Tantalum metal characteristics and properties. Tantalum - application Controversy and misconceptions

The rapid development of modern technologies today is certainly associated with the use of effective materials and substances that have quite practical and very useful properties and features.

From this perspective, it is worth paying attention to such a unique chemical element as tantalum. And this is not surprising, because due to its strength characteristics, today the use of tantalum is becoming quite relevant in many areas of industry.

To broaden the horizons of the layman in this topic, we will describe in detail the physicochemical features of tantalum and talk about where this metal is very successfully used today.

Technical features of tantalum

First of all, it should be understood that tantalum is a gray metal with a brilliant tint, which can be easily machined.

Among the features of the metal, it is worth noting a number of the following important aspects:

• serial number in the periodic table - 73;
• atomic weight - 180;
• the density of the substance is 60 g / cm 3;
• melting point - 3015 0 C;
• the boiling point of the substance is 5300 0 C.

metal properties

Thanks to these characteristics, tantalum undoubtedly has the following advantageous properties:

1. Tantalum is a refractory metal, and as a result, the element has the following properties:

• small index of linear expansion;
• good level of thermal conductivity;
• high mechanical strength and ductility.

1. It has excellent anti-corrosion properties. It is worth noting that tantalum under normal conditions is practically inert to sea water, but if it is saturated with oxygen, then the metal in this case only tarnishes.
2. Tantalum has good resistance to the following types of salts:

• chlorides of iron and copper;
• nitrates;
• sulfates;
• salts of organic acids, however, provided that they do not contain fluorine or fluorides in their composition.

1. Tantalum begins to lose its strength characteristics when it reacts with fluorine. It is also worth considering the fact that tantalum does not enter into a chemical reaction with bromine, iodine and liquid chlorine, unless a temperature of 150 0 C is reached.
2. Tantalum is sufficiently resistant to liquid structure metals having a low melting point.
3. Tantalum has excellent stability characteristics in air at temperatures up to 400 0 C, while a protective film of oxide appears during storage or processing.
4. Tantalum, melted by the electron beam method, has an increased plasticity property, which, when the metal is deformed, allows a greater degree of compression to be performed.
5. It is well converted into sheet metal, which lends itself well to forging.
6. Works well for cold forming. However, you need to understand that this metal should not be deformed in a hot state, since when heated, tantalum begins to absorb nitrogen, carbon dioxide, oxygen, and, as a result, the material becomes quite brittle.
7. One of the main operations for processing tantalum is cutting the material on high-speed equipment.

As for the connection of tantalum parts, it can be done in the following ways:

• welding;
• soldering;
• connection with rivets.

Here it is worth taking into account the fact that the last two methods are used quite rarely, so the quality of tantalum welded joints always remains at a high level.

Areas of application of tantalum

These properties make it possible to widely use it in various industries. Let us note in detail the main directions for the use of such a unique material as tantalum.

Metallurgical industry

Metallurgy is the main consumer of this metal. The metallurgical industry consumes 45% of the produced tantalum.

The main application of tantalum is in a number of the following important aspects:

• metal is the main alloying element in the manufacture of heat-resistant and anti-corrosion steel grades;
• Tantalum carbide is a reliable protection for steel molds in foundries.

Electrical industry

First of all, it is worth noting the fact that a quarter of the tantalum produced in the world is used in the electrical industry. And this is not surprising, because the following types of electrical products are produced using this metal:

• tantalum capacitors of an electrolytic type are characterized by the stability of their functioning;
• widely used in the manufacture of such structural elements of lamps as anodes, indirectly heated cathodes and grids;
• tantalum wire is used in the production of cryotron parts, which are integral elements of computer technology;
• heaters for furnaces with high-temperature operation are very successfully made from this metal.

Interesting fact! Tantalum capacitors tend to self-repair. For example, with a sudden occurrence of high voltage, a spark destroyed the insulating layer. In this case, an insulating oxide film is instantly formed at the site of the defect, while the capacitor will continue to function in normal operating mode!

Chemical industry

It is necessary, first of all, to note the fact that 20% of the used tantalum goes to the needs of the chemical industry. In particular, this metal is used in the following cases:

• production of the following types of acids:

1. nitrogen;
2. deer;
3. sulfuric;
4. phosphoric;
5. acetic.

• production of hydrogen peroxide, bromine and chlorine;
• production of chemical equipment of the following types:

1. aerators;
2. distillation plants;
3. coils of various types;
4. agitators;
5. valve.

