The atomic mass of niobium. The use of niobium. Niobium production in Russia. Application in electrodes and alloys

In the field of extraction and production of raw materials and metals, MetProd has been operating 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 product quality 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 grade 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, phosphoric, 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 various 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;
• accessories 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.

In ancient Greek. mythology * a. niobium; n. Niob, Niobium; f. niobium; and. niobio), is a chemical element of group V of the periodic system of Mendeleev, atomic number 41, atomic mass 92.9064. Has one natural isotope 93 Nb.

Niobium oxide was first isolated from columbite by the English chemist C. Hatchet in 1801. Metallic niobium was obtained in 1866 by the Swedish scientist K.V. Blomstrand.

Niobium properties

Niobium is a steel-colored metal, has a body-centered cubic lattice with a \u003d 0.3294 nm; density 8570 kg / m 3; melting point 2500 ° С, boiling point 4927 ° С; heat capacity (298 K) 24.6 J / (mol.K); thermal conductivity (273 K) 51.4 W / (m.K); temperature coefficient of linear expansion (63-1103 K) 7.9.10 -6 K -1; specific electrical resistance (293 K) 16.10 -8 Ohm.m; thermal coefficient of electrical resistance (273 K) 3.95.10 -3 K -1. The superconducting transition temperature is 9.46 K.

The oxidation state is +5, less often from +1 to +4. In terms of chemical properties, it is close to tantalum, extremely resistant to cold and, with low heating, to the action of many aggressive media, incl. and acids. Niobium dissolves only hydrofluoric acid, its mixture with nitric acid and alkali. Amphoterine. When interacting with halogens, forms niobium halides. When Nb 2 O 5 is fused with soda, salts of niobium acids - niobates - are obtained, although the acids themselves do not exist in a free state. Niobium can form double salts and complex compounds. Non-toxic.

Receiving and using

To obtain niobium, niobium concentrate is fused with sodium hydroxide or soda, and the resulting alloy is leached. The Nb and Ta contained in the undissolved precipitate are separated, and the niobium oxide is reduced separately from the tantalum oxide. Compact niobium is produced by powder metallurgy, electric arc, vacuum and electron beam melting.

Niobium is one of the main components for alloying heat-resistant steels and alloys. Niobium and its alloys are used as structural materials for parts of jet engines, rockets, gas turbines, chemical equipment, electronic devices, electrical capacitors, and superconducting devices. Niobates are widely used as ferroelectrics, piezoelectrics, and laser materials.

There are a fairly 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 rather unusual properties, which we will discuss in more detail below.

Getting 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 artificially. 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 that arise when it is obtained 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:

1. To begin with, the plant is supplied with concentrated ore, which goes through several stages of purification. In the production of niobium, the ore obtained is separated into pure elements, including tantalum.
2. 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:

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

The features of niobium pentoxide also include the following properties:

1. Increased durability.
2. High refractoriness. The substance is able to withstand temperatures up to 1490 degrees Celsius.
3. When heated, the surface is oxidized.
4. 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:

1. Resistant to various types of corrosion. The alloys obtained by introducing this element into the composition have high corrosion-resistant qualities.
2. 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.
3. The basic physical properties are also characterized by the ease of welding of the resulting alloys.
4. At low temperatures, the structure of the element remains practically unchanged, which allows maintaining the operational properties of the metal.
5. The special structure of the niobium atom determines the superconducting qualities of the material.
6. 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.

The following acids do not affect the crystal lattice:

1. sulfuric;
2. salt;
3. phosphoric;
4. 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.

Niobium Applications

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:

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

High physical and chemical 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:

1. iron;
2. niobium with tantalum;
3. silicon;
4. aluminum;
5. carbon;
6. sulfur;
7. phosphorus;
8. 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 5VMTs. 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.

It's worth starting with the fact that niobium is inextricably linked with a substance like tantalum. This is even despite the fact that these materials were not discovered at the same time.

What is niobium

What is known today about such a substance as niobium? It is a chemical element that is located in the 5th group of the periodic table, having an atomic number 41 and an atomic mass of 92.9. Like many other metals, this substance has a steel-gray sheen.

