Ural State Mining University

On the topic: Properties of niobium

Group: M-13-3

Student: Mokhnashin Nikita

1. General information about the element

Physical properties of niobium

Chemical properties of niobium

Free niobium

Niobium oxides and their salts

Niobium compounds

Leading countries in the production of niobium

1. General information about the element

Humanity has been familiar with the element occupying the 41st cell in the Mendeleev table for a long time. The age of its current name - niobium - is almost half a century younger. It so happened that item # 41 was opened twice. The first time - in 1801, the English scientist Charles Hatchet examined a sample of a faithful mineral sent to the British Museum from America. From this mineral, he isolated the oxide of a previously unknown element. Hatchet named the new element Colombia, thus marking its overseas origin. And the black mineral was named columbite. A year later, the Swedish chemist Ekeberg isolated from columbite the oxide of another new element called tantalum. The similarity of the compounds Columbium and tantalum was so great that for 40 years most chemists believed that tantalum and columbium were one and the same element.

In 1844, German chemist Heinrich Rose examined samples of columbite found in Bavaria. He rediscovered the oxides of two metals. One of them was an oxide of the already known tantalum. The oxides were similar, and to emphasize their similarity, Rose named the element that forms the second oxide niobium, after Niobe, daughter of the mythological martyr Tantalus. However, Rose, like Hatchet, was unable to obtain this element in a free state. Metallic niobium was first obtained only in 1866 by the Swedish scientist Blomstrand during the reduction of niobium chloride with hydrogen. At the end of the XIX century. two more methods have been found to obtain this element. First Moissan received it in an electric furnace, reducing niobium oxide with carbon, and then Goldschmidt was able to restore the same element with aluminum. And to call element no. 41 in different countries continued in different ways: in England and the United States - with colombium, in other countries - with niobium. The end of this discord was put by the International Union of Pure and Applied Chemistry (IUPAC) in 1950. It was decided to legitimize the name of the element "niobium" everywhere, and the name "columbite" was assigned to the main niobium mineral. Its formula is (Fe, Mn) (Nb, Ta) 2 O 6.

It is no coincidence that niobium is considered a rare element: it is indeed rare and in small quantities, always in the form of minerals and never in its native state. An interesting detail: in different reference publications the clarke (content in the earth's crust) of niobium is different. This is mainly due to the fact that in last years new deposits of minerals containing niobium have been found in African countries. In the "Chemist's Handbook", vol. 1 (M., "Chemistry", 1963) the figures are given: 3.2 · 10-5% (1939), 1 · 10-3% (1949) and 2, 4 10-3% (1954). But even the latest figures are underestimated: African deposits discovered in recent years were not included here. Nevertheless, it is estimated that approximately 1.5 million tons of metallic niobium can be smelted from the minerals of already known deposits.

Physical properties of niobium

Niobium is a shiny silver-gray metal.

Elemental niobium is an extremely refractory (2468 ° C) and high boiling (4927 ° C) metal that is highly resistant in many corrosive environments. All acids, with the exception of hydrofluoric acid, do not act on it. Oxidizing acids "passivate" niobium, covering it with a protective oxide film (No. 205). But at high temperatures, the reactivity of niobium increases. If at 150 ... 200 ° C only a small surface layer of the metal is oxidized, then at 900 ... 1200 ° C the thickness of the oxide film increases significantly.

The crystal lattice of niobium is body-centered cubic with a parameter a = 3.294 Å.

Pure metal is ductile and can be rolled into a thin sheet (up to a thickness of 0.01 mm) in the cold state without intermediate annealing.

It is possible to note such properties of niobium as a high melting and boiling point, a lower work function of electrons in comparison with other refractory metals - tungsten and molybdenum. The latter property characterizes the ability to electron emission (emission of electrons), which is used for the use of niobium in vacuum technology. Niobium also has a high superconducting transition temperature.

Density 8.57 g / cm 3(20 ° C); t pl 2500 ° C; t bale 4927 ° C; vapor pressure (in mm Hg; 1 mm Hg = 133.3 N / m 2) 1 10 -5(2194 ° C), 1 10 -4(2355 ° C), 6 10 -4(at t pl ), 1 10-3 (2539 ° C).

At ambient temperatures, niobium is stable in air. The onset of oxidation (tarnishing films) is observed when the metal is heated to 200 - 300 ° C. Above 500 °, rapid oxidation occurs with the formation of oxide Nb2 O 5.

Thermal conductivity in W / (m · K) at 0 ° C and 600 ° C, respectively 51.4 and 56.2, the same in cal / (cm · sec · ° C) 0.125 and 0.156. Specific volumetric electrical resistance at 0 ° C 15.22 10 -8ohm m (15.22 10 -6ohm cm). The superconducting transition temperature is 9.25 K. Niobium is paramagnetic. The work function of electrons is 4.01 eV.

Pure Niobium is easily pressurized in the cold and retains satisfactory mechanical properties at high temperatures. Its ultimate strength at 20 and 800 ° C is 342 and 312 MN / m, respectively. 2, the same in kgf / mm 234.2 & 31.2; elongation at 20 and 800 ° C, respectively, 19.2 and 20.7%. Brinell hardness of pure niobium 450, technical 750-1800 Mn / m 2... Impurities of some elements, especially hydrogen, nitrogen, carbon and oxygen, greatly impair the ductility and increase the hardness of niobium.

3. Chemical properties of niobium

Niobium is especially prized for its resistance to inorganic and organic substances.

There is a difference in the chemical behavior of powdered and lumpy metal. The latter is more stable. Metals do not act on it, even if heated to high temperatures. Liquid alkali metals and their alloys, bismuth, lead, mercury, tin can be in contact with niobium for a long time without changing its properties. Even such strong oxidants as perchloric acid, "aqua regia", not to mention nitric, sulfuric, hydrochloric and all others, can do nothing with it. Alkaline solutions also have no effect on niobium.

There are, however, three reagents that can convert niobium metal to chemical compounds. One of them is a molten hydroxide of an alkali metal:

Nb + 4NaOH + 5О2 = 4NaNbO3 + 2H2О

The other two are hydrofluoric acid (HF) or its mixture with nitric acid (HF + HNO). In this case, fluoride complexes are formed, the composition of which largely depends on the reaction conditions. The element is in any case included in the anion of the 2- or 2- type.

If we take powdered niobium, then it is somewhat more active. For example, in molten sodium nitrate, it even ignites, turning into oxide. Compact niobium begins to oxidize when heated above 200 ° C, and the powder becomes covered with an oxide film already at 150 ° C. At the same time, one of the wonderful properties of this metal is manifested - it retains plasticity.

In the form of sawdust, when heated above 900 ° C, it completely burns out to Nb2O5. Burns vigorously in a stream of chlorine:

Nb + 5Cl2 = 2NbCl5

Reacts with sulfur when heated. It is difficult to alloy with most metals. There are, perhaps, only two exceptions: iron, with which solid solutions of different ratios are formed, and aluminum, which has a compound Al2Nb with niobium.

What qualities of niobium help it resist the action of the strongest acid-oxidizing agents? It turns out that this refers not to the properties of the metal, but to the features of its oxides. When in contact with oxidizing agents, a very thin (and therefore invisible), but very dense layer of oxides appears on the metal surface. This layer becomes an insurmountable obstacle on the path of the oxidizing agent to a clean metal surface. Only some chemical reagents, in particular the fluorine anion, can penetrate through it. Therefore, essentially the metal is oxidized, but practically no oxidation results are noticeable due to the presence of a thin protective film. Passivity towards dilute sulfuric acid is used to create an alternating current rectifier. It is arranged simply: platinum and niobium plates are immersed in a 0.05 m sulfuric acid solution. Niobium in a passivated state can conduct current if it is a negative electrode - a cathode, i.e. electrons can pass through the oxide layer only from the metal side. The path of electrons from the solution is closed. Therefore, when an alternating current is passed through such a device, then only one phase passes, for which platinum is the anode, and niobium is the cathode.

niobium metal halogen

4. Niobium in a free state

It is so beautiful that at one time they tried to make jewelry out of it: with its light gray color, niobium resembles platinum. Despite its high melting (2500 ° C) and boiling points (4840 ° C), any product can be easily made from it. The metal is so ductile that it can be processed in the cold. It is very important that niobium retains its mechanical properties at high temperatures. True, as in the case of vanadium, even small impurities of hydrogen, nitrogen, carbon and oxygen greatly reduce the plasticity and increase the hardness. Niobium becomes brittle at temperatures ranging from -100 to -200 ° C.

Obtaining niobium in an ultrapure and compact form has become possible with the involvement of technology in recent years. The entire technological process is complex and time consuming. Basically, it is divided into 4 stages:

1.obtaining a concentrate: ferroniobium or ferrotantaloniobium;

.opening the concentrate - transfer of niobium (and tantalum) into any insoluble compounds in order to separate it from the bulk of the concentrate;

.separation of niobium and tantalum and obtaining their individual compounds;

.obtaining and refining metals.

The first two steps are fairly straightforward and common, albeit time consuming. The degree of separation of niobium and tantalum is determined by the third stage. The desire to obtain as much niobium and especially tantalum as possible forced the search for the latest separation methods: selective extraction, ion exchange, rectification of compounds of these elements with halogens. As a result, either oxide or tantalum and niobium pentachlorides are obtained separately. At the last stage, reduction with coal (soot) is used in a stream of hydrogen at 1800 ° C, and then the temperature is increased to 1900 ° C and the pressure is lowered. The carbide obtained by interaction with coal reacts with Nb2O5:

2Nb2O5 + 5NbC = 9Nb + 5CO3,

and niobium powder appears. If, as a result of the separation of niobium from tantalum, not an oxide is obtained, but a salt, then it is treated with metallic sodium at 1000 ° C and powdered niobium is also obtained. Therefore, upon further transformation of the powder into a compact monolith, remelting is carried out in an arc furnace, and electron beam and zone melting is used to obtain single crystals of highly pure niobium.

Niobium oxides and their salts

The number of compounds with oxygen in niobium is small, much less than that of vanadium. This is explained by the fact that in compounds corresponding to the oxidation state +4, +3 and +2, niobium is extremely unstable. If the atom of this element began to donate electrons, then it tends to donate all five in order to reveal a stable electronic configuration.

