How to identify niobium at home. Chemical properties of niobium. Molecule and atom of niobium

Ural State Mining University

On the topic: Properties of niobium

Group: M-13-3

Student: Mokhnashin Nikita

1. General information about item

Physical properties of niobium

Chemical properties niobium

Free niobium

Niobium oxides and their salts

Niobium compounds

Leading countries in the production of niobium

1. General information about the element

Humanity has been familiar with the element occupying the 41st cell in the Mendeleev table for a long time. The age of its current name - niobium - is almost half a century younger. It so happened that item # 41 was opened twice. The first time - in 1801, the English scientist Charles Hatchet examined a sample of a faithful mineral sent to the British Museum from America. From this mineral, he isolated the oxide of a previously unknown element. Hatchet named the new element Colombia, thus marking its overseas origin. And the black mineral was named columbite. A year later, the Swedish chemist Ekeberg isolated the oxide of another new element, called tantalum, from columbite. The similarity of the compounds 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, German chemist Heinrich Rose examined samples of columbite found in Bavaria. He rediscovered the oxides of two metals. One of them was an oxide of the already known tantalum. The oxides were similar, and to emphasize their similarity, Rose named the element that forms the second oxide niobium, after Niobe, daughter of the mythological martyr Tantalus. However, Rose, like Hatchet, was unable to obtain this element in a free state. Metallic niobium was first obtained only in 1866 by the Swedish scientist Blomstrand during the reduction of niobium chloride with hydrogen. At the end of the XIX century. two more methods have been found to obtain this element. First Moissan received it in an electric furnace, reducing niobium oxide with carbon, and then Goldschmidt was able to restore the same element with aluminum. And to call element no. 41 in different countries continued in different ways: in England and the United States - with colombium, in other countries - with niobium. The end of this discord was put by the International Union of Pure and Applied Chemistry (IUPAC) in 1950. It was decided to legitimize the name of the element "niobium" everywhere, and the name "columbite" was assigned to the main mineral of niobium. Its formula is (Fe, Mn) (Nb, Ta) 2 O 6.

It is not by chance that niobium is considered a rare element: it is indeed rare and in small quantities, always in the form of minerals and never in its native state. An interesting detail: in different reference editions, the clarke (content in the earth's crust) of niobium is different. This is mainly due to the fact that in last years new deposits of minerals containing niobium have been found in African countries. In the "Chemist's Handbook", vol. 1 (M., "Chemistry", 1963) the figures are given: 3.2 · 10-5% (1939), 1 · 10-3% (1949) and 2, 4 10-3% (1954). But even the latest figures are underestimated: African deposits discovered in recent years were not included here. Nevertheless, it is estimated that approximately 1.5 million tons of metallic niobium can be smelted from the minerals of already known deposits.

Physical properties of niobium

Niobium is a shiny silver-gray metal.

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

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

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

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

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

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

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

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

3. Chemical properties of niobium

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

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

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

Nb + 4NaOH + 5О2 = 4NaNbO3 + 2H2О

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

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

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

Nb + 5Cl2 = 2NbCl5

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

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

niobium metal halogen

4. Niobium in a free state

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

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

1.obtaining a concentrate: ferroniobium or ferrotantaloniobium;

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

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

.obtaining and refining metals.

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

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

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

Niobium oxides and their salts

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

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

O5 + 3Nа2СО3 = 2Nа3NbO4 + ЗС02

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

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

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

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

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

O5 + H2 = 2NbO2 + H2O

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

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

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

2NbO + 3Cl2 = 2NbOCl3

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

NbO + 6HCl = 2NbOCl3 + 3H2

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

К2 + 3Na = NbO + 2KF + 3NaF

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

Niobium compounds

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

Interaction of halogens with metallic niobium:

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

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

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

Solutions in hydrofluoric acid H2F2 contain various complex ions:

H2F2 = H2; + H2O = H2

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

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

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

2NbCl5 + 5F22NbF5 + 5Cl2

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

4H2O = 5HCl + H3NbO4

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

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

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

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

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

Application of niobium in various industries

The use of niobium for alloying metals

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

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

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

Now the properties and capabilities of niobium are appreciated at their true worth by aviation, mechanical engineering, radio engineering, chemical industry, and nuclear power. They all became consumers of niobium.

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

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

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

Use of niobium in other industries

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

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

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

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

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

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

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

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

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

Niobium is also included in various heat-resistant steels(for example, for gas turbines), as well as in 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 (fluoride complex salts, oxides) are used as catalysts.

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

Application of metal niobium

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

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

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

Niobium intermetallic compounds and alloys

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

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

Ferroniobium is added to stainless chromium-nickel steels to prevent them intergranular corrosion and destruction in steel of other types to improve their properties.

