In many cases, instead of tantalum with the same effect, one can use niobium close to it in properties or alloys of tantalum with niobium, since these metals form a continuous series of solid solutions whose properties are close to those of the parent metals.
An alloy of tantalum with niobium can be obtained by mixing separately obtained powders of tantalum and niobium, followed by pressing the mixture and sintering in vacuum, as well as by simultaneously reducing a mixture of tantalum and niobium compounds, for example, a mixture of complex fluorides K2TaF7 and K2NbF7, a mixture of chlorides, a mixture of oxides, etc. . P.
Usually, in the hydrofluoric acid method of separating tantalum and niobium, the latter is separated in the form of fluoroxyniobate K2NbOF5*H2O.
This salt is not suitable for sodium reduction for two reasons:
a) crystallization water, which is part of this salt, reacting with sodium, can lead to an explosion,
b) oxygen, which is part of the salt and associated with niobium, is not reduced by sodium and remains in the form of an oxide impurity in the reduction product.
Therefore, potassium fluoroxyniobate must be recrystallized through a solution of hydrofluoric acid with an HF concentration above 10%, resulting in the formation of a K2NbF7 salt suitable for sodium reduction.
Niobium can also be produced by electrolysis under conditions similar to those described for the production of tantalum. There is a lower current efficiency than in the electrolytic production of tantalum, as well as difficulties associated with a noticeable solubility in the electrolyte of niobium compounds of different valences.
Electrolysis from a mixed bath containing a mixture of Ta2O5 + Nb2O5 as decomposing components and K2TaF7 as a solvent is also possible. In this case, an alloy of niobium and tantalum is obtained.
To obtain niobium, a method was proposed for the carbon reduction of niobium pentoxide in vacuum.
Reduction of niobium pentoxide with carbon
To obtain niobium, K. Bolke developed a method for the reduction of niobium pentoxide with niobium carbide in vacuum according to the reaction:
In essence, this process is reduced to the reduction of niobium pentoxide with carbon.
Due to the high chemical strength of niobium pentoxide, carbon reduction at atmospheric pressure requires a high temperature (about 1800-1900 °), which can be obtained in a graphite tube furnace. Niobium has a high affinity for carbon (free energy of formation of niobium carbide -ΔF ° = 38.2 kcal ), therefore, in the presence of carbonaceous gases in the furnace and at a high diffusion rate in the solid phase developing at such a high temperature, niobium turns out to be contaminated with niobium carbide, even in the case of batching based on the reaction
In vacuum, the reduction reaction with carbon proceeds at a lower temperature (1600-1700°),
Briquettes are prepared from a mixture of niobium pentoxide and soot, taken in stoichiometric ratios based on the reaction
Rolling is carried out at 1800-1900° in a graphite tube furnace in a protective atmosphere (hydrogen, argon) or in vacuum at a temperature of 1600° until the emission of CO ceases. The resulting product is lightly sintered briquettes consisting of gray powdered carbide particles. The carbide is pulverized in a ball mill and mixed with pentoxide in proportions corresponding to reaction (1). The briquettes of the Nb2O5 + NbC mixture are again calcined in vacuum at a temperature of about 1600°.
To ensure sweat removal of carbon in the form of CO, a small excess of niobium pentoxide should be introduced into the composition of the Nb2O5 + NbC charge. In the subsequent operation of high-temperature sintering (welding) of rods pressed from powdered metallic niobium, the excess of niobium pentoxide is removed, since niobium oxides (as well as tantalum) evaporate in vacuum at a temperature below the melting point of the metal
Due to the inevitable time spent on creating a vacuum and cooling the product in it, the productivity of a vacuum furnace in the manufacture of initial niobium carbide is much lower than the productivity of a graphite tube furnace operating at atmospheric pressure, in which a continuous process can be carried out by advancing cartridges with briquettes of a mixture of Nb2O5 + C. Therefore, it is more expedient to obtain NbC continuously in a graphite tube furnace at atmospheric pressure, although at temperatures of 1800-1900 °.
It would be possible to obtain metallic niobium in a vacuum furnace directly by reacting pentoxide with soot according to reaction (2) with a slight excess of Nb2O5 in the charge. However, when loading the Nb2O5 + 5NbC mixture into a vacuum furnace, its productivity increases significantly compared to loading the Nb2O5 + 5C mixture, since the Nb2O5 + SNbC mixture contains 1.5 times more niobium (82.4%) than the Nb2O5 + 5C mixture ( 57.2%) In addition, the first mixture has an additive specific gravity 1.7 times greater than the second mixture (6.25 g/cm3 and 3.7 g/cm3, respectively).
In addition, it should be taken into account that niobium carbide, which constitutes the predominant part of the Nb2O5 + 5NbC mixture, is coarser-grained than dispersed Nb2O5 powders and carbon black, which is an additional reason for the higher bulk weight of the Nb2O5 + 5NbC mixture than the Nb2O5 + 5C mixture.
