Application of niobium. Niobium production in Russia

The element that occupies the 41st cell in the periodic table has been known to mankind for a long time. The age of its current name - niobium - is almost half a century less. It so happened that element #41 was opened twice. The first time - in 1801, the English scientist Charles Hatchet examined a sample of the right 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 columbia, thus marking its transatlantic origin. And the black mineral is called columbite.

A year later, the Swedish chemist Ekeberg isolated the oxide of another new element from columbite, called tantalum. The similarity of the compounds of Columbia and tantalum was so great that for 40 years most chemists believed that tantalum and columbium were one and the same element.

In 1844, the German chemist Heinrich Rose examined samples of columbite found in Bavaria. He again discovered oxides of two metals. One of them was an oxide of the already known tantalum. The oxides were similar, and emphasizing their similarity, Rosé named the element forming the second oxide niobium, after the name of Niobe, daughter of the mythological martyr Tantalus.

However, Rose, like Hatchet, failed 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 late XIX in. two more ways of obtaining this element were found. Moissan first obtained it in an electric furnace, reducing niobium oxide with carbon, and then Goldschmidt managed to reduce the same element with aluminum.

And call element #41 in different countries continued in different ways: in England and the USA - with Columbia, in other countries - with niobium. The International Union of Pure and Applied Chemistry (IUPAC) put an end to this discord in 1950. It was decided to legalize the name of the element “niobium” everywhere, and the name “columbite” was assigned to the main mineral of niobium. Its formula is (Fe, Mn) (Nb, Ta) 2 O 6.

Through the eyes of a chemist

Elemental niobium is an extremely refractory (2468°C) and high-boiling (4927°C) metal, very resistant in many aggressive environments. All acids, with the exception of hydrofluoric, do not act on it. Oxidizing acids "passivate" niobium, covering it with a protective oxide film (No. 205). But at high temperatures the chemical activity 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.

Niobium reacts actively with many non-metals. Halogens, nitrogen, hydrogen, carbon, sulfur form compounds with it. In this case, niobium can exhibit different valences - from two to five. But the main valence of this element is 5+. Pentavalent niobium can be included in the composition of the salt both as a cation and as one of the elements of the anion, which indicates the amphoteric nature of element No. 41.

Salts of niobic acids are called niobates. They are obtained as a result of exchange reactions after fusion of niobium pentoxide with soda:

Nb 2 O 5 + 3Na 2 CO 4 → 2Na 3 NbO 4 + 3CO 2.

Salts of several niobic acids, primarily methaniobic HNbO 3 , as well as diniobates and pentaniobates (K 4 Nb 2 O 7 , K 7 Nb 5 O 16 ) are quite well studied. m H2O). And salts in which element No. 41 acts as a cation are usually obtained by direct interaction simple substances, for example 2Nb + 5Cl 2 → 2NbCl 5 .

Brightly colored needle-shaped crystals of niobium pentahalides (NbCl - yellow, NbBr 5 - purple-red) easily dissolve in organic solvents - chloroform, ether, alcohol. But when dissolved in water, these compounds completely decompose, hydrolyze with the formation of niobates:

NbCl 5 + 4H 2 O → 5HCl + H 3 NbO 4.

Hydrolysis can be prevented if water solution add some strong acid. In such solutions, niobium pentahalides dissolve without hydrolyzing.

Niobium forms double salts and complex compounds, most easily - fluorine. Fluoroniobates are the names of these double salts. They are obtained by adding a metal fluoride to a solution of niobecic and hydrofluoric acids.

The composition of a complex compound depends on the ratio of the components reacting in solution. X-ray analysis of one of these compounds showed a structure corresponding to the formula K 2 NbF 7 . Oxo compounds of niobium can also be formed, for example, potassium oxofluoronpobate K 2 NbOF 5 H 2 O.

The chemical characterization of the element is not limited, of course, to this information. Today, the most important of element 41's compounds are its compounds with other metals.

Niobium and superconductivity

The amazing phenomenon of superconductivity, when, as the temperature of the conductor decreases, an abrupt disappearance of electrical resistance occurs in it, was first observed by the Dutch physicist G. Kamerling-Onnes in 1911. Mercury turned out to be the first superconductor, but not mercury, but niobium and some intermetallic compounds of niobium were destined to become the first technically important superconducting materials.

