Niobium (
Greek mythologyGreek mythology is the body of myths and legends belonging to the ancient Greeks concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
:
NiobeNiobe was a daughter of Tantalus and the sister of Pelops, all of whom figure in Greek mythology.Her father was the ruler of a city called either under his name, as "Tantalis" or "the city of Tantalus", or as "Sipylus", in reference to Mount Sipylus at the foot of which his city was located and...
, daughter of
TantalusIn Greek mythology Tantalus was a son of Zeus and the nymph Plouto. Thus he was a king in the primordial world, the father of a son Broteas whose very name signifies "mortals" . Other versions name his father as Tmolus "wreathed with oak," son of Sipylus, a king of Lydia. Both Tmolus and Mount...
), or
columbium , is the
chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
with the symbol
Nb and the
atomic numberIn chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
41. A rare, soft, grey, ductile
transition metalThe term transition metal has two possible meanings:*In the past it referred to any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table...
, niobium is found in the minerals
pyrochlorePyrochlore 2Nb2O6 is a solid solution between the niobium end member , and the tantalum end member . The mineral is associated with the metasomatic end stages of magmatic intrusions...
, the main commercial source for niobium, and
columbiteColumbite, also called niobite, niobite-tantalite and columbate [2O6], is a black mineral group that is an ore of niobium and tantalum. It has a submetallic luster and a high specific gravity and is a niobate of iron and manganese, containing tantalate of iron...
.
Niobium has physical and chemical properties similar to those of the element
tantalumTantalum is a chemical element with the symbol Ta and atomic number 73. A rare, hard, blue-gray, lustrous transition metal, tantalum is highly corrosion resistant and occurs naturally in the mineral tantalite, always together with the chemically similar niobium...
, and the two are therefore difficult to distinguish. The English chemist
Charles HatchettCharles Hatchett FRS was an English chemist who discovered the element niobium.- Life :Hatchett was born, raised, and lived in London...
reported a new element similar to tantalum in 1801, and named it columbium. In 1809, the English chemist
William Hyde WollastonWilliam Hyde Wollaston FRS was an English chemist and physicist who is famous for discovering two chemical elements and for developing a way to process platinum ore.-Biography:...
wrongly concluded that tantalum and columbium were identical. The German chemist
Heinrich RoseHeinrich Rose was a German mineralogist and analytical chemist. He was the brother of the mineralogist Gustav Rose and a son of Valentin 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. The name of the element was officially adopted as niobium in 1949.
It was not until the early 20th century that niobium was first used commercially.
BrazilBrazil , officially the Federative Republic of Brazil , is a country in South America. It is the fifth largest country by geographical area, occupying nearly half of South America, the fifth most populous country, and the fourth most populous democracy in the world. Bounded by the Atlantic Ocean...
is the leading producer of niobium and
ferroniobiumFerroniobium is an important iron niobium alloy, with a niobium content of 60-70% It is the main source for niobium alloying of HSLA steel and covers more than 80% of the world wide niobium production. The niobium is mined from pyrochlore deposits and is subsequently transformed into the niobium...
, an
alloyAn alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history...
of niobium and iron. Niobium is used mostly in alloys, the largest part in special
steelSteel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten...
such as that used in gas
pipelinesPipeline transport is the transportation of goods through a pipe. Most commonly, liquid and gases are sent, but pneumatic tubes that transport solid capsules using compressed air have also been used....
. Although alloys contain only a maximum of 0.1%, that small percentage of Niobium improves the strength of the steel. The temperature stability of niobium-containing
superalloyA superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys typically have a matrix with an austenitic face-centered cubic crystal structure. ...
s is important for its use in
jet engineA jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets...
s and
rocket engineA rocket engine or simply "rocket" is a jet engine[Rocket Propulsion Elements; 7th edition- chapter 1] that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...
s. Niobium is used in various
superconductingSuperconductivity is a phenomenon occurring in certain materials generally at very low temperatures, characterized by exactly zero electrical resistance and the exclusion of the interior magnetic field . It was discovered by Heike Kamerlingh Onnes in 1911. Like ferromagnetism and atomic spectral...
materials. These
superconducting alloyA Type-II superconductor is a superconductor characterised by its gradual transition from the superconducting to the normal state within an increasing magnetic field. Typically they superconduct at higher temperatures and magnetic fields than Type-I superconductors...
s, also containing
titaniumTitanium is a chemical element with the symbol Ti and atomic number 22. Sometimes called the “space age metal”, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color.Titanium can be alloyed with iron, aluminium, vanadium, molybdenum, among other...
and
tinTin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead, like the two possible oxidation states +2 and +4...
