongly, so they use thin tantalum tape (grade T or HDTV) or wire (grade HDTV) as a “hot fitting”, which is capable of working for a long time (tens of thousands of hours) and stably at high voltages and pulsating temperatures.

Tantalum in hard alloy metallurgy

In the metallurgical industry, tantalum is used to create super-hard refractory alloys, the components of which are tantalum carbides (TT grade) and tungsten. Tantalum-tungsten alloys (grades TV-15, TV-10, TV-5) are used to produce metal-cutting and processing tools, heavy-duty “crowns” for drilling holes in stone and composites. Tantalum and nickel carbide alloys easily process the surface of diamonds without being inferior to them in hardness. Tantalum (Brinell hardness up to 1250–3500 MPa) is used to make parts of cryogenic installations, dies and crucibles for melting and purifying rare earth metals, and vessels for cold pressing of metal powders.

Tantalum in chemical engineering

In chemical engineering, seamless cold-deformed tantalum tube (TVCh grade) and sheet are used in the construction of corrosion-resistant equipment operating in a chemically aggressive environment. Tantalum is used to produce various acid-resistant structures (coils, mixers, distillers, aerators, pipelines), laboratory equipment, heating and cooling devices that operate in contact with acids, including concentrated substances. Tantalum foil is used for cladding (thin thermomechanical coating) on ​​the surface of parts and equipment on lines for the production of sulfuric acid, ammonia, etc.

Tantalum in medicine

Tantalum has a unique compatibility with living tissues and is not rejected by them. In medicine, tantalum wire is used in the form of threads and staples to fasten muscle tissue, tendons, nerve fibers, and blood vessels. It is also used to make meshes for eye prostheses, and the sheet is used to make housings for cardiac pacemakers. In reconstructive surgery, tantalum rod and tape are considered to be the only materials for bone prosthetics and replacement. Tantalum sheet is of exceptional importance as a “repair” material for injuries to the skull.

Tantalum in the aerospace industry

As a high-temperature structural material, tantalum sheet is used in the aerospace industry to produce critical components of rockets and aircraft. For example, the nose parts of rockets and heat-resistant blades of gas turbines of turbojet engines are made from tantalum. liquid fuel. Tantalum alloys are used to produce nozzle parts, afterburners, etc.

Tantalum in the nuclear industry

Heat exchangers for nuclear energy systems, resistant to overheated melts and cesium vapors, are made from tantalum pipe (TVCh grade). Tantalum is used to make diffusion barriers for superconductors thermonuclear reactors. The radioactive isotope tantalum-182 is used in radiation therapy. Thin tantalum wire (50-100 microns) coated with platinum is used as an interstitial source of gamma radiation, affecting cancer cells. At the beginning of 2018, information appeared in the media that Chinese scientists were conducting experiments with tantalum-182 for military purposes. The essence of the experiments has not been disclosed, but most likely, we are talking about using the tantalum isotope as a “breeding” agent for “dirty” bombs.

Tantalum in electrical engineering and electronics

Tantalum powder (TU95.250-74) is used in the manufacture of modern capacitors for telecommunications, microelectronic and computer equipment. With their miniature size, they surpass most other electrolytic capacitors in terms of specific capacitance per unit volume, are distinguished by a wide range of operating temperatures, and are highly reliable. Tantalum capacitors retain their characteristics for up to 25 years in storage mode, and in operating mode they can operate up to 150 thousand hours. Today, tantalum capacitors are present on the microcircuits of almost every smartphone, computer, game console, as well as in military equipment. Tantalum is used in rectifiers electric current, since it has the ability to pass it in only one direction.

Figure 2. Tantalum capacitor.

Conclusion

In addition to the above, tantalum rod and sheet, foil, wire, powder are used to solve dozens and hundreds of other problems. In metallurgy, tantalum is used as an alloying stabilizing component in the production of ultra-strong, corrosion-resistant, heat-resistant steels and alloys. Tantalum compounds act as catalysts in processes chemical production, for example, synthetic rubber. Tantalum has shown high efficiency in optics, since when added to glass, it increases its refractive index, which makes it possible to make lenses not spherical, but thinner and flatter, even with large diopters. In jewelry, tantalum is used along with platinum in the production of bracelets, watches, and fountain pen nibs. There is no doubt that tantalum is one of the most popular and promising metals used in high-tech industries, and, as we see, not only in them.

Tantalum- light gray metal with a slightly bluish tint. In terms of refractoriness (melting point about 3000°C), it is second only to tungsten and rhenium. High strength and hardness are combined with excellent plastic characteristics. Pure tantalum lends itself well to various mechanical processing, is easily stamped, processed into the thinnest sheets (about 0.04 millimeters thick) and wire.

