Physical properties

The discovery of tantalum is closely related to the discovery of niobium. For several decades, chemists considered the element columbium, discovered by the English chemist Hatchett in 1802, and tantalum, discovered in 1802 by the Swede Ekeberg, as one element. Only in 1844 did the German chemist Rose finally prove that these are two different elements, very similar in their properties. And since tantalum was named after the hero of ancient Greek myths Tantalus, he proposed calling “Columbium” niobium after Tantalus’ daughter Niobe. Tantalum itself got its name from the expression “torment of Tantalum”, due to the futility of Ekeberg’s attempts to dissolve the oxide of this element he obtained in acids.

Receipt:

Tantalum almost always accompanies niobium in tantalites and niobites. The main deposits of tantalite are located in Finland, Scandinavia and North America.
The decomposition of tantalum ores in technology is carried out by heating them with potassium hydrogen sulfate in iron vessels, leaching the alloy with hot water and dissolving the remaining powdered tantalic acid residue with contaminated niobic acid. Then tantalum oxide is reduced with coal at 1000°C and the resulting metal is separated in the form of a black powder containing a small amount of oxide. Also, metal powder can be obtained by reducing TaCl 5 with hydrogen or magnesium, as well as potassium tritantalate with sodium: K 2 TaF 7 + 5Na = Ta + 2KF + 5NaF.
Metal powder is processed into compact metal using powder metallurgy methods, pressing into “stacks”, followed by plasma or electrobeam melting.

Physical properties:

Tantalum is a heavy, platinum-gray shiny metal with a bluish tint, quite hard, but extremely malleable and ductile; its ductility increases as it is cleaned. Melt = 3027°C (second only to tungsten and rhenium). Heavy, density 16.65 g/cm 3

Chemical properties:

At room temperature it has exceptional chemical resistance. Apart from hydrofluoric acid, tantalum is not affected by any other acids, not even aqua regia. It interacts with a mixture of hydrofluoric and nitric acids, sulfuric anhydride, solutions and melts of alkalis, when heated to 300-400°C with halogens, hydrogen, oxygen, nitrogen, above 1000°C - with carbon.
In compounds it exhibits an oxidation state of +5. However, tantalum compounds with lower oxidation states are also known: TaCl 4, TaCl 3, TaCl 2.

The most important connections:

Tantalum(V) oxide Ta 2 O 5 in a pure state is most conveniently obtained by calcination of pure tantalum metal in a stream of oxygen or by decomposition of Ta (OH) 5 hydroxide. Tantalum(V) oxide is a white, insoluble in water and acids (except for hydrofluoric acid) powder with a specific gravity of 8.02. It does not change when calcined in air, in an atmosphere of hydrogen sulfide or in sulfur vapor. However, at temperatures above 1000°C, the oxide reacts with chlorine and hydrogen chloride. Tantalum(V) oxide is dimorphic. At ordinary temperatures, its rhombic modification is stable.

Tantalates and tantalic acid. By fusing tantalum(V) oxide with alkalis or alkali metal carbonates, tantalates are obtained - salts of metatantalum HTaO 3 and orthotantalic acids H 3 TaO 4 . There are also salts with the composition M 5 TaO 5 . Crystalline substances. used as ferroelectrics.
Tantalic acids are white gelatinous precipitates with variable water content; even freshly prepared ones do not dissolve in hydrochloric and nitric acids. They dissolve well in HF and alkali solutions. In technology, tantalic acid is usually obtained by decomposing tantalum and potassium double fluoride (potassium heptafluorotantalate) with sulfuric acid.
Tantalum(V) chloride, crystals, hygroscopic, hydrolyzed by water, soluble in CS 2 and CCl 4. It is used in tantalum production and coating.
Tantalum pentafluoride. Can be obtained by reacting pentachloride with liquid hydrogen fluoride. It forms colorless prisms and is hydrolyzed by water. Melt=96.8°С, boil=229°С. Used for applying tantalum coatings.
Potassium heptafluorotantalate- K 2 TaF 7 is a complex compound that can be obtained by reacting tantalum pentafluoride with potassium fluoride. White crystals, stable in air. Hydrolyzed by water: K 2 TaF 7 + H 2 O -> Ta 2 O 5 *nH 2 O + KF + HF

Application:

Since tantalum combines excellent metallic properties with exceptional chemical resistance, it has proven highly suitable for the manufacture of surgical and dental instruments such as tweezer tips, injection needles, needles, etc. In some cases it can replace platinum.
They are also used for the manufacture of capacitors, cathodes of electron tubes, equipment in the chemical industry and nuclear energy, and dies for the production of artificial fibers. Carbide, silicide, tantalum nitride - heat-resistant materials, components of hard and heat-resistant alloys.
Heat-resistant alloys of tantalum with niobium and tungsten are used in rocket and space technology.

E. Rosenberg.

Sources: Tantalum // Popular library of chemical elements Publishing house "Science", 1977.
Tantalum // Wikipedia. Update date: 12/12/2017. (access date: 05/20/2018).
// S. I. Levchenkov. A brief outline of the history of chemistry/ SFU.

Metal Tantalum opened quite recently, namely in 1802. The Swedish chemist A.G. was lucky enough to discover this metal. Ekeberg. When studying two new minerals that were found in the Scandinavian countries, it turned out that in addition to the known elements, they also contained previously unstudied ones. The scientist was never able to isolate the metal from the mineral in its pure form, as great difficulties arose with this.