, are widely used in the
superconducting magnetA superconducting magnet is an electromagnet that is built using coils of superconducting wire. They must be cooled to cryogenic temperatures during operation...
s of
MRI scannersMagnetic Resonance Imaging , or nuclear magnetic resonance imaging , is primarily a medical imaging technique most commonly used in radiology to visualize the internal structure and function of the body...
. Other applications of niobium include its use in welding, nuclear industries, electronics, optics,
numismaticsNumismatics is the study or collection of currency, including coins, tokens, paper money, and related objects. While numismatists are often characterized as students or collectors of coins, the discipline also includes the broader study of money and other payment media used to resolve debts and...
and jewelry. In the last two applications, niobium's low toxicity and ability to be coloured by anodisation are particular advantages.
History
Niobium was discovered by the English chemist
Charles HatchettCharles Hatchett FRS was an English chemist who discovered the element niobium.- Life :Hatchett was born, raised, and lived in London...
in 1801. He found a new element in a mineral sample that had been sent to England from
MassachusettsThe Commonwealth of Massachusetts is a state in the New England region of the northeastern United States. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. Most of its population of...
,
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
in 1734 by a John Winthrop, and named the mineral
columbite and the new element
columbium after
Columbia, the poetical name for
AmericaThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The
columbium discovered by Hatchett was probably a mixture of the new element with tantalum.
Subsequently, there was considerable confusion over the difference between columbium (niobium) and the closely related tantalum. In 1809, the English chemist
William Hyde WollastonWilliam Hyde Wollaston FRS was an English chemist and physicist who is famous for discovering two chemical elements and for developing a way to process platinum ore.-Biography:...
compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm
3, and tantalum—
tantaliteTantalite, [2O6], is a mineral that is close to columbite. In fact, the two are often grouped together as a semi-singular mineral called columbite-tantalite in many mineral guides. However, tantalite has a much greater specific gravity than columbite...
, with a density 7.935 g/cm
3, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum. This conclusion was disputed in 1846 by the German chemist
Heinrich RoseHeinrich Rose was a German mineralogist and analytical chemist. He was the brother of the mineralogist Gustav Rose and a son of Valentin Rose....
, who argued that there were two different elements in the tantalite sample, and named them after children of
TantalusIn Greek mythology Tantalus was a son of Zeus and the nymph Plouto. Thus he was a king in the primordial world, the father of a son Broteas whose very name signifies "mortals" . Other versions name his father as Tmolus "wreathed with oak," son of Sipylus, a king of Lydia. Both Tmolus and Mount...
:
niobium (from
NiobeNiobe was a daughter of Tantalus and the sister of Pelops, all of whom figure in Greek mythology.Her father was the ruler of a city called either under his name, as "Tantalis" or "the city of Tantalus", or as "Sipylus", in reference to Mount Sipylus at the foot of which his city was located and...
), and
pelopiumPelopium was the proposed name for a new element found by the chemist Heinrich Rose in 1845. The name derived from the Greek goddess Pelops. During the analysis of the mineral tantalite he concluded that it does contain an element similar to niobium and tantalum...
(from
PelopsIn Greek mythology, Pelops , king of Pisa in the Peloponnesus, was venerated at Olympia, where his cult developed into the founding myth of the Olympic Games, the most important expression of unity, not only for the Peloponnesus, "island of Pelops", but for all Hellenes...
). This confusion arose from the minimal observed differences between tantalum and niobium. Both tantalum and niobium react with
chlorineChlorine Chlorine Chlorine ( , from the Greek word 'χλωρóς' (khlôros, meaning 'pale green'), is the chemical element with atomic number 17 and symbol Cl. It is a halogen, found in the periodic table in group 17 (formerly VII, VIIa, or VIIb). As the chloride ion, which is part of common salt and...
and traces of oxygen, including atmospheric concentrations, with niobium forming two compounds: the white volatile niobium pentachloride (NbCl
5) and the non-volatile niobium oxychloride (NbOCl
3). The claimed new elements
pelopium,
ilmeniumIlmenium was the proposed name for a new element found by the chemist R. Hermann in 1847. During the analysis of the mineral samarskite he concluded that it does contain an element similar to niobium and tantalum...
and
dianium were in fact identical to niobium or mixtures of niobium and tantalum.