Two characteristics of superconductors are practically important: the value of the critical temperature at which the transition to the state of superconductivity occurs, and the critical magnetic field(Even Kamerling-Onnes observed the loss of superconductivity by a superconductor when exposed to a sufficiently strong magnetic field). As of January 1, 1975, the superconductor - the "record holder" in terms of the critical temperature was an intermetallic compound of niobium and germanium of the composition Nb 3 Ge. Its critical temperature is 23.2°K; this is above the boiling point of hydrogen. (Most known superconductors become superconductors only at the temperature of liquid helium).

The ability to pass into the state of superconductivity is also inherent in Nb 3 Sn niobium stapnide, alloys of niobium with aluminum and germanium, or with titanium and zirconium. All these alloys and compounds are already being used for the manufacture of superconducting solenoids, as well as some other important technical devices.

Niobium - metal

Metallic niobium can be obtained by reducing its compounds, such as niobium chloride or potassium fluorine niobate, at high temperature:

K 2 NbF 7 + 5Na → Nb + 2KF + 5NaF.

But before reaching this essentially last stage of production, niobium ore goes through many stages of processing. The first of them is ore beneficiation, obtaining concentrates. The concentrate is fused with various fluxes: caustic soda or soda. The resulting alloy is leached. But it does not dissolve completely. The insoluble precipitate is niobium. True, here it is still in the composition of the hydroxide, is not separated from its analogue in the subgroup - tantalum - and is not purified from some impurities.

Until 1866, there was not a single method for the separation of tantalum and niobium suitable for production conditions. The first method to separate these extremely similar elements was proposed by Jean Charles Galissard de Marignac. The method is based on the different solubility of the complex compounds of these metals and is called fluoride. The complex tantalum fluoride is insoluble in water, while the analogous niobium compound is soluble.

The fluoride method is complicated and does not allow complete separation of niobium and tantalum. Therefore, nowadays it is almost never used. It was replaced by methods of selective extraction, ion exchange, rectification of halides, etc. These methods produce oxide and chloride of pentavalent niobium.

After the separation of niobium and tantalum, the main operation takes place - recovery. Niobium pentoxide Nb 2 O 5 is reduced with aluminum, sodium, carbon black or niobium carbide obtained by reacting Nb 2 O 5 with carbon; Niobium pentachloride is reduced with sodium metal or sodium amalgam. This is how powdered niobium is obtained, which must then be turned into a monolith, made plastic, compact, suitable for processing. Like other refractory metals, niobium-monolith is obtained by powder metallurgy, the essence of which is as follows.

From the resulting metal powder under high pressure (1 t/cm 2) pressed the so-called rods of rectangular or square section. In a vacuum at 2300°C, these rods are sintered, combined into rods, which are melted in vacuum arc furnaces, and the rods in these furnaces act as an electrode. This process is called consumable electrode melting.

Single-crystal plastic niobium is obtained by crucible-free zone electron-beam melting. Its essence is that a powerful electron beam is directed to powdered niobium (pressing and sintering operations are excluded!) which melts the powder. Drops of metal flow onto the niobium ingot, which gradually grows and is removed from the working chamber.

As you can see, the path of niobium from ore to metal is in any case quite long, and the methods of production are complex.

Niobium and metals

The story about the use of niobium is most logical to begin with metallurgy, since it was in metallurgy that he found the most wide application. And in non-ferrous metallurgy, and in ferrous.

Steel alloyed with niobium has good corrosion resistance. "So what? - says another sophisticated reader. “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, there is always carbon. But carbon combines with chromium to form carbide, which makes the steel more brittle. Niobium has a greater affinity for carbon than chromium. Therefore, when niobium is added to steel, niobl 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 chromium-mangaic steel niobium gives high wear resistance.

Many non-ferrous metals are also alloyed with niobium. So, aluminum, which is easily soluble 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 by aviation, mechanical engineering, radio engineering, chemical industry, nuclear power. All of them became consumers of niobium.

The 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 of thermal neutrons, made niobium a serious competitor to the metals recognized in the nuclear industry - aluminum, beryllium and zirconium. In addition, the artificial (induced) radioactivity of niobium is low. Therefore, it can be used to make containers for storage. radioactive waste or instructions for their use.

The chemical industry consumes relatively little niobium, but this can only be explained by its scarcity. From niobium-containing alloys and less often from sheet niobium, equipment for the production of high-purity acids is sometimes made. The ability of niobium to influence the speed of some chemical reactions used, for example, in the synthesis of alcohol from butadiene.