IN medical industry no more than 5% of the tantalum mined in the world is used. In medicine, this metal is very successfully used in plastic and bone surgery, as it is used to make tantalum elements for fastening bones, suturing, and so on. This is achieved due to the fact that tantalum does not harm the vital activity of the organism, while it does not irritate living tissue.

TANTALUM, Ta (named after the hero of ancient Greek mythology Tantalus; lat. Tantalum * a. tantalum; n. Tantal; f. tantale; and. tantalo), is a chemical element of group V of Mendeleev's periodic system, atomic number 73, atomic mass 180 .9479. It occurs in nature in the form of two isotopes: 181 Ta (99.9877%) and 180 Ta (0.0123%). There are 13 known artificial radioactive isotopes of tantalum with mass numbers from 172 to 186. Tantalum was discovered in 1802 by the Swedish chemist A. G. Ekeberg. Plastic metallic tantalum was first obtained by the German scientist W. Bolten in 1903.

Application and use

The main raw materials for the production of tantalum and its alloys are tantalite and loparite concentrates containing about 8% Ta 2 O 5 , 60% or more Nb 2 O 5 . Concentrates are decomposed by acids or alkalis, loparite concentrates are chlorinated. The separation of Ta and Nb is done 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 melting or powder metallurgy. From tantalum and its alloys, corrosion-resistant equipment for the chemical industry, spinnerets, laboratory glassware and crucibles are made; heat exchangers for nuclear power systems. In surgery, tantalum sheets, foil and wire are used to fasten tissues, nerves, suturing, making prostheses that replace damaged parts of bones (due to biological compatibility). Tantalum carbide is used in the production of hard alloys.

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 system of Dmitry Ivanovich Mendeleev. Tantalum in the free state under normal conditions is a platinum gray metal with a slightly lead tint, which is a consequence of the formation of an oxide film (Ta 2 O 5). Tantalum is a heavy, refractory, rather hard, but not brittle metal, at the same time it is very malleable, well machinable, 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) 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 identifying it. For a long time, the minerals columbite containing columbium (niobium) and tantalite containing tantalum were considered one and the same. After all, these two elements are frequent companions of each other and are similar in many respects. This opinion was considered true 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 metallic tantalum was first obtained by the German scientist W. von Bolton in 1903.

The main deposits of tantalum minerals are located in Finland, Scandinavia, 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 industry. In electronics, it is used to make electrolytic capacitors, anodes for 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! In tantalum crucibles, metals, such as rare earths, are melted. Heaters of 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 has been increasingly used as an alloying element in special steels - heavy-duty, corrosion-resistant, heat-resistant. In addition, many structural materials quickly lose their thermal conductivity: a poorly heat-conducting oxide or salt film forms 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, moreover, it has protective anti-corrosion properties.

Not only pure tantalum is of value, but also its compounds. So the high hardness of tantalum carbide is used in the manufacture of carbide tools for high-speed metal cutting. Tantalum-tungsten alloys give 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 and rejection of the body - tantalum has found wide application in medicine, mainly in reconstructive surgery - to restore the human body. Thin plates of tantalum are used for damage to the cranium - they close the fractures in the skull. Medicine knows the case when an artificial ear was made from a tantalum plate, while 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 in the restoration of damaged muscle tissue. Surgeons fasten the walls of the abdominal cavity with tantalum plates after operations. Even blood vessels can be connected using tantalum staples. Networks of this unique material are used in the manufacture of ocular prostheses. Tendons are replaced with threads of this metal and even nerve fibers are sewn together.

Tantalum pentoxide Ta 2 O 5 is no less widely used - its mixture with a small amount of iron trioxide is proposed to be used to accelerate blood coagulation.

In the last 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 mains or battery power supply, but due to autonomously functioning electret coatings (a dielectric that retains an uncompensated electric charge for a long time) deposited on implants for various purposes, widely used in medicine.

At present, positive results of 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, reduces the time of engraftment of the implant); orthopedic dentistry (covering prostheses made of acrylic plastics with a film of tantalum pentoxide eliminates all possible pathological manifestations caused by intolerance to acrylates); surgery (the use of an electret applicator in the treatment of defects in the skin and connective tissue with long-term non-healing wound processes, bedsores, neurotrophic ulcers, thermal lesions); 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 above areas where unique coatings of tantalum pentoxide are already being applied or introduced, there are developments that are at the very initial stages. These include developments for the following areas of medicine: cosmetology (production of a material based on coatings of tantalum pentoxide, which will replace the "golden threads"); cardiac surgery (application of electret films on the inner surface of artificial blood vessels, prevents the formation of blood clots); arthroplasty (reducing the risk of rejection of prostheses that are in constant interaction with bone tissue). In addition, a surgical instrument coated with a film of tantalum pentoxide is being created.