As a result of all this, 2.5-3 times more material (based on the content of niobium) in the form of briquettes of the Nb2O5 + 5NbC mixture can fit into the unit volume of the cartridge than briquettes of the Nb2O5 + 5C mixture.
In Bolke's work, there is no sufficiently strong evidence of the need to strictly adhere to the composition of the Nb2O5 + 5NbC mixture recommended by him, loaded into a vacuum furnace.
By calcining a mixture of Nb2O5 + 5C in a carbon-tube furnace at atmospheric pressure, it is possible to obtain a product with high productivity (in a continuous process) that is close in composition to metallic niobium with a small admixture of carbon. This niobium-rich powder with high specific gravity and bulk density can then be mixed with an appropriate amount of Nb2O5 (with a slight excess of Nb2O5 relative to the equivalent carbon impurity content of niobium) and the briquetted mixture calcined in a vacuum furnace to remove carbon in the form of CO.
With this option, the capacity and, consequently, the productivity of the vacuum furnace will be the highest. The small remaining excess of Nb2O5 will evaporate during further high-temperature sintering of niobium, and the latter will turn into a compact malleable metal.
When using low-carbon niobium instead of niobium carbide for interaction with pentoxide, some technological complications may arise. The fact is that when low-carbon niobium is obtained at atmospheric pressure in the reaction space of a graphite tube furnace, the presence of an admixture of nitrogen from the air that can enter the furnace is always possible. Niobium, having a high affinity for nitrogen, actively absorbs it. When obtaining niobium carbide, the possibility of contamination of the product with nitrogen is much less due to the greater affinity of niobium for carbon than for nitrogen.
Therefore, the production of metallic niobium using low-carbon niobium as a starting material is complicated by the need to create conditions that exclude the possibility of nitrogen entering the reaction space, which is difficult to achieve in a graphite-tube furnace freely connected to the atmosphere. To remove nitrogen from the furnace, it is necessary to carefully fill the furnace with pure hydrogen or argon, observe the tightness of the casing, avoid sucking air into the reaction tube when loading cartridges with an Nb2O5 + 5C mixture into it and when unloading niobium, etc.
Therefore, the question of the advantages of the variant of preliminary production of niobium carbide or low-carbon niobium at atmospheric pressure (with subsequent calcination of these products in a mixture with Nb2O5 in vacuum) can be solved by practical possibilities in each individual case.
The advantages of the process of carbon reduction of niobium according to one of the described options are: the use of a cheap reducing agent in the form of soot and a high direct recovery of niobium into the finished metal
The similarity of the properties of tantalum and niobium oxides makes it possible to use the described method for the production of malleable tantalum.
17.03.2020
The creation of three-dimensional models today is relevant not only for animation, but also for technical purposes. Also often with the help of 3D modeling create interior models....
16.03.2020
Like the currently popular laminate flooring, modern parquet boards are quite easy to install. Lay it on the floor in a residential or technical room at the owner's...
16.03.2020
Registration on the portal is almost instantaneous, you can create an account by entering an email address or use your own account in one of 20...
16.03.2020
No matter what gadget you have, you can play through the mobile version even from the oldest smartphone. To start the game, first of all, you have to register ....
16.03.2020
Among floor coverings, carpet is particularly interesting because it combines excellent insulating qualities, luxurious appearance and simple laying technology....
16.03.2020
First you need to understand how industrial chillers work. Such a device resembles an ordinary refrigerator, a special pump pumps out liquid, cooling ...
15.03.2020
When planning repairs in your home, you first need to decide on the spectrum of action. Depending on the condition of the premises, area, will depend ...
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.. Swedish scientist Blomstrand during the reduction of niobium chloride with hydrogen. At the end of the XIX century. were; found two more ways to obtain this element. 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 the 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,
elemental niobium- 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 (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 valences - from two to five. But the main valency 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 -rnH 2 O) are quite well studied. 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-like 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 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 element 41's compounds are its compounds with other metals.
Niobium and superconductivity
The amazing phenomenon of superconductivity, when an abrupt disappearance of electrical resistance occurs in it when the temperature of the conductor decreases, was first observed by the Dutch physicist G. Kamerling-Onnes in 1911. The first superconductor turned out to be, but not to her, 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).
Now more than 2000 superconducting metals, materials and compounds are already known, but the vast majority of them have not come and apparently will never come into technology, either because of the extremely low values of the critical parameters mentioned above, or because of unacceptable technological characteristics. Among superconductors of practical importance, niobium-titanium alloys are especially popular. Most of the superconducting magnets in use today are made from them. They are plastic, they can be used to make technical devices and conductors of complex shapes.