Tantalum has a body-centered cubic lattice (a = 3.296 Å); atomic radius 1.46 Å, ionic radii Ta 2+ 0.88 Å, Ta 5+ 0.66 Å; density 16.6 g/cm 3 at 20 °C; t pl 2996 °C; Kip temperature 5300 °C; specific heat at 0-100°C 0.142 kJ/(kg K); thermal conductivity at 20-100 °C 54.47 W/(m K). Temperature coefficient of linear expansion 8.0·10 -6 (20-1500 °C); specific electrical resistivity at 0 °C 13.2·10 -8 ohm·m, at 2000 °С 87·10 -8 ohm·m.

At 4.38 K it becomes a superconductor. Tantalum is paramagnetic, specific magnetic susceptibility 0.849·10 -6 (18 °C). Pure tantalum is a ductile metal that can be processed by pressure in the cold without significant hardening. It can be deformed with a reduction rate of 99% without intermediate annealing. The transition of tantalum from a ductile to a brittle state upon cooling to -196 °C was not detected.

The elastic modulus of tantalum is 190 H/m 2 (190·10 2 kgf/mm 2) at 25 °C. The tensile strength of annealed high purity Tantalum is 206 MN/m2 (20.6 kgf/mm2) at 27 °C and 190 MN/m2 (19 kgf/mm2) at 490 °C; relative elongation 36% (27 °C) and 20% (490 °C). The Brinell hardness of pure recrystallized tantalum is 500 Mn/m2 (50 kgf/mm2). The properties of tantalum depend largely on its purity; impurities of hydrogen, nitrogen, oxygen and carbon make the metal brittle.

The discovery of tantalum dates back to 1802. It was first introduced to the world by the scientist A. G. Ekeberg. He discovered two minerals in Finland and Sweden. It was in their composition that this substance was present. However, it was not possible to single it out separately at that time. It is precisely because of such a high complexity of its extraction in its pure form that it was named after one of the heroes of myths Ancient Greece. Today this element has found its way wide application in many industries.

Tantalum belongs to the category of metals. It has a silvery-white tint. He has something of his own appearance resembles lead because it has a strong oxide film on it.

This metal belongs to the category of the most rarely found in nature. To date, only twenty tantalum minerals are known. However, there are sixty more minerals that contain this metal. Along with it, niobium is necessarily present in such minerals. It has similar chemical properties.

Tantalum deposits

Tantalum ores are very rare.

However, the largest of them are located in countries such as:

• Egypt,
• France,
• Thailand,
• Australia,
• Mozambique.

The world's largest tantalum ore is located in Greenbush in Australia.

Tantalum has a high melting point. It is more than three thousand degrees Celsius. The boiling point of this metal exceeds five thousand degrees Celsius. The properties of tantalum are also represented by other characteristics. This substance has a fairly solid structure. However, the metal has a high level of ductility. In this parameter it is comparable to gold. It is excellent for machining products. Thanks to it, you can create the finest types of wire or sheets for finishing products.

Tantalum belongs to the category of low-active metals. Its oxidation rate under the influence of air is quite low. In air, it undergoes oxidation only if its temperature reaches 250 degrees Celsius.

Table. Characteristics of mica capacitors based on polycarbonate, polystyrene and tantalum.

Initially, in industry, this metal was used only to create thin wire for the production of well-known incandescent lamps. Today, tantalum is used quite widely. It is used for the production of industrial and household items, and in the creation of new types of weapons in the military industry.

A metal such as tantalum is indispensable in the production of objects and equipment that are resistant to corrosion. In addition, many of these products have high level heat resistance.

In the medical industry, the use of tantalum has long been considered the norm. Foil and wire made from this unique material are used to restore the activity of tissues and nerves of patients. They are also actively used to stitch the victim.

Due to the strength of tantalum, it began to be used for the production spacecraft. Tantalum beryllide has excellent resistance to oxidation in air.

This metal has found its application in the metallurgical industry. It is used to produce hard alloys for metalworking. A mixture of tantalum and tungsten carbides is used to create hard alloys that can be used to drill holes in the most durable materials, such as stones and composites.

This material has gained wide popularity in the military industry. With its help, ammunition is created that has a high level of durability. They are almost impossible to break through. The metal is used in laboratories at the Ministry of Internal Affairs to create nuclear weapons.

Australia has the largest reserves of tantalum. It is this state that is rightfully considered the leader in the production of this substance.

Important: Our country also has the opportunity to mine tantalum. However, there are a number of difficulties that are explained by the inaccessibility of the deposits.

Tantalum production in Russia

In our country, much of the production of tantalum already lies on the shoulders of the Solikamsk magnesium plant. Here this metal is obtained from loparite concentrates. They come to the plant from the Lovozero deposit. In some cases, imported raw materials are used for this purpose, which are represented by substances such as rutile, columbite, tantalite, struverite.

The leaders in tantalum production are the United States of America, China and Japan. There are approximately forty companies in the world that produce materials such as tantalum. The largest company producing this metal is a company from the United States of America, Cabot Corporation. Its branches are open in the territories different countries peace.

Tantalum price per gram is not quite high. On average, manufacturers sell one gram of tantalum for half a dollar. A kilogram today costs more than one thousand dollars.

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