Niobium, Nb, Atomic number 41

General

Niobium [nio ː p] (by Niobe, Tochter der des Tantalos) 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 5. Period and the 5.Nebengruppe (group 5) oder Vanadiumgruppe.

In Anglo-Saxon world is still by many metallurgists, Material suppliers and in private life, the old name for some time Columbium and the abbreviation Cb used.

The rarely occurring heavy metal is gray in color and well-malleable. Niobium can from the minerals columbite, Coltan (Columbit-Tantalit) be recovered and loparite. It is mainly used in metallurgy, to special steel to improve weldability and produce.

Niobium was 1801 discovered by Charles Hatchett. He found it in columbite ore (First record in a riverbed in Colombia), to the 1700 had been sent to England by John Winthrop. Hatchett gave the element the name Columbium. By the middle of the 19. Century, it was assumed, that it is at columbium and the 1802 discovered tantalum is the same element, because they occur together in minerals almost always (Paragenese).

Only 1844 showed the Berlin Professor Heinrich Rose, that niobium- tantalum and acid substances are different. Not knowing about the works and Hatchett's name, He called the rediscovered element due to its similarity with tantalum by Niobe, Tochter der of Tantalus.

Only after 100 Years of debate laid the International Union of Pure and Applied Chemistry (IUPAC) 1950 Niobium established as the official name of the element.

1864 Christian Wilhelm Blomstrand managed the production of metallic niobium from niobium chloride by reduction with hydrogen in the heat. 1866 Charles confirmed Marignac tantalum as a separate element.

1907 presented by Werner von Bolton reduction with sodium Heptafluoroniobats a very pure niobium represents.

Occurrence

Niobium is a rare element in the earth's crust, with a share of 1,8 · 10−3 %. It's not dignified ago. Due to the similar ionic radii are always twinned niobium and tantalum from. The main minerals are columbite (Faith, Mn)(Nb, Take)2The6, which is referred to, depending on the content of niobium or tantalum as niobite or tantalite, and pyrochlore (NaCaNb2The6F).

Other minerals are usually rare:

  • Euxenit [(And, As, This, You, Th)(Nb, Take, You)2The6].
  • Olmsteadit (KFe2(Nb,Take)[The|PO4]2 · H2The) and
  • Samarskit ((And,He)4[(Nb,Take)2The7]3)

Of economic interest Niobvorkommen in carbonatites, in the residual soils are enriched pyrochlore has. The annual production was 2006 bei fixed 60.000 t, 90 % which were promoted in Brazil. In recent years, production has risen sharply. Brazil and Canada are the major producers of niobium mineral concentrates. Large ore deposits are located in Nigeria, in the Democratic Republic of Congo and Russia.

Extraction and representation

Since niobium and tantalum always occur together, niobium are- and tantalum first opened up together and then separated by fractional crystallization or unterschiedlicheLöslichkeit in organic solvents. The first such industrial separation processes has been 1866 developed by de Marignac Galissard.

First the ore is a mixture of concentrated sulfuric- exposed and hydrofluoric acid at 50-80 ° C.. This forms the complex fluorides [NbF7]2− and [TaF7]2−, which are readily soluble.

By conversion into an aqueous phase and addition of potassium fluoride, the dipotassium salts of these fluorides are formed. It is only the tantalum fluoride sparingly soluble in water and precipitates. The slightly soluble niobium fluoride can be separated from the tantalum. But today is a separation by extraction with methyl isobutyl ketone usual. A third possibility is that the separation by fractional distillation of the chlorides NbCl5 and TaCl5. These are obtainable by reaction of ores, Coke and chlorine represented at high temperatures.

Niobium pentoxide from niobium fluoride is separated by reaction with oxygen initially produced. This is first reacted with either carbon to niobium carbide and niobium pentoxide with further in 2000 ° C in vacuum reduced to metal or obtained directly aluminothermically. Most of the niobium to the steel industry is thus produced, it is also added to iron oxide, an iron-niobium alloy (60 % Niobium) to obtain. Halides are used as starting material for the reduction, this is done with sodium as the reducing agent.

Properties

Niobium is a shiny gray, ductile heavy metal. The oxidation states are known -3, −1, 0, +1, +2, +3, +4, +5. Who beim Vanadium, standing in the periodic table of the niobium, is the stage +5 most resistant. The chemical behavior of niobium is almost identical to that of tantalum, which is directly below niobium in the periodic table.

Following the formation of a passive layer (Protective layer) Niobium is very resistant to air. Most acids at room temperature does not fall so. Only hydrofluoric acid, especially in mixture with nitric acid and hot concentrated sulfuric acid will corrode metallic niobium rapidly. In hot alkali niobium is also unstable, because they dissolve the passive film. At temperatures above 200 ° C it begins to oxidize in the presence of oxygen. A welding of niobium processing must take place because of its instability in air under a protective gas atmosphere.

The addition of niobium, tungsten and molybdenum to increase its heat resistance, Its strength aluminum.

Noteworthy are the high transition temperature of niobium from 9,25 K, it is below the superconducting, and its property, readily absorb gases. Thus, at room temperature, a niobium grams 100 absorb hydrogen cc, what was previously exploited in the vacuum tube technology.