If we compare the ions of the same oxidation state of two neighbors in the group - vanadium and niobium, then an increase in properties towards metals is found. The acidic character of Nb2O5 oxide is noticeably weaker than that of vanadium (V) oxide. It does not form acid when dissolved. Only when fusion with alkalis or carbonates does its acidic properties appear:

O5 + 3Nа2СО3 = 2Nа3NbO4 + ЗС02

This salt - sodium orthoniobate - is similar to the same salts of orthophosphoric and orthovanadic acids. However, in phosphorus and arsenic, the orthoform is the most stable, and an attempt to obtain orthoniobate in its pure form fails. When processing the alloy with water, it is not the Na3NbO4 salt that is released, but the NaNbO3 metaniobate. It is a colorless fine crystalline powder hardly soluble in cold water. Consequently, in niobium in the highest oxidation state, it is not the ortho-, but the meta-form of the compounds that is more stable.

Among other compounds of niobium (V) oxide with basic oxides, diniobates K4Nb2O7 are known, reminiscent of pyro acids, and polyniobates (as a shadow of polyphosphoric and polyvanadium acids) with approximate formulas K7Nb5O16.nH2O and K8Nb6O19.mH2O. The mentioned salts, corresponding to the higher niobium oxide, contain this element in the anion. The form of these salts allows us to consider them derivatives of niobium. acids. These acids cannot be obtained in their pure form, since they can rather be considered as oxides that have a bond with water molecules. For example, the meta-form is Nb2O5. H2O, and the orgo form is Nb2O5. 3H2O. Along with such compounds, niobium has others, where it is already included in the cation. Niobium does not form simple salts such as sulfates, nitrates, etc. When interacting with sodium hydrosulfate NaHSO4 or with nitrogen oxide N2O4, substances with a complex cation appear: Nb2O2 (SO4) 3. The cations in these salts resemble the vanadium cation with the only difference that here the ion is five-charged, and in vanadium, the oxidation state in the vanadyl ion is four. The same cation NbO3 + is included in the composition of some complex salts. Nb2O5 oxide dissolves quite easily in aqueous hydrofluoric acid. Complex salt K2 can be isolated from such solutions. H2O.

On the basis of the considered reactions, it can be concluded that niobium in its highest oxidation state can be included both in the composition of the anions and in the composition of the cation. This means that pentavalent niobium is amphoteric, but still with a significant predominance of acidic properties.

There are several ways to obtain Nb2O5. First, the interaction of niobium with oxygen when heated. Second, calcination of niobium salts in air: sulfide, nitride or carbide. Third, the most common method is hydrate dehydration. Hydrated oxide Nb2O5 is precipitated from aqueous solutions of salts with concentrated acids. xH2O. Then, when the solutions are diluted, a white oxide precipitate forms. The dehydration of the Nb2O5 xH2O sludge is accompanied by the release of heat. The whole mass is heating up. This is due to the transformation of the amorphous oxide into a crystalline form. Niobium oxide comes in two colors. Under normal conditions it is white, but turns yellow when heated. However, as soon as the oxide is cooled, the color disappears. Oxide is refractory (melting point = 1460 ° C) and non-volatile.

Lower oxidation states of niobium correspond to NbО2 and NbО. The first of these two is a black powder with a blue sheen. NbO2 is obtained from Nb2O5 by taking oxygen with magnesium or hydrogen at a temperature of about a thousand degrees:

O5 + H2 = 2NbO2 + H2O

In air, this compound easily converts back into the higher oxide Nb2O5. Its character is rather secretive, since the oxide is insoluble neither in water nor in acids. Yet he is credited with an acidic character on the basis of interaction with hot aqueous alkali; in this case, however, oxidation occurs to a five-charged ion.

It would seem that the difference of one electron is not that great, but unlike Nb2O5, NbO2 oxide conducts an electric current. Obviously, there is a metal-metal bond in this compound. If you take advantage of this quality, then when heated with a strong alternating current, you can make NbO2 give up its oxygen.

With the loss of oxygen, NbO2 transforms into oxide NbO, and then all oxygen is split off rather quickly. Little is known about the lower niobium oxide NbO. It has a metallic luster and is similar in appearance to metal. Perfectly conducts electric current. In a word, it behaves as if there is no oxygen in its composition at all. Even, like a typical metal, it reacts violently with chlorine when heated and turns into oxychloride:

2NbO + 3Cl2 = 2NbOCl3

It displaces hydrogen from hydrochloric acid (as if it were not an oxide at all, but a metal like zinc):

NbO + 6HCl = 2NbOCl3 + 3H2

NbO can be obtained in pure form by calcining the already mentioned complex salt of K2 with metallic sodium:

К2 + 3Na = NbO + 2KF + 3NaF

NbO oxide has the highest melting point of 1935 ° C of all niobium oxides. To purify niobium from oxygen, the temperature is increased to 2300 - 2350 ° C, then, simultaneously with evaporation, NbO decomposes into oxygen and metal. Refining (cleaning) of the metal takes place.

Niobium compounds

The story about the element would not be complete without mentioning its compounds with halogens, carbides and nitrides. This is important for two reasons. First, thanks to fluoride complexes, it is possible to separate niobium from its eternal companion tantalum. Secondly, these compounds reveal to us the qualities of niobium as a metal.

Interaction of halogens with metallic niobium:

Nb + 5Cl2 = 2NbCl5 can be obtained, all possible niobium penthalides.

Pentafluoride NbF5 (melting point = 76 ° C) is colorless in liquid state and in vapor. Like vanadium pentafluoride, it is polymeric in its liquid state. Niobium atoms are linked to each other through fluorine atoms. In solid form, it has a structure consisting of four molecules (Fig. 2).

Rice. 2. The solid structure of NbF5 and TaF5 consists of four molecules.

Solutions in hydrofluoric acid H2F2 contain various complex ions:

H2F2 = H2; + H2O = H2

Potassium salt K2. H2O is important for the separation of niobium from tantalum, since, unlike tantalum salt, it is highly soluble.

The rest of the niobium penthalides are brightly colored: NbCl5 yellow, NbBr5 purple-red, NbI2 brown. All of them sublime without decomposition in the atmosphere of the corresponding halogen; in pair they are monomers. Their melting and boiling points increase on going from chlorine to bromine and iodine. Some of the ways to obtain penthalides are as follows:

2Nb + 5I2 2NbI5; O5 + 5C + 5Cl22NbCl5 + 5CO ;.

2NbCl5 + 5F22NbF5 + 5Cl2

Penthalides are readily soluble in organic solvents: ether, chloroform, alcohol. However, they completely decompose with water - they are hydrolyzed. As a result of hydrolysis, two acids are obtained - hydrohalogenic and niobic. For example,

4H2O = 5HCl + H3NbO4

When hydrolysis is undesirable, then some strong acid is introduced and the equilibrium of the process described above is shifted towards NbCl5. In this case, the pentahalide dissolves without undergoing hydrolysis,

Niobium carbide deserves special gratitude from metallurgists. In any steel, there is carbon; niobium, binding it into carbide, improves the quality of alloy steel. Usually when welding stainless steel, the seam has a lower strength. The introduction of 200 g per ton of niobium helps to correct this deficiency. When heated, niobium forms a compound with carbon - carbide, before all other steel metals. This compound is quite plastic and at the same time is able to withstand temperatures up to 3500 ° C. A layer of carbide only half a millimeter thick is enough to protect metals and, most importantly, graphite from corrosion. Carbide can be obtained by heating a metal or niobium (V) oxide with carbon or carbon-containing gases (CH4, CO).

Niobium nitride is a compound that is not affected by any acids and even "aqua regia" when boiled; resistant to water. The only thing with which it can be forced to interact is boiling alkali. In this case, it decomposes with the release of ammonia.

NbN nitride is light gray with a yellowish tinge. It is refractory (temp. 2300 ° C), has a remarkable feature - at a temperature close to absolute zero (15.6 K, or -267.4 ° C), it has superconductivity.

Of the compounds containing niobium in a lower oxidation state, halides are best known. All lower halides are dark crystalline solids (from dark red to black). Their stability decreases as the oxidation state of the metal decreases.

Application of niobium in various industries

The use of niobium for alloying metals

Niobium alloy steel has good corrosion resistance. Chromium also increases the corrosion resistance of steel and is much cheaper than niobium. This reader is right and wrong at the same time. Wrong because I forgot about one thing.

In chromium-nickel steel, as in any other steel, there is always carbon. But carbon combines with chromium to form carbide, which makes steel more brittle. Niobium has a greater affinity for carbon than chromium. Therefore, when niobium is added to steel, niobium carbide is necessarily formed. Steel alloyed with niobium acquires high anti-corrosion properties and does not lose its ductility. The desired effect is achieved when only 200 g of metallic niobium is added to a ton of steel. And niobium gives chromium-mangaite steel high wear resistance.

Many non-ferrous metals are also alloyed with niobium. So, aluminum, which easily dissolves in alkalis, does not react with them if only 0.05% niobium is added to it. And copper, known for its softness, and many of its alloys, niobium seems to harden. It increases the strength of metals such as titanium, molybdenum, zirconium, and at the same time increases their heat resistance and heat resistance.

Now the properties and capabilities of niobium are appreciated at their true worth by aviation, mechanical engineering, radio engineering, the chemical industry, and nuclear power. All of them have become consumers of niobium.

A unique property - the absence of a noticeable interaction of niobium with uranium at temperatures up to 1100 ° C and, in addition, good thermal conductivity, a small effective absorption cross section for thermal neutrons made niobium a serious competitor to metals recognized in the nuclear industry - aluminum, beryllium and zirconium. Moreover, the artificial (induced) radioactivity of niobium is low. Therefore, it can be used to make containers for storing radioactive waste or installations for their use.

The chemical industry consumes relatively little niobium, but this is only due to its scarcity. Equipment for the production of high-purity acids is sometimes made from niobium-containing alloys and, more rarely, from sheet niobium. The ability of niobium to influence the rate of some chemical reactions is used, for example, in the synthesis of alcohol from butadiene.

Rocket and space technology also became consumers of element No. 41. It is no secret that some quantities of this element are already rotating in near-earth orbits. Some parts of rockets and onboard equipment of artificial earth satellites are made from niobium-containing alloys and pure niobium.

Use of niobium in other industries

Niobium sheets and bars are used to make "hot fittings" (ie heated parts) - anodes, grids, indirectly heated cathodes and other parts of electronic lamps, especially powerful generator lamps.

In addition to pure metal, tantalum-niobium alloys are used for the same purposes.

