What family does niobium belong to? Application of niobium in metallurgy and industry. Methods for obtaining niobium

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:

Natriothermic reduction from complex fluorides;

Reduction from oxides with carbon (carbothermic method);

Reduction from aluminum oxides (aluminothermic method);

Reduction 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 sintered sponges. The task of producing 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 blanks pressed from powders or melt them in a high vacuum.

Natriothermic method for the production of tantalum and niobium powders

Sodium thermal reduction of complex fluorides K2TaF7 and K2NbF7 is the first industrial method for the production of 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 given below:

Al<^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 using the example of tantalum production. The reduction of K2TaF7 with sodium proceeds with a large release of heat (even at a charge loading scale of up to 5 kg), sufficient for the process to proceed spontaneously. 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 vapor sodium are involved in the reduction:

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

The specific thermal effects of reactions (2.18) and (2.19) are equal to 1980 and 3120 kJ/kg of charge, respectively.

Reduction is carried out in a steel crucible, into which potassium fluorotantalate and sodium pieces (~120% of the stoichiometrically required amount) are loaded layer by layer, which are cut with special scissors. The mixture is covered with a layer of sodium chloride on top, which forms a low-melting mixture with KF and NaF. Molten salt protects particles from oxidation
tantalum powder In the simplest version of the process, to initiate the reaction, the crucible wall at the bottom is heated with a blowtorch flame until a red spot appears. The reaction proceeds quickly throughout the mass and ends in 1-2 minutes. With this process, due to short-term exposure of products at 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 the reaction crucible in a shaft electric furnace and keeping it in the furnace after the end of the reaction at 1000 °C.

The resulting tantalum is disseminated in the form of small particles in the 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 the sodium is “quenched” and the bulk of the salts are dissolved. Then the powder is sequentially washed with diluted sodium chloride (to more completely wash off the salts and dissolve iron and partially 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 regimes, niobium powders are obtained by reducing k2NbF7 with sodium. Dried niobium powders have the composition,%: Ti, Si, Fe 0.02-0.06; O about 0.5; N up to 0.1; From 0.1-0.15.

Carbothermic method for producing niobium and tantalum from oxides

This method 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 Nb205 + 5C charge 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 released per 1 kg of charge. These circumstances make it unprofitable to carry out the process according to reaction (2.20), since the productivity of the vacuum furnace is low. Therefore, the process is carried out in two stages:

Stage I - production of niobium carbide

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

Stage P - production of 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 the 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 ensures 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 (stage 1 of the process), a mixture of Nb2o5 with soot is briquetted and the briquettes are heated in a graphite-tube furnace in an atmosphere of hydrogen or argon at 1800-1900 ° C (briquettes are continuously moved along the furnace

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

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

Based on their stay in the hot zone for 1-1.5 hours). Crushed niobium carbide is mixed in a ball mill with Nb2o5, taken with a slight excess (3-5%) compared to what is 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 pipe) at 1800-1900 C. The exposure ends when a residual pressure reaches 1.3-0.13 Pa.

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

Nb2Os + C = 2Nb02 + CO; (2.23)

Nb02 + C = NbO + CO; (2.24)

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

Nb2C + C = 2NbC. (2.26)

Stage 1 reactions:

Nb2Os + 2NbC = 2Nb02 + Nb2C + CO; (2.27)

Nb02 + 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). Equilibrium pressure co for reaction (2.29) at 1800 °C > 1.3 Pa. Therefore, the process must be carried out at a residual pressure less than the equilibrium pressure for a given reaction (0.5-0.13 Pa).

The resulting sintered porous niobium briquettes contain, %: C 0.1-0.15; About 0.15-0.30; N 0.04-0.5. To obtain compact malleable metal, briquettes are melted in an electron beam furnace. Another way is to obtain 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 from the composition co, and excess oxygen in the composition of volatile lower oxides.

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

The carbothermic method can also produce tantalum and niobium-tantalum alloys.

Aluminathermic method for producing niobium and tantalum from higher oxides

The aluminometric method for producing niobium by reducing niobium pentoxide with aluminum, developed in recent years, has technical and economic advantages over other methods for producing niobium due to its low-step nature and simplicity of equipment.

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 charge of stoichiometric composition) makes it possible to carry out the process without external heating with the smelting of a niobium-aluminum alloy ingot. Successful out-of-furnace aluminothermic reduction is possible if the process temperature is higher than the melting point of A12о3 = 2030 °C) and the metal phase (Nb +10% ai alloy melts at 2050 °C). 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 occurrence of reduction, an increase in temperature by approximately 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% aluminum is obtained with a real niobium extraction of 98-98.5%.

