Niobium

Niobium is a chemical element with atomic number 41 located in group 5 of the periodic table of elements. It is symbolized as Nb. It is a ductile, gray, soft and little abundant transition metal. It is found in the mineral niobite, also called columbite, and is used in alloys. It is mainly used as an alloy in steels, to which it confers high resistance.

History

Niobium has similar physical and chemical properties to the element tantalum, and the two are therefore difficult to distinguish. The English chemist Charles Hatchett reported a new tantalum-like element in 1801 and named it columbium. In 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. German chemist Heinrich Rose determined in 1846 that tantalum minerals contained a second element, which he named niobium. In 1864 and 1865, a series of scientific discoveries clarified that niobium and columbium were the same element (as opposed to tantalum), and for a century the two names were used interchangeably. Niobium was officially adopted as the element name in 1949, but the name columbium remains in common use in metallurgy in the United States.

It wasn't until the 20th century that niobium was first used on the market. Brazil is the main producer of niobium and ferroniobium (an alloy of niobium and iron). Niobium is used primarily in alloys, most of it in special steel such as that used in oil and gas pipes. Although the alloys contain Only a maximum of 0.1%, this small percentage of niobium improves the strength of the steel. Niobium is used in various superconducting materials. These superconducting alloys also contain titanium and tin, which are widely used in the superconducting magnets of MRI scanners. Other niobium applications include its use in welding, nuclear, electronics, optics, numismatics, and jewelry industries. In the latter two applications, its low level of niobium toxicity and its ability to be colored by anodizing are particular advantages. Niobium is an important component of high-performance catalysts for the selective oxidation of propane to acrylic acid.

Properties

Physics

Niobium is a gray, ductile, and paramagnetic metal found in group 5 of the Periodic Table. Compared to the rest of the members of this group, it has an atypical configuration in its outermost electron shells. Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, which has the highest critical temperature of the elemental superconductors, niobium has a greater depth of magnetic penetration than any other element. Furthermore, it is one of the three elemental type II superconductors, along with vanadium and technetium. The superconducting properties are strongly dependent on the purity of the niobium metal. When it is very pure, it is relatively softer and more ductile, but impurities make it harder. The metal has a low cross section for thermal neutrons, which is why it is used in nuclear industries.

Chemicals

Metal takes on a bluish tint when exposed to air at room temperature for long periods of time. Despite presenting a high melting point, in elemental form (2468 °C), it has a low density compared to other refractory metals. In addition, it is resistant to corrosion, exhibits superconducting properties, and forms dielectric oxide layers.

Niobium is slightly less electropositive and more compact than its predecessor on the periodic table, zirconium, while being virtually identical in size to the heavier tantalum atoms, due to lanthanide contraction.

As a result, niobium's chemical properties are very similar to tantalum, which appears directly below niobium on the periodic table. Although its resistance to corrosion is not as remarkable as that of tantalum, niobium has a lower price and greater availability and this makes it attractive for less demanding uses, such as coatings in chemical plants.

Abundance

Niobium is estimated to be the 33rd most common element on Earth's surface, with 20 ppm. Some think that the abundance on Earth is much greater, but that the "lost" it may be located in the Earth's core due to the high density of the metal. The element does not occur free in nature, but niobium occurs in combination with other mineral elements. Minerals that contain niobium often also contain tantalum. Examples include columbite [(Fe, Mn)Nb₂O₆] and coltan [(Fe, Mn)(Nb, Ta)₂ >O₆]. Columbite-tantalite minerals (such as coltan) are generally found as accessory minerals in pegmatite granitic intrusions and in alkaline intrusive rocks. Less common are the niobates of calcium, uranium, thorium, and rare earth elements. Examples of such are pyrochlore [(Na, Ca)₂Nb₂O₆(OH, F)] and euxenite [(Y, Ca, Ce, U, Th)(Nb, Ta, Ti)₂O₆]. These large niobium deposits have been found associated with carbonatites (carbonate-silicate igneous rocks) and as a component of pyrochlore.