Niobium was used to make electrolytic capacitors and current rectifiers. Here, we used the ability of niobium to form a stable oxide film during anodic oxidation. The oxide film is stable in acidic electrolytes and passes current only in the direction from the electrolyte to the metal. Niobium capacitors with solid electrolyte are characterized by high capacitance with small dimensions, high insulation resistance.

Niobium capacitor elements are made from thin foil or porous plates pressed from metal powders.

Corrosion resistance of niobium in acids and other environments, combined with high thermal conductivity and plasticity, make it a valuable structural material for equipment in chemical and metallurgical industries. Niobium possesses a combination of properties that satisfy the requirements of the nuclear power industry for structural materials.

Up to 900 ° C, niobium weakly interacts with uranium and is suitable for the manufacture of protective shells for uranium fuel elements of power reactors. In this case, it is possible to use liquid metal heat carriers: sodium or an alloy of sodium with potassium, with which niobium does not interact up to 600 ° C. To increase the survivability of uranium fuel elements, uranium is doped with niobium (~ 7% niobium). The niobium additive stabilizes the protective oxide film on uranium, which increases its resistance to water vapor.

Niobium is found in various superalloys for gas turbines in jet engines. Niobium alloying of molybdenum, titanium, zirconium, aluminum and copper dramatically improves the properties of these metals, as well as their alloys. There are high-temperature alloys based on niobium as a structural material for parts of jet engines and missiles (manufacturing of turbine blades, leading edges of wings, nose ends of aircraft and missiles, and rocket skin). Niobium and alloys based on it can be used at operating temperatures of 1000 - 1200 ° C.

Niobium carbide is found in some tungsten carbide carbide grades used for cutting steels.

Niobium is widely used as an alloying additive in steels. The addition of niobium in an amount 6 to 10 times higher than the carbon content in steel eliminates intergranular corrosion of stainless steel and protects welds from destruction.

Niobium is also used in various high-temperature steels (for example, for gas turbines), as well as in tool and magnetic steels.

Niobium is introduced into steel in an alloy with iron (ferroniobium) containing up to 60% Nb. In addition, ferrotantaloniobium is used with a different ratio between tantalum and niobium in the ferroalloy.

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

The use and production of niobium is growing rapidly, which is due to the combination of its properties such as refractoriness, small cross-section for capture of thermal neutrons, the ability to form heat-resistant, superconducting and other alloys, corrosion resistance, getter properties, low work function of electrons, good workability by pressure in the cold and weldability. The main fields of application of niobium: rocketry, aviation and space technology, radio engineering, electronics, chemical apparatus engineering, nuclear power.

Application of metallic niobium

Parts of aircraft are made of pure niobium or its alloys; casings for uranium and plutonium fuel elements; containers and pipes; for liquid metals; parts for electrolytic capacitors; "Hot" fittings for electronic (for radar installations) and powerful generator lamps (anodes, cathodes, grids, etc.); corrosion-resistant equipment in the chemical industry.

Niobium is alloyed with other non-ferrous metals, including uranium.

Niobium is used in cryotrons - superconducting elements of computers. Niobium is also known for being used in accelerating structures at the Large Hadron Collider.

Niobium intermetallic compounds and alloys

Nb3Sn stannide and niobium-titanium-zirconium alloys are used to make superconducting solenoids.

Niobium and alloys with tantalum in many cases replace tantalum, which gives a great economic effect (niobium is cheaper and almost twice as light as tantalum).

Ferroniobium is introduced into stainless chromium-nickel steels to prevent their intergranular corrosion and destruction, and into other types of steel to improve their properties.

Niobium is used for minting collectible coins. Thus, the Bank of Latvia claims that niobium is used along with silver in collector's 1 lats coins.

Application of niobium compounds O5 catalyst in the chemical industry;

in the production of refractories, cermets, special. glass, nitride, carbide, niobates.

Niobium carbide (mp 3480 ° C) in an alloy with zirconium carbide and uranium-235 carbide is the most important structural material for fuel elements of solid-phase nuclear jet engines.

Niobium nitride NbN is used for the production of thin and ultrathin superconducting films with a critical temperature of 5 to 10 K with a narrow transition of the order of 0.1 K

Niobium in medicine

The high corrosion resistance of niobium has made it possible to use it in medicine. Niobium threads do not irritate living tissue and are well spliced ​​with it. Reconstructive surgery has successfully used such threads to suture torn tendons, blood vessels, and even nerves.

Application in jewelry

Niobium not only possesses a set of properties necessary for the technique, but also looks quite beautiful. Jewelers tried to use this white shiny metal for the manufacture of wrist watch cases. Alloys of niobium with tungsten or rhenium sometimes replace noble metals: gold, platinum, iridium. The latter is especially important, since the alloy of niobium with rhenium not only looks like metallic iridium, but is almost as wear-resistant. This allowed some countries to dispense with expensive iridium in the production of soldering for fountain pens.

Niobium mining in Russia

In recent years, the world production of niobium has been at the level of 24-29 thousand tons. It should be noted that the world niobium market is significantly monopolized by the Brazilian company CBMM, which accounts for about 85% of the world production of niobium.

Japan is the main consumer of niobium-containing products (ferroniobium primarily belongs to it). This country annually imports over 4 thousand tons of ferroniobium from Brazil. Therefore, Japanese import prices for niobium-containing products can be taken with great confidence to be close to the world average. In recent years, there has been an upward trend in prices for ferroniobium. This is due to its growing application for the production of low-alloy steels intended mainly for oil and gas pipelines. In general, it should be noted that over the past 15 years, the world consumption of niobium has been increasing by an average of 4-5% annually.

With regret, it must be admitted that Russia is on the "sidelines" of the niobium market. In the early 90s, according to Giredmet's experts, about 2 thousand tons of niobium (in terms of niobium oxide) were produced and consumed in the former USSR. At present, the consumption of niobium products by the Russian industry does not exceed only 100-200 tons. It should be noted that significant niobium production capacities were created in the former USSR, scattered across different republics - Russia, Estonia, Kazakhstan. This traditional feature of the development of industry in the USSR has now put Russia in a very difficult position in many types of raw materials and metals. The niobium market starts with the production of niobium containing raw materials. Its main type in Russia was and remains the loparite concentrate obtained at the Lovozersky GOK (now - JSC Sevredmet, Murmansk region). Before the collapse of the USSR, the enterprise produced about 23 thousand tons of loparite concentrate (the content of niobium oxide in it is about 8.5%). Subsequently, the production of concentrate steadily decreased, in 1996-1998. the enterprise was stopped several times due to lack of sales. Currently, according to estimates, the production of loparite concentrate at the enterprise is at the level of 700 - 800 tons per month.

It should be noted that the enterprise is quite rigidly tied to its only consumer - the Solikamsk Magnesium Plant. The fact is that loparite concentrate is a rather specific product that is obtained only in Russia. Its processing technology is rather complicated due to the complex of rare metals it contains (niobium, tantalum, titanium). In addition, the concentrate is radioactive, which is largely why all attempts to enter the world market with this product ended in vain. It should also be noted that ferroniobium cannot be obtained from loparite concentrate. In 2000, at the Sevredmet plant by the efforts of the Roredmet company, an experimental plant for processing loparite concentrate was launched to obtain, among other metals, marketable niobium-containing products (niobium oxide).

The main markets for SMZ niobium products are non-CIS countries: deliveries are made to the USA, Japan and European countries. The share of exports in the total production volume is over 90%. Significant capacities for the production of niobium in the USSR were concentrated in Estonia - at the Sillamäe Chemical and Metallurgical Production Association (Sillamäe). Now the Estonian company is called Silmet. In Soviet times, the enterprise processed loparite concentrate from Lovoozersky GOK, since 1992 its shipment has been stopped. Silmet currently processes only a small volume of niobium hydroxide at the Solikamsk Magnesium Plant. Most of the niobium-containing raw materials are currently received by the company from Brazil and Nigeria. The company's management does not exclude the supply of loparite concentrate, however, Sevredmet is trying to pursue a policy of processing it on the spot, since the export of raw materials is less profitable than the finished product.

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Tantalum and niobium are obtained by reduction from high-purity compounds: oxides, complex fluoride salts, chlorides. Industrial methods for producing metals can be divided into four groups:

Sodium-thermal reduction from complex fluorides;

Reduction from oxides with carbon (carbothermic method);

Reduction from aluminum oxides (aluminothermic method);

Recovery from chlorides with hydrogen;

Electrolysis of molten media.

Due to the high melting point of tantalum (~ 3000 C) and niobium (~ 2500 C), they are obtained as a result of reduction by all of the listed methods, except for the third, in the form of powders or a sintered sponge. The task of obtaining compact malleable tantalum and niobium is complicated by the fact that these metals actively absorb gases (hydrogen, nitrogen, oxygen), the impurities of which make them brittle. Therefore, it is necessary to sinter the workpieces pressed from the powders or melt them in a high vacuum.

Natriothermal method for the production of tantalum and niobium powders

The sodium-thermal reduction of complex fluorides K2TaF7 and K2NbF7 is the first industrial method for producing tantalum and niobium. It is still used today. Sodium, calcium and magnesium, which have a high affinity for fluorine, are suitable for the reduction of fluoride compounds of tantalum and niobium, as can be seen from the values ​​below:

E-mail<^ент Nb Та Na Mg Са

AG298, kJ / g-atom F. ... ... -339 -358 -543 -527 -582

Sodium is used for reduction, since sodium fluoride is soluble in water and can be separated by washing from tantalum and niobium powders, while magnesium and calcium fluorides are slightly soluble in water and acids.

Let's consider the process on the example of obtaining tantalum. The reduction of K2TaF7 with sodium proceeds with a large release of heat (even with a charge load of up to 5 kg), sufficient for the spontaneous flow of the process. After heating the charge in one place to 450-500 C, the reaction quickly spreads throughout the entire mass of the charge, and the temperature reaches 800-900 C. Since sodium melts at 97 C and boils at 883, it is obvious that liquid and vaporous sodium are involved in the reduction:

K2TaF7 + 5NaW = Ta + 5NaF + 2KF; K2TaF7 + 5Na (ra3) = Ta + 5NaF + 2KF.

Specific heat effects of reactions (2.18) and (2.19) are 1980 and 3120 kJ / kg of charge, respectively.