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

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

After turning on the fuse, the reaction proceeds quickly throughout the entire mass of the charge. The resulting alloy ingot is crushed into pieces and subjected to vacuum heat 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 (up to its content of 0.2%). Then refining smelting is carried out in an electron beam furnace, obtaining niobium ingots of high purity 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, aluminothermic production of tantalum is possible, but the process is somewhat more complicated. The specific thermal effect of the reduction reaction is 895 kJ/kg of charge. Due to the high melting point of tantalum and its alloys with aluminum, iron oxide is introduced into the charge to smelt the ingot (at the rate of obtaining an alloy with 7-7.5% iron and 1.5% aluminum), as well as a heating additive - potassium chlorate (bertholite salt) . The crucible with the charge is placed in the 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.

Preparation of tantalum and niobium by reduction from 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. The most promising are some options for reduction with hydrogen, in particular the method discussed below for the reduction of chloride vapors on heated substrates to produce a compact metal rod.

In Fig. Figure 30 shows a diagram of an installation for producing tantalum by reducing TaC15 vapor with hydrogen on a tantalum strip heated to 1200-1400 °C. TaCI5 vapor mixed with hydrogen flows from the evaporator into the reactor, in the center of which there is a tantalum strip, heated by direct passage of electric current to a given temperature. To uniformly distribute the steam-gas mixture along the length of the belt and 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 - clamp contacts; 4 - capacitor for unreacted chloride; 5 - tantalum tape; 6 - screens with holes, - 7 - reactor body; 8 - reactor heater; 9 - heated rotameter; 10 - needle valve; 11 - evaporator electric furnace; 12 - tantalum pentachloride evaporator; 13 - rotameter for hydrogen

Optimal conditions for tantalum deposition: tape temperature 1200-1300 °C, TaCI5 concentration 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 sheets, used for remelting in an electron beam furnace, or made into high-purity powders (by hydrogenating, grinding and dehydrogenating the powder). The degree of chloride conversion (direct extraction into coating) is 20-30%. The unreacted chloride is condensed and used again. Electricity consumption is 7-15 kWh per 1 kg of tantalum, depending on the adopted mode.

Hydrogen after separation of HCI vapors by absorption by water can be returned to the process.

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

Electrolytic method for producing tantalum

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

In industrial practice, the method is used to obtain tantalum. Thus, for a number of years, the electrolytic method of tantalum was used by the company Fensteel (USA); part of the tantalum produced in Japan is currently obtained by electrolysis. Extensive research and industrial testing of the method were carried out in the USSR.

The method for electrolytically producing tantalum is similar to the method for producing aluminum.

The electrolyte is based on molten salts K2TaF7 - KF - - KS1, in which tantalum oxide Ta205 is dissolved. The use of an electrolyte containing only one salt, K2TaF7, is practically impossible due to the continuous anodic 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 adjustment of the bath composition. This drawback 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 oxygen reacting with the graphite of the anode to form CO2 and CO. In addition, the introduction of Ta205 into the salt melt improves the wetting of the graphite anode with the melt and increases the critical current density.

The choice of electrolyte composition is based on data from studies of the K2TaF7-KCl-KF ternary system (Fig. 31). This system contains two double salts K2TaF7 KF (or KjTaFg) and K2TaF7 KS1 (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 similarly. The formation of tantalum oxofluoride complexes determines the solubility of Ta2O5 in the electrolyte. The limiting solubility depends on the K3TaF8 content in the melt and corresponds to the stoichiometry of the reaction (2.32).

Based on data on the influence of electrolyte composition on electrolysis performance (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 KS1 and KF in relation to 2 :1 (by weight). The concentration of introduced Ta2Os is 2.5-3.5% (by weight). In this electrolyte at temperatures of 700-800 °C using a graphite anode, the decomposition voltage of the oxofluoride complex is 1.4 V, while for KF and KS1 the decomposition voltages are ~3.4 V and ~4.6 V, respectively.

KS I K2TaF,-KCl KJaFf

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

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

Ta5+ + 2e > Ta3+ + bе * Ta0.

The processes at the anode can be represented by the reactions: TaOF63" - Ze = TaFs + F" + 0; 20 + C = C02; 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 gas composition is -95% CO2, 5-7% CO; 0.2-

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

Fig.32. Diagram of an electrolyzer for tantalum production:

1 - hopper with feeder Ta205; 2 - electromagnetic vibrator of the feeder; 3 - bracket with fastening for the anode; 4 - hollow graphite anode with holes in the wall; 5 - nichrome crucible-cathode; 6 - cover; 7 - heat-insulating glass; 8 - steering wheel for lifting the actuator; 9 - plug with rod for power supply

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

Electrolysis is carried out until 2/3 of the useful volume of the crucible is filled with cathode sediment. At the end of electrolysis, the anode is raised and the electrolyte along with the cathode deposit is cooled. Two methods of processing the cathode product are used 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 of separating the bulk of salts from tantalum by smelting (melting) in an argon atmosphere, followed by removal of the residue by evaporation in a vacuum at 900 C. The melted and condensed electrolyte is returned to electrolysis.

That by grinding with air separation 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 during discharge at the cathode, lower oxides are formed that pollute the metal. Current output is low.