The differences between tantalum and niobium were unequivocally demonstrated in 1864 by
Christian Wilhelm BlomstrandChristian Wilhelm Blomstrand was a Swedish mineralogist and chemist.Blomstrand was born in Växjö, Sweden and studied chemistry at the University of Lund, where he received his Ph.D in 1850 and his habilitation in 1854...
, and
Henri Etienne Sainte-Claire DevilleHenri Etienne Sainte-Claire Deville was a French chemist.He was born in the island of St Thomas, West Indies, where his father was French consul. Together with his elder brother Charles he was educated in Paris at the College Rollin...
, as well as Louis J. Troost, who determined the formulas of some of the compounds in 1865 and finally by the Swiss chemist
Jean Charles Galissard de MarignacJean Charles Galissard de Marignac was a Swiss chemist whose work with atomic weights suggested the possibility of isotopes and the packing fraction of nuclei and whose study of the rare earth elements led to his discovery of ytterbium in 1878 and codiscovery of gadolinium in 1880.- Life and work...
in 1866, who all proved that there were only two elements. These discoveries did not stop scientists from publishing articles about
ilmenium until 1871.
De Marignac was the first to prepare the metal in 1864, when he
reducedRedox describes all chemical reactions in which atoms have their oxidation number changed....
niobium chloride by heating it in an atmosphere of
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
.
Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was first used commercially, in incandescent lamp filaments. This use quickly became obsolete through the replacement of niobium with
tungstenTungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite...
, which has a higher melting point and thus is preferable for use in incandescent lamps. The discovery that niobium improves the strength of steel was made in the 1920s, and this remains its predominant use. In 1961 the American physicist Eugene Kunzler and coworkers at
Bell LabsBell Laboratories is the research and development organization of Alcatel-Lucent and previously of the American Telephone & Telegraph Company .Bell Laboratories has had its headquarters at Murray Hill, New Jersey, and it has research and development facilities...
discovered that
niobium-tinNiobium-tin or triniobium-tin is a metallic chemical compound of niobium and tin , used industrially as a type II superconductor...
continues to exhibit superconductivity in the presence of strong electric currents and magnetic fields, making it the first material known to support the high currents and fields necessary for making useful high-power magnets and electrically powered machinery. This discovery would allow—two decades later—the production of long multi-strand cables that could be wound into coils to create large, powerful
electromagnetAn electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases.- Introduction :...
s for rotating machinery, particle accelerators, or particle detectors.
Columbium (symbol
Cb) was the name originally given to this element by Hatchett, and this name remained in use in American journals—the last paper published by
American Chemical SocietyThe American Chemical Society is a learned society based in the United States that supports scientific inquiry in the field of chemistry...
with columbium in its title dates from 1953—while
niobium was used in Europe. To end this confusion, the name
niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949. A year later this name was officially adopted by the
International Union of Pure and Applied ChemistryThe International Union of Pure and Applied Chemistry is a non-governmental organization established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry. Its members are national chemistry societies...
(IUPAC) after 100 years of controversy, despite the chronological precedence of the name Columbium. The latter name is still sometimes used in US industry. This was a compromise of sorts; the IUPAC accepted
tungstenTungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite...
instead of wolfram, in deference to North American usage; and niobium instead of columbium, in deference to European usage. Not everyone agreed, and while many leading chemical societies and government organizations refer to it by the official IUPAC name, many leading metallurgists, metal societies, and the United States Geological Survey still refer to the metal by the original "
columbium".
Characteristics
Niobium is a
lustrousLustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. For example, a diamond is said to have an adamantine lustre and pyrite is said to have a metallic lustre...
, grey,
ductileDuctility is a mechanical property used to describe the extent to which materials can be deformed plastically without fracture.In materials science, ductility specifically refers to a material's ability to deform under tensile stress; this is often characterized by the material's ability to be...