It is known that tantalum is very resistant to aggressive media, a number of facts testify to this. 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!

A case is known when in one enterprise using gaseous hydrogen chloride, stainless steel parts failed after 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. They cover parts of a wide variety of shapes and sizes: crucibles, pipes, sheets, rocket nozzles and much more. Moreover, the material on which the 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 today. 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 production did not reach an industrial scale - the process turned out to be extremely expensive and complicated.

Modern electrolytic tantalum capacitors are stable in operation, 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 make their own repairs themselves! How does this happen? Suppose that the integrity of the insulation is violated due to a voltage drop, or for another reason - instantly an insulating oxide film forms again at the breakdown site, 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 work, can rightfully be attributed to tantalum.

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

In addition, tantalum is used as a substitute for the more expensive iridium in the production of nib nibs for automatic pens.

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

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

Story

Tantalus is the hero of ancient Greek myths, the Lydian or Phrygian king, the son of Zeus. He divulged the secrets of the Olympic gods, stole ambrosia from their feast and treated the Olympians to a dish prepared from the body of his own son Pelops, whom he also 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 leaning towards his head under the weight of ripe fruits. Only he cannot quench either thirst or hunger - the water goes down as soon as he tries to get drunk, and the branches are lifted by the wind, at the hands of a hungry killer. A rock hangs over Tantalus's head, which can collapse at any moment, forcing the unfortunate sinner to suffer forever from fear. Thanks to this myth, the expression "tantalum torment" arose, denoting unbearable suffering, incorporeal attempts to free oneself from torment. Apparently, in the course of unsuccessful attempts by the Swedish chemist Ekeberg to dissolve the “earth” discovered by him in 1802 in acids and isolate a new element from it, it was this expression that came to his mind. More than once it seemed to the scientist that he was close to the goal, but he failed to isolate a new metal in its pure form. This is how the “martyr” name of the new element appeared.

The discovery of tantalum is closely related to the discovery of another element - niobium, which appeared a year earlier and was originally called Columbia, which was given to it by the discoverer Gatchet. This element is a twin of tantalum 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 one and the same element. This delusion lasted for more than forty years, until in 1844 the famous German chemist Heinrich Rose, in the course of re-studying columbites and tantalites from various deposits, proved that columbium is an independent element. The Columbia studied by Gatchet was niobium with a high content of tantalum, which led the scientific world astray. In honor of such a family proximity of the two elements, Rosa assigned the new name Niobium to Colombia - in honor of the daughter of the Phrygian king Tantalus Niobia. And although Rose also made the mistake of allegedly discovering another new element, which he named Pelopius (in honor of 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 columbium. Hess, in his Foundations of Pure Chemistry, up to their sixth edition (1845), speaks only of tantalum, without mentioning Columbia; Dvigubsky (1824) has a name - tantalium. Such errors and reservations are understandable - a 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 a pure compact form only in the 20th century. The first who was able to obtain metallic tantalum was the German chemist von Bolton, and this happened only in 1903. Earlier, of course, attempts were made to obtain pure metallic tantalum, but all the efforts of chemists were unsuccessful. For example, the French chemist Moissan received a metal powder, according to him - 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 weight. Tantalum is a characteristic element of acid 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 deep parts of the earth's crust, the concentration of tantalum there is much lower: 1 .8∙10 -6%. In rocks of igneous origin, tantalum is dispersed, 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 proper and tantalum-containing ores, all of them were formed in connection with magmatic activity (tantalite, columbite, loparite, pyrochlore and others). In all minerals, tantalum is accompanied by niobium, which is explained by the extreme chemical similarity of the elements and the almost identical sizes of their ions.

Actually tantalum ores 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 manganotantalite (Ta 2 O 5 45-80%), wojinite (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), manganotantalite (MnO>FeO). Tantalite comes in many 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%), hatchettolite (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. Tantalo-niobates containing U, Th, TR are metamict, highly radioactive, and contain variable amounts of water; polymorphic modifications are common. Tantalo-niobates form small disseminations, large segregations are rare (crystals are typical mainly for loparite, pyrochlore and columbite-tantalite). Coloration 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 fine 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 amount of 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), a number of African states (Zaire, Nigeria, Southern Rhodesia).