Oxygen-free electrolytes are promising for niobium (as well as tantalum). 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 released at the cathode, and chlorine is released at the graphite anode.

Description and properties of niobium

Niobium– an element belonging to the fifth periodic group, atomic number – 41. Electronic formula of niobium— Nb 4d45sl. Graphic formula of niobium- Nb - 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 4d 4 5s 1. Discovered in 1801 - originally called “Columbia”, after the name of the river in which it was discovered. Later renamed.

Niobium – metal white-steel shade, has plasticity - easily rolled into sheets. Electronic structure of niobium endows it with certain characteristics. An indication of a high temperature during melting and the boiling point of the metal is noted. Due to this, the electronic outflow of electrons is noted as a feature. Superconductivity appears only at high temperatures. For oxidation, the metal requires a minimum temperature of about 300º C or higher. This creates a specific niobium oxide Nb2O5.

Niobium, properties which actively interacts with certain gases. These are hydrogen, oxygen and nitrogen, under their influence it can change certain characteristics. The higher the temperature, the more intensely hydrogen is absorbed, making niobium more fragile; when the control point of 600º C is reached, reverse evolution begins to occur, and the metal restores its lost properties. After this, the formation of NbN nitride begins, the melting of which requires 2300º C.

Carbon and gases containing it begin their interaction with niobium at the required temperature above 1200º C, resulting in the formation of carbide NbC - melting point - 3500º C. As a result of the interaction of silicon and boron with the metal niobium, boride NbB2 is formed - melting point - 2900º C.

Element niobium resistant to almost all known acids, except hydrofluoric acid, and especially its mixture with nitric acid. The metal is susceptible to alkalis, especially hot ones. When dissolved in them, an oxidation process occurs and niobic acid is formed.

Mining and origin of niobium

The metal content per ton of borrowed rock is relatively low - only 18 g per ton. The content is increased in more acidic rocks. Most often found in one deposit niobium and tantalum, due to their similar chemical properties, which allow them to be found in the same mineral and participate in common processes. Often in some minerals containing titanium, a replacement phenomenon occurs - "niobium - titanium".

About one hundred different minerals containing niobium are known. But only a few are used in industry. These are pyrochlore, loparite, torolite, etc. In ultramafic and alkaline rocks, niobium occurs in perovskite and eudialyte.

Niobium deposits available in Brazil, Australia, Canada, Congo, Nigeria and Rwanda.

Niobium production a rather complex process with three main stages. First, the concentrate is opened, then the niobium is separated into pure compounds. The final stage is the recovery processes and metal refining. The most common methods include carbothermic, aluminothermic and sodiumthermic methods.

For example, by mixing niobium oxide and soot at high temperatures in a hydrogen environment, carbide is obtained, then by mixing carbide and niobium oxide at the same temperatures, but in a complete vacuum, a metal is obtained, from which various niobium alloys. It is possible to obtain niobium alloys using powder metallurgy methods, using vacuum and electron beam arc melting methods.

Applications of niobium

Due to its unique properties, niobium is used in many areas of industry. Niobium alloys have refractoriness, heat resistance, superconductivity, getter and anti-corrosion properties. In addition, it is quite easy to process and weld. It is widely used in space and aviation technologies, radio and electrical engineering, the chemical industry and nuclear energy. In generator lamps, many heating elements are made using it. Its alloy with tantalum is also used for these purposes.

Electrical rectifiers and electrolytic capacitors also contain a certain amount of this metal. Its use in these devices is due to its characteristic transmission and oxidizing properties. Capacitors that include this metal, with relatively small dimensions, have high resistance. All capacitor elements are made of special foil. It is pressed from niobium powder.

Resistance to various acids, high thermal conductivity and pliability of the structure determine its popularity in chemistry and metallurgy, in the creation of various devices and structures. The combination of positive properties of this important metal is in demand even in nuclear energy.

Due to the weak effect of niobium with industrial uranium, at relatively low temperatures (900º C), the metal is suitable for creating a protective layer in nuclear reactors. With such a shell, it becomes possible to use sodium coolants, with which it also almost does not interact. Niobium significantly extends the service life of uranium elements by creating a protective oxide on their surface from the harmful effects of water vapor.

The heat-resistant properties of some can be improved by alloying with niobium. Niobium alloys have also proven themselves quite well. For example, this is an alloy niobium – zirconium, characterized by remarkable properties. Various parts for spacecraft and aircraft, as well as their skins, are made from such alloys. The operating temperature of such an alloy can reach up to 1200º C.

Some alloys for steel processing contain niobium carbide, which enhances the properties of the alloy. A relatively small addition of niobium to stainless steel enhances its anti-corrosion properties and improves the quality of the resulting welds. Many tool steels also contain niobium. As catalysis, its various compounds participate in the processes of artificial organic synthesis.