In this regard, the unexplored metal was named after a hero from the mythology of Ancient Greece, and after which it was written myth of Tantalus. After this, for more than 40 years, it was believed that tantalum and niobium- these are the same metal. However, one German chemist proved the difference between the metals, and after that another German isolated tantalum in its pure form, and this happened only in 1903.

Serial production of rolled products and tantalum products began only during the Second World War. Today this element is given the name “smart metal”, since rapidly developing electronics cannot do without it.

Description and properties of tantalum

Tantalum is a metal with high hardness and atomic density. In the periodic chemical elements, tantalum is located at position 73. In world practice, it is customary to denote this metal by a combination of two letters, namely Ta. At atmospheric pressure and room temperature, tantalum has a characteristic silvery-metallic color. The oxide film that forms on the surface of the metal will give it a leaden tint.

Tantalum element inactive at room temperature. Oxidation of the surface of this metal by air is possible only at temperatures above 280 degrees. Tantalum reacts with halogens at a temperature 30 degrees lower than with air. In this case, a protective film is formed on the surface, which prevents further penetration of oxidizing elements into the depth of the metal.

Tantalum chemical element with a fairly high melting point. So, it is 3290 K, and the boiling point reaches 5731 K. Despite the high density (16.7 g/cm3) and hardness, it is quite plastic. In terms of ductility, tantalum can be compared with. Pure metal is very easy and convenient to work with.

It is easy to machine, for example, it can be rolled out to a thickness of 1-10 microns. It should also be noted that tantalum is paramagnetic. An interesting feature of this metal begins to appear at a temperature of 800 degrees: tantalum absorbs 740 of its gas volumes.

There are already a number of facts in world practice that indicate the excellent durability of this metal in very aggressive environments. For example, it is known that tantalum is not damaged even by 70% nitric acid. Sulfuric acid up to 150 degrees also does not lead to corrosive destruction, but already at 200 degrees the metal will begin to dissolve at a rate of 0.006 mm/year.

Some production facts also indicate that tantalum is much more resistant than austenitic stainless steels. Therefore, there is a known case in which tantalum parts lasted 20 years longer than stainless steel parts.

Another interesting fact is that tantalum is used for catalytic separation of gold. Cathodes are made from it, onto which the noble metal is in turn deposited, and then washed off with aqua regia. In this case, the cathode and tantalum, due to its excellent resistance to acids, remain intact.

Applications of tantalum

Long ago, this metal was used to produce filaments in incandescent lamps. Today tantalum and tantalum alloys used in the following industries and products:

— when smelting heat-resistant and corrosion-resistant alloys (for example, aircraft engine parts);

— in the chemical industry to create corrosion-resistant equipment;

— in metallurgical production for the production of rare earth metals;

— during the construction of nuclear reactors (tantalum is the most resistant metal to cesium vapor);

— due to its high biocompatibility, tantalum is used for the manufacture of medical implants and prostheses;

- for the production of superconductors - cryotrons (these are elements of computer technology);

- used in the military industry for the manufacture of shells. The use of this metal increases the penetrating power of ammunition;

- more efficient low voltage capacitors are made from tantalum;

- Recently, tantalum has become firmly established in business. This is due to the ability of the metal to form strong oxide films on the surface, which can be of various colors and shades;

- a large number of modifications of tantalum accumulates in nuclear reactors. For laboratory or military purposes, this modification of the metal can be used as a source of gamma radiation;

— this metal is used as the main one (after platinum) for the manufacture of mass standards, which have increased accuracy;

- some intermetallic tantalum compounds have very high hardness and strength, as well as increased resistance to oxidation. These compounds are used in the aviation and space industries;

— tantalum carbides are used for the manufacture of cutting tools with increased red resistance. The tool is obtained by sintering a mixture of carbide powders. These tools are used in very difficult conditions, for example, during percussion drilling;

- pentavalent tantalum oxide necessary for welding glass in nuclear technology.

Tantalum deposits and mining

Tantalum is a rare metal. Its amount in the earth's crust is only 0.0002%. This amount includes two modifications of the metal: stable and radioactive. This rare metal occurs in the form of its own compounds and is part of many minerals. If tantalum is included in a mineral, it will always be together with niobium.

Deposits of tantalum compounds and minerals are found in many countries. The largest deposit of this element in Europe is located in France. On the African continent, Egypt has the most tantalum. China and Thailand also have high reserves of this metal. Smaller deposits are located in the CIS, Nigeria, Canada, Australia and other countries. However, the largest deposits discovered to date are in Australia.

About 420 tons of tantalum are mined annually in the world. The main processing plants for this metal are located in the USA and Germany. It is worth noting that the international community is declaring the need to increase the production of this rare metal. Such statements are primarily related to the increase in the production of electronics, in which this element is intensively used.

Thus, the number of developed fields increases every year. For example, to the main world developing fields, more places were added in Brazil, the USA and South Africa. However, it is worth noting that in the last 10 years there has been an intense reduction in tantalum production. The lowest production figure in the 21st century occurred in 2010.

Tantalum price

The cost of tantalum has fluctuated greatly over the past 15 years. So, in 2002-2003 buy tantalum it was possible at the lowest price. This year tantalum price ranged from 340 to 375 dollars per kilogram. In Russia today you can buy tantalum, price which is 2950 rubles per kilogram.