The reduction is carried out in a steel crucible, where potassium fluorotantalate and sodium pieces (~ 120% of the stoichiometrically required amount) are loaded in layers, which are cut with special scissors. Top of the charge is covered with a layer of sodium chloride, which forms a low-melting mixture with KF and NaF. Salt melt protects particles from oxidation by
tantalum dew. In the simplest version of the process, to initiate a reaction, the crucible wall at the bottom is heated with a blowtorch flame until a red spot appears. The reaction proceeds rapidly throughout the mass and ends in 1-2 minutes. With this implementation of the process, due to the short-term exposure of the products at the maximum temperature (800-900 C), fine tantalum powders are obtained, which, after washing the salts, contain up to 2% oxygen.

A coarser-grained powder with a lower oxygen content is obtained by placing a reaction crucible in a shaft electric furnace and keeping it in a furnace after the end of the reaction at 1000 ° C.

The resulting tantalum reduction is impregnated in the form of fine particles in a fluoride-chloride slag containing excess sodium. After cooling, the contents of the crucible are knocked out, crushed in a jaw crusher and loaded in small portions into a reactor with water, where sodium is "quenched" and the bulk of the salts are dissolved. Then the powder is sequentially washed with diluted nei (for a more complete washing of salts, dissolution of iron and partly titanium impurities). To reduce the content of tantalum oxides, the powder is sometimes additionally washed with cold dilute hydrofluoric acid. Then the powder is washed with distilled water, filtered and dried at 110-120 C.

Using the method described above, observing approximately the same conditions, niobium powders are obtained by reduction of k2NbF7 with sodium. Dried niobium powders have a composition,%: Ti, Si, Fe 0.02-0.06; About 0.5; N up to 0.1; C 0.1-0.15.

Carbothermal method for producing niobium and tantalum from oxides

This process was originally developed for the production of niobium from Nb2o5.

Niobium can be reduced from Nb2os with carbon at 1800-1900 ° C in a vacuum furnace:

Nb2Os + 5C = 2Nb + SCO. (2.20)

The charge Nb205 + 5C contains little niobium and even in the briquetted state has a low density (~ 1.8 g / cm3). At the same time, a large volume of co (~ 0.34 m3) is allocated per 1 kg of charge. These circumstances make it disadvantageous to carry out the process according to reaction (2.20), since the productivity of the vacuum furnace is low in this case. Therefore, the process is carried out in two stages:

I stage - obtaining niobium carbide

Nb203 + 1C = 2NbC + 5CO; (2.2l)

Stage P - obtaining niobium in vacuum furnaces

Nb2Os + 5NbC = 7Nb + 5CO. (2.22)

The briquetted charge of the її stage contains 84.2% (by weight) of niobium, the density of briquettes is ~ 3 g / cm3, the volume formed from 0.14 m3 per 1 kg of charge (~ 2.5 times less than in the case of the charge Nb2o5 + sc ). This provides a higher productivity of the vacuum furnace.

A significant advantage of the two-stage process is also that the first stage can be carried out at atmospheric pressure in graphite-tube resistance furnaces (Fig. 29).

To obtain niobium carbide (i stage of the process), a mixture of Nb2o5 with soot is briquetted and the briquettes are heated in a graphite-tube furnace in a hydrogen or argon atmosphere at 1800-1900 ° C (briquettes are continuously moving along the furnace

Rice. 29. Scheme of a graphite-tube resistance furnace:

1 - casing; 2 - graphite heating tube; 3 - shielding graphite pipe; 4- soot heat-insulating backfill; 5 - refrigerator; 6 - contact graphite cones; 7 - cooled contact head; 8 - hatch; 9 - busbars supplying current

Based on their stay in the hot zone 1-1.5 hours). The crushed niobium carbide is mixed in a ball mill with Nb2o5 taken with a slight excess (3-5%) against that required by reaction (2.22).

The charge is pressed into billets under a pressure of 100 MPa, which are heated in vacuum furnaces with graphite heaters (or vacuum induction furnaces with a graphite tube) at 1800-1900 C. The exposure ends when a residual pressure of 1.3-0.13 Pa is reached.

Reactions (2.21) and (2.22) are cumulative. They proceed through intermediate stages of the formation of lower oxides (Nt> o2 and NbO), as well as Nb2c carbide. The main reactions of stage I:

Nb2Os + C = 2NbO2 + CO; (2.23)

NbO2 + C = NbO + CO; (2.24)

2NbO + 3C = Nb2C + 2CO; (2.25)

Nb2C + C = 2NbC. (2.26)

Stage n reactions:

Nb2Os + 2NbC = 2NbO2 + Nb2C + CO; (2.27)

NbO2 + 2NbC = NbO + Nb2C + CO; (2.28)

NbO + Nb2C = 3Nb + CO. (2.29)

Metallic niobium is obtained by the final reaction of stage II of the process (2.29). The equilibrium pressure ω for reaction (2.29) at 1800 ° C is> 1.3 Pa. Therefore, it is necessary to carry out the process at a residual pressure lower than the equilibrium pressure for this reaction (0.5-0.13 Pa).

The resulting sintered porous briquettes of niobium contain,%: With 0.1-0.15; About 0.15-0.30; N 0.04-0.5. To obtain a compact malleable metal, briquettes are melted in an electron beam furnace. Another way is to obtain a powder from briquettes (by hydrogenation at 450 C, grinding and subsequent dehydrogenation in vacuum), pressing the bars and sintering them in vacuum at 2300-2350 C. In the processes of vacuum melting and sintering in vacuum, oxygen and carbon are removed in the composition co, and excess oxygen in the composition of volatile lower oxides.

The main advantages of the carbothermal method are a high direct metal yield (not less than 96%) and the use of a cheap reducing agent. The disadvantage of this method is the complexity of the design of high-temperature vacuum furnaces.

Tantalum and niobium-tantalum alloys can also be obtained by the carbothermal method.

Aluminothermic method for producing niobium and tantalum from higher oxides

The aluminometric method for the production of niobium by the reduction of niobium pentoxide with aluminum, developed in recent years, has technical and economic advantages over other methods of niobium production due to the low stage and simplicity of the hardware design.

The method is based on an exothermic reaction:

3Nb2Os + 10A1 = 6Nb + 5A1203; (2.30)

Dow = -925.3 + 0.1362t, kJ / mol Nb2o5.

The high specific thermal effect of the reaction (2640 kJ / kg of stoichiometric charge) makes it possible to carry out the process without external heating with the smelting of an ingot of niobium-aluminum alloy. Successful out-of-furnace alumothermal reduction is possible if the process temperature is higher than the melting point А12о3 = 2030 ° С) and the metal phase (the Nb + 10% ai alloy melts at 2050 ° С). With an excess of aluminum in the charge of 30-40% above the stoichiometric amount, the process temperature reaches ~ 2150-2200 C. Due to the rapid course of reduction, the temperature rise by about 100-150 C compared to the melting temperatures of the slag and metal phases is sufficient to ensure their separation. With the above-mentioned excess of aluminum in the charge, a niobium alloy with 8-10% of aluminum is obtained with a real extraction of niobium of 98-98.5%.

Aluminothermal reduction is carried out in a steel crucible with a rammed lining of calcined magnesium or aluminum oxides. For the convenience of unloading the products of melting, the crucible is made detachable. Contacts are introduced through the walls to supply an electric current (20 V, 15 A) to the fuse in the form of a nichrome wire placed in a charge. Another possible option is to carry out the process in a massive split copper crucible, at the walls of which a garnissage protective layer is formed.

A mixture of thoroughly dried Nb2o5 and aluminum powder with a particle size of ~ 100 microns is loaded into the crucible. It is advisable to place the crucible in a chamber filled with argon to avoid contact with air.

After the ignition is turned on, the reaction proceeds rapidly throughout the entire mass of the charge. The resulting alloy ingot is crushed into pieces and subjected to vacuum-thermal treatment at 1800-2000 C in a furnace with a graphite heater at a residual pressure of ~ 0.13 Pa in order to remove most of the aluminum (to its content of 0.2%). Then, refining smelting is carried out in an electron-beam furnace, obtaining ingots of high-purity niobium with an impurity content,%: A1< 0,002; С 0,005; Си < 0,0025; Fe < 0,0025; Mg, Mn, Ni, Sn < 0,001; N 0,005; О < 0,010; Si < 0,0025; Ті < < 0,005; V < 0,0025.

In principle, aluminothermal production of tantalum is possible, but the process is somewhat more complicated. The specific heat effect of the reduction reaction is 895 kJ / kg of charge. Due to the high melting temperature of tantalum and its alloys with aluminum, iron oxide is introduced into the charge to melt the ingot (based on the production of an alloy with 7-7.5% iron and 1.5% aluminum), as well as a heating additive - potassium chlorate (Berthollet's salt) ... The crucible with the charge is placed in a furnace. At 925 ° C, a spontaneous reaction begins. The extraction of tantalum into the alloy is about 90%.

After vacuum-thermal treatment and electron-beam melting, tantalum ingots have a high purity comparable to that given above for niobium.

Obtaining tantalum and niobium by reduction of their chlorides with hydrogen

Various methods have been developed for the reduction of tantalum and niobium from their chlorides: reduction with magnesium, sodium and hydrogen. Some variants of reduction with hydrogen are most promising, in particular, the method considered below for the reduction of chloride vapors on heated substrates to obtain a compact metal rod.

In fig. 30 shows a diagram of an installation for producing tantalum by reducing TaC15 vapors with hydrogen on a tantalum strip heated to 1200-1400 ° C. TaCI5 vapors mixed with hydrogen are fed from the evaporator to the reactor, in the center of which there is a tantalum ribbon heated by direct passage of an electric current to a predetermined temperature. For uniform distribution of the vapor-gas mixture along the length of the belt and to ensure a flow perpendicular to its surface, a stainless steel screen with holes is installed around the belt. A reaction occurs on a heated surface:

TaC15 + 2.5 H2 = Ta + 5 HCl; AG ° m k = -512 kJ. (2.31)

Rice. 30. Diagram of the installation for the reduction of tantalum pentachloride with hydrogen: 1 - reactor flange; 2 - insulated electrical supply; 3 - clamping contacts; 4 - condenser for unreacted chloride; 5 - tantalum tape; 6 - screens with holes, - 7 - reactor vessel; 8 - reactor heater; 9 - heated rotameter; 10 - needle valve; 11 - electric oven of the evaporator; 12 - evaporator of tantalum pentachloride; 13 - rotameter for hydrogen

Optimal conditions for the deposition of tantalum: tape temperature 1200-1300 ° C, concentration of TaCl5 in the gas mixture ~ 0.2 mol / mol of the mixture. The deposition rate under these conditions is 2.5-3.6 g / (cm2 h) (or 1.5-2.1 mm / h). Thus, in 24 hours a pure tantalum rod with an average diameter of 24-25 mm is obtained. which can be rolled into a sheet, used for remelting in an electron beam furnace, or converted into high-purity powders (by hydrogenation, grinding and dehydrogenation of the powder). The conversion of chloride (direct extraction to coating) is 20-30%. Unreacted chloride is condensed and reused. Electricity consumption is equal to 7-15 kWh per 1 kg of tantalum, depending on the adopted regime.