As a material for tape superconductors, an alloy of niobium with tin Nb 3 Sn, niobium stannide, discovered back in 1954, is valuable. Such stranded superconducting conductors are intended to be used in the new Tokomak-15 thermonuclear installations.
Another intermetallic compound of niobium, Nb 3 Ge, is of interest for practice. A thin film of this composition has a record high critical temperature of 24.3 K. True, cast Nb 3 Ge has a critical temperature of only 6 K, and the technology for preparing superconducting elements from this material is quite complicated.
Ternary alloys have rather high critical temperatures: niobium - germanium - aluminum, as well as some intermetallic compounds of vanadium. And yet it is with niobium and its compounds that the greatest hopes of specialists in superconductors are connected.
Niobium metal
Niobium metal can be obtained by reducing its compounds, such as niobium chloride or potassium fluoroniobate, 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 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 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 - a 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.
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. And 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. Niobium and tantalum oxides account 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 additional vapor (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 Russia there are large reserves of loparite, they are 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 a pleasing appearance has made niobium monocarbide a valuable coating material. Layers of this substance only 0.5 mm thick reliably protect many materials from corrosion at high temperatures, in particular graphite, which is virtually unprotected by other coatings. NbC is also used as a structural material in rocket and turbine manufacturing.
NERVE LINED 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 DECEIVE. 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.
LOWERED NUMBERS. 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. I (M., "Chemistry", 1963), the figures are given: 3.2-10 -5%, 1 * 10 -3% and 2.4 * 10 -3%. But even the latest figures are underestimated: African deposits discovered in recent years are not included here. Nevertheless, it is estimated that about 1.5 million tons of metallic niobium can be smelted from the minerals of already known deposits.
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
Niobium in the free state
Niobium oxides and their salts
Niobium compounds
Countries leading in the production of niobium
1. General information about the element
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.
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 following 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.
Physical properties of niobium
Niobium is a shiny, silvery-gray metal.
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.
The crystal lattice of Niobium is body-centered cubic with the parameter a = 3.294Å.
Pure metal is ductile and can be rolled into a thin sheet (up to a thickness of 0.01 mm) in a cold state without intermediate annealing.
It is possible to note such properties of niobium as a high melting and boiling point, a lower electron work function in comparison with other refractory metals - tungsten and molybdenum. The latter property characterizes the ability to electron emission (emission of electrons), which is used for the use of niobium in electrovacuum technology. Niobium also has a high superconducting transition temperature.
Density 8.57 g/cm 3(20 °С); t pl 2500 °С; t kip 4927 °С; vapor pressure (in mm Hg; 1 mm Hg = 133.3 N/m 2) 1 10 -5(2194 °С), 1 10 -4(2355 °С), 6 10 -4(at t pl ), 1 10-3 (2539 °C).
At ordinary temperatures, niobium is stable in air. The onset of oxidation (tint 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, respectively, 51.4 and 56.2, the same in cal / (cm s ° C) 0.125 and 0.156. Specific volume 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. The electron work function is 4.01 eV.
Pure niobium is easily processed by cold pressure and retains satisfactory mechanical properties at high temperatures. Its ultimate strength at 20 and 800°C is 342 and 312 MN/m, respectively. 2, the same in kgf/mm 234.2 and 31.2; relative elongation at 20 and 800°C, respectively, 19.2 and 20.7%. Hardness of pure Niobium according to Brinell 450, technical 750-1800 MN/m 2. Impurities of some elements, especially hydrogen, nitrogen, carbon and oxygen, greatly impair plasticity and increase the hardness of Niobium.
3. Chemical properties of niobium
Niobium is especially valued for its resistance to the action of inorganic and organic substances.
There is a difference in the chemical behavior of powdered and lumpy metal. The latter is more stable. Metals do not act on it, even if they are heated to high temperatures. Liquid alkali metals and their alloys, bismuth, lead, mercury, tin can be in contact with niobium for a long time without changing its properties. Even such strong oxidizing agents as perchloric acid, "royal vodka", 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 the hydroxide of an alkali metal:
Nb + 4NaOH + 5O2 \u003d 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 the 2- or 2- type.
If we take powdered niobium, then it is somewhat more active. For example, in molten sodium nitrate, it even ignites, turning into an oxide. Compact niobium begins to oxidize when heated above 200°C, and the powder is covered with an oxide film already at 150°C. In this case, one of the wonderful properties of this metal is manifested - it retains plasticity.