World production

Available data on global niobium production in 2019, in thousands of tons per year:

Post	Country	Thousands of tons
1	Brazil	88.9
2	Canada	6.8
	others	1.2

Uses

Steel production

Welders use niobium to bond stainless steel components. In addition, steel manufacturers add small amounts of a niobium-iron compound known as ferroniobium to increase the strength of their products, as well as resistance to temperatures and corrosion. Niobium-combined steel is widely used in the aerospace, chemical, electric power, and automotive industries.

Superconducting magnets

Alloyed with titanium, niobium can be extruded into a superconducting wire that can then be shaped into magnets that do not lose superconductivity when placed in external magnetic fields. There are also superconducting alloys of tin-niobium and aluminum-niobium. The metals find their use in gyroscopes for aerospace navigation, as well as magnetic resonance imaging artifacts.

Particle accelerators: High-energy physics researchers use some electron accelerators that include chambers molded from pure or alloyed niobium. When cooled to near absolute zero, these niobium chambers become highly magnetic and superconducting, allowing researchers to speed up subatomic particles without using increasing amounts of electricity.

Glass lenses and screens

Coating the crystal with a very fine powder of niobium enhances the crystal's ability to diffuse light without absorbing or refracting it. The coating also makes the glass more resistant to reflection. Niobium-coated glass finds its applications in camera lenses, as well as television and monitor screens. Niobium is also used as a protective layer for ceramic capacitors.

Sodium vapor lamps

A niobium-zirconium alloy serves as raw material for the metal base of some sodium vapor lamps. The alloy withstands the high temperatures reached by the lamp and does not become brittle with prolonged use.

Jewelry

In its natural state, niobium has a dull silver color. When the pure element is heated or passed through an electric field, however, it can take on many colors, ranging from blue to green and gold to red. This property has made niobium an increasingly popular choice for jewelers who want to create colored metal rings, studs, brooches, earrings and pins.

Coins

Given its property of changing its color by treating its surface layers, it is also used in the manufacture of bimetallic coins: 25 euros from Austria and 1 Latvia from Latvia.

Nomenclature

It is called niobium in honor of Niobe, daughter of Tantalus. Hatchett called it columbium, but thought he had it confused with tantalum; the name columbia is still used in some places. In 1844, H. Rose rediscovered it and gave it its current name. The name niobium was adopted by the IUPAC in 1950, 100 years after the controversy arose; despite everything, most chemists call it niobium, but many related to the metallurgy of the element (Anglo-Saxons) continue to call it columbium.

Production and appearance in nature

The largest niobium mine in the world is located in Araxá, Minas Gerais, Brazil, owned by the largest producer of Ferroniobio (FeNb) in the world, as well as other niobium-derived products, the company is called CBMM (Brazilian Company of Metallurgy and Mining)

Blomstrand first prepared it in 1864 by reduction: heating the chloride in an atmosphere of hydrogen. It was not until 1905 that a pure (Bolton) was obtained. It is never found in an elemental state and almost always appears accompanied by tantalum. It represents 2·10^-3% by weight of the bark.

The main mineral sources are: niobite (or columbite), niobite-tantalite and euxenite or polycrase [(Y,Ce,Er,U,Th,Ca,..)(Nb,Ta,Ti,Fe)₂OR₆]. Other minerals that contain it are: samarskite ((Y,Er,Ca,Fe,Mn,Sn,W,U,Ce)[(Nb,Ta)₂O₇]₃). fergusonite [(Nb,Ta)YO₄]. Large amounts of niobium have been found associated with silicocarbonate rocks (carbonatites).

Obtaining the metal involves a first stage of separating the tantalum using solvents and transforming it into Nb2O5. This is reduced in two stages with carbon; in the first, at 800 °C, NbC is formed, which in the second, at 2000 °C, acts as a reducing agent for the oxide and produces the metal.