After separation of HCI vapors by absorption in water, hydrogen can be returned to the process.

Niobium rods can also be obtained by the described method. Optimal conditions for the deposition of niobium: tape temperature 1000-1300 C, pentachloride concentration 0.1-0.2 mol / mol of the gas mixture. The deposition rate of the metal is 0.7-1.5 g / (cm2-h), the degree of conversion of chloride to metal is 15-30%, the power consumption is 17-22 kW * h / kg of metal. The process for niobium is facilitated by the fact that part of the NbCl5 is reduced in the volume of the reactor at a certain distance from the heated strip to the non-volatile NbCl3, which is deposited on the walls of the reactor.

Electrolytic method for producing tantalum

Tantalum and niobium cannot be isolated from aqueous solutions by electrolysis. All developed processes are based on the electrolysis of molten media.

In industrial practice, the method is used to obtain tantalum. So, for a number of years the electrolytic method of tantalum has been used by the Fenstil company (USA), part of the tantalum produced in Japan is currently obtained by electrolysis. Extensive research and industrial tests of the method were carried out in the USSR.

The method for electrolytic production of tantalum is similar to the method for production of aluminum.

The electrolyte is based on a molten salt K2TaF7 - KF - - KC1, in which tantalum oxide Ta205 is dissolved. The use of an electrolyte containing only one salt, K2TaF7, is practically impossible due to the continuous anode effect when using a graphite anode. Electrolysis is possible in a bath containing K2TaF7, KC1 and NaCl. The disadvantage of this electrolyte is the accumulation of fluoride salts in it during electrolysis, which leads to a decrease in the critical current density and requires adjusting the composition of the bath. This disadvantage is eliminated by introducing Ta205 into the electrolyte. The result of electrolysis in this case is the electrolytic decomposition of tantalum oxide with the release of tantalum at the cathode, and at the anode of oxygen, which reacts with the graphite of the anode to form CO2 and CO. In addition, the introduction of Ta205 into the molten salt improves the wetting of the graphite anode by the melt and increases the critical current density.

The choice of the electrolyte composition is based on the data of studies of the K2TaF7-KCl-KF ternary system (Fig. 31). This system contains two double salts K2TaF7 KF (or KjTaFg) and K2TaF7 KC1 (or K3TaF7Cl), two ternary eutectics Ei and E2 melting at 580 and 710 C, respectively, and a peritectic point P at 678 ° C. When Ta205 is introduced into the melt, it interacts with fluorotantalates to form oxofluorotantalate:

3K3TaF8 + Ta2Os + 6KF = 5K3TaOF6. (2.32)

The reaction with K3TaF7Cl proceeds in a similar way. The formation of oxofluoride complexes of tantalum determines the solubility of Ta205 in the electrolyte. The limiting solubility depends on the content of K3TaF8 in the melt and corresponds to the stoichiometry of the reaction (2.32).

Based on the data on the influence of the electrolyte composition on electrolysis indicators (critical current density, current efficiency, extraction, quality of tantalum powder), Soviet researchers proposed the following optimal electrolyte composition: 12.5% ​​(by weight) K2TaF7, the rest KC1 and KF in relation to 2 : 1 (by weight). The concentration of the introduced Ta2Os is 2.5-3.5% (by weight). In this electrolyte at temperatures of 700-800 ° C when using a graphite anode, the decomposition voltage of the oxofluoride complex is 1.4 V, while for KF and KC1 the decomposition voltages are ~ 3.4 V and ~ 4.6 V, respectively.

КС I K2TaF, -KCl KJaFf

Rice. 31. Melting diagram of the K2TaF7-KF-KCl system

During electrolysis, a stepwise discharge of Ta5 + cations occurs at the cathode:

Ta5 + + 2e> Ta3 + + be * Ta0.

The processes at the anode can be represented by the reactions: TaOF63 "- Ze = TaFs + F" + 0; 20 + C = CO2; CO2 + C = 2CO; TaFj + 3F ~ = TaF | ~. TaF | ~ ions, reacting with Ta2Os introduced into the melt, again form TaOF | ~ ions. At electrolysis temperatures of 700-750 ° C, the composition of gases contains -95% CO2, 5-7% CO2; 0.2-

Among the electrolytic cell designs tested in the USSR, the best results were obtained in those where the cathode is a nickel crucible (or an alloy of nickel with chromium), in the center

Fig. 32. Electrolytic cell for tantalum production:

1 - bunker with a Ta205 feed feeder; 2 - electromagnetic vibrator of the feeder; 3 - bracket with fastening for the anode; 4 - hollow graphite anode with holes in the wall; 5 - crucible-cathode made of nichrome; 6 - cover; 7 - heat insulating glass; 8 - steering wheel for lifting the car; 9 - plug with a rod for supplying current

Which is a hollow graphite anode with holes in the walls (Fig. 32). Tantalum oxide is fed periodically by an automatic vibrating feeder to the hollow anode. With this method of feeding, mechanical contamination of the cathode deposit with undissolved tantalum pentoxide is excluded. The gases are removed through an onboard suction. At an electrolysis temperature of 700-720 C, a continuous supply of the Ta205 bath (i.e., with a minimum number of anode effects), a cathode current density of 30-50 A / dm2 and a ratio DjDk = 2 * 4, the direct extraction of tantalum is 87-93%, the yield is current 80%.

Electrolysis is carried out until 2/3 of the useful volume of the crucible is filled with the cathode sediment. At the end of the electrolysis, the anode is raised and the electrolyte, together with the cathode deposit, is cooled. There are two methods of processing the cathode product in order to separate the electrolyte from the particles of tantalum powder: grinding with air separation and vacuum-thermal cleaning.

The vacuum-thermal method, developed in the USSR, consists in separating the bulk of the salts from tantalum by smelting (melting) in an argon atmosphere, followed by removing the residue by evaporation in vacuum at 900 C. The melted and condensed electrolyte is returned to electrolysis.

That by grinding with air separation of 30-70 microns, and when using vacuum heat treatment - 100-120 microns.

The production of niobium from oxyfluoride-chloride electrolytes, like tantalum, did not give positive results due to the fact that lower oxides are formed at the cathode during the discharge, contaminating the metal. Current output is low.

For niobium (as well as for tantalum), oxygen-free electrolytes are promising. Niobium and tantalum pentachlorides dissolve in molten alkali metal chlorides to form complex salts A / eNbCl6 and MeTaCl6. During the electrolytic decomposition of these complexes, coarse-crystalline deposits of niobium and tantalum are formed at the cathode, and chlorine at the graphite anode.

Socio-economic and human sciences

UDC 553.98 "=."

NIOBIUM MINING IN RUSSIA

G.Yu. Boyarko *, V. Yu. Khatkov **

, * Tomsk Polytechnic University

** Office of the Government of the Russian Federation. ""

Email: [email protected]

Niobium is mined in Russia at the Lovozerskoe deposit (Murmansk region) in the form of loparite concentrate and at the Tatar deposit ( Krasnoyarsk region) in the form of pyrochloric acid concentrate, and processing ~ at the Solikamsk magnesium (Perm region) and Klyuchevskoy ferroalloy (Sverdlovsk region) plants. the Tomtor niobium deposit (Republic of Sakha-Yakutia) and the restoration of the previous level of production at the Etykinsky tantalum-niobium deposit (Chita region) Due to the presence of a natural world monopoly of Brazilian niobium producers, Russian niobium mining enterprises should focus primarily on the metallurgical market of Russia, Ukraine, Kazakhstan and China.

Niobium is a heavy refractory metal with high ductility, corrosion resistance, good weldability, and a small thermal neutron capture cross section. It is a part of heat-resistant and superconducting alloys, and steels alloyed with niobium have high strength and significant ductility, frost-freeze and corrosion resistance. The main consumption of niobium falls on the production of large-diameter pipes for main pipelines from low-alloyed (0.07 ... 0.08% N)) steels. Low-alloyed niobium steels are used in the manufacture of building structures, bridge building, road and mining engineering, aircraft and automobile manufacturing, in the manufacture of equipment for deep oil drilling, equipment for the chemical and petrochemical industries, etc. Alloys of niobium with tin, titanium and zirconium are widely used in the manufacture of superconducting solenoids for powerful electromagnets used in magnetic separators, charged particle accelerators, and MHD generators. Synthetic single crystals of lithium and lead niobates are used in optical shutters and acoustoelectronic devices. The volume of world consumption of niobium is 25 ... 26 thousand tons per year, and its clear growth is observed by 2 ... 2.5% per year. The leaders in the consumption of niobium are Japan (30% of world demand), the USA (about 25%) and the countries of the European Union. Prices for niobium products are shown in the table. G

Niobium is extracted by hydrometallurgical and pyrometallurgical methods from concentrates of niobium minerals - pyrochlore (NaCaNb206F) (up to 90% of the world supply), columbite-tantalite ((Fe, Mn) (Nb, Ta) 206) (up to 5%) and loparite (( Ca, TR) (Ti, Ta, Nb) 02) (only in Russia). During their processing, tantalum is simultaneously extracted (in the ratio Ta / Nb = 1/10), and rare earth metals and titanium are also extracted from loparite.

