The formula of niobium is structural chemical.

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Niobium

The element that occupies the 41st cell in the periodic table has been known to mankind for a long time. Its current name niobium is almost half a century younger. It so happened that element #41 was opened twice. For 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 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 the end of the XIX century. 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 in different countries they continued to call element No. 41 differently: in England and the USA columbium, in other countries 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 to 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 (Nb 2 O 5). 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 valencies 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 3 → 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 of simple substances, for example, 2Nb + 5Cl 2 → 2NbCl 5.

Brightly colored needle-shaped crystals of niobium pentahalides (NbCl 5 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 by adding some strong acid to the aqueous solution. 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 fluoride of any metal to a solution of niobic and hydrofluoric acids.

The composition of a complex compound depends on the ratio of the components reacting in solution. X-ray diffraction 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 oxofluoroniobate 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 the compounds of element #41 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 "record holder" for the highest critical temperature was an intermetallic compound of niobium and germanium with 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 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 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 enrichment, 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 hydroxide, has not been separated from its analogue in the subgroup tantalum and has not been 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, the reduction, takes place. 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 is in metallurgy that it has found the widest application. And in non-ferrous metallurgy, and in ferrous.

Steel alloyed with niobium has good corrosion resistance. "So what? another sophisticated reader will say. 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, niobium carbide is necessarily formed. Steel alloyed with niobium acquires high anti-corrosion properties and does not lose its ductility. The desired effect is achieved when only 200 g of metallic niobium is added to a ton of steel. A chromium-manganese 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, the chemical industry, and 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 storing radioactive waste or installations 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 rate of some chemical reactions is 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. Of niobium-containing alloys and pure niobium, some parts of rockets and onboard equipment of artificial Earth satellites are made.

Niobium minerals

Columbite (Fe, Mn) (Nb, Ta) 2 O 6 was the first niobium mineral known to mankind. And this 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 ductility and high temperature resistance with pleasing appearance has made niobium monocarbide a valuable coating material. 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 products, accelerated and reduced the cost of their assembly processes. 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 recent years new deposits of minerals containing niobium have been found in African countries. Figures are given in: 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.

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 the end of the XIX century. 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 they continued to call element No. 41 differently in different countries: in England and the USA - Colombia, in other countries - 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 of 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 by adding some strong acid to the aqueous solution. 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 is in metallurgy that it has found the widest 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, the chemical industry, and 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 storing radioactive waste or installations 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 rate of some chemical reactions is 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. Of niobium-containing alloys and pure niobium, some parts of rockets and onboard equipment of artificial Earth satellites are made.

Niobium minerals

Columbite (Fe, Mn) (Nb, Ta) 2 O 6 was the first niobium mineral 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 ductility and high heat resistance with pleasing "appearance" made niobium monocarbide a valuable material for 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 recent years new deposits of minerals containing niobium have been found in African countries. 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.

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

Niobium price per gram

Since the main uses of niobium are related to nuclear and space programs, it is classified as a strategic material. Processing is much more financially profitable than the development and extraction of new ores, which makes niobium in demand in the secondary metal market.

The value of its price is determined by several factors:

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

Indicative overview of prices in Moscow:

• Niobium NB-2. The price varies between 420-450 rubles. per kg.
• Niobium shavings. 500-510 rub. per kg.
• Nbsh00 niobium staff. Differs in increased prices due to the negligible content of impurities. 490-500 rub. per kg.
• Niobium rod NBSh-0. 450-460 rub. per kg.
• Niobium NB-1 in the form of a rod. The price is 450-480 rubles. per kg.

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

The scientific community continues to work on finding and developing a substitute for such an expensive material. But so far, no concrete results have been obtained. And this means that in the near future the fall in price of niobium is not expected.

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

• Niobium ingots. Their size and weight are standardized by GOST 16099-70. Depending on the purity of the metal, they are divided into 3 grades: niobium NB-1, niobium NB-2 and, accordingly, niobium NB-3.
• Niobium rod. It has a higher percentage of impurities.
• Niobium foil. It is made up to 0.01 mm thick.
• Niobium rod. According to TU 48-4-241-73, it is supplied with NbP1 and NbP2 brands.

Physical properties of niobium

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

Mechanical characteristics are also at a high level. Density is 8570 kg/m3, while the same index of steel is 7850 kg/m3. Resistant to work both under dynamic loads and cyclic. Tensile strength - 34.2 kg/mm2. It has high plasticity. The coefficient of relative elongation varies within 19-21%, which makes it possible to obtain sheet rolled niobium with a thickness of up to 0.1 mm from it.

Hardness is related to the purity of the metal from harmful impurities and increases with their increase in composition. Pure niobium has a 450 Brinell hardness scale.

Niobium lends itself well to pressure treatment at temperatures below -30 ºС and is poorly cut.

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

Extremely resistant to acidic conditions. Such common acids as sulfuric, hydrochloric, orthophosphoric, nitric do not affect its chemical structure.

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

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

Varieties of alloys

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

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

It should be noted that the categories listed above are conditional and give only a general idea of ​​the method of application of a particular alloy.

We should also mention such compounds as ferroniobium and niobium oxide.

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

Niobium pentoxide is a white crystalline powder. Not susceptible to dissolution in acid and water. Produced by burning niobium in an oxygen environment. Completely amorphous. Melting point 1500 ºС.

Application of niobium

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

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

DEFINITION

Niobium is the forty-first element of the 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 of an element (A r)- how many times the average mass of atoms of a chemical element is greater 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 masses coincide. 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. Of particular importance are heat-resistant niobium alloys, which are used in the production of gas turbines, jet engines, and rockets.

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

Exercise

Indicate the valency and oxidation state of niobium in the compounds: Gd 2 Nb 2 O 7 and Pb(NbO 3) 2 .

Answer

To determine the valence of niobium in oxygen-containing compounds, the following sequence of actions must be strictly observed. Consider the example of Gd 2 Nb 2 O 7 . Determine the number of oxygen atoms in the molecule. It is equal to 7 - mi. We calculate the total number of valency units for oxygen: We calculate the total number of valency units for gadolinium: We find the difference between these values: Determine the number of niobium atoms in the compound. It is equal to 2. The valency of niobium is IV (8/2 = 4). To find the oxidation state of niobium in the same compound, we take its value as x and take into account the fact that the charge of the molecule is 0: 2x3 + 2xx +7x(-2) = 0 The oxidation state of niobium is +4. Similarly, we determine that the valency and oxidation state of niobium in Pb(NbO 3) 2 are IV and +1, respectively.