Niobium price

The main form for sale on the world market is niobium ingots, but other forms of storage are quite possible. There has always been a demand in the world for niobium, price which until the beginning of 2000 remained at a stable level. Confident growth in demand associated with the development of the economies of many countries and an increase in production volumes in the field of innovative technologies, metallurgical and chemical industries contributed to a sharp rise in prices by 2007 from $12 to $32 per kilogram of metal.

In subsequent years, due to the global crisis in the economic sector, until 2012, there was a slight decline. The rate of trade turnover decreased accordingly. But by 2012, prices had crept up again, and even then buy niobium it was possible only at $60 per kilogram, and the growth has not yet stopped. The question of equivalent, but more accessible substitutes has long been raised. And they exist, but their properties are clearly inferior to niobium. Therefore, it is still in price.

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 niobium production

1. General information about the element

Mankind has been familiar with the element that occupies the 41st cell in the periodic table for a long time. Its current name, niobium, is almost half a century younger. It so happened that element No. 41 was opened twice. The first time - in 1801, the English scientist Charles Hatchet examined a sample of the true 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 columbium, thereby noting its overseas origin. And the black mineral was called columbite. A year later, the Swedish chemist Ekeberg isolated the oxide of another new element from columbite, called tantalum. The similarity between the compounds Columbia and tantalum was so great that for 40 years most chemists believed that tantalum and columbium were the same element.

In 1844, German chemist Heinrich Rose examined samples of columbite found in Bavaria. He again discovered oxides of two metals. One of them was the oxide of the already known tantalum. The oxides were similar, and, emphasizing their similarity, Rose named the element forming the second oxide niobium, after Niobe, the 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 19th century. two more ways to obtain this element were found. First, Moissan obtained it in an electric furnace, reducing niobium oxide with carbon, and then Goldschmidt was able to reduce the same element with aluminum. And element No. 41 continued to be called differently in different countries: in England and the USA - Columbia, in other countries - niobium. The International Union of Pure and Applied Chemistry (IUPAC) put an end to this controversy in 1950. It was decided to legitimize 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 ABOUT 6.

It is no coincidence that niobium is considered a rare element: it is indeed found infrequently and in small quantities, always in the form of minerals and never in the native state. An interesting detail: in different reference publications the clarke (content in the earth’s crust) of niobium is different. This is mainly explained by the fact that in recent years new deposits of minerals containing niobium have been found in African countries. The Chemist's Handbook, vol. 1 (M., Chemistry, 1963) gives the following figures: 3.2 10-5% (1939), 1 10-3% (1949) and 2, 4·10-3% (1954). But the latest figures are also 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 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, very resistant to many aggressive environments. All acids, with the exception of hydrofluoric acid, have no effect 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 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 parameter a = 3.294 Å.

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

One can note such properties of niobium as high melting and boiling points, lower electron work function compared to other refractory metals - tungsten and molybdenum. The last property characterizes the ability for electron emission (electron emission), which is used for the use of niobium in electric vacuum technology. Niobium also has a high transition temperature to the superconducting state.

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

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

Pure Niobium is easily processed by cold pressure and retains satisfactory mechanical properties at high temperatures. Its tensile strength at 20 and 800 °C is respectively 342 and 312 Mn/m 2, the same in kgf/mm 234.2 and 31.2; relative elongation at 20 and 800 °C is 19.2 and 20.7%, respectively. The Brinell hardness of pure Niobium is 450, technical 750-1800 Mn/m 2. Impurities of certain 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 valued for its resistance to inorganic and organic substances.

There is a difference in the chemical behavior of powdered and lump metal. The latter is more stable. Metals have no effect on it, even if heated to high temperatures. Liquid alkali metals and their alloys, bismuth, lead, mercury, and tin can be in contact with niobium for a long time without changing its properties. Even such strong oxidizing agents as perchloric acid, aqua regia, not to mention nitric, sulfuric, hydrochloric and all the others, cannot do anything with it. Alkali solutions also have no effect on niobium.

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

Nb+4NaOH+5O2 = 4NaNbO3+2H2O

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. In any case, the element is part of an anion of type 2- or 2-.

If you take powdered niobium, it is somewhat more active. For example, in molten sodium nitrate it even ignites, turning into an 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 manifests itself - it retains its ductility.

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

Nb + 5Cl2 = 2NbCl5

When heated, it reacts with sulfur. 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 the compound Al2Nb with niobium.

What qualities of niobium help it resist the action of the strongest oxidizing acids? It turns out that this does not refer to the properties of the metal, but to the characteristics of its oxides. Upon contact with oxidizing agents, a thin (therefore unnoticeable) but very dense layer of oxides appears on the metal surface. This layer becomes an insurmountable barrier on the way of the oxidizing agent to a clean metal surface. Only certain chemical reagents, in particular fluorine anion, can penetrate through it. Consequently, the metal is essentially oxidized, but practically the results of oxidation are invisible due to the presence of a thin protective film. Passivity towards dilute sulfuric acid is used to create an AC rectifier. It is designed 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, that is, electrons can pass through the oxide layer only from the metal side. The path for electrons out of the solution is closed. Therefore, when alternating current is passed through such a device, only one phase passes through, 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 from it: with its light gray color, niobium resembles platinum. Despite the high melting points (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 ductility and increase hardness. Niobium becomes brittle at temperatures from - 100 to - 200 °C.