Tantalum (Ta) is an element with atomic number 73 and atomic weight 180.948. It is an element of a secondary subgroup of the fifth group, the sixth period of the periodic table of Dmitry Ivanovich Mendeleev. Tantalum in the free state under normal conditions is a platinum-gray metal with a slightly leaden tint, which is a consequence of the formation of an oxide film (Ta 2 O 5). Tantalum is a heavy, refractory, fairly hard, but not brittle metal; at the same time, it is very malleable, easily machined, especially in its pure form.

In nature, tantalum is found in the form of two isotopes: stable 181 Ta (99.99%) and radioactive 180 Ta (0.012%) with a half-life of 10 12 years. Of the artificially obtained radioactive 182 Ta (half-life 115.1 days), it is used as an isotope tracer.

The element was discovered in 1802 by the Swedish chemist A. G. Ekeberg in two minerals found in Finland and Sweden. It was named after the hero of ancient Greek myths Tantalus due to the difficulty of isolating him. For a long time, the minerals columbite, which contains columbium (niobium), and tantalite, which contains tantalum, were considered to be one and the same. After all, these two elements are frequent companions of each other and are similar in many ways. This opinion was considered correct for a long time among chemists of all countries, only in 1844 the German chemist Heinrich Rose again studied columbites and tantalites from various places and found in them a new metal, similar in properties to tantalum. It was niobium. Plastic pure metal tantalum was first obtained by the German scientist W. von Bolton in 1903.

The main deposits of tantalum minerals are located in Finland, Scandinavian countries, North America, Brazil, Australia, France, China and a number of other countries.

Due to the fact that tantalum has a number of valuable properties - good ductility, high strength, weldability, corrosion resistance at moderate temperatures, refractoriness and a number of other important qualities - the use of the seventy-third element is very wide. The most important areas of application of tantalum are electronics and mechanical engineering. Approximately a quarter of the world's tantalum production goes to the electrical and vacuum industries. In electronics, it is used for the manufacture of electrolytic capacitors, anodes of high-power lamps, and grids. In the chemical industry, tantalum is used to make machine parts used in the production of acids, because this element has exceptional chemical resistance. Tantalum does not dissolve even in such a chemically aggressive environment as aqua regia! Metals, such as rare earths, are melted in tantalum crucibles. Heaters for high-temperature furnaces are made from it. Due to the fact that tantalum does not interact with living tissues of the human body and does not harm them, it is used in surgery to hold bones together in case of fractures. However, the main consumer of such a valuable metal is metallurgy (over 45%). In recent years, tantalum is increasingly used as an alloying element in special steels - ultra-strong, corrosion-resistant, heat-resistant. In addition, many structural materials quickly lose thermal conductivity: an oxide or salt film that conducts heat poorly is formed on their surface. Structures made of tantalum and its alloys do not face such problems. The oxide film formed on them is thin and conducts heat well, and also has protective anti-corrosion properties.

Not only pure tantalum is valuable, but also its compounds. Thus, the high hardness of tantalum carbide is used in the manufacture of carbide tools for high-speed cutting of metal. Tantalum-tungsten alloys impart heat resistance to parts made from them.

Biological properties

Due to its high biological compatibility - the ability to get along with living tissues without causing irritation or rejection by the body - tantalum has found wide use in medicine, mainly in reconstructive surgery - to restore the human body. Thin plates of tantalum are used for damage to the skull - they close breaks in the skull. Medicine knows of a case where an artificial ear was made from a tantalum plate, and the skin transplanted from the thigh took root so well and quickly that soon the artificial organ could not be distinguished from the real one. Tantalum threads are used to restore damaged muscle tissue. Surgeons use tantalum plates to fasten the walls of the abdominal cavity after operations. Even blood vessels can be connected using tantalum paper clips. Networks made from this unique material are used in the manufacture of eye prostheses. Threads made of this metal are used to replace tendons and even sew together nerve fibers.

No less widespread is the use of tantalum pentoxide Ta 2 O 5 - its mixture with a small amount of iron trioxide is proposed to be used to accelerate blood clotting.

Over the past decade, a new branch of medicine has been developing, based on the use of short-range static electric fields to stimulate positive biological processes in the human body. Moreover, electric fields are formed not due to traditional electrical energy sources with network or battery power supply, but due to autonomously functioning electret coatings (a dielectric that retains an uncompensated electric charge for a long time), applied to implants for various purposes, widely used in medicine.

Currently, positive results from the use of electret films of tantalum pentoxide have been obtained in the following areas of medicine: maxillofacial surgery (the use of implants coated with Ta 2 O 5 eliminates the occurrence of inflammatory processes and reduces the time of implant engraftment); orthopedic dentistry (coating dentures made of acrylic plastics with a film of tantalum pentoxide eliminates all possible pathological manifestations caused by intolerance to acrylates); surgery (use of an electret applicator in the treatment of defects of the skin and connective tissue in long-term non-healing wound processes, bedsores, neurotrophic ulcers, thermal injuries); traumatology and orthopedics (acceleration of bone tissue development in the treatment of fractures and diseases of the human musculoskeletal system under the influence of a static field created by an electret coating film).

All these unique scientific developments became possible thanks to the scientific work of specialists from the St. Petersburg State Electrotechnical University (LETI).

