14 julio, 2024

Niobium (Nb): structure, properties, uses, obtaining

He niobium It is a chemical element that belongs to group V of the oeridic table. It belongs to the metals of the second transition series. Its chemical symbol is Nb. Most of its characteristics and behavior correspond to those of a metal, however, some of its chemical properties in the +5 oxidation state are very similar to those of a non-metal.

When it was discovered in 1801, it was given the name of columbium, in honor of Christopher Columbus, as it was part of a mineral sample brought from America to England.

For some time columbium (Cb) and tantalum (Ta) were considered the same element, until after much difficulty the differences between the two were identified.

The columbium was then, due to its similarity with tantalum, called niobium, a term derived from Niobe, daughter of Tantalus, who is a character from Greek mythology condemned to eternal frustration and son of the god Jupiter. In the United States metallurgical industry niobium is still called columbium.

It is a refractory metal, so it resists very high temperatures without melting or decomposing. When molten it can be mixed in any proportion with iron.

For this reason it is used in the production of steel for various applications, including the aviation and aerospace industries. It is also used in bone implants due to its biocompatibility with living tissues.

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Electronic structure and configuration

The electronic configuration of this element is:

1yes2 2yes2 2p6 3yes23p6 3d10 4yes2 4p6 4dFour. Fiveyes1,

or also:

[Kr] 4dFour. Fiveyes1,

This configuration explains why its strongest oxidation state is +5, since when it loses 5 electrons from its outermost layers (4dFour. Fiveyes1) acquires the stable configuration of the noble gas krypton (Kr). However, it also has other valences.

The crystalline structure of niobium is centered cubic, which means that 8 atoms are located forming a cube and in the center of this there is also an atom.

Nomenclature

Niobium, chemical symbol Nb Columbia, chemical symbol Cb

Properties

Atomic number

41

physical state

Metallic solid with silver sheen.

Atomic weight

92.9

Melting point

2477ºC

Boiling point

4741ºC

Density

8.57 g/cm3

Solubility

When it is in a liquid state, that is, molten, it is completely miscible with iron. It is insoluble in water.

Chemical properties

It has a high resistance to corrosion and many chemical substances. For this reason it is very resistant to acids, however it is attacked by hydrofluoric acid (HF) and reacts vigorously with a mixture of this with nitric acid (HNO3).

It dissolves slowly in molten sodium hydroxide (NaOH) or potassium hydroxide (KOH), but is resistant to ammonia (NH3) solutions.

The +5 oxidation state is the one that generates the most stable compounds of this element, such as fluoride, tartrate, oxalate and peroxide. However, it also has compounds with other valences.

Mechanical properties

Depending on its purity, it can be very ductile, that is, it can be easily deformed, even allowing wires to be obtained. However, as the elongation of the material increases, it becomes harder and more resistant, losing ductility, but without being brittle.

It is a highly heat resistant material, withstanding very high temperatures without melting or decomposing, maintaining its mechanical properties, therefore it belongs to the class of refractory metals.

other properties

It has superconducting properties, which means that when cooled below a certain temperature it offers no resistance to the passage of electric current, becoming a perfect electrical conductor.

Obtaining

The most important sources of this element are the minerals columbite, also called niobite or ferrocolumbite, and pyrochlore. Columbite also contains tantalum (Ta), so Nb must be separated from that metal.

One of the extraction methods is based on the difference in boiling points between Nb and Ta chloride. It begins by treating the mineral with chlorine gas (Cl2), so that metal chlorides are formed.

Then a distillation is carried out; Tantalum chloride (TaCl5) has a boiling point of 236 °C, while NbCl5 boils at 248 °C. Therefore, when heating the mixture, the tantalum chloride is recovered first and then the niobium chloride.

Nb is also generated as a by-product during tin extraction.

Applications

In the metallurgical industry

It is very useful in the manufacture of steel, in which at elevated temperatures it combines with carbon and nitrogen to form very fine particles of niobium carbide (NbC) and niobium nitride (NbN).

For this reason, its presence in said material helps to control the grain size and improve the resistance to corrosion.

It also increases the mechanical resistance of alloys, especially at low temperatures, making it useful in the aviation industry, where it is used in rockets and jet engines. As an additional advantage in this application, among the refractory metals it is the one with the lowest density.

Its alloys are used in beams for building structures and oil drilling platforms, and in gas and oil pipelines. Some of the alloys of niobium with chromium molybdenum steel are used in high temperature applications such as kettles.

It is also useful in wear and abrasion resistant tool steel. And due to its high ductility, it can be used in forming processes, among which we can mention pressing, bending and stamping.

in electromagnets

Due to its superconducting properties, it is used to make superconducting magnets that are used in particle accelerators, used by researchers in subatomic particle physics.

These magnets are also used in nuclear magnetic resonance equipment for the analysis of structures of chemical compounds and in magnetic resonance imaging scanners, which are used to obtain internal images of the human body for medical diagnostic purposes.

In glasses for glasses

Niobium oxides are added to corrective lens glass preparations to increase their refractive index and allow thinner glasses to be made.

Other apps

Through the anodizing process, a dense layer of oxide with certain substances is applied to this metal, which allows it to shine with attractive colors and in this way decorative wires are made and it is also inserted on coins.

Corrosion resistant evaporation vessels are produced with niobium and are useful in coating technology. Special crucibles are also manufactured.

It is also used in materials that are used for bone implants, because it is highly biocompatible with the tissues of the human body.

References

Royal Society of Chemistry. (2020). Periodic Table. Niobium. Retrieved from rsc.org. Cotton, F. Albert and Wilkinson, Geoffrey. (1980). Advanced Inorganic Chemistry. fourth edition. John Wiley & Sons. Gasik, MI (2013). Technology of Niobium Ferroalloys. Properties of Niobium. In Handbook of Ferroalloys. Retrieved from sciencedirect.com. Marczenko, Z. and Balcerzak, M. (2000). Separation, Preconcentration and Spectrophotometry in Inorganic Analysis. Niobium. In Analytical Spectroscopy Library. Retrieved from sciencedirect.com. Agulyansky, A. (2004). Introduction. Refining processes. In Chemistry of Tantalum and Niobium Fluoride Compounds. Retrieved from sciencedirect.com. Plan SE. (2020). Niobium. Recovered from plansee.com. Lyons, S.B. (2010). Corrosion and Degradation of Engineering Materials. Historical Information. In Sheir’s Corrosion. Retrieved from sciencedirect.com.

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