niobium

Niobium, Nb, atomic number 41

Niobium price, occurrence, extraction and use

Niobium [ˈnioːp] (after Niobe, the daughter of tantalum) is a chemical element with the element symbol Nb and the atomic number 41. It is one of the transition metals, in the periodic table it is in the 5th period and the 5th subgroup (group 5) or vanadium group.

In the Anglo-Saxon language area is still today many metallurgists, material suppliers and in private use the long outdated designation columbium and the abbreviation Cb .

The rarely occurring heavy metal is gray in color and easily malleable. Niobium can be extracted from the minerals columbite, coltan (columbite-tantalite) and loparite. It is mainly used in metallurgy to make special steels and improve weldability.

Niobium was discovered by Charles Hatchett in 1801. He found it in columbite ore (first find in a river bed in Colombia), which had been sent to England by John Winthrop around 1700. Hatchett named the element columbium. Until the middle of the 19th century it was assumed that columbium and tantalum, discovered in 1802, were the same element, since they almost always occur together in minerals (paragenesis).

It was not until 1844 that the Berlin professor Heinrich Rose showed that niobium and tantalic acid are different substances. Not knowing about Hatchett's work and its naming, he named the rediscovered element because of its similarity to tantalum after Niobe, the daughter of Tantalus.

It was not until after 100 years of debate that the International Union of Pure and Applied Chemistry (IUPAC) put forward in 1950 niobium as the official name of the element.

In 1864 Christian Wilhelm Blomstrand succeeded in producing metallic niobium by reducing niobium chloride with hydrogen in the heat. In 1866, Charles Marignac confirmed tantalum as a separate element.

In 1907 Werner von Bolton produced very pure niobium by reducing a heptafluoroniobate with sodium.

occurrence 

Niobium is a rare element with a share of 1,8 · 10 in the earth's crust−3 %. It doesn't appear dignified. Due to the similar ionic radii, niobium and tantalum are always siblings. The most important minerals are columbite (Fe, Mn) (Nb, Ta)2O6, which is also known as niobite or tantalite depending on the content of niobium or tantalum, as well as pyrochlore (NaCaNb2O6F).

Other mostly rare minerals are:

  • Euxenite [(Y, Ca, Ce, U, Th) (Nb, Ta, Ti)2O6].
  • Olmsteadit (KFe2(Nb, Ta) [O | PO4]2 · H2O) and
  • Samarskit ((Y, He)4[(Nb, Ta)2O7]3)

Niobium deposits in carbonatites, where pyrochlore has accumulated in the weathered soils, are of economic interest. The annual production in 2006 was almost 60.000 t, 90% of which was mined in Brazil. In recent years production has increased significantly. Brazil and Canada are the main producers of niobium-containing mineral concentrates. Large ore deposits are also located in Nigeria, the Democratic Republic of the Congo, and Russia.

Extraction and presentation 

Since niobium and tantalum always occur together, niobium and tantalum ores are first digested together and then separated by fractional crystallization or different solubility in organic solvents. The first such industrial separation process was developed by Galissard de Marignac in 1866.

First, the ores are exposed to a mixture of concentrated sulfuric and hydrofluoric acid at 50–80 ° C. The complex fluorides [NbF7]2− and [TaF7]2−that are easily soluble.

The dipotassium salts of these fluorides can be formed by converting them into an aqueous phase and adding potassium fluoride. Only the tantalum fluoride is sparingly soluble in water and precipitates. The easily soluble niobium fluoride can thus be separated from the tantalum. Nowadays, however, separation by extraction with methyl isobutyl ketone is common. A third possibility of separation is by fractional distillation of the chlorides NbCl5 and TaCl5. These can be produced by reacting ores, coke and chlorine at high temperatures.

Niobium pentoxide is first produced from the separated niobium fluoride by reacting with oxygen. This is either first converted to niobium carbide with carbon and then reduced to the metal with further niobium pentoxide at 2000 ° C in a vacuum or obtained directly by aluminothermically. Most of the niobium for the steel industry is produced in this way, with iron oxide being added to obtain an iron-niobium alloy (60% niobium). If halides are used as the starting material for the reduction, this is done with sodium as the reducing agent.

Features

Niobium is a ductile heavy metal with a gray sheen. The oxidation states −3, −1, 0, +1, +2, +3, +4, +5 are known. As with vanadium, which is above niobium in the periodic table, the +5 level is the most consistent. The chemical behavior of niobium is almost identical to that of tantalum, which is directly below niobium in the periodic table.

As a result of the formation of a passive layer (protective layer), niobium is very resistant to air. Most acids therefore do not attack it at room temperature. Only hydrofluoric acid, especially when mixed with nitric acid, and hot, concentrated sulfuric acid, corrode metallic niobium quickly. Niobium is also unstable in hot alkalis, as they dissolve the passive layer. At temperatures above 200 ° C it begins to oxidize in the presence of oxygen. Welding processing of niobium must take place in a protective gas atmosphere because of its instability in air.

The addition of tungsten and molybdenum to niobium increases its heat resistance and aluminum increases its strength.

The high transition temperature of niobium of 9,25 K, below which it is superconducting, and its ability to easily absorb gases are remarkable. One gram of niobium can absorb 100 cm³ of hydrogen at room temperature, which was previously used in vacuum tube technology.