World production of niobium is 25.7 thousand tons (2002), with 22 thousand tons accounted for by the Brazilian company Companhia Brasileira de Metalurgia e Minera ^ So Cia Brasileira de Metalurgia Minera? Ao (CBMM), which is a natural monopoly in production pyrochlore concentrates, ferroniobium (up to 18 thousand tons per year), niobium

Table. Prices for niobium (and associated tantalum) products

Commodity products Prices, US $ per kg

Pyrochloric concentrate (in terms of N ^ 05) 6.0 ... 6.5

Columbite concentrate (in terms of N1 ^ 05) 6.5 ... 7.0

Tantalite concentrate (in terms of Ta205) 65 .. / 75

Loparite concentrate 1,1-

Ferroniobium 14.5 ... 15.5

Niobium metal 14.0 .. L 4.5

Tantalum powder ■ 200 ... 230

Metallic tantalum 200 ... 210

thallic and tantalum. It is mining the areal weathering crust on the Arasha carbonatite massif (Amazonas state) with an average content of 2.5% Nb205 (4.3 billion tons of ore) and the Pitanga tin ore deposit containing 4.3% Nb205 (30 million tons of ore). Part of the CBMM concentrates is processed by the consolidated company Catalao de Goäis (Mineralo Cataloa), which produces up to 3.5 thousand tons of ferroniobium per year. As a reserve in Brazil within national park Pico da Neblina is the Seis Lagos deposit with reserves of 2.9 billion tons of ore with an average Nb205 grade of 2.8%. In Canada, niobium ore is mined at the Saint Honore deposit (Niobec mine, Quebec) with an average Nb205 grade of 0.6%. Two companies are involved in the extraction of ores and the processing of concentrates - Teck Corp. and Cambior Inc., which supplied 3.2 thousand tons of ferroniobium to the world market in 2002. In extremely small quantities, various niobium products (mainly pyrochlore concentrates) are produced in Australia (Green Bushes), Nigeria (Joe Plateau), Mozambique (Mbeya), Zambia (Luesh) and Congo (Manono Kitololo).

In the era of the planned economy, the USSR mined and produced up to 2,000 tons of niobium products (in terms of niobium oxide), ranking third in terms of production (after Brazil and Canada) and fourth in terms of consumption (after Japan, the United States and Germany). After the collapse of the common economic space into national enclaves of the CIS, the technological chain of the rare metal industry was broken, and some of its fragments became unprofitable. As a result, Russian consumers were forced to meet their needs for niobium by exporting 100 ... 200 tons of niobium alloys per year (mainly from Brazil).

The only surviving mining enterprise in Russia is OJSC Severnye Rare Metals (former Lovozersky GOK) in the village of Lovozero, Revdinsky District, Murmansk Region, and its mining operator, OJSC Lovozero Mining Company, at the Karnasurt and Umbozero mines. Here, at the Lovozero rare-earth-niobium-tantalum deposit, unique in terms of reserves (poor in Nb205 content - only 0.24%), up to 25 thousand tons of loparite concentrate was mined from loparite-containing nepheline syenites per year, containing 6 ... 8% Nb, 0, 5% Ta, 36 ... 38% TR and 38 ... 42% Ti. Up to 10 thousand tons of loparite concentrate is processed at the Solikamsk Magnesium Plant OJSC (the main owner is the Russia Growth Fund JV), where niobium hydroxide is obtained by chlorination, which is a middling product for the production of metallic niobium (at the Irtysh chemical and metallurgical plant in Ust -Kamenogorsk, Kazakhstan). At present, the Solikamsk Magnesium Plant produces annually 700 ... 750 tons of niobium oxides and 70 ... 80 tons of tantalum oxide, which are completely ex-

port. The rest 10 ... 12 thousand. Tloparite concentrate was previously processed in A5> 8Pte1 (Sillamae, Estonia) according to the sulfuric acid scheme to metallic niobium and ferroniobium. Currently, 5Pte1 has given up buying loparite raw materials and switched to more technologically advanced pyrochlore concentrates from Brazil and Nigeria. Accordingly, the production of loparite concentrate by Sev-redmet also fell (to 8 ... 10 thousand tons), which brought this enterprise to the brink of bankruptcy. An attempt to organize in 2000 its own hydrometallurgical production with the production of ferroniobium due to the lack of required investments (US $ 100 million) was not crowned with success. Currently, the owner of AO Sevredmet is the company CJSC Company FTK (Finance, Technology, Consulting) (Moscow), co-owner of the Solikamsk Magnesium Plant (14% of shares), but there is no real way out of the current situation of limited demand for loparite raw materials. The Irtysh Chemical and Metallurgical Plant was also on the verge of bankruptcy and by 1996 had stopped the production of niobium products, but in 2000 a capable subdivision of KazNiobiy IHMZ LLP was separated from it, which began to produce up to 60 ... 80 tons of metal niobium per year, using Solikamsk niobium hydroxide is used as a raw material. Processing of tantalum industrial products in the CIS is carried out at OJSC Ulba Metallurgical Plant NAK Kazatomprom (Ust-Kamenogorsk, Republic of Kazakhstan), where niobium products are produced - powder, ingots, rolled products.

Other Russian enterprises, which had previously worked on richer ores, had developed them by the 90s of the XX century and, during the transition to a market economy, closed their unprofitable industries. These are the Vishnevogorsk Ore Administration (Chelyabinsk Region), which developed the deposit of the same name, Malyshevskoe RU (Sverdlovsk Region), a completely exhausted deposit of rare-metal pegmatites Linden Meadow, Orlovsky GOK (Chita Region), which worked out the Orlovskoye deposit and Zabaikalsky GOK (Chita Region), which stopped Zavitkovskoye and Etykinskoye fields. Pyrochlore and columbite-tantalite concentrates of these enterprises were processed at the Klyuchevskoy Ferroalloy Plant (Dvurechensk settlement, Sysertsky District, Sverdlovsk Region), which produced ferroniobium and niobium master alloys from them.

The improvement of the rare metal industry in Russia took place on the initiative of niobium consumers - the Cherepovets metallurgists of OAO Severstal (Cherepovets, Vologda Oblast). In order to eliminate export dependence on niobium, this holding organized a subsidiary of JSC Stalmag (Krasnoyarsk) for the extraction of pyrochlore concentrates from the weathering crust of the Tatar vermiculite-niobate-phosphorus deposit on the carbonatite massif of the same name,

laid in the Motyginsky district of the Krasnoyarsk Territory | 9 |. At the end of 2000t. a primary processing plant with a capacity of up to 90 thousand tons of ore per year was launched at this deposit. From the obtained concentrate supplied to the Klyuchevsky Ferroalloy Plant, 150: .. 200 tons of ferroniobium are produced per year. With the introduction of the second stage, the productivity of the mine will be doubled,

In 2001, Zabaikalsky GOK (Pervomaisky settlement, Shilkinsky district, Chita region), which has been mining fluorite and gold in recent years, resumed mining the Etykinsky tantal-niobium-tin deposit in the rare-metal granites of the Etykinsky massif. The average content of tantalum in ores is 0.031%, niobium is 0.1%, and tin is 0.2%. In 2001 ^ mined (in terms of metal) 40 tons of tantalum, 60 tons of niobium, 100 tons of tin. By 2005, it is planned to increase the production capacity by five times. The construction of a hydrometallurgical shop for the production of potassium fluorotantalate and niobium pentoxide is underway on the basis of the Zabaikalsky GOK in the village of Pervomaysky. From: Etykinskiy ores can also be extracted "and lithium concentrates with an average grade of N20 in ores - 0.11%. Within the framework of the state program" Extraction, production and consumption of lithium, beryllium, tantalum, tin, niobium (LIBTON) "it is also planned to resume mining Zabaikalsky GOK at the Zavitinsky lithium-niobium deposit of spodumene pegmatites.

good products with an average content of Ta205 in ores -0.0139% and N> 205 -0.02%.

The company ZAO Alrosa (Mirny, Republic of Sakha-Yakutia), under the program to diversify its diamond business, is preparing a mining project for the development of the Burny site, the Tomtor niobium-rare earth deposit, unique in terms of reserves and ore quality, in the Oleneksky ulus of the Republic of Sakha-Yakutia. This fragment of the deposit is a near-drift lacustrine placer formed due to the washing of the weathering crust of the Tomtor carbonatite massif. The average content of Lb205 here is 6.71%, Y - 0.59%, ST11 - 9.53%. The development project of the Burny site plans an initial annual volume of rock mass processing of 13.73 thousand m3, and the extraction of pyrochlore concentrate containing 583 t of Lb205, and a rare earth concentrate containing 690 t of rare earth metal oxides (V203, CeO2, La203, Pr6Ou, Ssh203, No. 203, Eu203, 8s203). In the future, it is planned to increase the production capacity to 30 thousand m3 of ore and to produce up to 2000 tons of pyrochlore concentrate in terms of No. 205.

A small pilot production facility existed during the exploration of the Beloziminsky niobium-phosphate deposit (1984-1986) in the Tulunsky region Irkutsk region... Ore formations represent areal weathering crust over carbonatites (containing 0.24% Ni> 205), in rich blocks of which in the Main and Yagodny areas the average content of ML205 is 1.06 and 1.39%, respectively. However, the cross-cutting

Drawing. Layout of niobium. deposits and companies that extract and process niobium.

1) niobium deposits ■ 2) holdings of niobium mining companies; 3 ~ 5) mines: 3) operating, 4) being put into production, 5) closed or stopped; 6) processing enterprises

the extraction of Nb205 in these experiments did not exceed 30%. Phosphate (apatite + frankolite) concentrate can be obtained as a by-product from Belozimin ores, with the initial content of Р205 in ores being 11.25%.

On the basis of the liquidated Orlovsky GOK in 2000, a new enterprise, OJSC Novo-Orlovsky GOK (Novoorlovsky settlement, Aginsky District, Chita Region) was formed, a pilot dressing plant No. 1 and a tantalum section of dressing plant No. 2 were restored. complex) of the tungsten production of Orlovsky GOK, containing 5190 tons of W, 550 tons of Nb and 440 tons of Ta. The estimated output of tantalum and niobium is up to 10 ... 20 tons per year.

In order to extract tantalum and niobium at the Klyuchevskoy Ferroalloy Plant, tin smelting slags are periodically processed at the Novosibirsk Tin Plant OJSC. In terms of annual sales, the output of niobium and tantalum from the raw materials of the Novosibirsk Tin Plant did not exceed the first tons.

Other niobium and tantalum-niobium deposits in Russia should be noted:

Bolshetagninskoe phosphorus-niobium deposit, located 12 km west of the Belo-Ziminsky deposit (Irkutsk region) and confined to the calcite-microcline carbonatites of the carbonatite massif of the same name. The average content of Nb205 in ores is 1.02%.

Sredneziminskoe damage-niobium-phosphorus deposit located 18 km south of the Belo-Ziminsky deposit (Irkutsk region) and confined to calcite-microcline carbonatites. The average content of Nb205 in ores is 0.10 ... 0.18%, uranium up to 0.02%, phosphorus - 2.5 ... 3.5%. The deposit is problematic, first of all, due to low concentrations of useful components and high radioactivity of ores.