,
paramagneticParamagnetism is a form of magnetism which occurs only in the presence of an externally applied magnetic field. Paramagnetic materials are attracted to magnetic fields, hence have a relative magnetic permeability of ≥1 .The magnetic moment induced by the applied field is linear in the field...
metalA metal is a chemical element that is a good conductor of both electricity and heat, forms cations and ionic bonds with non-metals. In chemistry, a metal is an element, compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions...
in
group 5A Group 5 element is one in the series of elements in group 5 in the periodic table, which consists of vanadium , niobium , tantalum , and dubnium ....
of the
periodic tableThe periodiс table of the chemical elements is a tabular display of the chemical elements...
(see table to right),
| Z In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
| Element A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
| No. of electrons/shell An electron shell may be thought of as an orbit followed by electrons around an atom nucleus. Because each shell can contain only a fixed number of electrons, each shell is associated with a particular range of electron energy, and thus...
|
|---|
| 23 |
vanadium Vanadium is the chemical element with the symbol V and atomic number 23. It is a soft, silvery grey, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation. Andrés Manuel del Río discovered vanadium in 1801 by analyzing the mineral vanadinite, and named it...
|
2, 8, 11, 2 |
| 41 |
niobium |
2, 8, 18, 12, 1 |
| 73 |
tantalumTantalum is a chemical element with the symbol Ta and atomic number 73. A rare, hard, blue-gray, lustrous transition metal, tantalum is highly corrosion resistant and occurs naturally in the mineral tantalite, always together with the chemically similar niobium...
|
2, 8, 18, 32, 11, 2 |
| 105 |
dubniumDubnium is a chemical element with the symbol Db and atomic number 105.This is a radioactive synthetic element whose most stable isotope is 268Db with a half life of 28 hours. An element of with a half-life as long as this would be much easier to work with, than some other elements such...
|
2, 8, 18, 32, 32, 11, 2 |
although it has an atypical configuration in its outermost
electron shellAn electron shell may be thought of as an orbit followed by electrons around an atom nucleus. Because each shell can contain only a fixed number of electrons, each shell is associated with a particular range of electron energy, and thus...
s compared to the rest of the members. (This can be observed in the neighborhood of niobium (41),
rutheniumRuthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....
(44),
rhodiumRhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst. It is abbreviated to Rh and has atomic number 45...
(45), and
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
(46).)
The metal takes on a bluish tinge when exposed to air at room temperature for extended periods. Despite presenting a high melting point in elemental form (2,468 °C), it has a low density in comparison to other refractory metals. Furthermore, it is corrosion resistant, exhibits superconductivity properties, and forms
dielectricA dielectric is a nonconducting substance, i.e. an insulator. The term was coined by William Whewell in response to a request from Michael Faraday...
oxideAn oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon...
layers. These properties— especially the superconductivity —are strongly dependent on the purity of the niobium metal. When very pure, it is comparatively soft and ductile, but impurities make it harder.
The atoms of niobium is slightly less electropositive and smaller than the atoms of its predecessor in the periodic table,
zirconiumZirconium is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray-white, strong transition metal that resembles titanium. Zirconium is used as an alloying agent due to its high resistance to corrosion. It is never found as a native metal; it is obtained mainly from...
, while it is virtually identical in size to the heavier tantalum atoms as a consequence of the
lanthanide contractionLanthanide contraction is a term used in chemistry to describe different but closely related concepts associated with smaller than expected ionic radii of the elements in the lanthanide series .-Cause:...
. As a result, niobium's chemical properties are very similar to the chemical properties of tantalum, which appears directly below niobium in the
periodic tableThe periodiс table of the chemical elements is a tabular display of the chemical elements...
. Although its corrosion resistance is not as outstanding as that of tantalum, its lower price and greater availability make niobium attractive for less exact uses such as linings in chemical plants.
Isotopes
Naturally occurring niobium is composed of one stable
isotopeIsotopes are different types of atoms of the same chemical element, each having a different number of neutrons. Correspondingly, isotopes differ in mass number but not in atomic number. The difference in the number of nucleons comes from a difference how many neutrons are in the atomic nucleus...