Obtaining niobium in ultra-pure and compact form has become possible with the use of technology in recent years. The entire technological process is complex and labor-intensive. Basically it is divided into 4 stages:

1.obtaining concentrate: ferroniobium or ferrotantaloniobium;

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

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

.production and refining of metals.

The first two stages are quite simple and common, although labor intensive. 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 us to find the latest separation methods: selective extraction, ion exchange, and rectification of compounds of these elements with halogens. As a result, either oxide or pentachlorides of tantalum and niobium are obtained separately. At the last stage, reduction with coal (soot) in a stream of hydrogen at 1800°C is used, and then the temperature is raised to 1900°C and the pressure is reduced. The carbide resulting from interaction with coal reacts with Nb2O5:

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

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

Niobium oxides and their salts

The number of compounds with oxygen in niobium is small, significantly less than in vanadium. This is explained by the fact that in compounds corresponding to the oxidation state +4, +3 and +2, niobium is extremely unstable. If an atom of this element begins to give up electrons, then it tends to give up all five to expose a stable electron configuration.

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

O5 + 3Nа2СО3 = 2Nа3NbO4 + 3С02

This salt - sodium orthoniobate - is similar to the same salts of orthophosphoric and orthovanadic acids. However, in phosphorus and arsenic the ortho form is the most stable, and an attempt to obtain orthoniobate in its pure form failed. When the alloy is treated with water, it is not Na3NbO4 salt that is released, but NaNbO3 methaniobate. It is a colorless, poorly soluble fine-crystalline powder in cold water. Consequently, in niobium in the highest degree of oxidation, 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, reminiscent of pyroacids, and polyniobates (as a shadow of polyphosphoric and polyvanadium acids) with the approximate formulas K7Nb5O16.nH2O and K8Nb6O19.mH2O are known. The mentioned salts, corresponding to higher niobium oxide, contain this element as part of the anion. The shape of these salts allows us to consider them niobium derivatives. acids These acids cannot be obtained in their pure form, since they can rather be considered as oxides bound to water molecules. For example, the meta form is Nb2O5. H2O, and the orgo form is Nb2O5. 3H2O. Along with this kind of compounds, niobium has others where it is already part of the cation. Niobium does not form simple salts such as sulfates, nitrates, etc. When interacting with sodium hydrogen sulfate NaHSO4 or 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 vanadium has an oxidation state of four in the vanadyl ion. The same cation NbO3+ is included in the composition of some complex salts. Nb2O5 oxide dissolves quite easily in aqueous hydrofluoric acid. From such solutions, the K2 complex salt can be isolated. H2O.

Based on the reactions considered, we can conclude that niobium in its highest oxidation state can be part of both the anions and 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. Firstly, the interaction of niobium with oxygen when heated. Secondly, calcination of niobium salts in air: sulfide, nitride or carbide. Thirdly, the most common method is dehydration of hydrates. Hydrated oxide Nb2O5 is precipitated from aqueous salt solutions with concentrated acids. xH2O. Then, when the solutions are diluted, a white oxide precipitate forms. Dehydration of the Nb2O5 xH2O sediment is accompanied by the release of heat. The whole mass is heating up. This occurs 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 when heated it turns yellow. However, as soon as the oxide is cooled, the color disappears. The oxide is refractory (tmelt = 1460°C) and non-volatile.

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

O5 + H2 = 2NbO2 + H2O

In air, this compound easily transforms back into the higher oxide Nb2O5. Its character is rather secretive, since the oxide is insoluble in either water or acids. Yet it is attributed an acidic character on the basis of its 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 so great, but unlike Nb2O5, NbO2 oxide conducts electric current. Obviously, in this compound there is a metal-metal bond. If you take advantage of this quality, then when heated with a strong alternating current, you can force NbO2 to give up its oxygen.

When oxygen is lost, NbO2 turns into NbO oxide, and then all the oxygen is split off quite quickly. Little is known about the lower niobium oxide NbO. It has a metallic luster and is similar in appearance to metal. Conducts electricity perfectly. 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 calcination of the already mentioned complex salt K2 with metallic sodium:

K2 + 3Na = NbO + 2KF + 3NaF

NbO oxide has the highest melting point of all niobium oxides, 1935°C. 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 occurs.

Niobium compounds

A story about the element would not be complete without mentioning its compounds with halogens, carbides and nitrides. This is important for two reasons. Firstly, 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.

Reaction of halogens with metallic niobium:

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

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

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

Solutions in hydrofluoric acid H2F2 contain various complex ions:

H2F2 = H2 ;+ H2O = H2

Potassium salt K2. H2O is important for separating niobium from tantalum because, unlike tantalum salt, it is highly soluble.

