Niobium
Niobium | |||||||||||||||||||||||||||||||||||||||||
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Pronunciation | /naɪˈoʊbiəm/ | ||||||||||||||||||||||||||||||||||||||||
Appearance | Gray metallic, bluish when oxidized | ||||||||||||||||||||||||||||||||||||||||
Standard atomic weight Ar°(Nb) | |||||||||||||||||||||||||||||||||||||||||
Niobium in the periodic table | |||||||||||||||||||||||||||||||||||||||||
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kJ/mol | |||||||||||||||||||||||||||||||||||||||||
Heat of vaporization | 689.9 kJ/mol | ||||||||||||||||||||||||||||||||||||||||
Molar heat capacity | 24.60 J/(mol·K) | ||||||||||||||||||||||||||||||||||||||||
Vapor pressure
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Atomic properties | |||||||||||||||||||||||||||||||||||||||||
Discovery | Charles Hatchett (1801) | ||||||||||||||||||||||||||||||||||||||||
First isolation | Christian Wilhelm Blomstrand (1864) | ||||||||||||||||||||||||||||||||||||||||
Recognized as a distinct element by | Heinrich Rose (1844) | ||||||||||||||||||||||||||||||||||||||||
Isotopes of niobium | |||||||||||||||||||||||||||||||||||||||||
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Niobium is a
English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. German chemist Heinrich Rose determined in 1846 that tantalum ores contain a second element, which he named niobium. In 1864 and 1865, a series of scientific findings clarified that niobium and columbium were the same element (as distinguished from tantalum), and for a century both names were used interchangeably. Niobium was officially adopted as the name of the element in 1949, but the name columbium remains in current use in metallurgy in the United States.
It was not until the early 20th century that niobium was first used commercially. Niobium is an important addition to high-strength low-alloy steels. Brazil is the leading producer of niobium and
Niobium is used in various
History
Niobium was
Subsequently, there was considerable confusion[13] over the difference between columbium (niobium) and the closely related tantalum. In 1809, English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm3, and tantalum—tantalite, with a density over 8 g/cm3, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum.[13] This conclusion was disputed in 1846 by German chemist Heinrich Rose, who argued that there were two different elements in the tantalite sample, and named them after children of Tantalus: niobium (from Niobe) and pelopium (from Pelops).[14][15] This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements pelopium, ilmenium, and dianium[16] were in fact identical to niobium or mixtures of niobium and tantalum.[17]
The differences between tantalum and niobium were unequivocally demonstrated in 1864 by
De Marignac was the first to prepare the metal in 1864, when he
Naming the element
Columbium (symbol Cb)
Characteristics
Physical
Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), with an electron configuration in the outermost shells atypical for group 5. Similarly atypical configurations occur in the neighborhood of ruthenium (44), rhodium (45), and palladium (46).
Z | Element | No. of electrons/shell |
---|---|---|
23 | vanadium | 2, 8, 11, 2 |
41 | niobium | 2, 8, 18, 12, 1 |
73 | tantalum | 2, 8, 18, 32, 11, 2 |
105 | dubnium | 2, 8, 18, 32, 32, 11, 2 |
Although it is thought to have a
Niobium becomes a
When very pure, it is comparatively soft and ductile, but impurities make it harder.[36]
The metal has a low capture cross-section for thermal neutrons;[37] thus it is used in the nuclear industries where neutron transparent structures are desired.[38]
Chemical
The metal takes on a bluish tinge when exposed to air at room temperature for extended periods.[39] Despite a high melting point in elemental form (2,468 °C), it is less dense than other refractory metals. Furthermore, it is corrosion-resistant, exhibits superconductivity properties, and forms dielectric oxide layers.
Niobium is slightly less
Isotopes
Niobium in Earth's crust comprises one stable
At least 25
Occurrence
Niobium is estimated to be the
The three largest currently mined deposits of pyrochlore, two in Brazil and one in Canada, were found in the 1950s, and are still the major producers of niobium mineral concentrates.