In the form of sawdust, when heated above 900°C, it burns completely to Nb2O5. Burns vigorously in a stream of chlorine:
Nb + 5Cl2 = 2NbCl5
When heated, it reacts with sulfur. With most metals, it alloys with difficulty. There are, perhaps, only two exceptions: iron, with which solid solutions of different ratios are formed, and aluminum, which has an Al2Nb compound 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 features of its oxides. When in contact with oxidizing agents, a very thin (and therefore invisible) but very dense layer of oxides appears on the metal surface. This layer becomes an insurmountable barrier on the way of the oxidizing agent to a clean metal surface. Only some chemical reagents, in particular the fluorine anion, can penetrate through it. Therefore, essentially the metal is oxidized, but practically the results of the oxidation are imperceptible due to the presence of a thin protective film. Passivity in relation to dilute sulfuric acid is used to create an alternating current rectifier. It is arranged simply: platinum and niobium plates are immersed in a 0.05 m solution of sulfuric acid. Niobium in the passivated state can conduct current if it is a negative electrode - a cathode, i.e., electrons can pass through the oxide layer only from the side of the metal. From the solution, the path for electrons is closed. Therefore, when an alternating current is passed through such a device, only one phase passes, for which platinum is the anode, and niobium is the cathode.
niobium metal halogen
4. Niobium in the free state
It is so beautiful that at one time they tried to make jewelry out of it: with its light gray color, niobium resembles platinum. Despite the high melting points (2500°C) and boiling points (4840°C), any product can easily be 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 ranging from -100 to -200°C.
Obtaining niobium in an ultrapure and compact form has become possible with the involvement of technology in recent years. The entire technological process is complex and time-consuming. Basically, it is divided into 4 stages:
1.obtaining a concentrate: ferroniobium or ferrotantaloniobium;
.opening of the concentrate - the transfer of niobium (and tantalum) into any insoluble compounds in order to separate it from the main mass of the concentrate;
.separation of niobium and tantalum and obtaining their individual compounds;
.obtaining and refining metals.
The first two stages are quite simple and common, although time-consuming. The degree of separation of niobium and tantalum is determined by the third stage. The desire to get as much niobium and especially tantalum as possible made it necessary to find the latest separation methods: selective extraction, ion exchange, and rectification of compounds of these elements with halogens. As a result, either an oxide or tantalum and niobium pentachlorides are obtained separately. At the last stage, reduction with carbon (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 obtained by interaction with coal reacts with Nb2O5:
2Nb2O5 + 5NbC = 9Nb + 5CO3,
and niobium powder appears. If as a result of the separation of niobium from tantalum, not an oxide, but a salt is obtained, then it is treated with metallic sodium at 1000 ° C and powdered niobium is also obtained. Therefore, during the further transformation of the powder into a compact monolith, remelting is carried out in an arc furnace, and electron beam and zone melting is used to obtain single crystals of highly pure niobium.
Niobium oxides and their salts
The number of compounds with oxygen in niobium is small, much less than 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 began to donate electrons, then it tends to give up all five in order to expose a stable electronic configuration.
If we compare ions of the same oxidation state of two neighbors in the group - vanadium and niobium, then an increase in properties towards metals is found. The acidic nature 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, its acidic properties appear:
O5 + 3Na2CO3 = 2Na3NbO4 + 3C02
This salt - sodium orthoniobate - is similar to the same salts of orthophosphoric and orthovanadic acids. However, phosphorus and arsenic have the most stable ortho form, and attempts to obtain pure orthoniobate fail. When the alloy is treated with water, not Na3NbO4 salt is released, but NaNbO3 methaniobate. It is a colorless finely crystalline powder, hardly soluble in cold water. Consequently, in niobium in the highest oxidation state, not the ortho-, but the meta-form of the compounds 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 polyvanadic acids) with approximate formulas K7Nb5O16.nH2O and K8Nb6O19.mH2O are known. The aforementioned salts corresponding to the higher oxide of niobium contain this element in the composition of the anion. The shape of these salts allows us to consider them derivatives of niobium salts. acids. These acids cannot be obtained in pure form, since they can rather be considered as oxides that have a bond with water molecules. For example, the meta form is Nb2O5. H2O, while the orgo form is Nb2O5. 3H2O. Along with this kind of compounds, niobium also 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 hydrosulfate NaHSO4 or with nitric oxide N2O4, substances with a complex cation appear: Nb2O2 (SO4) 3. The cations in these salts resemble the vanadium cation, with the only difference being that here the ion is five-charged, while in vanadium the oxidation state in the vanadyl ion is four. The same NbO3+ cation is included in some complex salts. The oxide Nb2O5 is quite easily soluble in aqueous hydrofluoric acid. Complex salt K2 can be isolated from such solutions. H2O.
Based on the reactions considered, it can be concluded that niobium in its highest oxidation state can be included both in the composition of anions and in the composition of the cation. This means that pentavalent niobium is amphoteric, but still with a significant predominance of acidic properties.