Application

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

Nowadays, tantalum, due to its unique properties, is used in electronics (production of high specific capacitance capacitors). Approximately a quarter of the world production of tantalum goes to the electrical and vacuum industry. 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. Mini tantalum 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 - heavy-duty, corrosion-resistant, heat-resistant. The addition of this element to ordinary chromium steels increases their strength and reduces brittleness after hardening and annealing. The production of heat-resistant alloys is a great necessity for rocket and space technology. In cases where rocket nozzles are cooled by a liquid metal that can cause corrosion (lithium or sodium), it is simply impossible to do without an alloy of tantalum and tungsten. In addition, heat-resistant steels are used to manufacture heaters for high-temperature vacuum furnaces, heaters, and stirrers. 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 metalworking conditions and percussive rotary 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 - the whole apparatus. Tantalum cathodes are used in the electrolytic separation of gold and silver. The advantage of these cathodes is that the deposit of gold and silver can be washed off them with aqua regia, which does not harm the tantalum.

In addition, tantalum is used in instrumentation (X-ray equipment, control instruments, diaphragms); in medicine (material for reconstructive surgery); in nuclear power - as a heat exchanger for nuclear power systems (tantalum is the most stable of all metals in superheated melts and cesium-133 vapor). The high ability of tantalum to absorb gases is used to maintain a deep vacuum (electrovacuum 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 for melting 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 in the production of butadiene from ethyl alcohol.

Production

It is known that ores containing tantalum are rare and poor in this particular 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 technology for the production of tantalum is quite complex and is carried out in three stages: opening or decomposition; separating 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 with the help of alkalis (fusion) or with the help of hydrofluoric acid (decomposition) or a mixture of hydrofluoric and sulfuric acids. Then they proceed to the second stage of production - extraction extraction and separation of tantalum and niobium. The latter 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 as early as 1866 by the Swiss chemist Marignac, who took advantage of the different solubility of potassium fluorotantalate and potassium fluoroniobate in dilute hydrofluoric acid. In modern industry, several methods are used for the separation of tantalum and niobium: extraction with organic solvents, selective reduction of niobium pentachloride, fractional crystallization of complex fluoride salts, separation using ion exchange resins, and rectification of chlorides. Currently, the most commonly used method of separation (it is also the most perfect) is extraction from solutions of tantalum and niobium fluoride compounds containing hydrofluoric and sulfuric acids. At the same time, tantalum and niobium are also purified from impurities of other elements: silicon, titanium, iron, manganese and other related elements. As for loparite ores, their concentrates are processed by the chlorine method, with the production of a condensate of tantalum and niobium chlorides, which are further separated by the rectification method. Separation of a mixture of chlorides consists of the following stages: preliminary rectification (separation of tantalum and niobium chlorides from accompanying impurities), main rectification (to obtain pure NbCl 5 and TaCl 5 concentrate) and final rectification of the tantalum fraction (obtaining pure TaCl 5). Following the separation of related metals, the tantalum phase is precipitated and purified to obtain high purity potassium fluorotantalate (using KCl).

Tantalum metal is obtained by reducing its compounds of high purity, 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 (carbothermal 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 blanks pre-compressed 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 that, the purity of the metal increases significantly, becoming equal to 99.9-99.95%.