The remaining niobium pentahalides are brightly colored: NbCl5 yellow, NbBr5 purple-red, NbI2 brown. All of them sublime without decomposition in an atmosphere of the corresponding halogen; in pairs they are monomers. Their melting and boiling points increase when moving from chlorine to bromine and iodine. Some of the methods for preparing pentahalides are:

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

2NbCl5+5F22NbF5+5Cl2

Pentahalides dissolve well in organic solvents: ether, chloroform, alcohol. However, they are completely decomposed by water - hydrolyzed. As a result of hydrolysis, two acids are obtained - hydrohalic acid and niobic acid. For example,

4H2O = 5HCl + H3NbO4

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

Niobium carbide has earned special gratitude from metallurgists. In any steel, there is carbon; niobium, binding it into carbide, improves the quality of alloy steel. Typically, when welding stainless steel, the weld has less strength. The introduction of niobium in an amount of 200 g per ton helps to correct this deficiency. When heated, niobium, before all other steel metals, forms a compound with carbon - carbide. This compound is quite plastic and at the same time capable of withstanding temperatures up to 3500°C. A layer of carbide just half a millimeter thick is enough to protect metals and, what is especially valuable, graphite from corrosion. Carbide can be obtained by heating 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 “regia vodka” when boiled; resistant to water. The only thing it can be forced to interact with is boiling alkali. In this case, it decomposes, releasing ammonia.

NbN nitride is light gray with a yellowish tint. It is refractory (temp. mp. 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, the 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

Application of niobium for metal alloying

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

Chromium-nickel steel, like any other, always contains 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, 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 niobium metal is added to a ton of steel. And niobium imparts high wear resistance to chrome-manganese steel.

Many non-ferrous metals are also alloyed with niobium. Thus, 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 seem to be hardened by niobium. 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, the chemical industry, and nuclear energy. All of them became consumers of niobium.

The unique property - the absence of 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 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 storing radioactive waste or installations for their use.

The chemical industry consumes relatively little niobium, but this can only be explained by its scarcity. Equipment for the production of high-purity acids is sometimes made from niobium-containing alloys and, less commonly, from sheet niobium. Niobium's ability to influence the rate of certain 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 on-board equipment of artificial Earth satellites are made from niobium-containing alloys and pure niobium.

Uses of niobium in other industries

“Hot fittings” (i.e. heated parts) are made from niobium sheets and bars - anodes, grids, indirectly heated cathodes and other parts of electronic lamps, especially powerful generator lamps.

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

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

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

The corrosion resistance of niobium in acids and other media, combined with high thermal conductivity and ductility, make it a valuable structural material for equipment in chemical and metallurgical industries. Niobium has a combination of properties that meet the requirements of nuclear energy 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 coolants: sodium or an alloy of sodium and 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 a component of various heat-resistant alloys for jet engine gas turbines. Alloying molybdenum, titanium, zirconium, aluminum and copper with niobium dramatically improves the properties of these metals, as well as their alloys. There are heat-resistant alloys based on niobium as a structural material for parts of jet engines and rockets (manufacture of turbine blades, leading edges of wings, nose ends of aircraft and rockets, rocket skins). Niobium and alloys based on it can be used at operating temperatures of 1000 - 1200°C.

Niobium carbide is a component of some grades of tungsten carbide-based carbide 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 added to various heat-resistant steels (for example, for gas turbines), as well as to 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 different ratios 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 are rapidly increasing, which is due to a combination of such properties as refractoriness, a small cross section for thermal neutron capture, the ability to form heat-resistant, superconducting and other alloys, corrosion resistance, getter properties, low electron work function, good workability under cold pressure and weldability. The main areas of application of niobium are: rocketry, aviation and space technology, radio engineering, electronics, chemical engineering, nuclear energy.

Applications of metallic niobium

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

Other non-ferrous metals, including uranium, are alloyed with niobium.

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.

Intermetallic compounds and alloys of niobium

Nb3Sn stannide and alloys of niobium with titanium and zirconium are used for the manufacture of 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 in the minting of collectible coins. Thus, the Bank of Latvia claims that niobium is used along with silver in 1 lat collection coins.

Application of niobium compounds O5 catalyst in the chemical industry;

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

Niobium carbide (mp 3480 °C) alloyed 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 to produce thin and ultra-thin 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 cause irritation to living tissue and adhere well to it. Reconstructive surgery has successfully used such threads to stitch together torn tendons, blood vessels and even nerves.

Application in jewelry

Niobium not only has a set of properties necessary for technology, 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 is not only externally similar to the metallic iridium, but is almost as wear-resistant. This allowed some countries to do without expensive iridium in the production of soldering tips for fountain pen nibs.

Niobium mining in Russia

In recent years, global niobium production 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 SVMM, which accounts for about 85% of the world niobium production.