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

Application of niobium compounds O5 catalyst in the chemical industry;

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

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

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

Niobium in medicine

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

Application in jewelry

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

Niobium mining in Russia

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

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

It is regrettable to admit that Russia is on the sidelines of the niobium market. In the early 90s, according to Giredmet experts, in the former USSR produced and consumed about 2 thousand tons of niobium (in terms of niobium oxide). Current consumption Russian industry niobium production 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 put Russia in a very difficult situation for 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 the loparite concentrate obtained at the Lovozersky GOK (now - JSC Sevredmet, Murmansk region). Before the collapse of the USSR, the enterprise produced about 23 thousand tons of loparite concentrate (the content of niobium oxide in it is about 8.5%). Subsequently, the production of concentrate steadily decreased, in 1996-1998. the enterprise was 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 rigidly tied to its only consumer - the Solikamsk Magnesium Plant. The fact is that loparite concentrate is a rather specific product that is obtained only in Russia. Its processing technology is rather complicated due to the complex of rare metals it contains (niobium, tantalum, titanium). In addition, the concentrate is radioactive, which is largely why all attempts to enter the world market with this product ended in vain. It should also be noted that ferroniobium cannot be obtained from loparite concentrate. In 2000, at the Sevredmet plant, the Roredmet company launched an experimental plant for the processing of loparite concentrate to obtain, among other metals, marketable niobium-containing products (niobium oxide).

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

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MetProd has been operating in the field of extraction and production of raw materials and metals for over 20 years, and during this time we have achieved the highest quality of our products. We are engaged in the extraction of rare refractory metals, which include the element niobium - a metal whose properties and field of application allow it to be used in the most demanding industries. We can guarantee the quality of products, because We develop niobium deposits on our own.

Niobium and its features

This metal is very resistant to various chemical influences - this determines its popularity in industry and its high cost. Among the areas of its application, the most responsible are medicine, the diamond and rocket industry, and the production of coins. In addition, the material is quite malleable during processing if carried out at low temperatures. Niobium has a high transition temperature - this property is very important in the production of superconducting wires and magnets.

It is supplied in ingots, powder or ligature. So, the most famous powder of the N6PM brand contains, in addition to niobium, carbon, nitrogen, oxygen, iron, titanium, tantalum and silicon and can have one of four grains (40–100 microns).

The chemical stability of niobium manifests itself when interacting with substances such as nitric, orthophosphoric, sulfuric and hydrochloric acids. It can be dissolved only in caustic alkali of very high concentration or sulfuric acid, also concentrated and preheated to 150 ° C.

What is niobium used for?

Metals with unique properties are very much needed by different branches of metallurgy, because it significantly optimizes the characteristics of steels. Alloys with the participation of niobium are used to produce such important products as:

pipes and containers for gas pipelines, oil pipelines, for molten metals;
shells of atomic and nuclear reactors;
parts of electrolytic capacitors;
various refractory materials, special glasses and lamp fittings;
carbides;
devices for the chemical industry requiring high corrosion resistance;
"Hot" fittings for generator and electronic tubes for radars - cathodes, anodes, grids, etc.

Currently, the demand for niobium is increasing, and the company is trying to satisfy all market demands: in order to be able to buy niobium at a low price, we ourselves control its extraction and production at all stages. We offer pure metal, as well as its alloys, which are used in rocketry, for the production of parts for aviation and space technology, in electronics and radio engineering, nuclear power and chemical apparatus engineering.

About half of all niobium on the market today is used for alloying steels, and about 30% is used to obtain alloys with the desired properties. It is alloyed with non-ferrous metals, including uranium, and introduced into steel to avoid intergranular corrosion and improve its properties.

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

Retrieving an item

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

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

The relatively low concentration of a substance in the earth's rock is aggravated by the difficulties arising from its production from a concentrate. It should be borne in mind that niobium NBSh can be obtained only from a rock that is saturated with tantalum. The features of the production process are the following points:

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

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

Niobium oxides

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

Niobium oxide is a white crystalline powder that has a creamy hue.
The substance is insoluble in water.
The resulting substance retains its structure when mixed with most acids.

The features of niobium pentoxide also include the following properties:

Increased strength.
High refractoriness. The substance is able to withstand temperatures up to 1490 degrees Celsius.
When heated, the surface is oxidized.
Reacts to chlorine, can be reduced with hydrogen.

In most cases, niobium hydroxide is used to obtain high-alloy steel grades that have rather attractive performance characteristics.

Physical and chemical properties

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

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

The main advantage of the substance is precisely its refractoriness. That is why it has come to be used in a wide variety of industries. The substance melts at a temperature of about 2,500 degrees Celsius. Some alloys even melt at a record temperature of 4,500 degrees Celsius. The density of the substance is quite high, it is 8.57 grams per cubic centimeter. It should be borne in mind that the metal is paramagnetic.

On the crystal lattice the following acids have no effect:

sulfuric;
salt;
phosphoric;
chlorine.