For further refining and obtaining 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 plasticity and reduces the transition temperature to a brittle state. Tantalum of such purity retains high ductility at temperatures close to absolute zero! The surface of the tantalum ingot is melted (to give the required indicators on 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 metallic tantalum and were able to study in detail the properties of this light gray metal with a slightly bluish lead tint. What are the qualities of this element? 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 in it with excellent plastic characteristics. Pure tantalum lends itself well to machining, is easily stamped, processed into the thinnest sheets (about 0.04 mm thick) and wire (tantalum's modulus of elasticity is 190 Gn/m 2 or 190 10 2 kgf/mm 2 at 25 °C). In the cold, the metal can be processed without significant work hardening, it is subjected to deformation with a compression ratio of 99% without intermediate firing. The transition of tantalum from a plastic state to a brittle state is not observed even when it is cooled to -196 °C. Tensile strength of high purity annealed tantalum is 206 MN/m2 (20.6 kgf/mm2) at 27°C and 190 MN/m2 (19 kgf/mm2) at 490°C; elongation 36% (at 27°C) and 20% (at 490°C). Tantalum has a cubic body-centered 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 sheet tantalum 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, such as carbon or nitrogen (the Brinell hardness of a tantalum sheet after the absorption of 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 reduce ductility characteristics and increase cold brittleness, in other words, 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 ° C) and refractoriness (perhaps the most an important physical property of tantalum) - it melts at almost 3,000 ° C (more precisely, at 2,996 ° C), yielding in this 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 capacity at temperatures from 0 to 100 ° C is 0.142 kJ / (kg K) or 0.034 cal / (g ° C); temperature coefficient of linear expansion of tantalum 8.0 10 -6 (at temperatures of 20-1500 °C). The specific electrical resistance 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 is 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, plasticity. In addition, it is distinguished by high strength - it lends itself well to pressure treatment by 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 anode 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 stable 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 MeTaO 3 metatantalates, Me 3 TaO 4 orthotantalates, salts of the Me 5 TaO 5 type, where Me is an alkali metal; in the presence of hydrogen peroxide, pertantalates are also formed. The most important are alkali metal tantalates - 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, high resistance to this effect. The metal begins to oxidize only at 280 ° C, being 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, as the temperature rises to 500 °C, the oxide film gradually becomes porous, stratifies 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 the metal is oxidized to a considerable depth in air. The presence of nitrogen and oxygen increases the hardness and strength of tantalum, 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 1100 ° 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 up to heating to 350 °C, the reaction rate increases significantly only from 450 °C (tantalum hydride is formed and tantalum becomes brittle). The same heating in vacuum (over 800 °C) helps to get rid of hydrogen, during which the mechanical properties of tantalum are restored, and hydrogen is completely removed.

Fluorine acts on tantalum already at room temperature, hydrogen fluoride also reacts with the metal. Dry chlorine, bromine and iodine have a chemical effect on tantalum at a temperature 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; in this case, refractory tantalum carbides are formed, which are very resistant to acids. With boron, tantalum combines to form borides - solid refractory compounds resistant to aqua regia. With many metals, tantalum forms continuous solid solutions (molybdenum, niobium, titanium, tungsten, vanadium, and others). With gold, aluminum, nickel, beryllium and silicon, tantalum forms limited solid solutions. Does not form any compounds of tantalum 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 special type of metal that belongs to the noble group. It was discovered back in 1802, but is considered a young element. Despite its rarity, it is widely used not only in jewelry, but also in industry. It is especially common in electronics - almost every device contains it in the composition.

The mass use of this metal began in the 40s of the last century and continues to this day. He gained his popularity due to the increased strength properties. However, it has many unique physical and chemical properties.

Physical and chemical properties

Among the physical properties of this metal, one should highlight the high melting point, which is 3017 degrees Celsius, which distinguishes it from many analogues. Due to this, it is used in those areas where increased resistance to extreme conditions is required. At the same time, the characteristics of tantalum include plasticity and hardness, the combination of which is quite rare in nature.

The melting point of tantalum is 3017 °C.

The above-mentioned properties of tantalum make it possible to process metal without much effort, to create the necessary shapes and sizes. The special structure of the atom is very important for the creation of parts and mechanisms of structures of increased responsibility. Tantalum lends itself well to forging and rolling. In this case, the cold deformation method can also be successfully used. High thermal conductivity should be highlighted.

Due to its high density, the metal can be used to produce small gears, parts of electrical appliances that are resistant to wear and do not break down after a long period of use.

In some cases, it is used as a gas absorber. The electronic configuration should be distinguished: the metal has different electrical conductivity properties in the normal state and at high temperatures.

The connection of tantalum parts can be carried out by soldering, welding or riveting. The welding method is most often used, since the quality of the welded seam is characterized by high strength and resistance to physical stress.

Among the chemical properties, it is worth highlighting the high resistance to oxidation and alkali. However, when melted, it is partially affected by alkali. Oxidation is impossible at temperatures below 250 degrees.

Chemical properties of this metal are very similar to glass. It is almost impossible to dissolve in acid unless hydrofluoric and nitric acid are used. Even exposure to sulfuric acid does not affect the structure and shape of the metal. Perhaps only the appearance of a small film on the surface. Also, it is not subject to destruction during prolonged exposure to sea water.

Finding in nature and production of tantalum

Tantalum, as a chemical element, is very rare in nature, making up only 0.0002% of the earth's crust. It is very rarely found in its pure form, most often in the composition of various minerals, in the vicinity of another metal - niobium.