The main consumer of niobium-containing products (this primarily includes ferroniobium) is Japan. 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 as being close to the world average. In recent years, there has been a tendency for prices for ferroniobium to rise. This is due to its growing use 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, global consumption of niobium has increased by an average of 4-5% annually.

It is with regret that we must admit that Russia is on the sidelines of the niobium market. In the early 90s, according to Giredmet specialists, about 2 thousand tons of niobium (in terms of niobium oxide) were produced and consumed in the former USSR. Currently, the consumption of niobium products by the Russian industry does not exceed only 100 - 200 tons. It should be noted that in the former USSR significant niobium production capacities were created, 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 situation regarding many types of raw materials and metals. The niobium market begins with the production of niobium-containing raw materials. Its main type in Russia was and remains loparite concentrate produced at the Lovozersky GOK (now Sevredmet JSC, Murmansk region). Before the collapse of the USSR, the enterprise produced about 23 thousand tons of loparite concentrate (the content of niobium oxide is about 8.5%). Subsequently, concentrate production steadily decreased, in 1996-1998. The company stopped several times due to lack of sales. Currently, it is estimated that 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 strictly 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 quite complex 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 it is impossible to obtain ferroniobium from loparite concentrate. In 2000, at the Sevredmet plant, the Rosredmet company launched an experimental installation for processing loparite concentrate to produce, among other metals, commercial niobium-containing products (niobium oxide).

The main markets for SMZ's niobium products are non-CIS countries: deliveries are made to the USA, Japan and European countries. The share of exports in total production is over 90%. Significant niobium production capacities in the USSR were concentrated in Estonia - at the Sillamae Chemical and Metallurgical Production Association (Sillamae). Now the Estonian company is called Silmet. In Soviet times, the enterprise processed loparite concentrate from the Lovoozersk mining and processing plant; since 1992, its shipment was stopped. Currently, Silmet processes only a small volume of niobium hydroxide from the Solikamsk magnesium plant. The company currently receives most of its niobium-containing raw materials from Brazil and Nigeria. The management of the enterprise does not exclude the supply of loparite concentrate, however, Sevredmet is trying to pursue a policy of processing it locally, since exporting raw materials is less profitable than finished products.

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There are quite a large number of elements that, when combined with other substances, form alloys with special performance properties. An example is niobium, an element that was first called “columbium” (after the name of the river where it was first found), but was later renamed. Niobium is a metal with rather unusual properties, which we will discuss in more detail later.

Getting an element

When considering the properties of niobium, it should be noted that the content of this metal per ton of rock is relatively small, approximately 18 grams. That is why, after its discovery, quite a few attempts were made to obtain the metal artificially. Due to its similar chemical composition, this substance is often mined together with tantalum.

Niobium deposits are located almost all over the world. Examples include mines in Congo, Rwanda, Brazil and many other countries. However, this element cannot be called widespread; in many regions it is practically not found even in low concentrations.

The relatively small concentration of the substance in the earth's rock is aggravated by the difficulties encountered in obtaining it from concentrate. It is worth considering that NBS niobium can only be obtained from rock that is saturated with tantalum. The following are the features of the production process:

To begin with, concentrated ore is supplied to the plant, which goes through several stages of purification. When producing niobium, the resulting ore is separated into pure elements, including tantalum.
The final processing process involves refining the metal.

Despite the difficulties encountered in the extraction and processing of the ore in question, every year the production volume of the alloy in question increases significantly. This is due to the fact that the metal has exceptional performance qualities and is widely used in a wide variety of industries.

Niobium oxides

The chemical element in question can become the basis of various compounds. The most common is niobium pentoxide. Among the features of this connection, the following points can be noted:

Niobium oxide is a white crystalline powder that has a creamy tint.
The substance does not dissolve in water.
The resulting substance retains its structure when mixed with most acids.

The features of niobium pentoxide also include the following properties:

Increased strength.
High refractoriness. The substance can withstand temperatures up to 1490 degrees Celsius.
When heated, the surface oxidizes.
Reacts to chlorine and can be reduced by hydrogen.

Niobium hydroxide is in most cases used to produce high-alloy steel grades, which have quite attractive performance properties.

Physical and chemical properties

Niobium has chemical properties similar to those of tantalum. When considering the main characteristics of niobium, you need to pay attention to the following points:

Resistant to various types of corrosion. The alloys obtained by introducing this element into the composition have high corrosion-resistant qualities.
The chemical element in question exhibits a high melting point. As practice shows, most alloys have a melting point of more than 1,400 degrees Celsius. this complicates the processing process, but makes metals indispensable in various fields of activity.
The basic physical properties are also characterized by the ease of welding of the resulting alloys.
At subzero temperatures, the structure of the element remains virtually unchanged, which allows the performance properties of the metal to be preserved.
The special structure of the niobium atom determines the superconducting qualities of the material.
The atomic mass is 92.9, the valence depends on the characteristics of the composition.