,
93Nb. As of 2003, at least 32 radioisotopes have also been synthesized, ranging in
atomic massThe atomic mass is the mass of an atom, most often expressed in unified atomic mass units. The atomic mass may be considered to be the total mass of protons, neutrons and electrons in a single atom...
from 81 to 113. The most stable of these is
92Nb with a
half-lifeHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
of 34.7 million years. One of the least stable is
113Nb, with an estimated half-life of 30 milliseconds. Isotopes that are lighter than the stable
93Nb tend to decay by
β+ decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted. In the case of electron emission, it is referred to as beta minus , while in the case of a positron emission as beta plus...
, and those that are heavier tend to decay by
β- decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted. In the case of electron emission, it is referred to as beta minus , while in the case of a positron emission as beta plus...
, with some exceptions.
81Nb,
82Nb, and
84Nb have minor β
+ delayed
proton emissionProton emission is a type of radioactive decay in which a proton is ejected from a nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state of very...
decay paths,
91Nb decays by
electron captureElectron capture is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom and insufficient energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron emission...
and
positron emissionPositron emission is a type of beta decay, sometimes referred to as "beta plus" . In beta plus decay, a proton is converted, via the weak force, to a neutron, a positron , and a neutrino.Isotopes which undergo this decay and thereby emit positrons include carbon-11, potassium-40,...
, and
92Nb decays by both
β+The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of , and the same mass as an electron. When a low-energy positron collides with a low-energy electron, annihilation occurs, resulting in the production...
and
β-An electron is a subatomic particle that carries a negative electric charge. It has no known substructure and is believed to be a point particle. An electron has a mass that is approximately 1836 times less than that of the proton. The intrinsic angular momentum of the electron is a half integer...
decay.
At least 25
nuclear isomerA nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons. A nuclear isomer occupies a higher energy state than the corresponding non-excited nucleus, called the ground state. Most nuclear excited states decay by gamma ray emission or...
s have been described, ranging in atomic mass from 84 to 104. Within this range, only
96Nb,
101Nb, and
103Nb do not have isomers. The most stable of niobium's isomers is
93mNb with a half-life of 16.13 years. The least stable isomer is
84mNb with a half-life of 103 ns. All of niobium's isomers decay by
isomeric transitionAn isomeric transition is a radioactive decay process that occurs in an atom where the nucleus is in an excited meta state . The extra energy in the nucleus is released by the emission of a gamma ray, returning the nucleus to the ground state...
or
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted. In the case of electron emission, it is referred to as beta minus , while in the case of a positron emission as beta plus...
except
92m1Nb, which has a minor
electron captureElectron capture is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom and insufficient energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron emission...
decay chainIn nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
.
Chemistry
Niobium is in many ways similar to its predecessors in
group 5A Group 5 element is one in the series of elements in group 5 in the periodic table, which consists of vanadium , niobium , tantalum , and dubnium ....
. It reacts with most nonmetals at high temperatures: niobium reacts with
fluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. Fluorine forms a single bond with itself in elemental form, resulting in the diatomic F
2 molecule. F
2 is a supremely reactive, poisonous, pale, yellowish brown gas. Elemental fluorine is the...
at room temperature, with
chlorineChlorine Chlorine Chlorine ( , from the Greek word 'χλωρóς' (khlôros, meaning 'pale green'), is the chemical element with atomic number 17 and symbol Cl. It is a halogen, found in the periodic table in group 17 (formerly VII, VIIa, or VIIb). As the chloride ion, which is part of common salt and...
and
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
at 200 °
CCelsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
, and with
nitrogenNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
at 400 °C, giving products that are frequently interstitial and nonstoichiometric. The metal begins to oxidize in air at 200 °
CCelsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
, and is resistant to corrosion by fused
alkalisThe alkali metals are a series of chemical elements forming Group 1 of the periodic table: lithium , sodium , potassium , rubidium , caesium , and francium ....
and by acids, including
aqua regiaAqua regia or aqua regis is a highly corrosive, fuming yellow or red solution, also called nitro-hydrochloric acid. The mixture is formed by freshly mixing concentrated nitric acid and concentrated hydrochloric acid, usually in a volumetric ratio of 1:3 respectively...
