Niobium

{ syn. }

{ syn. }

100 %

{ syn. }

{ syn. }

{ syn. }

Risk

Powder

Niobium [ nio ː p] (after Niobe, daughter of Tantalus ) is a chemical element with the atomic symbol Nb and atomic number 41 It is one of the transition metals in the periodic table it is in the fifth period and the fifth sub-group ( Group 5 ) or vanadium group.

In the Anglo -Saxon world is still used today by many metallurgists, material providers and private handling the already long outdated name columbium and the abbreviation Cb.

The rarely occurring heavy metal is gray in color and well malleable. Niobium can be recovered from the ore columbite, coltan ( columbite - tantalite ) and loparite. It is mainly used in metallurgy to produce special steels and improving the weldability.

History

Niobium was discovered in 1801 by Charles Hatchett. He found it in a sample of columbite ore from a riverbed in Massachusetts, which had been sent to England to 1743. Hatchett named the element columbium ( to Columbia, the personification of the United States). Until the mid-19th century, it was assumed that it is the same element in columbium and tantalum discovered in 1802, as they almost always occur together in minerals ( paragenesis ).

Only in 1844 was the Berlin Professor Heinrich Rose, that niobium and tantalum acid are different substances. Not to work Hatchetts and its naming knowing he named the rediscovered element due to its similarity with tantalum after Niobe, daughter of Tantalus.

Only after 100 years of dispute, the International Union of Pure and Applied Chemistry (IUPAC) in 1950 put niobium established as the official name of the element.

Succeeded in 1864 William Christian Blomstrand producing niobium metal by the reduction of niobium with hydrogen in the heat. 1866 confirmed Charles Marignac tantalum as a separate element.

In 1907, Werner von Bolton by reduction with sodium Heptafluoroniobats a very pure niobium dar.

Occurrence

Niobium is a rare element with a portion of the earth's crust of 1.8 × 10-3 %. It's not dignified. Due to the similar ionic radii of niobium and tantalum occur is always found together. The main minerals are columbite (Fe, Mn) (Nb, Ta) 2O6, which is called depending on the content of niobium or tantalum as Niobit or tantalite, and pyrochlore ( NaCaNb2O6F ).

More generally rare minerals are:

• Euxenite [ (Y, Ca, Ce, U, Th) (Nb, Ta ​​, Ti) 2O6 ].
• Olmsteadit ( KFE2 (Nb, Ta) [O | PO4 ] 2 · H2O) and
• Samarskite ( (Y, Er) 4 [ (Nb, Ta) 2o7 ] 3)

Of economic interest Niobvorkommen are in carbonatites, in their weathering soils pyrochlore has enriched. The annual production in 2006 was almost 60,000 tonnes, 90 % of 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, the Democratic Republic of Congo and Russia.

Production and representation

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 in 1866 by Galissard de Marignac.

First, the ore is subjected to a mixture of concentrated sulfuric acid and hydrofluoric acid at 50-80 ° C.. And [ TaF7 ] - 2 -, which are readily soluble In this case, the complex fluorides [ NbF7 ] 2 form.

By conversion into an aqueous phase and addition of potassium fluoride, the dipotassium salts of these fluorides can be formed. Only the tantalum fluoride in water is slightly soluble and precipitates. The slightly soluble niobium fluoride can be separated from the tantalum. These days, however, a separation by extraction with methyl isobutyl ketone usual. A third possibility is the separation by fractional distillation of the chlorides NbCl5 and TaCl5. These can be represented by the reaction of ore, coke and chlorine at high temperatures.

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

Properties

Niobium is a shiny gray, ductile heavy metal. The oxidation -3, -1, 0, 1, 2, 3, 4, 5, are known. As in the case of vanadium, which is the periodic table on the niobium, the state 5 is most stable. The chemical behavior of niobium is almost identical to that of tantalum, which is in the periodic table directly below niobium.

Due to the formation of a passive layer (protective layer) is niobium in air very stable. Most acids attack it at room temperature therefore not to. Only hydrofluoric acid, especially in the mixture with nitric acid and hot concentrated sulfuric acid corrode metallic niobium rapidly. In hot alkaline niobium is also impermanent, because they dissolve the passive layer. At temperatures above 200 ° C it begins to oxidize in the presence of oxygen. A welding machining of niobium must occur under a protective gas atmosphere because of its instability in air.

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

Remarkable are the high transition temperature of niobium of 9.25 K, below which it is superconducting, as well as his property, easily accommodate gases. At room temperature can take a gram of niobium 100 cc of hydrogen, which was formerly used in the vacuum tube technology.

Use

Niobium (eg tubes for hydrochloric acid production) and non-ferrous alloys used as an alloying element for stainless steels, stainless steels, as niobium - alloyed materials are characterized by an increased mechanical strength. Already in concentrations of 0.01 to 0.1 percent by weight niobium may increase in combination with thermomechanical rolling, the strength and toughness of steel considerably. Initial attempts to use of niobium as an alloying element (replacement of tungsten) found in 1925 in the USA. Of such refined steels ( pipeline construction) are frequently used in pipeline construction. As a strong carbide former niobium is alloyed in welding consumables for binding carbon.

As more uses are to perform:

• Application in nuclear technology due to the low capture cross section for thermal neutrons.
• Production niobstabilisierter welding electrodes as filler for stainless steels, 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 coins ) the color of the niobium core can vary greatly by physical processes (eg, at 25 - euro coins from Austria ).

• Significant quantities are used as ferro-niobium and nickel niobium in the metallurgical industry for the production of super alloys ( nickel, cobalt and iron-based alloys). From this static parts for stationary and flying gas turbines, rocket parts and heat-resistant components for furnace construction are made.
• Niobium is used as the anode material in the niobium electrolytic capacitors. An oxide of niobium, niobium (V ) oxide, having a high withstand voltage. It is applied in a so-called Formierverfahren on the surface of niobium anode and serves as dielectric, this capacitor. Niobium electrolytic capacitors are in competition with the better-known tantalum electrolytic capacitors.
• The glass bulb of halogen incandescent lamps with the outside vapor deposition, for example, niobium, wherein part of the heat radiation from the tungsten filament is reflected back towards the inside. Thereby can be achieved with lower energy consumption and thus a higher operating temperature greater light output.
• As a catalyst (e.g., hydrochloric acid in the production of biodiesel and synthesis in the production of alcohols from butadiene ).
• As potassium ( chemical compound of potassium, niobium and oxygen), which is used as a single crystal in laser technology and nonlinear optical systems use and
• Use as an electrode material for sodium vapor high pressure lamp
• Superconductivity: At temperatures below 9.5 K pure niobium is a superconductor of type II niobium alloys ( with N, O, Sn, AlGe, Ge) include in addition to the three pure elements niobium, vanadium and technetium to the substances, the type II superconductors are: The critical temperatures of these alloys are between 18.05 K ( niobium-tin, Nb3Sn ) and 23.2 K ( Niobgermanium, Nb3Ge ). Made of niobium superconducting cavity resonators (among XFEL and FLASH at DESY in Hamburg ) used in particle accelerators. In order to generate high magnetic fields up to about 20 Tesla superconducting magnets are used here with wires made ​​of niobium - tin and niobium - titanium. So 600 t and 250 t niobium-tin niobium-titanium are used for the experimental fusion reactor ITER. The superconducting magnets of the LHC are made of niobium.

Safety

Although niobium is considered not toxic but irritated metallic Niobstaub eyes and skin. Niobstaub is highly flammable.

A physiological effect of the niobium is unknown.