The third largest producer of niobium is the carbonatite-hosted
Production
After the separation from the other minerals, the mixed oxides of tantalum Ta2O5 and niobium Nb2O5 are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acid:[42]
- Ta2O5 + 14 HF → 2 H2[TaF7] + 5 H2O
- Nb2O5 + 10 HF → 2 H2[NbOF5] + 3 H2O
The first industrial scale separation, developed by
- H2[NbOF5] + 2 KF → K2[NbOF5]↓ + 2 HF
Followed by:
- 2 H2[NbOF5] + 10 NH4OH → Nb2O5↓ + 10 NH4F + 7 H2O
Several methods are used for the
- 3 Nb2O5 + Fe2O3 + 12 Al → 6 Nb + 2 Fe + 6 Al2O3
Small amounts of oxidizers like
As of 2013[update], CBMM from Brazil controlled 85 percent of the world's niobium production.[61] The United States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006.[62][63] Worldwide resources are estimated to be 4.4 million tonnes.[63] During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995.[64] Between 2009 and 2011, production was stable at 63,000 tonnes per year,[65] with a slight decrease in 2012 to only 50,000 tonnes per year.[66]
Country | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Brazil | 30,000 | 22,000 | 26,000 | 29,000 | 29,900 | 35,000 | 40,000 | 57,300 | 58,000 | 58,000 | 58,000 | 58,000 | 63,000 | 53,100 | 53,000 | 58,000 | 57,000 | 60,700 | 59,000 | 88,900 | 59,800 |
Canada | 2,290 | 3,200 | 3,410 | 3,280 | 3,400 | 3,310 | 4,167 | 3,020 | 4,380 | 4,330 | 4,420 | 4,630 | 5,000 | 5,260 | 5,000 | 5,750 | 6,100 | 6,980 | 7,700 | 6,800 | 6,500 |
Australia | 160 | 230 | 290 | 230 | 200 | 200 | 200 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Nigeria | 35 | 30 | 30 | 190 | 170 | 40 | 35 | ? | ? | ? | ? | ? | ? | ? | ? | 29 | 104 | 122 | 181 | 150 | ? |
Rwanda | 28 | 120 | 76 | 22 | 63 | 63 | 80 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Mozambique | ? | ? | 5 | 34 | 130 | 34 | 29 | ? | ? | 4 | 10 | 29 | 30 | 20 | ? | ? | ? | ? | ? | ? | ? |
Congo D.R. | ? | 50 | 50 | 13 | 52 | 25 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
World | 32,600 | 25,600 | 29,900 | 32,800 | 34,000 | 38,700 | 44,500 | 60,400 | 62,900 | 62,900 | 62,900 | 63,000 | 50,100 | 59,400 | 59,000 | 64,300 | 63,900 | 69,100 | 68,200 | 97,000 | 67,700 |
Lesser amounts are found in Malawi's Kanyika Deposit (Kanyika mine).
Compounds
In many ways, niobium is similar to
Although niobium exhibits all of the formal oxidation states from +5 to −1, the most common compounds have niobium in the +5 state.[36] Characteristically, compounds in oxidation states less than 5+ display Nb–Nb bonding. In aqueous solutions, niobium only exhibits the +5 oxidation state. It is also readily prone to hydrolysis and is barely soluble in dilute solutions of hydrochloric, sulfuric, nitric and phosphoric acids due to the precipitation of hydrous Nb oxide.[59] Nb(V) is also slightly soluble in alkaline media due to the formation of soluble polyoxoniobate species.[70][71]
Oxides, niobates and sulfides
Niobium forms oxides in the oxidation states +5 (Nb2O5),[72] +4 (NbO2), and the rarer oxidation state, +2 (NbO).[73] Most common is the pentoxide, precursor to almost all niobium compounds and alloys.[56][74] Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are lithium niobate (LiNbO3) and lanthanum niobate (LaNbO4). In the lithium niobate is a trigonally distorted perovskite-like structure, whereas the lanthanum niobate contains lone NbO3−
4 ions.[56] The layered niobium sulfide (NbS2) is also known.[36]
Materials can be coated with a thin film of niobium(V) oxide chemical vapor deposition or atomic layer deposition processes, produced by the thermal decomposition of niobium(V) ethoxide above 350 °C.[75][76]
Halides
Niobium forms halides in the oxidation states of +5 and +4 as well as diverse
Anionic halide compounds of niobium are well known, owing in part to the
- Nb2Cl10 + 2 Cl− → 2 [NbCl6]−
As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being [Nb6Cl18]4−.[78]
Nitrides and carbides
Other
Applications
Out of 44,500 tonnes of niobium mined in 2006, an estimated 90% was used in high-grade structural steel. The second-largest application is superalloys.[80] Niobium alloy superconductors and electronic components account for a very small share of the world production.[80]
Steel production
Niobium is an effective
These same niobium alloys are often used in pipeline construction.[83][84]