,
hydrochloricHydrochloric acid is the solution of hydrogen chloride in water. It is a highly corrosive, strong mineral acid and has major industrial uses. It is found naturally in gastric acid....
,
sulfuricSulfuric acid, , is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry. World production in 2001 was 165 million tonnes, with an approximate value of US$8 billion...
,
nitricNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure older samples tend to acquire a stronger yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as...
and
phosphoric acidPhosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more...
s. Niobium is attacked by hot, concentrated
mineral acidA mineral acid is an acid derived from one or more inorganic compounds. A mineral acid does not contain any carbon atoms and all mineral acids release hydrogen ions when dissolved in water.-Characteristics:...
s, such as fluorhydric acid and fluorhydric/nitric acid mixtures. Although niobium exhibits all the formal oxidation states from +5 down to -1, its most stable state is +5.
Niobium is able to form
oxideAn oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon...
s with the
oxidation stateIn chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
s +5 (
Nb2O5Niobium pentoxide, is the chemical compound with the formula Nb2O5. It is used mainly in the production of capacitors, lithium niobate, and optical glass....
), +4 (
NbO2Niobium dioxide, is the chemical compound with the formula NbO2. It is a bluish black non-stoichiometric solid with a composition range of NbO1.94-NbO2.09 It can be prepared by reacting Nb2O5 with H2 at 800-1350 °C...
) and +3 (Nb
2O
3), as well as with the rarer oxidation state +2 (
NbO-Niobium monoxide:Niobium monoxide, is the chemical compound with the formula NbO. It is a grey solid with metallic conductivity. It has an unusual cubic crystal structure, related to the rock salt structure, where both niobium and oxygen atoms are four coordinate square planar...
). The most stable oxidation state is +5, the pentoxide which, along with the dark green
non-stoichiometricNon-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined natural numbers, and therefore violate the law of definite proportions. Often, they are solids that contain crystallographic point defects, such as interstitial...
dioxide, is the most common of the oxides. Niobium pentoxide is used mainly in the production of capacitors, optical glass, and as starting material for several niobium compounds. The compounds are created by dissolving the pentoxide in
basicIn chemistry, a base is most commonly thought of as an aqueous substance that can accept hydrogen ions. Bases are also the oxides or hydroxides of metals. A soluble base is also often referred to as an alkali if hydroxide ions are involved. This refers to the Brønsted-Lowry theory of acids and bases...
hydroxideIn chemistry, hydroxide is the name for the diatomic anion OH−, consisting of oxygen and hydrogen atoms, usually derived from the dissociation of a base. It is one of the simplest diatomic ions known....
solutions or by melting it in another metal oxide. Examples are
lithium niobateLithium niobate is a compound of niobium, lithium, and oxygen. Its single crystals are an important material for optical waveguides, mobile phones, optical modulators and various other linear and non-linear optical applications.-Properties:...
(LiNbO
3) and lanthanum niobate (LaNbO
4). In the lithium niobate, the niobate ion NbO
3− is not alone but part of a trigonally distorted perovskite-like structure, while the lanthanum niobate contains lone NbO
43− ions. Lithium niobate, which is a ferroelectric, is used extensively in mobile telephones and optical modulators, and for the manufacture of
surface acoustic wave]A surface acoustic wave is an acoustic wave traveling along the surface of a material exhibiting elasticity, with an amplitude that typically decays exponentially with depth into the substrate.-Discovery:...
devices. It belongs to the
ABO3A perovskite structure is any material with the same type of crystal structure as calcium titanium oxide , known as the perovskite structure, or
XIIA
2+VIIB
4+X
2-3 with the oxygen in a fcc...
structure ferroelectrics like
lithium tantalateLithium tantalate , is a crystalline solid which possesses unique optical, piezoelectric and pyroelectric properties which make it valuable for non-linear optics, passive infrared sensors such as motion detectors, terahertz generation and detection, surface acoustic wave applications, cell phones...
and
barium titanateBarium titanate is an oxide of barium and titanium with the chemical formula BaTiO
3. It is a ferroelectric ceramic material, with a photorefractive effect and piezoelectric properties. It has five phases as a solid, listing from high temperature to low temperature: hexagonal, cubic,...
.