There are several ways to obtain Nb2O5. First, the interaction of niobium with oxygen during heating. Secondly, calcination in air of niobium salts: sulfide, nitride or carbide. Thirdly, the most common method is the dehydration of hydrates. Hydrated oxide Nb2O5 precipitates from aqueous solutions of salts with concentrated acids. xH2O. Then, when the solutions are diluted, a white oxide precipitate occurs. Dehydration of Nb2O5 xH2O precipitate is accompanied by heat release. The whole mass is heating up. This happens due to the transformation of an amorphous oxide into a crystalline form. Niobium oxide can be of two colors. Under normal conditions, it is white, but when heated, it becomes yellow. Once the oxide is cooled, however, 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 he is credited with an acidic character on the basis of interaction with hot aqueous alkali; in this case, however, oxidation to a five-charged ion occurs.
It would seem that the difference of one electron is not so great, but unlike Nb2O5, NbO2 oxide conducts an 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 make NbO2 give up its oxygen.
With the loss of oxygen, NbO2 passes into NbO oxide, and then all the oxygen is eliminated fairly quickly. Little is known about the lower niobium oxide NbO. It has a metallic sheen and looks similar to metal. Excellent conductor of electricity. 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 is not an oxide at all, but a metal like zinc):
NbO + 6HCl = 2NbOCl3 + 3H2
Pure NbO can be obtained by calcining 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 at 1935°C. To purify niobium from oxygen, the temperature is raised to 2300 - 2350 ° C, then, simultaneously with evaporation, NbO decomposes into oxygen and metal. There is a refining (cleaning) of the metal.
Niobium compounds
The story about the element would not be complete without mentioning its compounds with halogens, carbides and nitrides. This is important for two reasons. First, thanks to fluoride complexes, it is possible to separate niobium from its eternal companion tantalum. Secondly, these compounds reveal to us the qualities of niobium as a metal.
Interaction of halogens with metallic niobium:
Nb + 5Cl2 = 2NbCl5 can be obtained, all possible niobium pentahalides.
Pentafluoride NbF5 (tmelt = 76 °C) in the liquid state and in vapor is colorless. Like vanadium pentafluoride, it is polymeric in the liquid state. 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 \u003d H2; + H2O \u003d H2
Potassium salt K2. H2O is important for separating niobium from tantalum because, unlike the 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; when paired, they are monomers. Their melting and boiling points increase with the transition from chlorine to bromine and iodine. Some of the ways to obtain pentahalides are as follows:
2Nb+5I2 2NbI5;O5+5C+5Cl22NbCl5+5CO;.
2NbCl5+5F22NbF5+5Cl2
Pentahalides dissolve well in organic solvents: ether, chloroform, alcohol. Water, however, is completely decomposed - hydrolyzed. As a result of hydrolysis, two acids are obtained - hydrohalic and niobic. For example,
4H2O = 5HCl + H3NbO4
When hydrolysis is undesirable, then some strong acid is introduced and the equilibrium of the process described above is shifted towards NbCl5. In this case, the pentahalide dissolves without undergoing hydrolysis,
Niobium carbide deserved special appreciation from metallurgists. In any steel, there is carbon; niobium, binding it into carbide, improves the quality of alloy steel. Usually when welding stainless steel, the weld has less strength. The introduction of niobium in the 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 able to withstand temperatures up to 3500°C. A layer of carbide only half a millimeter thick is enough to protect metals and, most importantly, graphite from corrosion. Carbide can be obtained by heating 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 “royal vodka” when boiled; resistant to water. The only thing with which it can be forced to interact is boiling alkali. In this case, it decomposes with the release of ammonia.
NbN nitride is light gray with a yellowish tint. It is refractory (temp. pl. 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 degree of oxidation of the metal decreases.
The use of niobium in various industries
The use of niobium for alloying metals
Steel alloyed with niobium has good corrosion resistance. Chromium also increases the corrosion resistance of steel and is much cheaper than niobium. This reader is right and wrong at the same time. Wrong because I forgot about one thing.
In chromium-nickel steel, as in any other, 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. 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.
Uses of niobium in other industries
From niobium sheets and rods, “hot fittings” (i.e., heated parts) are made - anodes, grids, indirectly heated cathodes and other parts of electronic lamps, especially powerful generator lamps.
In addition to pure metal, tantalonium-obium alloys are used for the same purposes.
Niobium was used to make electrolytic capacitors and 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 a solid electrolyte are characterized by high capacitance at small sizes, high insulation resistance.
Niobium capacitor elements are made from thin foil or porous plates pressed from metal powders.
Corrosion resistance of niobium in acids and other media, combined with high thermal conductivity and plasticity, 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 with potassium, with which niobium does not interact up to 600°C. To increase the survivability of uranium fuel elements, uranium is alloyed 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 gas turbines of jet engines. Alloying molybdenum, titanium, zirconium, aluminum and copper with niobium sharply 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 an ingredient in some grades of tungsten carbide-based carbides used for cutting steels.