Deposits of this element are found in many countries. Large deposits are found in France, Egypt, China and Thailand. But the largest deposits of this element are in Australia. Tantalum is mined in the amount of more than 400 tons annually. At the same time, the need for its use is constantly growing, which is associated with an increase in the volume of electrical engineering produced using this metal. Based on this, there is a constant development of new deposits.

In our country, the production of tantalum is concentrated at the Solikamsk magnesium plant. The metal is obtained after the processing of loparite concentrates. In other countries, other minerals are also used, such as rutile, struverite, tantalite and columbite.

The largest producers of this metal in the world are the USA, Japan and China. The number of world manufacturers does not exceed 40 firms. Cost - from 1000 dollars per kg.

Alloys based on tantalum

Due to its special physical properties, this metal in its pure form is very often used in industry. However, to increase strength and resistance to high temperatures, alloys based on it can be used, appropriate alloying components can be added.

Tantalum alloys can maintain a solid state at a temperature of about 1700 degrees. This is necessary when using tantalum compounds in the energy sector, the chemical industry, the production of high-precision devices and metallurgy. Very often, various alloys are used in the construction of space rockets.

The type of alloying components used depends on the desired final properties. To improve the quality of work, elements are used that give the alloy improved plasticity properties.

It should be noted that very often tantalum in alloys is used not as a base, but as an alloying component. Its addition to various materials results in increased resistance to high temperatures and corrosion.

Diagram of a tantalum capacitor

Tantalum TAV-10 is a widely used alloy based on this metal. It is produced with the addition of tungsten, the amount of which is about 10%. This results in a material with improved heat resistance. It is used for the production of heating elements and for medical purposes, since its components do not irritate the human skin.

Application of tantalum

The use of tantalum is not limited to one area. It is necessary to highlight the areas in which tantalum products are most widely used:

1. Metallurgy. Almost half of this metal is used in the metallurgical industry. This is due to the fact that it is easy to use to create various alloys, especially anti-corrosion steels that are resistant to high temperatures. Tantalum wire is used in various fields where increased strength and heat resistance are required. Tantalum carbide is also widely used in the production of crucibles for refractory metals.
2. Electrical engineering. About 25% is used in the production of electrical engineering and electrical appliances. Capacitors using this element are characterized by increased stability of operation. Moreover, in case of destruction of the surface of the capacitor, a film of tantalum oxide is formed, which protects it. It is also necessary to highlight such elements as anodes, cathodes, lamps and other metal parts, which are also produced on its basis.
3. Chemical industry. One fifth of the produced volume is used in the chemical industry. This is due to the fact that it is resistant to most acids, salts and alkalis.
4. Medicine. Tantalum in medicine is used in industries such as bone and plastic surgery. Elements of this material hold the bones together to achieve increased strength without irritating the organic tissue.
5. military sphere. In the military sphere, targets are made of tantalum and the shell of cumulative projectiles.
6. Instrumentation. This metal is used for the production of precision instruments, control equipment and various diaphragms, as well as vacuum devices, as it has the property of absorbing gases.
7. Nuclear energy. In this area, the metal acts as a heat exchanger.

It should be noted that the scope of tantalum is limited only by a small volume of its production. If the volume of production increases, the scope will expand significantly.

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. However, it was not possible to separate it 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 the myths of Ancient Greece. Today, this element has found its wide application in many industries.

Tantalum belongs to the category of metals. It has a silvery white tint. It is somewhat reminiscent of lead in its appearance, because it has a strong oxide film on it.

This metal belongs to the category of the most rare in nature. To date, only twenty minerals of tantalum 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 to it.

Deposits of tantalum

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 found in Greenbush, Australia.

Tantalum has a high melting point. It is over 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. According to this parameter, it is comparable to gold. It is excellent for mechanical processing of products. Thanks to it, you can create the thinnest types of wire or sheets for finishing products.

Tantalum belongs to the category of low-active metals. Its rate of oxidation under the influence of air is rather 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 has a fairly wide application. It is used both for the production of industrial and household items, and for the creation of new types of weapons in the military industry.

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

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

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

This metal has found its application in the metallurgical industry. It is used to produce hard alloys for metalworking. A mixture of tantalum, tungsten carbides is used to create hard alloys that can be used to drill holes in the most durable materials, represented by 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: In our country, there is also an 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, many of the production of tantalum 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 such substances as rutile, columbite, tantalite, struvite.

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

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

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