In addition to the areas listed above where unique tantalum pentoxide coatings are already being used or are being introduced, there are developments that are in the very early stages. These include developments for the following areas of medicine: cosmetology (production of a material based on tantalum pentoxide coatings, which will replace “golden threads”); cardiac surgery (applying electret films to the inner surface of artificial blood vessels, preventing the formation of blood clots); endoprosthetics (reducing the risk of rejection of prostheses that are in constant interaction with bone tissue). In addition, a surgical instrument coated with tantle pentoxide film is being created.

It is known that tantalum is very resistant to aggressive environments, as evidenced by a number of facts. So at a temperature of 200 °C this metal is not affected by seventy percent nitric acid! In sulfuric acid at a temperature of 150 °C, tantalum corrosion is also not observed, and at 200 °C the metal corrodes, but only by 0.006 mm per year!

There is a known case where at one enterprise that used hydrogen chloride gas, stainless steel parts failed after just a couple of months. However, as soon as steel was replaced by tantalum, even the thinnest parts (0.3...0.5 mm thick) turned out to be practically indefinite - their service life increased to 20 years!

Tantalum, along with nickel and chromium, is widely used as an anti-corrosion coating. It covers parts of a wide variety of shapes and sizes: crucibles, pipes, sheets, rocket nozzles and much more. Moreover, the material on which tantalum coating is applied can be very diverse: iron, copper, graphite, quartz, glass and others. What is most interesting is that the hardness of the tantalum coating is three to four times higher than the hardness of technical tantalum in annealed form!

Due to the fact that tantalum is a very valuable metal, the search for its raw materials continues to this day. Mineralogists have discovered that ordinary granites, in addition to other valuable elements, also contain tantalum. An attempt to extract tantalum from granite rocks was made in Brazil, the metal was obtained, but such extraction did not reach an industrial scale - the process turned out to be extremely expensive and complex.

Modern electrolytic tantalum capacitors are stable, reliable and durable. Miniature capacitors made from this material, used in various electronic systems, in addition to the above advantages, have one unique quality: they can carry out their own repairs on their own! How does this happen? Suppose that the integrity of the insulation is damaged due to a voltage drop or for another reason - instantly an insulating oxide film is formed again at the site of the breakdown, and the capacitor continues to work as if nothing had happened!

Undoubtedly, the term “smart metal”, which appeared in the middle of the 20th century, that is, a metal that helps smart machines operate, can rightfully be assigned to tantalum.

In some areas, tantalum replaces and sometimes even competes with platinum! Thus, in jewelry work, tantalum often replaces a more expensive noble metal in the manufacture of bracelets, watch cases and other jewelry. In another area, tantalum successfully competes with platinum - standard analytical balances made from this metal are not inferior in quality to platinum ones.

In addition, tantalum is replacing the more expensive iridium in the production of nibs for automatic pens.

Due to its unique chemical properties, tantalum has found application as a material for cathodes. Thus, tantalum cathodes are used in the electrolytic separation of gold and silver. Their value lies in the fact that the sediment of noble metals can be washed off with aqua regia, which does not harm tantalum.

One can definitely talk about the fact that there is something symbolic, if not mystical, in the fact that the Swedish chemist Ekeberg, trying to saturate a new substance with acids, was struck by its “thirst” and gave the new element a name in honor of the mythical villain who killed his own son and betrayed the gods. And two hundred years later it turned out that this element is capable of literally “sewing” a person and even “replacing” his tendons and nerves! It turns out that the martyr, languishing in the underworld, atones for his guilt by helping man, tries to beg forgiveness from the gods...

Story

Tantalus is a hero of ancient Greek myths, a Lydian or Phrygian king, the son of Zeus. He divulged the secrets of the Olympian gods, stole ambrosia from their feast and treated the Olympians to a dish prepared from the body of his own son Pelops, whom he killed. For his atrocities, Tantalus was sentenced by the gods to eternal torment of hunger, thirst and fear in the underworld of Hades. Since then, he has been standing up to his neck in transparent crystal clear water, branches bending towards his head under the weight of ripe fruits. Only he cannot quench his thirst or hunger - the water goes down as soon as he tries to drink, and the branches are lifted by the wind, at the hands of a hungry killer. A rock hangs over Tantalus's head, which could collapse at any moment, forcing the unfortunate sinner to forever suffer from fear. Thanks to this myth, the expression “Tantalum’s torment” arose, denoting unbearable suffering, ethereal attempts to free oneself from torment. Apparently, during the unsuccessful attempts of the Swedish chemist Ekeberg to dissolve the “earth” he discovered in 1802 in acids and isolate a new element from it, it was this expression that came to his mind. More than once the scientist thought that he was close to his goal, but he was never able to isolate the new metal in its pure form. This is how the “martyrdom” name of the new element appeared.