Niobium is widely used as an alloying addition in steels. The addition of niobium in an amount 6 to 10 times the carbon content of steel eliminates intergranular corrosion of stainless steel and protects welds from destruction.
Niobium is also introduced into the composition of various heat-resistant steels (for example, for gas turbines), as well as into the composition of tool and magnetic steels.
Niobium is introduced into steel in an alloy with iron (ferroniobium) containing up to 60% Nb. In addition, ferrotantaloniobium is used with a different ratio between tantalum and niobium in the ferroalloy.
In organic synthesis, some niobium compounds (fluorine complex salts, oxides) are used as catalysts.
The use and production of niobium is rapidly increasing, which is due to a combination of its properties such as refractoriness, a small thermal neutron capture cross section, the ability to form heat-resistant, superconducting and other alloys, corrosion resistance, getter properties, low electron work function, good cold workability and weldability. The main areas of application of niobium: rocket science, aviation and space technology, radio engineering, electronics, chemical apparatus building, nuclear power engineering.
Applications of metallic niobium
Aircraft parts are made from pure niobium or its alloys; shells for uranium and plutonium fuel elements; containers and pipes; for liquid metals; details of electrolytic capacitors; "hot" fittings of electronic (for radar installations) and powerful generator lamps (anodes, cathodes, grids, etc.); corrosion-resistant equipment in the chemical industry.
Niobium is alloyed with other non-ferrous metals, including uranium.
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 to fabricate 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 minting collectible coins. Thus, the Bank of Latvia claims that niobium is used in the collection coins of 1 lats along with silver.
The use of niobium compounds O5 catalyst in the chemical industry;
in the production of refractories, cermets, special glass, nitride, carbide, niobates.
Niobium carbide (mp. 3480 °C) in an alloy with zirconium carbide and uranium-235 carbide is the most important structural material for fuel rods of solid-phase nuclear jet engines.
Niobium nitride NbN is used for the production of thin and ultra-thin superconducting films with a critical temperature of 5 to 10 K with a narrow transition, of the order of 0.1 K
Niobium in medicine
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.
Application in jewelry
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 mining in Russia
In recent years, the world production of niobium has been at the level of 24-29 thousand tons. It should be noted that the world market of niobium is significantly monopolized by the Brazilian company CBMM, which accounts for about 85% of the world output of niobium.
Japan is the main consumer of niobium-containing products (primarily ferroniobium). This country annually imports over 4,000 tons of ferroniobium from Brazil. Therefore, Japanese import prices for niobium-containing products can be taken with great confidence as close to the world average. In recent years, there has been a trend of rising prices for ferroniobium. 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, the world consumption of niobium has been increasing on average by 4-5% annually.
It must be admitted with regret that Russia is on the sidelines of the niobium market. In the early 1990s, according to Giredmet experts, the former USSR produced and consumed about 2,000 tons of niobium (in terms of niobium oxide). At present, 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 capacities for the production of niobium were created, scattered across different republics - Russia, Estonia, Kazakhstan. This traditional feature of the development of industry in the USSR has now placed Russia in a very difficult position with regard to 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, obtained 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 in it is about 8.5%). Subsequently, the production of concentrate was constantly decreasing, in 1996-1998. the company was repeatedly stopped due to lack of sales. Currently, according to estimates, the production of loparite concentrate at the enterprise is at the level of 700 - 800 tons per month.
It should be noted that the enterprise is quite 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 rather complicated due to the complex of rare metals (niobium, tantalum, titanium) contained in it. 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 plant for processing loparite concentrate with the production of commercial niobium-containing products (niobium oxide) among other metals.
The main markets for niobium products of SMZ 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 capacities for the production of niobium in the USSR were concentrated in Estonia - at the Sillamäe Chemical and Metallurgical Production Association (Sillamäe). Now the Estonian enterprise is called "Silmet". In Soviet times, the enterprise processed loparite concentrate from the Lovoozersky GOK, since 1992 its shipment was stopped. Now Silmet processes only a small amount of niobium hydroxide from the Solikamsk magnesium plant. Most of the raw materials containing niobium are currently sourced from Brazil and Nigeria. The company's management does not exclude the supply of loparite concentrate, however, "Sevredmet" is trying to pursue a policy of its processing on the spot, since the export of raw materials is less profitable than finished products.
Tutoring
Need help learning a topic?
Our experts will advise or provide tutoring services on topics of interest to you.
Submit an application indicating the topic right now to find out about the possibility of obtaining a consultation.
Niobium
NIOBIUM-I; m.[lat. Niobium] Chemical element (Nb), a hard, refractory and malleable grayish-white metal (used in the production of chemically resistant and heat-resistant steels).