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

Niobium minerals

Columbite (Fe, Mn) (Nb, Ta) 2 O 6 was the first mineral of niobium, known to mankind. And the same mineral is the richest in element No. 41. The share of oxides of niobium and tantalum accounts for up to 80% of the weight of columbite. There is much less niobium in pyrochlore (Ca, Na) 2 (Nb, Ta, Ti) 2 O 6 (O, OH, F) and loparite (Na, Ce, Ca) 2 (Nb, Ti) 2 O 6 . In total, more than 100 minerals are known, which include niobium. There are significant deposits of such minerals in different countries: the USA, Canada, Norway, Finland, but the African state of Nigeria has become the largest supplier of niobium concentrates to the world market. In the USSR there are large reserves of loparite, they were found on the Kola Peninsula.

Pink carbide

Niobium monocarbide NbC is a plastic substance with a characteristic pinkish luster. This important compound is quite easily formed by the interaction of metallic niobium with hydrocarbons. The combination of good malleability and high heat resistance with pleasant "external data" made niobium monocarbide valuable material for making coatings. A layer of this substance only 0.5 mm thick reliably protects many materials from corrosion at high temperatures, in particular graphite, which is practically unprotected by other coatings. NbC is also used as a structural material in rocket and turbine manufacturing.

Nerves sutured with niobium

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

Appearance is not deceiving

Niobium not only has a set of properties required by the technique, but also looks quite beautiful. Jewelers tried to use this white shiny metal to make 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 do without expensive iridium in the production of soldering for fountain nibs.

Niobium and welding

At the end of the 20s of our century, electric and gas welding began to displace riveting and other methods of connecting components and parts. Welding improved the quality of parts, made their assembly process faster and cheaper. Welding seemed especially promising during the installation of large installations operating in corrosive environments or under high pressure. But then it turned out that when welding stainless steel, the weld has a much lower strength than the steel itself. To improve the properties of the seam, various additives began to be introduced into the "stainless steel". The best of them was niobium.

Understated figures

It is no coincidence that niobium is considered a rare element: it really does not occur often and in small quantities, and always in the form of minerals and never in a native state. A curious 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 in African countries found new deposits of minerals containing niobium. In the "Handbook of a chemist", 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 are 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.

DEFINITION

Niobium- forty-first element Periodic table. Designation - Nb from the Latin "niobium". Located in the fifth period, VBA group. Refers to metals. The nuclear charge is 41.

The earth's crust of niobium contains 0.002% (mass.). This element is in many ways similar to vanadium. In the free state, it is a refractory metal, hard, but not brittle, well machinable (Fig. 1 .. The density of niobium is 8.57 g / cm 3, the melting point is 2500 o C.

Niobium is stable in many aggressive environments. It is not affected by hydrochloric acid and aqua regia, since a thin, but very strong and chemically resistant oxide film forms on the surface of this metal.

Rice. 1. Niobium. Appearance.

Atomic and molecular weight of Niobium

DEFINITION

Relative molecular weight of a substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass element (A r)- how many times the average mass of atoms chemical element more than 1/12 of the mass of a carbon atom.

Since niobium exists in the free state in the form of monatomic Nb molecules, the values ​​of its atomic and molecular weight match. They are equal to 92.9063.

Isotopes of niobium

It is known that niobium can occur in nature in the form of the only stable isotope 93Nb. The mass number is 93, the nucleus of an atom contains forty-one protons and fifty-two neutrons.

There are artificial unstable isotopes of zirconium with mass numbers from 81 to 113, as well as twenty-five isomeric states of nuclei, among which the 92 Nb isotope with a half-life of 34.7 million years is the longest-lived.

Niobium ions

On the outer energy level of the niobium atom, there are five electrons that are valence:

1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 3 5s 2 .

As a result of chemical interaction, niobium gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Nb 0 -1e → Nb + ;

Nb 0 -2e → Nb 2+;

Nb 0 -3e → Nb 3+;

Nb 0 -4e → Nb 4+;

Nb 0 -5e → Nb 5+.

Molecule and atom of niobium

In the free state, niobium exists in the form of monatomic Nb molecules. Here are some properties that characterize the atom and molecule of niobium:

Niobium alloys

Niobium is one of the components of many heat-resistant and corrosion-resistant alloys. Especially great importance have heat-resistant niobium alloys, which are used in the production of gas turbines, jet engines, missiles.