The discovery of tantalum is closely related to the discovery of another element - niobium, which was born a year earlier and was originally named Columbia, which was given to it by its discoverer Hatchet. This element is a twin of tantalum and is close to it in a number of properties. It was this proximity that misled chemists, who, after much debate, came to the erroneous conclusion that tantalum and columbium were the same element. This misconception lasted for more than forty years, until in 1844 the famous German chemist Heinrich Rose, during a repeated study of columbites and tantalites from various deposits, proved that columbium is an independent element. The Columbia studied by Gatchet was niobium with a high tantalum content, which misled the scientific world. In honor of such a close relationship between the two elements, Rose gave Colombia the new name Niobium - in honor of the daughter of the Phrygian king Tantalus Niobia. Although Rose also made the mistake of allegedly discovering another new element, which he named Pelopius (after Tantalus's son Pelops), his work became the basis for a strict distinction between niobium (Columbium) and tantalum. Only, even after Rose’s evidence, tantalum and niobium were confused for a long time. So tantalum was called columbium, in Russia columbus. Hess, in his "Principles of Pure Chemistry" up to its sixth edition (1845), speaks only of tantalum, without mentioning Columbia; Dvigubsky (1824) mentions the name tantalium. Such errors and reservations are understandable - the method for separating tantalum and niobium was developed only in 1866 by the Swiss chemist Marignac, and as such, pure elemental tantalum did not yet exist: after all, scientists were able to obtain this metal in its pure compact form only in the 20th century. The first who was able to obtain tantalum metal was the German chemist von Bolton, and this happened only in 1903. Previously, of course, attempts were made to obtain pure tantalum metal, but all the efforts of chemists were unsuccessful. For example, the French chemist Moissan obtained a metal powder, which he claimed was pure tantalum. However, this powder, obtained by reducing tantalum pentoxide Ta 2 O 5 with carbon in an electric furnace, was not pure tantalum; the powder contained 0.5% carbon.

As a result, a detailed study of the physicochemical properties of the seventy-third element became possible only at the beginning of the twentieth century. For several more years, tantalum did not find practical use. Only in 1922 could it be used in AC rectifiers.

Being in nature

The average content of the seventy-third element in the earth's crust (clarke) is 2.5∙10 -4% by mass. Tantalum is a characteristic element of acidic rocks - granite and sedimentary shells, in which its average content reaches 3.5∙10 -4%, as for ultrabasic and basic rocks - the upper parts of the mantle and the deep parts of the earth's crust, the concentration of tantalum there is much lower: 1 .8∙10 -6%. Tantalum is scattered in rocks of igneous origin, as well as in the biosphere, since it is isomorphic with many chemical elements.

Despite the low content of tantalum in the earth's crust, its minerals are very widespread - there are more than a hundred of them, both tantalum minerals themselves and tantalum-containing ores, all of them formed in connection with magmatic activity (tantalite, columbite, loparite, pyrochlore and others). In all minerals, tantalum's companion is niobium, which is explained by the extreme chemical similarity of the elements and the almost identical sizes of their ions.

Tantalum ores themselves have a ratio of Ta 2 O 5: Nb 2 O 5 ≥1. The main minerals of tantalum ores are columbite-tantalite (Ta 2 O 5 content 30-45%), tantalite and manganotantalit (Ta 2 O 5 45-80%), wodginite (Ta, Mn, Sn) 3 O 6 (Ta 2 O 5 60-85%), microlite Ca 2 (Ta, Nb) 2 O 6 (F, OH) (Ta 2 O 5 50-80%) and others. Tantalite (Fe, Mn)(Ta, Nb) 2 O 6 has several varieties: ferrotantalite (FeO>MnO), manganotantalit (MnO>FeO). Tantalite comes in different shades from black to red-brown. The main minerals of tantalum-niobium ores, from which, along with niobium, much more expensive tantalum is extracted, are columbite (Ta 2 O 5 5-30%), tantalum-containing pyrochlore (Ta 2 O 5 1-4%), loparite (Ta 2 O 5 0.4-0.8%), gatchettolite (Ca, Tr, U) 2 (Nb, Ta) 2 O 6 (F, OH)∙nH 2 O (Ta 2 O 5 8-28%), ixiolite (Nb , Ta, Sn, W, Sc) 3 O 6 and some others. Tantalum-niobates containing U, Th, TR are metamict, highly radioactive and contain variable amounts of water; polymorphic modifications are common. Tantalum-niobates form small disseminations, large allocations are rare (crystals are typical mainly for loparite, pyrochlore and columbite-tantalite). Color black, dark brown, brownish-yellow. Usually translucent or slightly translucent.

There are several main industrial and genetic types of tantalum ore deposits. Rare-metal pegmatites of the natro-lithium type are represented by zoned vein bodies consisting of albite, microcline, quartz, and, to a lesser extent, spodumene or petalite. Rare-metal tantalum-bearing granites (apogranites) are represented by small stocks and domes of microcline-quartz-albite granites, often enriched in topaz and lithium micas containing thin dissemination of columbite-tantalite and microlite. Weathering crusts, deluvial-alluvial and alluvial placers arising in connection with the destruction of pegmatites contain cassiterite and minerals of the columbite-tantalite group. Loparite-bearing nepheline syenites of lujavrite and foyalite composition.

In addition, deposits of complex tantalum-niobium ores, represented by carbonatites and associated forsterite-apatite-magnetite rocks, are involved in industrial use; microcline-albite riebeckite alkaline granites and granosyenites and others. Some tantalum is extracted from wolframites of greisen deposits.

The largest deposits of titanium ores are located in Canada (Manitoba, Bernick Lake), Australia (Greenbushes, Pilbara), Malaysia and Thailand (tantalum-bearing tin placers), Brazil (Paraiba, Rio Grande do Norte), and a number of African states (Zaire, Nigeria, Southern Rhodesia).