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

Application of niobium

A wide variety of niobium products are made, most of which are associated with the production of aircraft. An example is the use of niobium in the manufacture of parts that are installed when assembling missiles or aircraft. In addition, the following application of this element can be distinguished:

Production of elements from which radar installations are made.
As noted earlier, the alloy under consideration can be used to obtain cheaper capacitive electric capacitors.
Foil cathodes and anodes are also made using the element in question, which is associated with high heat resistance.
You can often find designs of powerful generating lamps that have a grid inside. In order for this mesh to withstand the impact high temperature it is made from the alloy in question.

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

Niobium alloys

Considering such alloys, it should be borne in mind that this element is often used for the production of ferroniobium. This material is widely used in the foundry industry, as well as in the manufacture of electronic coatings. Includes:

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

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

Alternative ferroniobium alloys can be called niobium 5VMC. When it is obtained, tungsten, zirconium and molybdenum are used as alloying elements. In most cases, this spawn is used for the production of semi-finished products.

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

DEFINITION

Niobium- 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 contains niobium 0.002% (wt.). This element is very similar to vanadium. In a free state, it is a refractory metal, hard, but not brittle, well amenable to mechanical processing (Fig. 1 .. The density of niobium is 8.57 g / cm 3, the melting point is 2500 o C.

Niobium is resistant to 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 the 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 is the average mass of atoms chemical element more than 1/12 of the mass of a carbon atom.

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

Niobium isotopes

It is known that in nature niobium can be found in the form of the only stable isotope 93 Nb. The mass number is 93, the nucleus of the 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 longest-lived isotope 92 Nb with a half-life of 34.7 million years.

Niobium ions

At the outer energy level of the niobium atom, there are five electrons, which 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 high temperature and corrosion resistant alloys. Especially great importance have heat-resistant niobium alloys, which are used in the production of gas turbines, jet engines, rockets.

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

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

The task

Indicate the valence 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. We calculate the total number of valence units for oxygen:

We calculate the total number of valence units for gadolinium:

We find the difference between these values:

Determine the number of niobium atoms in the compound. It is equal to the 2nd. The valence 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:

2 × 3 + 2 × x + 7 × (-2) = 0

The oxidation state of niobium is +4.

In a similar way, we determine that the valence and oxidation state of niobium in Pb (NbO 3) 2 are equal to IV and +1, respectively.

The use of niobium for alloying metals

Use of niobium in other industries

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

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

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

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

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

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

Application of metal niobium

Parts of aircraft are made from pure niobium or its alloys; casings for uranium and plutonium fuel elements; containers and pipes; for liquid metals; parts for electrolytic capacitors; "Hot" fittings for electronic (for radar installations) and powerful generator lamps (anodes, cathodes, grids, etc.); corrosion-resistant equipment in the chemical industry.
Niobium is alloyed with other non-ferrous metals, including uranium.
Niobium is used in cryotrons - superconducting elements of computers. Niobium is also known for being used in accelerating structures at the Large Hadron Collider.

Niobium intermetallic compounds and alloys

Nb 3 Sn stannide and alloys of niobium with titanium and zirconium are used for the manufacture of superconducting solenoids.
Niobium and alloys with tantalum in many cases replace tantalum, which gives a great economic effect (niobium is cheaper and almost twice as light as tantalum).
Ferroniobium is introduced into stainless chromium-nickel steels to prevent their intergranular corrosion and destruction, and into other types of steel to improve their properties.
Niobium is used for minting collectible coins. Thus, the Bank of Latvia claims that niobium is used along with silver in collector's 1 lats coins.

Applications of niobium compounds

Nb 2 O 5 catalyst in the chemical industry;
in the production of refractories, cermets, special. glass, nitride, carbide, niobates.
Niobium carbide (mp 3480 ° C) in an alloy with zirconium carbide and uranium-235 carbide is the most important structural material for fuel elements of solid-phase nuclear jet engines.
Niobium nitride NbN is used for the production of thin and ultrathin superconducting films with a critical temperature of 5 to 10 K with a narrow transition of the order of 0.1 K

Niobium in medicine

Application in jewelry

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

Niobium as a first-generation superconducting material

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

Two characteristics of superconductors are of practical importance: the critical temperature at which the transition to the superconducting state occurs, and the critical magnetic field(even Kamerlingh Onnes observed the loss of superconductivity by a superconductor when exposed to a sufficiently strong magnetic field). In 1975, an intermetallic compound of niobium and germanium of the composition Nb 3 Ge became a superconductor - the record holder for the value of the critical temperature. Its critical temperature is 23.2 ° K; this is above the boiling point of hydrogen. (Most of the known superconductors become superconductors only at the temperature of liquid helium.)

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

One of the actively used superconductors (superconducting transition temperature 9.25 K). Niobium compounds have a superconducting transition temperature of up to 23.2 K (Nb 3 Ge).
The most commonly used industrial superconductors are NbTi and Nb 3 Sn.
Niobium is also used in magnetic alloys.
It is used as an alloying additive.
Niobium nitride is used to produce superconducting bolometers.

The exceptional durability of niobium and its alloys with tantalum in superheated cesium-133 vapor makes it one of the most preferred and cheapest construction materials for high-power thermionic generators.