Niobium is also introduced into stainless steels. It dramatically improves their mechanical properties and corrosion resistance. Steels containing from 1 to 4% niobium are characterized by high heat resistance and are used as a material for the manufacture of high-pressure boilers.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

The physical properties of niobium Nb are given depending on the temperature in the range from -223 to 2527°C. The following properties of solid and liquid niobium are considered:

• niobium density d;
• specific mass heat capacity Cp;
• thermal diffusivity a;
• coefficient of thermal conductivity λ ;
• specific electrical resistance ρ ;
• coefficient of linear thermal expansion α .

Physical properties niobium depends on temperature in different ways. Its change has greatest influence on the electrical resistivity of niobium. For example, when the temperature of this metal rises from 0°C to the melting point, its resistivity increases by more than 8 times (up to a value of 109·10 -8 Ohm·m).

Niobium is a ductile refractory metal with a melting point of 2477°C and a density of 8570 kg/m 3 (at 20°C). The boiling point of niobium is 4744°C, the lattice structure is body-centered cubic with a period of 0.33 nm.

The density of niobium decreases when heated. Niobium in the molten state has a density significantly lower than in the solid state: at a temperature of 2477°C, the density of liquid niobium is 7580 kg/m 3 .

The specific heat capacity of niobium at room temperature is 268 J/(kg deg) and increases upon heating. Note that the value of this physical property of niobium changes insignificantly during melting, and in the liquid state its specific heat capacity is 1.7 times greater than the classical value 3R.

The thermal conductivity of niobium at 0°C is 48 W/(m deg), it is close in size to . The temperature dependence of the thermal conductivity of niobium is characterized by a flat minimum in the region of room temperatures and a positive temperature coefficient— above 230°C. When approaching the melting point of niobium, its thermal conductivity increases.

The thermal diffusivity of niobium also has a flat minimum near room temperature and then a flat maximum at 900...1500°C. The coefficient of thermal linear expansion of niobium is relatively low. It is comparable in value with the expansion coefficient of metals such as tungsten, iridium and.

0.145 nm, (coordination number is indicated in brackets) Nb 2+ 0.085 nm (6), Nb 3+ 0.086 nm (6), Nb 4+ 0.082 nm (6), 0.092 nm (8), Nb 5 + 0.062 nm ( 4), 0.078 nm (6), 0.083 nm (7), 0.088 nm (8).

Content in the earth's crust 2 . 10 -3% by weight. It occurs in nature usually together with Ta. Naib. important are columbite-tantalite, and loparite. Columbite-tantalite (Fe, Mn) (Nb, Ta) 2 O 6 contains 82-86% Nb and Ta. When the content of niobium is higher than Ta, called. columbite, with the opposite ratio - tantalite. (Na,Ca,Ce) 2 (Nb,Ti) 2 (OH,F)O 6 usually contains 37.5-65.6% Nb 2 O 5 ; loparite (Na, Ce, Ca, SrXNb, Ti) O 3 -8-10% Nb 2 O 5. niobium are weakly paramagnetic and radioactive due to U and Th impurities.

Columbite is found in igneous pegmatites, biotites and alkaline granites, sometimes in alluvial deposits (Nigeria), and is often mined as a by-product of tin concentrate enrichment. found in carbonatites, alkaline (Canada), nepheline-syenite pegmatites, in eluvial weathering products of syenite-carbonatites (Brazil). There are large deposits of loparite in the USSR.

The total world reserves of niobium (without the USSR) were estimated (1980) at 18 million tons; deposits - approx. 3.4 million tons (of which 3.2 million tons in Brazil).

Properties. Niobium - Brilliant Silver Grey; crystalline body-centric grating cubic type a-Fe, a = 0.3294 nm, z = 2, spaces. group Im3m; m.p. 2477 °С, b.p. OK. 4760 °С; dense 8.57 g/cm 3 ; C 0 p 24.44 J / (. K); DH 0 pl 31.0 kJ/ (2477 °С), DH 0 ex 720 kJ/ (0 K), DH 0 exp 662 kJ/ (4760 °С); S 0 298 36.27 JDmol K); temperature dependence over liquid niobium: lgr (Pa) = 13.877-40169 / T (2304<= Т<= 2596 К); температурный коэф. линейного расширения 7,1 . 10 -6 К -1 (0-100 °С); 52,3 Вт/(м. К) при 20 °С и 65,2 Вт/(м. К) при 600 °С; r 1,522 . 10 -9 Ом. м при 0°С, температурный коэф. r 3,95 х х 10 -3 К -1 (0-100°С). Ниобий парамагнитен, уд. магн. восприимчивость + 2,28 . 10 -6 (18 °С). Т-ра перехода в сверхпрово-дящее состояние 9,28 К.