One of the most important physical parameters of this is its refractoriness. It is thanks to this characteristic that the use of niobium has become widespread in many industries. The melting point of this substance is 2468 degrees Celsius, and the boiling point is 4927 degrees Celsius.

The chemical properties of this substance are also at a high level. It is characterized by a high level of resistance to negative temperatures, as well as to the effects of most aggressive environments.

Production

It should be said that the presence of an ore that contains the element Nb (niobium) is much higher than that containing tantalum, but the problem lies in the scarcity of the content of the element itself in this ore.

Most often, in order to obtain this element, a thermal reduction process is carried out, in which aluminum or silicon is involved. As a result of this operation, ferroniobium and ferrotantaloniobium compounds are obtained. It should be noted that the metal version of this substance is obtained from the same ore, but a more complex technology is used. Niobium crucibles and other materials obtained are characterized by very high performance characteristics.

Methods for obtaining niobium

At present, one of the most developed directions for obtaining this material is aluminothermal, sodium thermal, and carbothermal. The difference between these types also lies in the precursors that are used to reduce niobium. Let's say K2NbF7 is used in the sodium thermal method. But, for example, in the aluminothermic method, niobium pentoxide is used.

If we talk about the carbothermal production method, then this technology implies mixing Nb with soot. This process should take place in a high-temperature and hydrogen environment. As a result of this operation, niobium carbide will be obtained. The second stage is that the hydrogen medium is replaced by a vacuum one, while the temperature is maintained. At this moment, its oxide is added to the niobium carbide and the metal itself is obtained.

It is important to note that niobium in ingots is quite common among the forms of the produced metal. This product is intended for the production of metal-based alloy and other various semi-finished products.

A bar of this material can also be produced, which is divided into several categories depending on the purity of the substance. The smallest amount of impurities is contained in the bar with the NBSh-00 marking. The NBSh-0 class is characterized by a higher presence of elements such as iron, titanium and tantalum silicon. The category that has the highest impurity index is НБШ-1. It can be added that niobium in ingots does not have such a classification.

Alternative production methods

Alternative methods include crucible-free electron beam zone melting. This process makes it possible to obtain single crystals of Nb. Niobium crucibles are manufactured using this method. It belongs to powder metallurgy. It is used in order to first obtain an alloy of this material, and then its pure sample. The availability of this method is the reason why niobium purchase advertisements are quite common. This method makes it possible to use for obtaining pure metal not the ore itself, which is quite difficult to extract, or the concentrate from it, but secondary raw materials.

Another alternative production method is rolled niobium. It is worth noting that most of the different companies prefer buying rods, wire or sheet metal.

Rolled and foil

Foil made from this material is a fairly common semi-finished product. It is the thinnest rolled sheet of this substance. It is used for the production of some products and parts. Niobium foil is obtained from pure raw materials by cold rolling Nb ingots. The resulting products are characterized by such indicators as high resistance to corrosion, aggressive environments, and high temperatures. Rolled niobium and its ingots also provide such characteristics as the product's resistance to wear, high ductility, and good machinability.

The products obtained in this way are most often used in such fields of activity as aircraft construction, rocketry, medicine (surgery), radio engineering, electrical engineering, nuclear power, and nuclear power. Niobium foil is packed in spools and stored in a dry, protected from moisture, and also in a protected place from mechanical impact from the outside.

Application in electrodes and alloys

The use of niobium is very widespread. It can be used like chromium and nickel as a material that is part of the iron alloy used to make electrodes. Due to the fact that niobium, like tantalum, is capable of forming superhard carbide, it is often used for the production of superhard alloys. It can be added that they are currently trying with the help of this material to improve the properties of alloys obtained on the basis of

Since niobium is a raw material capable of creating carbide elements, it, like tantalum, is used as an alloying mixture in steel production. It should be noted that for a long time the use of niobium as an impurity for tantalum was considered a negative effect. However, today the opinion has changed. It has been found that Nb can act as a substitute for tantalum, with greater success, since, due to the lower atomic mass, less substance can be used, while retaining all the old capabilities and effects of the product.