Use

Niobium is used as an alloying element for stainless steels, Special stainless steels (of. B. Tubes for hydrochloric acid production) and non-ferrous alloys used, because niobium-alloyed materials are characterized by an increased mechanical strength. At concentrations 0,01 to 0,1 Mass percent niobium to increase the strength and toughness of steel in combination with essential thermomechanical rolling. Initial trials on the use of niobium as an alloying element (Replacement of tungsten) were 1925 place in the USA. Of such coated steels are widely used in pipeline construction (Pipeline construction) used. As a strong carbide former is niobium alloyed welding consumables in the setting of carbon.

Among the other uses to perform:

  • Application in nuclear technology due to the low capture cross section for thermal neutrons.
  • Niobstabilisierter production welding electrodes for welding stainless steels as, Special stainless steels and nickel-based alloys.
  • Because of its bluish color, it is used for body piercing jewelry and for making jewelery.
  • For coins with niobium (Bimetallic coin) the color of the niobium core by physical methods vary widely (of. B. at 25 euro coins from Austria).

  • Significant quantities are as Ferroniobium and nickel niobium in the metallurgical industry for the production of super alloys (Nickel-, Cobalt- and iron-based alloys) used. Hence, static and flying parts for stationary gas turbines, Missile parts and heat-resistant components for furnaces manufactured.
  • Niobium is used as anode material in Niobium Electrolytic Capacitors. An oxide of niobium, Niobium(In)-oxide, has a high dielectric strength. It is called a. Formierverfahren applied on the surface of Niobanode and serves in this capacitor as a dielectric. Niobium electrolytic capacitors are in competition with the better-known tantalum electrolytic capacitors.
  • If the glass bulb of halogen bulbs outside with z. B. Vaporized niobium, thereby, a part of the heat radiation from the tungsten filament back inwardly reflected. This allows for lower power consumption, a higher operating temperature and thus higher light yield can be achieved.
  • As a catalyst (of. B. in hydrochloric acid production and in the production of alcohols from butadiene),
  • Als Kaliumniobat (chemical compound composed of potassium, Niobium and oxygen), The single crystals used in laser technology and non-linear optical systems is used and
  • Use as electrode material for sodium vapor high pressure lamp
  • Superconductivity: At temperatures below 9,5 K is pure niobium a Type II superconductor. Niobium alloys (with N, The, Sn, AlGe, Ge) include not only the three pure elements niobium, Vanadium and technetium to the substances, the type-II superconductors: The transition temperatures of these alloys are between 18,05 K (Niobzinn, Nb3Sn) and 23,2 K (Niobgermanium, Nb3Ge). Made of niobium superconducting cavity resonators are inTeilchenbeschleunigern (you. a. XFEL and FLASH at DESY in Hamburg) used. To generate high magnetic fields up to about 20 Tesla superconducting magnets will be while using wires made of niobium-tin and niobium-titanium used. Thus, for the experimental ITER fusion reactor 600 t niobium-tin and 250 t niobium-titanium used. Also, the superconducting magnets of the LHC consist of niobium.

Safety

Niobium is regarded as non-toxic, However, irritated eyes and skin metallic Niobstaub. Niobstaub is highly flammable.

A physiological effect of the niobium is unknown.

General
Name, Symbol,Atomic number Niobium, Nb, 41
Series Transition metals
group, Period, Block 5, 5, d
Appearance gray metallic
CAS-Nummer 7440-03-1
Mass fraction of derErdhülle 19 ppm
Atomic
Atomic mass 92,90638 you
Atomradius (calculated) 145 (164) pm
Kovalenter 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 body centered cubic
Density 8,57 g/cm3 (20 ° C)
Mohs 6,0
Magnetism paramagnetisch (\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
Schmelzwärme 26,8 kJ / mol
Speed ​​of sound 3480 m / s at 293,15 K
Electrical conductivity 6,58 · 106 A/(In · m)
Thermal conductivity 54 W /(m · K)
Chemical
Oxidation states 2, 5
Normalpotential -1.1 V (Nb2+ + 2 and → Nb)
Electronegativity 1,6 (Pauling-Scale)
Isotope
Isotope NH t1/2 ZA ZE (MeV) ZP
91Nb {a son.} 680 a e 1,253 91Zr
92Nb {a son.} 3,47 · 107 a e 2,006 92Zr
b 0,356 92Mo
93Nb 100 % Stable
93goalNb {a son.} 16,13 a IT 0,031 93Nb
94Nb {a son.} 20300 a b 2,045 94Mo
95Nb {a son.} 34,975 d b 0,926 95Mo
NMR properties
Spin γ in
wheel·T−1·s−1
Itr(1H) fThe at
B = 4,7 T
in MHz
93Nb 9/2 6,567 · 107 0,488 24,47
Safety
GHS Hazard Identification

02 – Leicht-/Hochentzündlich

Risk

H- and P-sets H: 250
EUH: no EUH sets
P: 222-​231-​422
Hazardous Materials IdentificationPowder

Leichtentzündlich
Slightly-
flammable
(F)
R- and S-phrases R: 11
S: 43

 

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