The Neske-Vara site of the Vuoriyarvinsky niobium deposit is located in the Kandalakshinsky district of the Murmansk region. It is a large

Ore block of apatite-magnetite composition with impregnation of baddeleyite and pyrochlore. The average content of Nb2Os in the ores of the site is 0.53%, Ta205 - 0.017%. The deposit is located in close proximity to the operating enterprise OJSC Kovdorsky GOK, which extracts iron ores with associated production of apatite and badceleite (Zr- and TR-containing) concentrates. The deposit is shallow - only 6.2 thousand tons of Nb205 and 200 tons of Ta205, but these ores fit into the technological chain of the Kovdors GOK, and this object can easily be brought into operation.

The Ulug-Tanzoksky niobium-rare earth deposit (Republic of Tyva) is a mineralized zone of ore-bearing (pyrochlore, columbite-tantalite, zircon, lithium, beryllium and rare earth minerals) quartz-albite-microcline metasomatites. The deposit was estimated in the 90s of the XX century and remained underexplored. Content No. 205 -0.2%, Ta205 - 0.0155%, BTI - 0.063% (the proportion of yt-triium elements is 30 ... 40%), 1l20 - 0.086.1xOr - 0.4%. The technological scheme of ore beneficiation provides for the production of No.>, Ta, bg, Shch

TI (Y), and, and, YL.

The Katuginskoe yttrium-niobium-zirconium deposit of ore-bearing near-fault alkaline (quartz-albite-microcline) metasomatites is located in the north of the Chita Region, 140 km from Novaya Chara station on the Baikal-Amur Mainline. The average content of Ni> 205 in ores is 0.31, Ta205 is 0.019%, 8ТYa is 0.25% (the proportion of yttrium elements is 40 ... 50%), g02 is 1.38%. The investment project for the development of this field is being developed by the Zabaikalsky GOK.

The Gornoozerskoe niobium deposit is located in the Ust-Maisky ulus of the Republic of Sakha-Yakutia and is confined to the carbon-titite massif of the same name. The deposit has been studied only from the surface, its assessment is very poor. Pyrochlore mineralization is confined to linear zones of magnesian carbonatites. The average content of #> 205 for a limited number of samples is 0.25%. The deposit also revealed a pyrochlore lacustrine placer, which remained unappreciated. By analogy with the Tomtor deposit, it can be quite rich.

The Vishnyakovskoye tantalum deposit is located in the Irkutsk region, 110 km from the Taishet station and is connected with it by a road. Vein bodies of rare-metal pegmatites up to 40 m thick contain tantalite, beryllium, and lipedolite (lithium) mineralization. The average content of Ta205 is 0.0198%, and for individual veins of the Ryabinovy ​​area - 0.023 ... 0.03%. Possible associated extraction of lithium with an average content of 1l20 -0.086%, as well as beryllium. The content of №> 205 is not high - 0.02%, but during the extraction of tantalum raw materials, niobium will be extracted already as a by-product. The deposit requires additional exploration.

In general, the operating capacities for the extraction of niobium raw materials already meet the needs of Russian metallurgists in niobium alloying additives (200 ... 250 tons per year), and even taking into account the growth in the demand for pipe products for main pipelines, only the planned development of the capacities of Stalmag and Zabaikalsky GOK can over-

cover new volumes of demand up to 2005 (up to 600 ... 800 tons).

The problems of Sevredmet and Solikamsk Iron and Steel Works need to be addressed by their owners (FTK Company and Russia Growth Fund) as part of the creation of a unified technology for processing complex niobium-rare earth raw materials to obtain final marketable products (individual rare earth metals and their oxides, ferroniobium, metallic niobium and tantalum) and the creation of sufficient capacities for the annual processing of 22 ... 25 thousand tons of loparite concentrate. This holding can produce up to 1000 tons of niobium and up to 100 tons of tantalum products per year. ... : ■.

The sale of the products of the reconstructed Sevredmet and the new Ap-Rosy mining enterprise at the Tomtor field already requires going beyond the Russian market. Entering the world market is limited by the policy of the world monopoly of niobium products - the Brazilian company SVMM. Having the lowest cost of production and processing of niobium raw materials, it can control the level of world prices, preventing the emergence of serious competitors. Russian producers of excess niobium products need to focus on the solidary metallurgy market of the CIS countries (Ukraine, Kazakhstan) and the growing consumption market of metallurgy in China. In addition to the metallurgy sector, it is necessary to seriously study the development trends in the next 20 years of world energy-saving technologies based on superconducting power transmission systems based on niobium alloys, the production of which will require up to 5 thousand tons per year.

The existing production capacity of the Klyuchevskoy Ferroalloy Plant is sufficient to sell

BIBLIOGRAPHY

1. Elyutin A.V., Chistov LB, Epshtein E.M. Development problems mineral resource base niobium // Mineral resources of Russia. Economics and management

"laziness. - 1999. - No. 3. - S. 22-29.

2. Kudrin B.C., Kushparenko Yu..S., Petrova N.V. et al. "Mineral raw materials. Niobium and tantalum. Handbook.

M .: Geoinformark, 1998 .-- 63 p.

3. Mineral resources of the world at the beginning of 2001. -M .: Aerogeology, 2002 .-- T. 2.- 476 p.

4. Mineral commodity summaries "2003. - Pittsburgh, PA (USA): USGS, 2003. - 196 p."!

5. Niobium. Mineral annual review 2001. - Pittsburgh, PA (USA): USGS, 2002. - P. 21.1-28.14.

6. Metal prices in the United States through 1998. -Pittsburgh, PA (USA): USGS; 1998 .-- 179 p.

8. Zhevelyuk I. "Hunting for" movable "property // Nord-West-Courier. - No. 41 (54): - November 21-27, 2002. t

production of 1500 tons of ferroniobium per year, 1000 tons of N¿-N5 alloy and 500 tons of Cr-N-M-master alloy. Thus, the volumes of pyrochlore products offered for processing by Stalmag, Zabaikalsky and Novo-Orlovsky GOKs, as well as those planned for delivery from the Tomtor deposit, can be accepted for redistribution by this enterprise. For the production of commercial metal products from niobium and tantalum Russian companies you can use tolling schemes for working with Kazakh companies KazNiobiy - Irtysh Chemical and Metallurgical Plant and Ulba Metallurgical Plant. In the event of an improvement in the conjuncture of superconducting materials, the option of organizing a production of niobium rolled products on the territory of Russia is also realistic. Such production existed earlier at the Experimental Chemical and Metallurgical Plant of GIREDMED (Podolsk, Moscow Region) and the Experimental Plant of Refractory Metals and Hard Alloys (Moscow).

The creation of new industries for the extraction and production of niobium products is also possible within the framework of their associated extraction during the development of deposits of other minerals - for example, Katuginsky yttrium-rare earth-zirconium, Vishnyakovsky tantalum, Zavitinsky lithium, etc. niobium, which cannot seriously affect the market for its demand.

The development of the deposits of the distant reserve (Ulug-Tanzeksky in the Republic of Tyva and Gusinoozersky in the Republic of Sakha-Yakutia) in the conditions of an excess supply of niobium raw materials by more capable companies operating on rich and easy-dressing ores is hardly advisable.

9. Semenenko Y. Russian niobium. The first swallow from Siberia // Prirodo-resourcenye vedomosti. - August 31, 2001, http://gazeta.priroda.ru.

10. Sites Yu.G., Kharitonov Yu.F., Shevchuk G.A. Mineral resource base of the Chita region. Prospects for exploration and development: Part 2 // Mineral resources of Russia. Economics and Management. - 2002. -№ 5. - S. 8-20.

11. Temnov A.B. Geological and technical problems of mining ultra-rich rare-metal ores of the Tomtor deposit // Natural and technogenic placers and deposits of weathering crusts at the turn of the millennium. Abstracts. report XII Int. conference ". - M .: IGEM RAN, 2000. - S! 345-347.

12. Epshtein E.M., Usova T.Yu., Danilchenko N.A. et al. Niobium of Russia: state, prospects of development and development of the mineral resource base // Mineral raw materials. Geological and economic series, No. 8. - M .: VIMS, 2000. - 103 p.

13. Kudrin B.C., Rozhanets A.B., Chistov L.B. and others. Tantalum of Russia: state, prospects of development and development of the mineral resource base // Mineral raw materials *. Geological and economic series, No. 4. - M .: VIMS, 1999.-90 p.

Physical properties of niobium

Niobium is a shiny silver-gray metal.

Elemental niobium is an extremely refractory (2468 ° C) and high boiling (4927 ° C) metal that is highly resistant in many corrosive environments. All acids, with the exception of hydrofluoric acid, do not act on it. Oxidizing acids "passivate" niobium, covering it with a protective oxide film (No. 205). But at high temperatures, the reactivity of niobium increases. If at 150 ... 200 ° C only a small surface layer of the metal is oxidized, then at 900 ... 1200 ° C the thickness of the oxide film increases significantly.

The crystal lattice of niobium is body-centered cubic with a parameter a = 3.294A.

Pure metal is ductile and can be rolled into a thin sheet (up to a thickness of 0.01 mm) in the cold state without intermediate annealing.

It is possible to note such properties of niobium as a high melting and boiling point, a lower work function of electrons in comparison with other refractory metals - tungsten and molybdenum. The latter property characterizes the ability to electron emission (emission of electrons), which is used for the use of niobium in vacuum technology. Niobium also has a high superconducting transition temperature.

Density 8.57 g / cm3 (20 ° C); tm 2500 ° C; tboil 4927 ° C; vapor pressure (in mm Hg; 1 mm Hg = 133.3 N / m2) 1 10-5 (2194 ° C), 1 10-4 (2355 ° C), 6 10- 4 (at tm), 1 · 10-3 (2539 ° C).

At ambient temperatures, niobium is stable in air. The onset of oxidation (tarnishing films) is observed when the metal is heated to 200 - 300 ° C. Above 500 °, rapid oxidation occurs with the formation of the oxide Nb2O5.

Thermal conductivity in W / (m · K) at 0 ° C and 600 ° C, respectively 51.4 and 56.2, the same in cal / (cm · sec · ° C) 0.125 and 0.156. Specific volumetric electrical resistance at 0 ° C 15.22 · 10-8 ohm · m (15.22 · 10-6 ohm · cm). The superconducting transition temperature is 9.25 K. Niobium is paramagnetic. The work function of electrons is 4.01 eV.