Pure niobium is easily processed in the cold; heat resistant; s rast 342 MPa (20 °C) and 312 MPa (800 °C); relates. elongation 19.2% (20°C) and 20.7% (800°C); according to Brinell 450 MPa for clean and 750-1800 MPa for technical. Impurities H, N, C and O reduce niobium and increase it. In a brittle state, niobium passes at temperatures from - 100 to - 200 ° C.

Chemically, niobium is quite stable. In a compact form, it begins to oxidize at temperatures above 200 ° C, giving, interaction. with Cl 2 above 200 ° C, with F 2 and H 2 - above 250 ° C (intensively with H 2 - at 360 ° C), with N 2 - above 400 ° C, with C and hydrocarbons - at 1200-1600 ° FROM. In the cold, not sol. in, hydrochloric and sulfuric to-max, does not react with HNO 3, H 3 PO 4, HclO 4, aqueous p-rum NH 3. Melt resistant. Li, Na, K, Sn, Pb, Bi, and also Hg. Solv. in hydrofluoric to-those, its mixtures with HNO 3 in the melt. NH 4 HF 2 and NaOH. Reversibly absorbs H 2 , forming a solid solution of the introduction (up to 10 at.% H) and the composition NbH x (x = 0.7-1.0) with rhombic. crystalline lattice; for NbH 0.761 DH 0 arr - 74.0 kJ/; p-value in niobium varies from 104 cm 3 /g at 20 ° C to 4.0 cm 3 / g at 900 ° C, above 1000 ° C H 2 is practically insoluble. in niobium. are also formed in the first stages of niobium in the hydrofluoricto-those, its mixtures with HNO 3 and NH 4 HF 2, as well as with to-t from niobium (in this way NbH 2.00 was obtained). niobium and when heated. used to obtain finely dispersed.

When niobium interacts with C, one of three phases is formed: a solid solution of C in, Nb 2 C or NbC. Solid solution contains 2 at. % С at 2000 °С; p-value C in niobium drops sharply with decreasing temperature. Carb and d Nb 2 C forms three polymorphic modifications: rhombic is stable up to 1230 ° C. a-phase (space group Pbcn), at 1230°C it turns into. into a hexagon. b-phase (space group P6 3 22), edges at 2450 ° C passes into another hexagon. -g-phase (space group P6 3 /mmc); m.p. OK. 2990 °С (incongruent, with the release of solid NbС x). For a-Nb 2 C: C 0 p 63.51 J / (. K); DH 0 arr - 188 kJ/; S 0 298 64.10 JDmol. TO); temperature of transition to the superconducting state 9.2 K. NbC crystals or gray-brown, homogeneity range from NbC 0.70 to NbC 1.0; at 377 °C, a polymorphic transition is observed, high-temperature cubic. phase (a \u003d 0.4458 nm, space group Pt3t, density 7.81 g / cm 3) melts incongruently approx. 3390 °С; DH 0 arr - 135 kJ/; S 0 298 35.4 JDmol K); t-ra transition to the superconducting state 12.1 K. Phase NbC 0.80 has so pl. ~ 3620 °С. NbC forms solid solutions with TaC, TiC, ZrC, etc. In the NbC industry, interaction is obtained. Nb 2 O 5 from approx. 1800 ° C in H 2; m.b. also obtained from the elements or by heating volatile niobium halides to 2300-2900 °C.