Application

Tantalum found its technical application quite late - at the beginning of the 20th century it was used as a material for incandescent filaments of electric lamps, which was due to the quality of this metal, such as refractoriness. However, it soon lost its importance in this area, replaced by the less expensive and more refractory tungsten. Tantalum again became “technically unsuitable” until the twenties of the 20th century, when it began to be used in alternating current rectifiers (tantalum, coated with an oxide film, passes current in only one direction), and a year later - in radio tubes. After which the metal gained recognition and soon began to conquer more and more new areas of industry.

Nowadays, due to its unique properties, tantalum is used in electronics (production of capacitors with high specific capacitance). About a quarter of the world's tantalum production goes to the electrical and vacuum industries. Due to the high chemical inertness of both tantalum itself and its oxide film, electrolytic tantalum capacitors are very stable in operation, reliable and durable: their service life can reach more than twelve years. In radio engineering, tantalum is used in radar equipment. Tantalum mini capacitors are used in radio transmitters, radar installations and other electronic systems.

The main consumer of tantalum is metallurgy, which uses over 45% of the metal produced. Tantalum is actively used as an alloying element in special steels - ultra-strong, corrosion-resistant, heat-resistant. The addition of this element to conventional chromium steels increases their strength and reduces brittleness after hardening and annealing. The production of heat-resistant alloys is a great need for rocket and space technology. In cases where rocket nozzles are cooled by liquid metal that can cause corrosion (lithium or sodium), it is simply impossible to do without a tantalum-tungsten alloy. In addition, heaters for high-temperature vacuum furnaces, heaters, and mixers are made from heat-resistant steels. Tantalum carbide (melting point 3,880 °C) is used in the production of hard alloys (mixtures of tungsten and tantalum carbides - grades with the TT index, for the most difficult conditions of metalworking and rotary impact drilling of the strongest materials (stone, composites).

Steels alloyed with tantalum are widely used, for example in chemical engineering. After all, such alloys have exceptional chemical resistance, they are ductile, heat-resistant and heat-resistant; it is thanks to these properties that tantalum has become an indispensable structural material for the chemical industry. Tantalum equipment is used in the production of many acids: hydrochloric, sulfuric, nitric, phosphoric, acetic, as well as bromine, chlorine and hydrogen peroxide. Coils, distillers, valves, mixers, aerators and many other parts of chemical apparatus are made from it. Sometimes - entire devices. Tantalum cathodes are used in the electrolytic separation of gold and silver. The advantage of these cathodes is that gold and silver deposits can be washed off with aqua regia, which does not harm tantalum.

In addition, tantalum is used in instrument making (X-ray equipment, control instruments, diaphragms); in medicine (material for reconstructive surgery); in nuclear energy - as a heat exchanger for nuclear energy systems (tantalum is the most stable of all metals in superheated melts and cesium-133 vapors). The high ability of tantalum to absorb gases is used to maintain high vacuum (electric vacuum devices).

In recent years, tantalum has been used as a jewelry material due to its ability to form durable oxide films of any color on the surface.

Tantalum compounds are also widely used. Tantalum pentoxide is used in nuclear technology to melt glass that absorbs gamma radiation. Potassium fluorotantalate is used as a catalyst in the production of synthetic rubber. Tantalum pentoxide also plays the same role when producing butadiene from ethyl alcohol.

Production

It is known that ores containing tantalum are rare and poor in this element. The main raw materials for the production of tantalum and its alloys are tantalite and loparite concentrates containing only 8% Ta 2 O 5 and more than 60% Nb 2 O 5. In addition, even those ores that contain only hundredths of a percent (Ta, Nb) 2 O 5 are processed!

The tantalum production technology is quite complex and is carried out in three stages: opening or decomposition; separation of tantalum from niobium and obtaining their pure chemical compounds; recovery and refining of tantalum.

The opening of tantalum concentrate, in other words, the extraction of tantalum from ores is carried out using alkalis (fusion) or using hydrofluoric acid (decomposition) or a mixture of hydrofluoric and sulfuric acids. After which they move on to the second stage of production - extraction extraction and separation of tantalum and niobium. The last task is very difficult due to the similarity of the chemical properties of these metals and the almost identical size of their ions. Until recently, metals were separated only by the method proposed back in 1866 by the Swiss chemist Marignac, who took advantage of the different solubility of potassium fluorotantalate and potassium fluoroniobate in dilute hydrofluoric acid. Modern industry uses several methods for separating tantalum and niobium: extraction with organic solvents, selective reduction of niobium pentachloride, fractional crystallization of complex fluoride salts, separation using ion exchange resins, rectification of chlorides. Currently, the most commonly used separation method (it is also the most advanced) is extraction from solutions of tantalum and niobium fluoride compounds containing hydrofluoric and sulfuric acids. At the same time, tantalum and niobium are purified from impurities of other elements: silicon, titanium, iron, manganese and other related elements. As for loparite ores, their concentrates are processed using the chlorine method to produce a condensate of tantalum and niobium chlorides, which are further separated by rectification. The separation of a mixture of chlorides consists of the following stages: preliminary rectification (separation of tantalum and niobium chlorides from accompanying impurities occurs), main rectification (to obtain pure NbCl 5 and TaCl 5 concentrate) and final rectification of the tantalum fraction (to obtain pure TaCl 5). Following the separation of related metals, the tantalum phase is precipitated and purified to produce potassium fluorotantalate of increased purity (using KCl).