Pure Niobium is easily pressurized in the cold and retains satisfactory mechanical properties at high temperatures. Its ultimate strength at 20 and 800 ° C, respectively, is 342 and 312 MN / m2, the same in kgf / mm234.2 and 31.2; elongation at 20 and 800 ° C, respectively, 19.2 and 20.7%. Brinell hardness of pure niobium is 450, technical hardness is 750-1800 Mn / m2. Impurities of some elements, especially hydrogen, nitrogen, carbon and oxygen, greatly impair the ductility and increase the hardness of niobium.

Chemical properties of niobium

Niobium is especially prized for its resistance to inorganic and organic substances.

There is a difference in the chemical behavior of powdered and lumpy metal. The latter is more stable. Metals do not act on it, even if heated to high temperatures. Liquid alkali metals and their alloys, bismuth, lead, mercury, tin can be in contact with niobium for a long time without changing its properties. Even such strong oxidants as perchloric acid, "aqua regia", not to mention nitric, sulfuric, hydrochloric and all others, can do nothing with it. Alkaline solutions also have no effect on niobium.

There are, however, three reagents that can convert niobium metal to chemical compounds. One of them is a molten hydroxide of an alkali metal:

4Nb + 4NaOH + 5О2 = 4NaNbO3 + 2H2О

The other two are hydrofluoric acid (HF) or its mixture with nitric acid (HF + HNO). In this case, fluoride complexes are formed, the composition of which largely depends on the reaction conditions. The element is in any case included in the anion of the 2- or 2- type.

If we take powdered niobium, then it is somewhat more active. For example, in molten sodium nitrate, it even ignites, turning into oxide. Compact niobium begins to oxidize when heated above 200 ° C, and the powder becomes covered with an oxide film already at 150 ° C. At the same time, one of the wonderful properties of this metal is manifested - it retains plasticity.

In the form of sawdust, when heated above 900 ° C, it completely burns out to Nb2O5. Burns vigorously in a stream of chlorine:

2Nb + 5Cl2 = 2NbCl5

Reacts with sulfur when heated. It is difficult to alloy with most metals. There are, perhaps, only two exceptions: iron, with which solid solutions of different ratios are formed, and aluminum, which has a compound Al2Nb with niobium.

What qualities of niobium help it resist the action of the strongest acids - oxidizing agents? It turns out that this refers not to the properties of the metal, but to the features of its oxides. When in contact with oxidizing agents, a very thin (and therefore invisible), but very dense layer of oxides appears on the metal surface. This layer becomes an insurmountable obstacle on the path of the oxidizing agent to a clean metal surface. Only some chemical reagents, in particular the fluorine anion, can penetrate through it. Therefore, essentially the metal is oxidized, but practically no oxidation results are noticeable due to the presence of a thin protective film. Passivity towards dilute sulfuric acid is used to create an alternating current rectifier. It is arranged simply: platinum and niobium plates are immersed in a 0.05 m sulfuric acid solution. Niobium in a passivated state can conduct current if it is a negative electrode - a cathode, i.e. electrons can pass through the oxide layer only from the metal side. The path of electrons from the solution is closed. Therefore, when an alternating current is passed through such a device, then only one phase passes, for which platinum is the anode, and niobium is the cathode.

niobium metal halogen

A chemical element named after the ancient Niobe - a woman who dared to laugh at the gods and paid for it with the death of her children. Niobium epitomizes humanity's transition from industrial to digital production; from steam locomotives to launch vehicles; from coal-fired power plants to nuclear power. In the world, the price of niobium per gram is quite high, as is the demand for it. Most of the latest advances in science are closely related to the use of this metal.

Niobium price per gram

Since the main uses of niobium are associated with nuclear and space programs, it belongs to the group of strategic materials. Processing is much more profitable financially than the development and extraction of new ores, which makes niobium in demand in the secondary metal market.

The value of the price for it is determined by several factors:

• The purity of the metal. The more foreign matter, the lower the price.
• Delivery form.
• Scope of delivery. Directly proportional to metal prices.
• The location of the scrap collection point. Each region has a different need for niobium and, accordingly, the price for it.
• The presence of rare metals. Alloys containing elements such as tantalum, tungsten, molybdenum are higher in price.
• The value of quotes on world exchanges. It is these values ​​that are basic when setting a price.

Indicative overview of prices in Moscow:

• Niobium NB-2. The price varies between 420-450 rubles. per kg.
• Niobium shavings. RUB 500-510 per kg.
• Niobium headquarters НБШ00. Differs in increased prices due to the negligible content of impurities. RUB 490-500 per kg.
• Niobium head NBSh-0. RUB 450-460 per kg.
• Niobium NB-1 in the form of a rod. The price is 450-480 rubles. per kg.

Despite the high cost, the demand for niobium in the world continues to grow. This is due to its enormous potential for use and the shortage of metal. There are only 18 grams of niobium per 10 tons of earth.

The scientific community continues to work on finding and developing a substitute for such an expensive material. But so far concrete result in this did not receive. This means that a drop in niobium prices is not expected in the near future.

To regulate the price and increase the rate of turnover, the following categories are provided for niobium products:

• Niobium ingots. Their size and weight are standardized by GOST 16099-70. Depending on the purity of the metal, they are subdivided into 3 grades: niobium NB-1, niobium NB-2 and, accordingly, niobium NB-3.
• Niobium stick. Differs in a higher percentage of impurities.
• Niobium foil. Manufactured up to 0.01 mm thick.
• Niobium bar. According to TU 48-4-241-73 it is supplied with the brands NBP1 and NBP2.

Physical properties of niobium

The metal is gray with a white tint. Refers to the group of refractory alloys. The melting point is 2500 ºС. The boiling point is 4927 ºС. Differs in increased value of heat resistance. Does not lose its properties at operating temperatures above 900 ºС.

The mechanical properties are also at a high level. The density is 8570 kg / m3 with a similar indicator of steel 7850 kg / m3. Resistant to work under both dynamic and cyclic loads. Tensile strength - 34.2 kg / mm2. Possesses high plasticity. The coefficient of relative elongation varies in the range of 19-21%, which makes it possible to obtain from it sheet metal niobium with a thickness of up to 0.1 mm.

Hardness is associated with the purity of the metal from harmful impurities and increases with their increase in composition. Pure niobium has 450 Brinell hardness units.

Niobium lends itself well to working by pressure at temperatures below -30 ºС and poorly cutting.

Thermal conductivity does not change significantly with large temperature fluctuations. For example, at 20 ºС it is 51.4 W / (m K), and at 620 С it increases by only 4 units. Niobium competes for electrical conductivity with elements such as copper and aluminum. Electrical resistance - 153.2 nΩ m. Belongs to the category of superconducting materials. The temperature at which the alloy goes into superconducting mode is 9.171 K.

Extremely acid-resistant. Such common acids as sulfuric, hydrochloric, phosphoric, nitric do not affect its chemical structure in any way.

At temperatures above 250 ºС, niobium begins to actively oxidize with oxygen, as well as enter into chemical reactions with hydrogen and nitrogen molecules. These processes increase the brittleness of the metal, thereby reducing its strength.

• Does not apply to allergenic materials. Introduced into the human body, it does not cause a rejection reaction by the body.
• It is a metal of the first group of weldability. The welds are tight and do not require preparatory operations. Crack resistant.

Varieties of alloys

According to the value of mechanical properties at elevated temperatures, niobium alloys are subdivided:

1. Low strength. Operate within 1100-1150 ºС. They have a simple set of alloying elements. This mainly includes zirconium, titanium, tantalum, vanadium, hafnium. Strength is 18-24 kg / mm2. After passing the critical temperature threshold, it drops sharply and becomes similar to pure niobium. The main advantage is high plastic properties at temperatures up to 30 ºС and good pressure workability.
2. Medium strength. Their working temperature is in the range of 1200-1250 ºС. In addition to the above alloying elements, they contain impurities of tungsten, molybdenum, tantalum. The main purpose of these additives is to maintain mechanical properties with increasing temperature. They have moderate plasticity and work well with pressure. A striking example of an alloy is niobium 5VMTs.
3. High strength alloys. They are used at temperatures up to 1300 ºС. With short-term exposure up to 1500 ºС. They differ in chemical composition of higher complexity. They consist of 25% additives, the main share of which is tungsten and molybdenum. Some types of these alloys are distinguished by a high carbon content, which has a positive effect on the value of their heat resistance. The main disadvantage of high-strength niobium is its low ductility, which makes it difficult to carry out technological processing. And, accordingly, the production of semi-finished products.

It should be borne in mind that the categories listed above are conditional and give only a general idea of ​​the method of using this or that alloy.

Also mention should be made of such compounds as ferroniobium and niobium oxide.

Ferroniobium is a compound of niobium with iron, where the content of the latter is at the level of 50%. In addition to the basic elements, it includes hundredths of titanium, sulfur, phosphorus, silicon, carbon. The exact percentage of elements is standardized by GOST 16773-2003.

Niobium pentaxide is a white crystalline powder. Not susceptible to dissolution in acid and water. It is produced by burning niobium in an oxygen atmosphere. Completely amorphous. Melting temperature 1500 ºС.

Niobium Applications

All of the above properties make the metal extremely popular in various industries. Among the many ways to use it, the following positions are distinguished:

• Use in metallurgists as an alloying element. Moreover, both ferrous and non-ferrous alloys are alloyed with niobium. For example, adding only 0.02% of it to the composition of stainless steel 12X18H10T increases its wear resistance by 50%. Enhanced with niobium (0.04%), aluminum becomes completely insensitive to alkali. Niobium acts on copper as a hardening of steel, increasing its mechanical properties by an order of magnitude. Note that even uranium is doped with niobium.
• Niobium pentoxide is the main component in the manufacture of highly refractory ceramics. He also found application in the defense industry: armored glasses of military equipment, optics with a large angle of refraction, and so on.
• Ferroniobium is used for alloying steels. Its main task is to increase corrosion resistance.
• In electrical engineering, they are used for the manufacture of capacitors and current rectifiers. Such capacitors are characterized by high capacitance and insulation resistance, small dimensions.
• Compounds of silicon and germanium with niobium are widely used in the field of electronics. Superconducting solenoids and elements of current generators are made of them.