Application in electrical engineering

It is worth emphasizing that the use of niobium, like its brother tantalum, is possible in rectifiers, due to the fact that they have the property of unipolar conductivity, that is, these substances pass electric current in only one direction. It is possible to use this metal to create devices such as anodes, which are used in powerful generators and amplifier tubes.

It is very important to note that the use of niobium has reached the nuclear power industry. In this industry, products made from this substance are used as construction materials. This became possible because the presence of Nb in the parts makes them resistant to heat and also gives them high qualities of chemical resistance.

The excellent physical characteristics of this metal have led to the fact that it is widely used in rocket technology, in jet aircraft, and in gas turbines.

Niobium production in Russia

If we talk about the reserves of this ore, then in total there are about 16 million tons. The largest deposit, accounting for about 70% of the total volume, is located in Brazil. On the territory of Russia, about 25% of the reserves of this ore are located. This indicator is considered to be a significant part of all niobium reserves. The largest deposit of this substance is located in Eastern Siberia, as well as in the Far East. Today, in the territory of the Russian Federation, the company Lovozersky GOK is engaged in the extraction and production of this substance. It can be noted that the company "Stalmag" was also engaged in the production of niobium in Russia. She developed the Tatar deposit of this ore, but was closed in 2010.

You can also add that it is engaged in the production of niobium oxide. They get it by processing loparite concentrate. This plant produces between 400 and 450 tons of this substance, most of which is exported to countries such as the USA and Germany. Part of the remaining oxide goes to the Chepetsk Mechanical Plant, which produces both pure niobium and its alloys. Significant capacities are located there, allowing the production of up to 100 tons of material per year.

Niobium metal and its cost

Despite the fact that the scope of this substance is quite wide, the main purpose is the space and nuclear industries. For this reason, Nb is classified as a strategic material.

The main parameters that affect the cost of niobium:

• purity of the alloy, a large amount of impurities reduces the price;
• the form of delivery of the material;
• volumes of supplied material;
• location of the ore receiving point (different regions need a different amount of an element, which means that the price for it is different).

An approximate list of prices for material in Moscow:

• niobium of the NB-2 brand costs in the range of 420-450 rubles per kg;
• niobium shavings cost from 500 to 510 rubles per kg;
• a staff of the brand NBSh-00 costs from 490 to 500 rubles per kg.

It should be noted that, despite the enormous cost of this product, the demand for it is only increasing.

The production of niobium, along with tantalum, as well as tantalum-niobium alloys, is of great economic importance from the point of view of the integrated use of both valuable metals.
In many cases, instead of tantalum with the same effect, it is possible to use niobium, which is close to it in properties, or alloys of tantalum with niobium, since these metals form a continuous series of solid solutions, the properties of which 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 simultaneous joint reduction of 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, with the hydrofluoric acid method of separating tantalum and niobium, the latter is separated in the form of fluorooxyniobate K2NbOF5 * H2O.
This salt is not suitable for sodium reduction for two reasons:
a) water of crystallization included in the specified salt, reacting with sodium, can lead to an explosion,
b) oxygen, which is part of the salt and bound with niobium, is not reduced by sodium and remains in the form of an oxide impurity in the reduction product.
Therefore, potassium fluorooxyniobate must be recrystallized through a solution of hydrofluoric acid with an HF concentration of more than 10%, as a result of which the K2NbF7 salt is formed, which is suitable for sodium reduction.
Niobium can also be produced by electrolysis under conditions similar to those described for the production of tantalum. A lower current efficiency than in the electrolytic production of tantalum is noted, as well as difficulties associated with the noticeable solubility of niobium compounds of different valences in the electrolyte.
Electrolysis from a mixed bath is also possible, containing a mixture of Ta2O5 + Nb2O5 as decomposing components and K2TaF7 as a solvent. In this case, an alloy of niobium with tantalum is obtained.
To obtain niobium, a method was proposed for the carbon reduction of niobium pentoxide in a 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, reduction with carbon 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 ° \u003d 38.2 kcal ), therefore, in the presence of carbonaceous gases in the furnace and at a high diffusion rate in the solid phase, which develops at such a high temperature, niobium turns out to be contaminated with niobium carbide, even if the charge is compiled based on the reaction