Tantalum metal is obtained by reducing its high-purity compounds, for which several methods can be used. This is either the reduction of tantalum from pentoxide with soot at a temperature of 1800-2000 ° C (carbothermic method), or the reduction of potassium fluorotantalate with sodium when heated (sodium thermal method), or electrochemical reduction from a melt containing potassium fluorotantalate and tantalum oxide (electrolytic method). One way or another, the metal is obtained in powder form with a purity of 98-99%. In order to obtain metal in ingots, it is sintered in the form of pre-compressed billets from powder. Sintering occurs by passing current at a temperature of 2,500–2,700 °C or by heating in a vacuum at 2,200–2,500 °C. After which the purity of the metal increases significantly, becoming equal to 99.9-99.95%.

For further refining and production of tantalum ingots, electric vacuum melting is used in arc furnaces with a consumable electrode, and for deeper refining, electron beam melting is used, which significantly reduces the content of impurities in tantalum, increases its ductility and reduces the temperature of transition to a brittle state. Tantalum of such purity retains high ductility at temperatures close to absolute zero! The surface of a tantalum ingot is melted (to give the required characteristics to the surface of the ingot) or processed on a lathe.

Physical properties

Only at the beginning of the 20th century did scientists get their hands on pure tantalum metal and were able to study in detail the properties of this light gray metal with a slightly bluish lead tint. What qualities does this element have? Definitely, tantalum is a heavy metal: its density is 16.6 g/cm 3 at 20 ° C (for comparison, iron has a density of 7.87 g/cm 3, the density of lead is 11.34 g/cm 3) and for transporting one cubic meter This element would require six three-ton trucks. High strength and hardness are combined with excellent plastic characteristics. Pure tantalum lends itself well to mechanical processing, is easily stamped, processed into the thinnest sheets (about 0.04 mm thick) and wire (elastic modulus of tantalum 190 Hn/m2 or 190·102 kgf/mm2 at 25 °C). In the cold, the metal can be processed without significant work hardening and is subject to deformation with a compression ratio of 99% without intermediate firing. The transition of tantalum from a ductile to a brittle state is not observed even when it is cooled to -196 °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% (at 27 °C) and 20% (at 490 °C). Tantalum has a body-centered cubic lattice (a = 3.296 A); atomic radius 1.46 A, ionic radii Ta 2+ 0.88 A, Ta 5+ 0.66 A.

As mentioned earlier, tantalum is a very hard metal (the Brinell hardness of tantalum sheets in the annealed state is 450-1250 MPa, in the deformed state 1250-3500 MPa). Moreover, it is possible to increase the hardness of the metal by adding a number of impurities to it, for example carbon or nitrogen (the Brinell hardness of a tantalum sheet after absorbing gases during heating increases to 6000 MPa). As a result, interstitial impurities contribute to an increase in Brinell hardness, tensile strength, and yield strength, but they reduce the plasticity characteristics and increase cold brittleness; in other words, they make the metal brittle. Other characteristic features of the seventy-third element are its high thermal conductivity, at 20–100 °C this value is 54.47 W/(m∙K) or 0.13 cal/(cm·sec·°С) and refractoriness (perhaps the most an important physical property of tantalum) - it melts at almost 3,000 °C (more precisely, at 2,996 °C), second only to tungsten and rhenium. The boiling point of tantalum is also extremely high: 5,300 °C.

As for other physical properties of tantalum, its specific heat at temperatures from 0 to 100 °C is 0.142 kJ/(kg K) or 0.034 cal/(g °C); the temperature coefficient of linear expansion of tantalum is 8.0·10 -6 (at temperatures of 20–1,500 °C). The electrical resistivity of the seventy-third element at 0 °C is 13.2 10 -8 ohm m, at 2000 °C 87 10 -8 ohm m. At 4.38 K the metal becomes a superconductor. Tantalum is paramagnetic, specific magnetic susceptibility 0.849·10 -6 (at 18 °C).

So, tantalum has a unique set of physical properties: high heat transfer coefficient, high ability to absorb gases, heat resistance, refractoriness, hardness, and plasticity. In addition, it is distinguished by high strength - it lends itself well to pressure treatment using all existing methods: forging, stamping, rolling, drawing, twisting. Tantalum is characterized by good weldability (welding and soldering in argon, helium, or in vacuum). In addition, tantalum has exceptional chemical and corrosion resistance (with the formation of an anodic film), low vapor pressure and low electron work function, and, in addition, it gets along well with living tissue of the body.

Chemical properties

Definitely, one of the most valuable properties of tantalum is its exceptional chemical resistance: in this respect it is second only to noble metals, and even then not always. It is resistant to hydrochloric, sulfuric, nitric, phosphoric and organic acids of all concentrations (up to a temperature of 150 ° C). In terms of its chemical stability, tantalum is similar to glass - it is insoluble in acids and their mixtures, even aqua regia does not dissolve it, against which gold and platinum and a number of other valuable metals are powerless. The seventy-third element is soluble only in a mixture of hydrofluoric and nitric acids. Moreover, the reaction with hydrofluoric acid occurs only with metal dust and is accompanied by an explosion. Even in hot hydrochloric and sulfuric acids, tantalum is more resistant than its twin brother niobium. However, tantalum is less resistant to alkalis - hot solutions of caustic alkalis corrode the metal. Salts of tantalic acids (tantalates) are expressed by the general formula: xMe 2 O yTa 2 O 5 H 2 O, these include metatantalates MeTaO 3, orthotantalates Me 3 TaO 4, salts like Me 5 TaO 5, where Me is an alkali metal; in the presence of hydrogen peroxide, pertantalates are also formed. The most important alkali metal tantalates are KTaO 3 and NaTaO 3; these salts are ferroelectrics.