The main advantage of the substance is considered to be its refractoriness. That is why it began to be used in a wide variety of industries. The substance melts at a temperature of about 2,500 degrees Celsius. Some alloys even melt at a record temperature of 4,500 degrees Celsius. The density of the substance is quite high, 8.57 grams per cubic centimeter. It is worth considering that the metal is characterized by paramagneticity.

The following acids do not affect the crystal lattice:

sulfuric;
salt;
phosphorus;
chlorine

Does not affect metal and aqueous chlorine solutions. With a certain impact on the metal, a dielectric oxide film is formed on its surface. That is why the metal began to be used in the production of miniature high-capacity capacitors, which are also made from more expensive tantalum.

Applications of niobium

A wide variety of niobium products are manufactured, most of which are associated with the production of aircraft. An example is the use of niobium in the manufacture of parts that are installed during the assembly of rockets or aircraft. In addition, the following uses of this element can be distinguished:

Production of elements from which radar installations are made.
As previously noted, the alloy in question can be used to produce cheaper capacitive electrical capacitors.
Cathodes and anodes from foil are also made using the element in question, which is associated with high heat resistance.
You can often find designs of powerful generator lamps that have a grid inside. In order for this mesh to withstand high temperatures, it is made from the alloy in question.

High physical and chemical qualities determine the use of niobium in the production of pipes for transporting liquid metals. In addition, alloys are used to produce containers for various purposes.

Alloys with niobium

When considering such alloys, it should be taken into account that this element is often used for the production of ferroniobium. This material is widely used in the foundry industries, as well as in the manufacture of electronic coatings. Includes:

iron;
niobium with tantalum;
silicon;
aluminum;
carbon;
sulfur;
phosphorus;
titanium.

The concentration of the main elements can vary over a fairly wide range, which determines the performance of the material.

An alternative ferroniobium alloy can be called niobium 5VMC. When producing it, tungsten, zirconium and molybdenum are used as alloying elements. In most cases, this resin is used for the production of semi-finished products.

In conclusion, we note that niobium is used in the production of coins in some countries. This is due to the fairly high cost of the material. With the mass production of alloys that contain niobium as the main element, unique ingots are created.

Application of niobium for metal alloying

Uses of niobium in other industries

“Hot fittings” (i.e. heated parts) are made from niobium sheets and bars - anodes, grids, indirectly heated cathodes and other parts of electronic lamps, especially powerful generator lamps.

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

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

Niobium carbide is a component of some grades of tungsten carbide-based carbide used for cutting steels.

Niobium is also added to various heat-resistant steels (for example, for gas turbines), as well as to tool and magnetic steels.

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

Applications of metallic niobium

Aircraft parts are made from pure niobium or its alloys; claddings for uranium and plutonium fuel elements; containers and pipes; for liquid metals; parts of electrolytic capacitors; “hot” fittings for electronic (for radar installations) and powerful generator lamps (anodes, cathodes, grids, etc.); corrosion-resistant equipment in the chemical industry.
Other non-ferrous metals, including uranium, are alloyed with niobium.
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.

Intermetallic compounds and alloys of niobium

Nb 3 Sn stannide and alloys of niobium with titanium and zirconium are used for the manufacture of 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 in the minting of collectible coins. Thus, the Bank of Latvia claims that niobium is used along with silver in 1 lat collection coins.

Application of niobium compounds

Nb 2 O 5 catalyst in the chemical industry;
in the production of refractories, cermets, specials. glass, nitride, carbide, niobates.
Niobium carbide (mp 3480 °C) alloyed 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 to produce thin and ultra-thin 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

Application in jewelry

Niobium not only has a set of properties necessary for technology, 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 niobium-rhenium alloy not only looks similar to the metallic iridium, but is almost as wear-resistant. This allowed some countries to do without expensive iridium in the production of soldering tips for fountain pen nibs.

Niobium as a first generation superconducting material

The amazing phenomenon of superconductivity, when when the temperature of a conductor decreases, an abrupt disappearance of electrical resistance occurs in it, was first observed by the Dutch physicist G. Kamerlingh-Onnes in 1911. The first superconductor turned out to be mercury, but not it, 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 (Kamerlingh Onnes also observed the loss of superconductivity by a superconductor when exposed to a sufficiently strong magnetic field). In 1975, the intermetallic compound of niobium and germanium with the composition Nb 3 Ge became the record holder for the highest critical temperature. Its critical temperature is 23.2°K; This is higher than the boiling point of hydrogen. (Most known superconductors become superconductors only at the temperature of liquid helium).

The ability to transition to a state of superconductivity is also characteristic of niobium stannide Nb 3 Sn, alloys of niobium with aluminum and germanium or with titanium and zirconium. All these alloys and compounds are already used to make superconducting solenoids, as well as some other important technical devices.

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.
Used as an alloying additive.
Niobium nitride is used to produce 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 cheapest structural materials for high-power thermionic generators.

What family does niobium belong to? Application of niobium in metallurgy and industry. Methods for obtaining niobium

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Niobium oxides

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Alloys with niobium

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