In the Nb-N system, the following are formed: a solid interstitial solution in niobium (a-phase), n and tr and ds of Nb 2 N (hexagon. p-phase) and NbN (cubic. d- and hexagon. q -phases) and several more. phases. R-value N 2 in niobium at atm. is described by the equation c = 180exp (- 57300/RT) at. % (1073<= T<= 1873 К). b-Фаза гомогенна в области NbN 0,4 -NbN 0,5 ; для нее а = 0,3056 нм с = 0,4995 нм, пространств. группа Р6 3 /ттс- С 0 p 67 ДжДмоль. К); DH 0 обр - 249 кДж/ ; S 0 298 79 ДжДмоль. К). Светло-серая с желтоватым блеском d-фаза гомогенна в области NbN 0,88 -NbN l,06 , для нее а = 0,4373-0,4397 нм, пространств. группа Fm3m. Для q-фа-зы: С 0 р 37,5 ДжДмоль. К), DH 0 oбр -234 кДж/ , S 0 298 33,3 ДжДмоль К). не раств. в соляной к-те, HNO 3 и H 2 SO 4 , при кипячении со выделяют NH 3 , при нагр. на окисляются. Т-ры перехода в сверхпроводящее состояние для NbN x с x = 0,80, 0,90, 0,93 и 1,00 равны соотв. 13,8, 16,0, 16,3 и 16,05 К. получают нагреванием или ниобия в N 2 или NH 3 до 1100-1800 °С или взаимод. летучих галогенидов ниобия с NH 3 . Известны карбо- (получают взаимод. Nb, N 2 или NH 3 с выше 1200°С) и оксинитриды ниобия.

Receipt. OK. 95% of niobium is obtained from pyrochlore, tantalite-columbite and loparite. enrich gravity. methods and , as well as electromagnet. or radiometric. , releasing pyrochlore and columbite concentrates containing up to 60% Nb 2 O 5 .

Concentrates are processed to ferroniobium or tech. Nb 2 O 5, less often, up to NbCl 5 and K 2 NbF 7 (see). Niobium metal is obtained from Nb 2 O 5 , K 2 NbF 7 or NbCl 5 .

In the production of ferroniobium, a mixture of pyrochlore concentrates with Fe 2 O 3, powdered Al and flux is loaded into vertical water-cooled steel or copper reactors and with the help of special. fuse initiate exothermic. p-tion: 3Nb 2 O 5 + 10Al6Nb + + 5Al 2 O 3; Fe 2 O 3 + 2Al2Fe + Al 2 O 3. Then the slag is drained, cooled and crushed. The yield of niobium into an ingot at a concentrate loading mass of up to 18 tons reaches 98%.

Tech. Nb 2 O 5 receive Nb and Ta from concentrates and slags of tin melting by the action of hydrofluoric to-you with the latter. purification and separation of Nb and Ta with 100%, cyclohexanone, (rarely other extractants), re-extraction of niobium by the action of an aqueous solution of NH 4 F, from the re-extract of Nb, and its calcination.

According to the sulfate method, the concentrates are treated with H 2 SO 4 or its mixture with (NH 4) 2 SO 4 at 150-300 ° C, p-rimes are leached, Nb and Ta are separated from Ti, Nb and Ta are separated and purified from their fluoride or oxofluoride complexes , then isolating Nb 2 O 5 .

The chloride method involves mixing the concentrate with, briquetting and briquettes in a mine at 700-800 ° C or directly powdered concentrate and in a salt chloride based on NaCl and KCl. Next, the separation of volatile Nb and Ta is carried out, their separation and purification, and separate with calcination of the niobium precipitate. Ferroniobium or waste products are sometimes chlorinated.

Restore Nb 2 O 5 to alumino- or carbothermal or by heating a mixture of Nb 2 O 5 and NbC at 1800-1900 ° C in. Sodium-thermic is also used. K 2 NbF 7, electrolytic. Nb 2 O 5 or K 2 NbF 7 in K 2 NbF 7 and. Particularly pure or coatings of niobium on others receive NbCl 5 at temperatures above 1000 ° C.

Powdered niobium is briquetted, bars are sintered and remelted into electric arc or electron beam. At the initial stages of purification, it is also used with the spent KCl-NaCl.

True, empirical, or gross formula: Nb

Molecular weight: 92.906

Niobium- an element of a side subgroup of the fifth group of the fifth period of the periodic system of chemical elements of D. I. Mendeleev, atomic number - 41. It is denoted by the symbol Nb (lat. Niobium). The simple substance niobium (CAS number: 7440-03-1) is a shiny silver-gray metal with a cubic body-centered crystal lattice of the α-Fe type, a = 0.3294. For niobium, isotopes with mass numbers from 81 to 113 are known.