Superalloys
Quantities of niobium are used in nickel-, cobalt-, and iron-based superalloys in proportions as great as 6.5%[81] for such applications as jet engine components, gas turbines, rocket subassemblies, turbo charger systems, heat resisting, and combustion equipment. Niobium precipitates a hardening γ''-phase within the grain structure of the superalloy.[85]
One example superalloy is Inconel 718, consisting of roughly 50% nickel, 18.6% chromium, 18.5% iron, 5% niobium, 3.1% molybdenum, 0.9% titanium, and 0.4% aluminium.[86][87]
These superalloys were used, for example, in advanced air frame systems for the
Niobium-based alloys
C-103 alloy was developed in the early 1960s jointly by the Wah Chang Corporation and Boeing Co. DuPont, Union Carbide Corp., General Electric Co. and several other companies were developing Nb-base alloys simultaneously, largely driven by the Cold War and Space Race. It is composed of 89% niobium, 10% hafnium and 1% titanium and is used for liquid-rocket thruster nozzles, such as the main engine of the Apollo Lunar Modules.[88]
The
The nozzle of the
Niobium-based superalloys are used to produce components to hypersonic missile systems.[90]
Superconducting magnets
Other superconductors
The
The high sensitivity of superconducting niobium nitride bolometers make them an ideal detector for electromagnetic radiation in the THz frequency band. These detectors were tested at the Submillimeter Telescope, the South Pole Telescope, the Receiver Lab Telescope, and at APEX, and are now used in the HIFI instrument on board the Herschel Space Observatory.[98]
Other uses
Electroceramics
Hypoallergenic applications: medicine and jewelry
Niobium and some niobium alloys are physiologically inert and hypoallergenic. For this reason, niobium is used in prosthetics and implant devices, such as pacemakers.[101] Niobium treated with sodium hydroxide forms a porous layer that aids osseointegration.[102]
Like titanium, tantalum, and aluminium, niobium can be heated and
Numismatics
Niobium is used as a precious metal in commemorative coins, often with silver or gold. For example, Austria produced a series of silver niobium euro coins starting in 2003; the colour in these coins is created by the diffraction of light by a thin anodized oxide layer.[106] In 2012, ten coins are available showing a broad variety of colours in the centre of the coin: blue, green, brown, purple, violet, or yellow. Two more examples are the 2004 Austrian €25 150-Year Semmering Alpine Railway commemorative coin,[107] and the 2006 Austrian €25 European Satellite Navigation commemorative coin.[108] The Austrian mint produced for Latvia a similar series of coins starting in 2004,[109] with one following in 2007.[110] In 2011, the Royal Canadian Mint started production of a $5 sterling silver and niobium coin named Hunter's Moon[111] in which the niobium was selectively oxidized, thus creating unique finishes where no two coins are exactly alike.
Other
The arc-tube seals of high pressure
Niobium is used in arc welding rods for some stabilized grades of stainless steel[115] and in anodes for cathodic protection systems on some water tanks, which are then usually plated with platinum.[116][117]
Niobium is used to make the high voltage wire of the
Research has been conducted to allow niobium based catalysts to be used for recycling polyethylene terephthalate (PET).[119][120]
Precautions
Hazards | |
---|---|
NFPA 704 (fire diamond) |
Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is often used in jewelry and has been tested for use in some medical implants.[121][122]
Short- and long-term exposure to niobates and niobium chloride, two water-soluble chemicals, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a median lethal dose (LD50) between 10 and 100 mg/kg.[123][124][125] For oral administration the toxicity is lower; a study with rats yielded a LD50 after seven days of 940 mg/kg.[123]
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External links
- Los Alamos National Laboratory – Niobium
- Tantalum-Niobium International Study Center
- Niobium for particle accelerators eg ILC. 2005
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- Niobium at The Periodic Table of Videos(University of Nottingham)