Niobium forms halogen compounds in the oxidation states of +5, +4, and +3 of the type , , and , although multi-core complexes and substoichiometric compounds are also formed. Niobium pentafluoride (NbF
5) is a white solid with a melting point of 79.0 °C and niobium pentachloride (NbCl5) is a yellowish-white solid (see image at left) with a melting point of 203.4 °C. Both are hydrolyzed by water and react with additional niobium at elevated temperatures by forming the black and highly hygroscopicHygroscopy is the ability of a substance to attract water molecules from the surrounding environment through either absorption or adsorption.Hygroscopic substances include sugar, honey, glycerol, ethanol, methanol, sulfuric acid, methamphetamine, iodine, many chloride and hydroxide salts, and a...
niobium tetrafluoride (NbF4) and niobium tetrachloride (NbCl4). While the trihalogen compounds can be obtained by reduction of the pentahalogens with hydrogen, the dihalogen compounds do not exist. Spectroscopically, the monochloride (NbCl) has been observed at high temperatures. The fluorides of niobium can be used after its separation from tantalum. The niobium pentachloride is used in organic chemistryOrganic chemistry is a discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation of chemical compounds that contain carbon...
as a Lewis acidA Lewis acid, A, is a chemical compound that can accept a pair of electrons from a Lewis base, B, that acts as an electron-pair donor, forming an adduct, AB:
A + :B → A—B...
in activating alkeneIn organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s for the carbonyl-ene reaction and the Diels-Alder reaction. The pentachloride is also used to generate the organometallic compound niobocene dichlorideNiobocene dichloride is the organometallic compound with the formula 2NbCl2, abbreviated Cp2NbCl2. This paramagnetic brown solid is a starting reagent for the synthesis of other organoniobium compounds...
, which in turn is used as a starting material for other organoniobium compounds.
Other binary compoundA binary compound is a chemical compound that contains exactly two different elements. Examples are NaCl , NaF , and MgO .-Metals with variable valences:...
s of niobium include niobium nitrideNiobium nitride is a compound of niobium and nitrogen with the chemical formula NbN. At low temperatures, niobium nitride becomes a superconductor, and is used in detectors for infrared light.- Uses :*Niobium nitride's main use is as a superconductor...
(NbN), which becomes a superconductor at low temperatures and is used in detectors for infrared light, and niobium carbideNiobium carbide is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. It is usually processed by sintering and is a frequent additive in cemented carbides. It has the appearance of a brown-gray metallic powder with purple lustre...
, an extremely hard, refractoryIn metallurgy, refraction is a property of metals that indicates their ability to withstand heat. Metals with a high degree of refraction are referred to as refractory. These metals derive their high melting points from their strong intermolecular forces...
, ceramicA ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
material, commercially used in tool bitThe term tool bit generally refers to a non-rotary cutting tool used in metal lathes, shapers, and planers. Such cutters are also often referred to by the set-phrase name of single-point cutting tool. The cutting edge is ground to suit a particular machining operation and may be resharpened or...
s for cutting tools. The compounds niobium-germaniumNiobium-germanium is a metallic chemical compound of niobium and germanium . It has A15 phase structure.It is a superconductor with a critical temperature of 23.2 kelvins ....
and niobium-tinNiobium-tin or triniobium-tin is a metallic chemical compound of niobium and tin , used industrially as a type II superconductor...
, as well as the niobium-titaniumNiobium-titanium is an alloy of niobium and titanium, used industrially as a type II superconductor wire for superconducting magnets...
alloyAn alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history...
, are used as a type II superconductor wire for superconducting magnetA superconducting magnet is an electromagnet that is built using coils of superconducting wire. They must be cooled to cryogenic temperatures during operation...
s. Niobium sulfide as well as a few interstitial compoundAn interstitial compound or interstitial alloy is a compound that is formed when an atom of sufficiently small radius sits in an interstitial “hole” in a metal lattice. Examples of small atoms are hydrogen, boron, carbon and nitrogen...
s of niobium with siliconSilicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon...
are also known.
Occurrence
According to estimates, niobium is 33rd on the list of the most common elements in the Earth’s crustThis table shows the abundance of elements in Earth's crust. Numbers show percentage in mass.Note that numbers are estimates, and they will vary depending on source and method of estimation...
with 20 ppmParts-per notation is used, especially in science and engineering, to denote relative proportions in measured quantities; particularly in low-value proportions at the parts-per-million , parts-per-billion , and parts-per-trillion level...