Story

Niobium was discovered in 1801 by the English scientist Charles Hatchet in a mineral sent back in 1734 to the British Museum from Massachusetts by John Winthrop (grandson of John Winthrop Jr.). The mineral was named columbite, and the chemical element was named "columbium" (Cb) after the country from which the sample was obtained - Colombia (at that time a synonym for the United States).
In 1802, A. G. Ekeberg discovered tantalum, which coincided in almost all chemical properties with niobium, and therefore for a long time it was believed that this was one and the same element. Only in 1844 did the German chemist Heinrich Rose establish that it was an element different from tantalum and renamed it "niobium" in honor of Tantalus's daughter Niobe, which emphasized the similarities between the elements. However, in some countries (USA, England), the original name of the element, columbium, was retained for a long time, and only in 1950, by decision of the International Union of Pure and Applied Chemistry (IUPAC, IUPAC), the element was finally given the name niobium.
For the first time, pure niobium was obtained at the end of the 19th century by the French chemist Henri Moissan by electrothermal means, reducing niobium oxide with carbon in an electric furnace.

Being in nature

Clark of niobium - 18 g/t. The content of niobium increases from ultramafic (0.2 g/t Nb) to acidic rocks (24 g/t Nb). Niobium is always accompanied by tantalum. The close chemical properties of niobium and tantalum determine their joint presence in the same minerals and participation in common geological processes. Niobium is able to replace titanium in a number of titanium-containing minerals (sphene, orthite, perovskite, biotite). The form of finding niobium in nature can be different: scattered (in rock-forming and accessory minerals of igneous rocks) and mineral. In total, more than 100 minerals containing niobium are known. Of these, only a few are of industrial importance: columbit-tantalite ( , ) (Nb, Ta) 2 O 6, pyrochlore ( , Ca, TR, U) 2 (Nb, Ta, Ti) 2 O 6 (OH, F) (Nb 2 O 5 0 - 63%), loparite (, Ca, Ce) (Ti, Nb) O 3 ((Nb, Ta) 2 O 5 8 - 10%), euxenite, thorolite, ilmenorutil, as well as minerals are sometimes used, containing niobium in the form of impurities (ilmenite, cassiterite, wolframite). In alkaline - ultrabasic rocks, niobium is dispersed in minerals such as perovskite and in eudialyte. In exogenous processes, niobium and tantalum minerals, being stable, can accumulate in deluvial-alluvial placers (columbite placers), sometimes in bauxites of the weathering crust. The concentration of niobium in sea water is 1·10 −5 mg/l.

Place of Birth

Niobium deposits are located in the USA, Japan, Russia (Kola Peninsula), Brazil, Canada.

Receipt

Niobium ores are usually complex and poor in metal. Ore concentrates contain Nb 2 O 5: pyrochlore - not less than 37%, loparite - 8%, columbite - 30-60%. Most of them are processed by alumino- or silicothermic reduction into ferroniobium (40-60% Nb) and ferrotantaloniobium. Metal niobium is obtained from ore concentrates using a complex technology in three stages:

• opening of the concentrate,
• separation of niobium and tantalum and obtaining their pure chemical compounds,
• recovery and refining of metallic niobium and its alloys.

isotopes

Natural niobium consists of a single stable isotope, 93 Nb. All other artificially obtained isotopes of niobium with mass numbers from 81 to 113 are radioactive (a total of 32 are known). The longest-lived isotope is 92 Nb with a half-life of 34.7 million years. Also known are 25 metastable states of the nuclei of its various isotopes.

Chemical properties

Chemically, niobium is quite stable, but inferior in this respect to tantalum. It is practically not affected by hydrochloric, orthophosphoric, diluted sulfuric, nitrogen. The metal dissolves in hydrofluoric acid HF, a mixture of HF and HNO 3, concentrated caustic solutions, and also in concentrated sulfuric acid when heated above 150 ° C. When calcined in air, it oxidizes to Nb 2 O 5 . About 10 crystalline modifications have been described for this oxide. At ordinary pressure, the β-form of Nb 2 O 5 is stable.