The high corrosion resistance of tantalum is also indicated by its interaction with atmospheric oxygen, or rather, its high resistance to this influence. The metal begins to oxidize only at 280 °C, becoming covered with a protective film of Ta 2 O 5 (tantalum pentoxide is the only stable metal oxide), which protects the metal from the action of chemical reagents and prevents the flow of electric current from the metal to the electrolyte. However, with an increase in temperature to 500 ° C, the oxide film gradually becomes porous, delaminates and separates from the metal, depriving the surface of the protective layer against corrosion. Therefore, it is advisable to carry out hot pressure treatment in a vacuum, since in air the metal oxidizes to a significant depth. The presence of nitrogen and oxygen increases the hardness and strength of tantalum, while simultaneously reducing its ductility and making the metal brittle, and, as mentioned earlier, tantalum forms a solid solution and oxide Ta 2 O 5 with oxygen (with an increase in the O 2 content in tantalum, a sharp increase in strength properties occurs and a strong decrease in ductility and corrosion resistance). Tantalum reacts with nitrogen to form three phases - a solid solution of nitrogen in tantalum, tantalum nitrides: Ta 2 N and TaN - in the temperature range from 300 to 1,100 ° C. It is possible to get rid of nitrogen and oxygen in tantalum under high vacuum conditions (at temperatures above 2,000 °C).

Tantalum reacts weakly with hydrogen until heated to 350 °C; the reaction rate increases significantly only from 450 °C (tantalum hydride is formed and tantalum becomes brittle). The same heating in a vacuum (over 800 °C) helps to get rid of hydrogen, during which the mechanical properties of tantalum are restored and the hydrogen is completely removed.

Fluorine acts on tantalum already at room temperature, and hydrogen fluoride also reacts with the metal. Dry chlorine, bromine and iodine have a chemical effect on tantalum at temperatures of 150 °C and above. Chlorine begins to actively interact with the metal at a temperature of 250 °C, bromine and iodine at a temperature of 300 °C. Tantalum begins to interact with carbon at very high temperatures: 1,200–1,400 °C, and the formation of refractory tantalum carbides, which are very resistant to acids, occurs. Tantalum combines with boron to form borides - solid, refractory compounds that are resistant to the effects of aqua regia. Tantalum forms continuous solid solutions with many metals (molybdenum, niobium, titanium, tungsten, vanadium and others). Tantalum forms limited solid solutions with gold, aluminum, nickel, beryllium and silicon. Tantalum does not form any compounds with magnesium, lithium, potassium, sodium and some other elements. Pure tantalum is resistant to many liquid metals (Na, K, Li, Pb, U-Mg and Pu-Mg alloys).

Tantalum is a silver-white metal with a high melting point. This figure is 3017 degrees Celsius. Tantalum has a high value for modern industry, as it is characterized by hardness, but at the same time it is ductile like gold. The metal has proven itself well in machining; it can be rolled into thin wire and can be stamped.

Tantalum was first discovered by the Swedish chemist A.G. Ekeberg. This mineral was part of two minerals that were found in Finland and Sweden. At that time, no method had been found that would allow obtaining this metal in its pure form. The metal began to be mined on an industrial scale relatively recently - in 1922.

Tantalum has excellent paramagnetic properties. Pure metal does not react with alkalis, organic and inorganic acids. Oxidation of tantalum in air occurs at temperatures exceeding 250 degrees Celsius. If we talk about its chemical resistance to reagents, then in this regard it is similar to glass.

Mining and production of tantalum

Tantalum is classified as a rare metal. In nature, it exists in the form of isotopes - stable and radioactive. At the moment, about twenty tantalum minerals and about sixty minerals that contain this metal are isolated. The largest tantalum deposit was discovered in Australia. This mineral is also mined in China, France, CIS countries, Brazil, and Canada. The bulk of tantalum, which was discovered in deposits of the Russian Federation, is mined in the Murmansk region.

Tantalum has a rather complex production technology. To obtain it, more than three thousand tons of ore are processed, due to which the metal has a very high cost, exceeding $4,500 per kilogram.

Applications of tantalum

The metal has received a wide range of uses. At the initial stage of production, it was used mainly to produce wire for incandescent lamps. Nowadays, a wide range of products are produced using metal and its alloys. The most popular and highly in demand include equipment for the chemical industry and heat exchangers for nuclear energy systems. Tantalum wire is actively used in cryotrons.

The metal has found wide application in modern medicine. Here it is used to produce wire, foil and sheets intended for fastening tissues and nerves and producing prostheses.

Tantalum is in quite high demand in the manufacture of jewelry. In this area, its ability to form a durable oxide film that has an iridescent appearance has been appreciated. The metal is used in the nuclear and military industries, where it is used to produce weapons. Along with hafnium, it can serve as an ideal source of gamma radiation. In the production of aerospace equipment, titanium berylide is used, which is famous for its excellent hardness and resistance to negative environmental factors.

In the future, the scope of application of this metal will expand even more, as it has excellent chemical and physical properties.

Buying tantalum

One of the activities of our company is the purchase of tantalum. We offer favorable terms of cooperation. Products can be returned either at a collection point or sent by mail.

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 capacity 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.