◁ Niobium; niobium, -th, -th.
niobium(lat. Niobium), a chemical element of group V of the periodic system. Named after Niobe - the daughter of the mythological Tantalum (the proximity of the properties of Nb and Ta). Light gray refractory metal, density 8.57 g / cm 3, t mp 2477°C, superconducting transition temperature 9.28 K. Very chemically resistant. Minerals: pyrochlore, columbite, loparite, etc. A component of chemically resistant and heat-resistant steels, from which parts of rockets, jet engines, chemical and oil refinery equipment are made. Niobium and its alloys are coated with fuel elements (TVELs) of nuclear reactors. Stannide Nb 3 Sn, germanide Nb 3 Ge, alloys of niobium with Sn, Ti and Zr are used for the manufacture of superconducting solenoids (Nb 3 Ge is a superconductor with a superconducting transition temperature of 23.2 K).
NIOBIUMNIOBIUM (lat. Niobium, on behalf of Niobe (cm. NIOBE)
), Nb (read "niobium"), a chemical element with atomic number 41, atomic mass 92.9064. Natural niobium consists of one stable isotope 93 Nb. Configuration of two outer electron layers 4 s 2
p 6
d 4
5s 1
. Oxidation states +5, +4, +3, +2 and +1 (valencies V IV, III, II and I). It is located in group VB, in the 5th period of the Periodic Table of the Elements.
The radius of the atom is 0.145 nm, the radius of the Nb 5+ ion is from 0.062 nm (coordination number 4) to 0.088 nm (8), the Nb 4+ ion is from 0.082 to 0.092 nm, the Nb 3+ ion is 0.086 nm, the Nb 2+ ion is 0.085 nm. Sequential ionization energies are 6.88, 14.32, 25.05, 38.3 and 50.6 eV. The electron work function is 4.01 eV. Electronegativity according to Pauling (cm. PAULING Linus)
1,6.
Discovery history
Discovered in 1801 by C. Hatchet (cm. HATCHET Charles)
. Investigating a black mineral sent from America, he isolated the oxide of a new element, which he called columbium, and the mineral containing it, columbite. A year later, from the same mineral, A. G. Ekeberg (cm. EKEBERG Anders Gustav)
isolated another oxide, which he called tantalum (cm. tantalum (chemical element))
. The properties of columbium and Ta were very close, and they were considered as one element for a very long time. In 1844 G. Rose (cm. ROSE (German scientists, brothers))
proved that these are two different elements. He retained the name tantalum while the other named niobium. Only in 1950 IUPAC (World Organization of Chemists) finally assigned the name niobium to element No. 41. Metallic Nb was first obtained in 1866 by K. Blomstrand (cm. BLOMSTRAND Christian Wilhelm)
.
Being in nature
The content in the earth's crust is 2·10 -3% by weight. Niobium does not occur in free form; it accompanies tantalum in nature. Of the ores, columbite-tantalite is the most important. (cm. COLUMBITE)
(Fe,Mn)(Nb,Ta) 2 O 6 , pyrochlore (cm. PYROCHLOR)
and loparite (cm. LOPARIT)
.
Receipt
About 95% of Nb is obtained from pyrochlore, columbite-tantalite and loparite ores. Ores are enriched by gravity methods and flotation (cm. FLOTATION)
. Concentrates containing up to 60% Nb 2 O 5 are processed to ferroniobium (an alloy of iron and niobium), pure Nb 2 O 5 or NbCl 5 . Niobium is reduced from its oxide, fluoride or chloride by aluminum or carbothermia. High-purity niobium is obtained by high-temperature reduction of volatile NbCl 5 with hydrogen.
The resulting niobium powder is briquetted, sintered in vacuum in electric arc or electron beam furnaces.
Physical and chemical properties
Niobium is a shiny silver-gray metal with a cubic body-centered crystal lattice of the a-Fe type, a= 0.3294 nm. Melting point 2477°C, boiling point 4760°C, density 8.57 kg/dm 3 .
Chemically, niobium is quite stable. When calcined in air, it oxidizes to Nb 2 O 5 . About 10 crystalline modifications have been described for this oxide. At normal pressure, the b-form of Nb 2 O 5 is stable. When Nb 2 O 5 is fused with various oxides, niobates are obtained: Ti 2 Nb 10 O 29, FeNb 49 O 124. Niobates can be considered as salts of hypothetical niobic acids. They are divided into metaniobates MNbO 3, orthoniobates M 3 NbO 4, pyroniobates M 4 Nb 2 O 7 or polyniobates M 2 O . n Nb 2 O 5 (M is a singly charged cation, and n= 2-12). Niobates of two- and three-charged cations are known. Niobates react with HF, melts of alkali metal hydrofluorides (KHF 2) and ammonium (cm. AMMONIUM (in chemistry))
. Some niobates with a high M 2 O/Nb 2 O 5 ratio are hydrolyzed:
6Na 3 NbO 4 + 5H 2 O \u003d Na 8 Nb 6 O 19 + 10NaOH
Niobium forms NbO 2 , NbO and a number of oxides intermediate between NbO 2.42 and NbO 2.50 and similar in structure to the b-form Nb 2 O 5 .