• When Nb 2 O 5 is fused with various oxides, niobates are obtained: Ti 2 Nb 10 O 29, FeNb 49 O 124. Niobates can be considered as salts of hypothetical niobic acids. They are divided into metaniobates MNbO 3 , orthoniobates M 3 NbO 4 , pyroniobates M 4 Nb 2 O 7 or polyniobates M 2 O nNb 2 O 5 (M is a singly charged cation, n = 2-12). Niobates of two- and three-charged cations are known.
• Niobates react with HF, melts of alkali metal hydrofluorides (KHF 2) and ammonium. Some niobates with a high M 2 O / Nb 2 O 5 ratio are hydrolyzed: 6Na 3 NbO 4 + 5H 2 O \u003d Na 8 Nb 6 O 19 + 10NaOH.
• Niobium forms NbO 2 , NbO, a number of oxides intermediate between NbO 2 , 42 and NbO 2 , 50 and similar in structure to the β-form of Nb 2 O 5 .
• With halogens, niobium forms NbHa 15 pentahalides, NbHa 14 tetrahalides, and NbHa 12, 67 - NbHa 13 +x phases, which contain Nb 3 or Nb 2 groups. Niobium pentahalides are readily hydrolyzed by water.
• In the presence of water vapor and oxygen, NbC 15 and NbBr 5 form oxyhalides NbOC 13 and NbOBr 3 - loose cotton-like substances.
• When niobium and graphite interact, Nb 2 C and NbC carbides, solid heat-resistant compounds, are formed. In the Nb - N system, there are several phases of variable composition and nitrides Nb 2 N and NbN. Niobium behaves similarly in systems with phosphorus and arsenic. The interaction of niobium with sulfur produced sulfides: NbS, NbS 2 and NbS 3 . Double fluorides Nb and potassium (sodium) - K 2 are synthesized.
• It has not yet been possible to isolate niobium electrochemically from aqueous solutions. Possible electrochemical production of alloys containing niobium. Metallic niobium can be isolated by electrolysis of anhydrous salt melts.

Application

The use and production of niobium is rapidly increasing, which is due to a combination of its properties such as refractoriness, a small thermal neutron capture cross section, the ability to form heat-resistant, superconducting, and other alloys, corrosion resistance, getter properties, low electron work function, good cold workability and weldability. The main areas of application of niobium: rocket science, aviation and space technology, radio engineering, electronics, chemical apparatus building, nuclear power engineering.

Applications of metallic niobium

• Aircraft parts are made from pure niobium or its alloys; shells for uranium and plutonium fuel elements; containers and pipes for liquid metals; details of electrolytic capacitors; "hot" fittings of 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. For example, aluminum, if only 0.05% niobium is introduced into it, does not react at all with alkalis, although under normal conditions it dissolves in them. An alloy of niobium with 20% copper has a high electrical conductivity and at the same time it is twice as hard and stronger than pure copper
• Niobium is used in cryotrons - superconducting elements of computers. Niobium is also known for its use in the accelerating structures of the Large Hadron Collider.
• Niobium and tantalum are used to produce electrolytic capacitors with high specific capacitance. Tantalum allows the production of higher quality capacitors than metallic niobium. However, niobium oxide capacitors are the most reliable and fire resistant.

Intermetallic compounds and alloys of niobium

• Nb 3 Sn stannide (triniobium stannide, also known as niobium-tin alloy), Nb 3 Ge germanide (germaniumtriniobium), NbN nitride, and niobium-titanium (niobium-titanium) and zirconium alloys are used to make superconducting solenoids. Thus, the windings of the superconducting magnets of the Large Hadron Collider are made of 1200 tons of niobium-titanium alloy cable.
• 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 (up to 0.6% niobium) into stainless chromium-nickel steels to prevent their intergranular corrosion (including that which would otherwise begin after stainless steel welding) and destruction, and in other types of steel to improve their properties.
• Niobium is used in minting collectible coins. Thus, the Bank of Latvia claims that niobium is used in the collection coins of 1 lats along with silver.

Application of niobium compounds

• Nb 2 O 5 - catalyst in the chemical industry;
• in the production of refractories, cermets, special glasses, 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 rods of solid-phase nuclear jet engines.
• Niobium nitride NbN is used for the production of thin and ultra-thin superconducting films with a critical temperature of 5 to 10 K with a narrow transition, on the order of 0.1 K.

Superconducting materials of the first generation

• One of the actively used superconductors (superconducting transition temperature 9.25 K). Niobium compounds have a superconducting transition temperature of up to 23.2 K (Nb 3 Ge).
• The most commonly used industrial superconductors are NbTi and Nb 3 Sn.
• Niobium is also used in magnetic alloys.
• It is used as an alloying additive.
• Niobium nitride is used to manufacture superconducting bolometers.
• The exceptional resistance of niobium and its alloys with tantalum in superheated cesium-133 vapor makes it one of the most preferred and cheap structural materials for high power thermionic generators.

Biological role

There is currently no information about the biological role of niobium.

Physiological action

Niobium metal dust is flammable and irritating to eyes and skin. Some niobium compounds are highly toxic. MPC of niobium in water is 0.01 mg/l. When ingested, it causes irritation of internal organs and subsequent paralysis of the limbs.