Usage 

Niobium is used as an alloy additive for stainless steels, special stainless steels (e.g. pipes for hydrochloric acid production) and non-ferrous alloys, as niobium-alloyed materials are characterized by increased mechanical strength. Even in concentrations of 0,01 to 0,1 mass percent, niobium in combination with thermomechanical rolling can significantly increase the strength and toughness of steel. First attempts to use niobium as an alloying element (replacement of tungsten) took place in the USA in 1925. Steels refined in this way are often used in pipeline construction. As a strong carbide former, niobium is also added to welding consumables to bind carbon.

Other uses include:

  • Application in nuclear technology because of the low capture cross-section for thermal neutrons.
  • Production of niobium-stabilized welding electrodes as welding fillers for stainless steels, special stainless steels and nickel-based alloys
  • Because of its bluish color, it is used for piercing jewelry and jewelry making.
  • In the case of coins with niobium (bimetal coins), the color of the niobium core can vary greatly due to physical processes (e.g. 25 euro coins from Austria).
  • Significant quantities are used as ferroniobium and nickel niobium in the metallurgical industry for the production of superalloys (nickel, cobalt and iron-based alloys). Static parts for stationary and flying gas turbines, rocket parts and heat-resistant components for furnace construction are manufactured from this.
  • Niobium is used as the anode material in niobium electrolytic capacitors. An oxide of niobium, niobium (V) oxide, has a high dielectric strength. It is applied to the surface of the niobium anode in a so-called forming process and serves as a dielectric in this capacitor. Niobium electrolytic capacitors compete with the more popular tantalum electrolytic capacitors.
  • Are the glass bulbs of halogen bulbs outside with z. B. niobium, part of the thermal radiation of the tungsten filament is reflected back to the inside. As a result, a higher operating temperature and thus greater luminous efficiency can be achieved with lower energy consumption.
  • As a catalyst (e.g. in hydrochloric acid production and in the production of alcohols from butadiene),
  • As potassium niobate (chemical compound of potassium, niobium and oxygen), which is used as a single crystal in laser technology and for non-linear optical systems
  • Use as electrode material for high pressure sodium vapor lamps
  • Superconductivity: At temperatures below 9,5 K, pure niobium is a type II superconductor. Niobium alloys (with N, O, Sn, AlGe, Ge) belong to the three pure elements niobium, vanadium and technetium as well as type II substances -Superconductors are: The transition temperatures of these alloys are between 18,05 K (niobium tin, Nb3Sn) and 23,2 K (niobium germanium, Nb3Ge). Superconducting cavity resonators made from niobium are used in particle accelerators (including XFEL and FLASH at DESY in Hamburg). To generate high magnetic fields of up to around 20 Tesla, superconducting magnets with wires made of niobium-tin and niobium-titanium are used. For example, 600 tons of niobium-tin and 250 tons of niobium-titanium are used for the experimental ITER fusion reactor. The superconducting magnets of the LHC are also made of niobium alloys.

safety instructions

Although niobium is considered to be non-toxic, metallic niobium dust irritates the eyes and skin. Niobium dust is highly flammable.

A physiological mode of action of niobium is unknown.

General
Name, symbol, atomic number Niobium, Nb, 41
Series Transition metals
Group, period, block 5, 5, d
Appearance gray metallic
CAS number 7440-03-1
Mass fraction of the earth shell 19 ppm
Atomic
atomic mass 92,90638 u
Atomic radius (calculated) 145 (164) pm
Covalent radius 137 pm
electron configuration [Kr] 4d4 5s1
1. ionization 652,1 kJ / mol
2. ionization 1380 kJ / mol
3. ionization 2416 kJ / mol
4. ionization 3700 kJ / mol
5. ionization 4877 kJ / mol
Physically
Physical state fixed
crystal structure cubic body-centered
density 8,57 g / cm3 (20 ° C)
Mohs hardness 6,0
magnetism paramagnetic (\ Chi_ {m} = 2,3 10−4)
melting point 2750 K (2477 ° C)
boiling point 5017 K (4744 ° C)
Molar volume 10,83 · 10−6 m3/ mol
Heat of vaporization 690 kJ / mol
heat of fusion 26,8 kJ / mol
speed of sound 3480 m / s at 293,15 K
Electric conductivity 6,58 · 106 A / (V · m)
thermal conductivity 54 W / (m K)
Chemical
oxidation states 2, 5
normal potential −1,1 V (Nb2+ + 2 e- → Nb)
electronegativity 1,6 (Pauling scale)
isotope
isotope NH t1/2 ZA ZE (MeV) ZP
91Nb {Syn.} 680 a ε 1,253 91Zr
92Nb {Syn.} 3,47 · 107 a ε 2,006 92Zr
β- 0,356 92Mo
93Nb 100 % Sturdy
93metaNb {Syn.} 16,13 a IT 0,031 93Nb
94Nb {Syn.} 20300 a β- 2,045 94Mo
95Nb {Syn.} 34,975 d β- 0,926 95Mo
NMR properties
Spin γ in
rad * T−1· s−1
Er(1H) fL consider
W = 4,7 T
in MHz
93Nb 9/2 6,567 · 107 0,488 24,47
safety instructions
GHS hazardous substances labeling

02 - Light / Extremely flammable

Danger

H and P phrases H: 250
EUH: no EUH rates
P: 222-231-422
Hazardous Informationpowder

Highly flammable
Light-
flammable
(F)
R and S phrases R: 11
S: 43

 

Niobium prices

Niobium price -> prices for strategic metals

 

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