With halogens (cm. HALOGENS)
Nb forms NbHal 5 pentahalides, NbHal 4 tetrahalides, and NbHal 2,67 -NbHal 3+x phases containing Nb 3 or Nb 2 groups. Niobium pentahalides are easily hydrolyzed by water. The melting points of pentachloride, pentabromide and niobium pentiodide are 205, 267.5 and 310°C. Above 200-250°C these pentahalides are volatile.
In the presence of water vapor and oxygen, NbCl 5 and NbBr 5 form oxyhalides NbOCl 3 (NbOBr 3) - loose cotton-like substances.
When Nb and graphite interact, Nb 2 C and NbC carbides, solid heat-resistant compounds, are formed. In the Nb - N system, there are several phases of variable composition and nitrides Nb 2 N and NbN. Nb behaves similarly in systems with phosphorus and arsenic. In the interaction of Nb with sulfur, sulfides were obtained: NbS, NbS 2 and NbS 3. Double fluorides Nb and K (Na) - K 2 have been synthesized.
Application
50% of the produced niobium is used for microalloying of steels, 20-30% - for the production of stainless and heat-resistant alloys. Niobium intermetallides (Nb 3 Sn and Nb 3 Ge) are used in the manufacture of solenoids for superconducting devices. Niobium nitride NbN is used in the manufacture of targets for television transmission tubes. Niobium oxides are components of refractory materials, cermets, glasses with high refractive indices. Double fluorides - in the isolation of niobium from natural raw materials, in the production of metallic niobium. Niobates are used in acoustic and optoelectronics as laser materials.
Physiological action
Niobium compounds are poisonous. MPC of niobium in water is 0.01 mg/l.
encyclopedic Dictionary. 2009 .
Synonyms:See what "niobium" is in other dictionaries:
- (new lat. niobium). One of the rare metals found in tantalite. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. NIOBIUM metal, occurs in the form of oxides in rare minerals, has no practical significance ... Dictionary of foreign words of the Russian language
- (Niobium), Nb, chemical element of group V of the periodic system, atomic number 41, atomic mass 92.9064; metal, mp 2477 shC. Niobium is used for alloying steels, obtaining heat-resistant, hard and other alloys. Niobium was discovered by English ... ... Modern Encyclopedia
Niobium- (Niobium), Nb, chemical element of group V of the periodic system, atomic number 41, atomic mass 92.9064; metal, mp 2477 °C. Niobium is used for alloying steels, obtaining heat-resistant, hard and other alloys. Niobium was discovered by English ... ... Illustrated Encyclopedic Dictionary
- (symbol Nb), brilliant gray-white transition chemical element, metal. Discovered in 1801. It is found, as a rule, in pyrochlore ores. Being a soft and malleable metal, niobium is used in the production of special stainless steels and alloys ... ... Scientific and technical encyclopedic dictionary
Nb (lat. Niobium; from the name of Niobe, the daughter of Tantalus in other Greek mythology * a. niobium; n. Niob, Niobium; f. niobium; and. niobio), chem. element of group V periodic. Mendeleev systems, at. n. 41, at. m. 92.9064. It has one natural isotope 93Nb. ... ... Geological Encyclopedia
NIOBIUM, one of the metals discovered by chemists. Dahl's Explanatory Dictionary. IN AND. Dal. 1863 1866 ... Dahl's Explanatory Dictionary
NIOBIUM- chem. element, symbol Nb (lat. Niobium), at. n. 41, at. m. 92.90; light gray metal, density 8570 kg/m3, t = 2500 °C; has a high chem. tenacity. In nature, it occurs in minerals together with tantalum, separation from which causes ... ... Great Polytechnic Encyclopedia
- (lat. Niobium) Nb, a chemical element of group V of the periodic system, atomic number 41, atomic mass 92.9064. Named on behalf of Niobe, the daughter of the mythological Tantalus (the proximity of the properties of Nb and Ta). Light gray refractory metal, density 8.57 ... ... Big Encyclopedic Dictionary
- (Niobium), Nb, chem... Physical Encyclopedia
Exist., number of synonyms: 2 metal (86) element (159) ASIS synonym dictionary. V.N. Trishin. 2013 ... Synonym dictionary
- (Niobium French and English, Niob German; chemical), Nb =: 94. in group V of the periodic system of elements there are two rare metals, H. and tantalum, which are related to vanadium in the same way that molybdenum and tungsten are related to chromium; last three metal members… … Encyclopedia of Brockhaus and Efron