In a vacuum, the reduction reaction with carbon proceeds at a lower temperature (1600-1700 °),
Briquettes are prepared from a mixture of niobium pentoxide and carbon black, 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 a vacuum at a temperature of 1600 ° until the evolution of CO stops. The resulting product is a slightly sintered briquettes, consisting of particles of powdered gray carbide. Carbide is ground into powder in a ball mill and mixed with pentoxide in proportions corresponding to reaction (1). Briquettes of the Nb2O5 + NbC mixture are re-calcined in vacuum at a temperature of about 1600 °.
To ensure sweaty removal of carbon in the form of CO, a small excess of niobium pentoxide should be added to the Nb2O5 + NbC mixture. In the subsequent operation of high-temperature sintering (welding) of rods pressed from powdered metal niobium, excess niobium pentoxide is removed, since niobium oxides (like tantalum) volatilize in vacuum at temperatures below the melting point of the metal
Due to the inevitable expenditure of time for creating a vacuum and cooling the product in it, the productivity of a vacuum furnace in the manufacture of the 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 Nb2O5 + C mixture. 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 the pentoxide with soot according to reaction (2) with a slight excess of Nb2O5 in the charge. However, when a mixture of Nb2O5 + 5NbC is loaded into a vacuum furnace, its productivity is significantly increased compared to loading a mixture of Nb2O5 + 5C, since the mixture Nb2O5 + SNbC contains niobium (82.4%) 1.5 times more than the mixture Nb2O5 + 5C ( 57.2%) In addition, the first mixture has an additive specific gravity 1.7 times higher than the second mixture (6.25 g / cm3 and 3.7 g / cm3, respectively).
In addition, it should be borne in mind that niobium carbide, which constitutes the predominant part of the Nb2O5 + 5NbC mixture, is coarser than dispersed Nb2O5 and soot powders, which is an additional reason for the larger bulk density of the Nb2O5 + 5NbC mixture than the Nb2O5 + 5C mixture.
As a result of all this, a unit volume of the cartridge can accommodate 2.5-3 times more material (based on the niobium content) in the form of briquettes of a mixture of Nb2O5 + 5NbC than briquettes of a mixture of Nb2O5 + 5C.
In Bolke's work, there is no sufficiently compelling evidence of the need to strictly adhere to the recommended composition of the Nb2O5 + 5NbC mixture loaded into the vacuum furnace.
By calcining the Nb2O5 + 5C mixture in a carbon-tube furnace at atmospheric pressure, it is possible to obtain with high productivity (in a continuous process) a product close in composition to metallic niobium with a small admixture of carbon. This high density and bulk density niobium-rich powder can then be mixed with an appropriate amount of Nb2O5 (with a slight excess of Nb2O5 relative to the equivalent carbon impurity in niobium) and the briquetted mixture calcined in a vacuum oven to remove carbon in the form of CO.
With this option, the capacity and, consequently, the productivity of the vacuum furnace will be the greatest. A 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 to react 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, it is always possible for an admixture of nitrogen from the air to enter the furnace. Niobium, having a high affinity for nitrogen, actively absorbs it. In the production of niobium carbide, the possibility of contamination of the product with nitrogen is much less due to the higher affinity of niobium for carbon than for nitrogen.
Therefore, obtaining metallic niobium when using low-carbon niobium as a starting material is complicated by the need to create conditions that exclude the possibility of nitrogen ingress into 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 thoroughly 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 a mixture of Nb2O5 + 5C into it and when unloading niobium, etc.
Therefore, the question of the advantages of the option of preliminary production of niobium carbide or low-carbon niobium at atmospheric pressure (followed by calcining these products in a mixture with Nb2O5 in vacuum) can be solved by practical possibilities in each 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 closeness of the properties of the oxides of tantalum and niobium makes it possible to use the described method for producing malleable tantalum.

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