. The abundance on Earth should be much greater, but the “missing” niobium may be located in the Earth’s core due to the metal's high density. The free element is not found in nature, but it does occur in minerals.
Minerals that contain niobium often also contain tantalum, for example, columbite ((Fe,Mn)(Nb,Ta)2O6), columbite-tantalite (or coltan, (Fe,Mn)(Ta,Nb)2O6) and pyrochlorePyrochlore 2Nb2O6 is a solid solution between the niobium end member , and the tantalum end member . The mineral is associated with the metasomatic end stages of magmatic intrusions...
((Na,Ca)2Nb2O6(OH,F)). Columbite-tantalite minerals are most usually found as accessory minerals in pegmatiteA pegmatite is a very coarse-grained, intrusive igneous rock comprised of interlocking grains usually larger than 2.5 cm in diameter; such rocks are referred to as pegmatitic....
intrusions, and in alkaline intrusive rocks. Less common are the niobates of calciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust...
, uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
, thoriumThorium is a chemical element with the symbol Th and atomic number 90. It is a naturally occurring, slightly radioactive metal. Thorium is estimated to be about three to four times more abundant than uranium in the earth's crust...
and the rare earth elements such as pyrochlore and euxeniteEuxenite or euxenite- is a brownish black mineral with a metallic luster. It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other metals. The chemical formula is: 2O6. It occurs in granite pegmatites and detrital...
((Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6). These large deposits of niobium have been found associated with carbonatiteCarbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....
s (carbonateCarbonate minerals are those minerals containing the carbonate ion: CO32-.-Anhydrous carbonates:*Calcite group: Trigonal**Calcite CaCO3**Gaspeite CO3**Magnesite MgCO3...
-silicateA silicate is a compound containing an ion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate , [SiF6]2−, but the silicate species that are encountered most often...
igneous rocks) and as a constituent of pyrochlore.
The two largest deposits of pyrochlore were found in the 1950s in Brazil and Canada, and both countries are still the major producers of niobium mineral concentrates. The largest deposit is hosted within a carbonatite intrusion at AraxáAraxá is a city and municipality in southwest Minas Gerais state, Brazil. The population was 87,764 inhabitants and the area of the municipality is 1,283 km², with 345 km² making up the urban perimeter. -Geography:...
, Minas GeraisMinas Gerais is one of the 26 states of Brazil, the second most populous and fourth largest by area in the federation. The capital is the city of Belo Horizonte, located near the central area...
Brazil, owned by CBMM ; the other deposit is located at CatalãoCatalão is a small city and municipality located in the south of the state of Goiás, in Brazil. It is a large producer of grains, cattle, and phosphates and has a John Deere and Mitsubishi factory.-Demographics:...
, GoiásGoiás is a state of Brazil, located in the central part of the country. The most central of the Brazilian states and most populous of the region, Goiás is characterized by a landscape of chapadões...
owned by Anglo American plc (through its subsidiary Mineração Catalão), also hosted within a carbonatite intrusion. Altogether these two Brazilian mines produce around 75% of world supply. The third largest producer of niobium is the carbonatite-hosted Niobec Mine, Saint-Honoré near Chicoutimi, QuebecQuebec is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking identity and the only one whose sole official language is French at the provincial level....
owned by Iamgold Corporation LtdIAMGOLD Corporation is a Toronto based international gold producer. The company is engaged in the exploration, development, and production of mineral resource properties throughout the world.-Operations:...
, which produces around 7% of world supply.
Extensive though unexploited resources are located in NigeriaNigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising thirty-six states and one Federal Capital Territory. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger...
, Democratic Republic of Congo, TanzaniaThe United Republic of Tanzania is a country in central East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi and the Democratic Republic of the Congo to the west, and Zambia, Malawi and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.The United...
, MalawiThe Republic of Malawi is a landlocked country in southeast Africa that was formerly known as Nyasaland. It is bordered by Zambia to the northwest, Tanzania to the northeast and Mozambique, which surrounds it on the east, south and west. The country is separated from Tanzania and Mozambique by...
, AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
and RussiaRussia , officially known as both Russia and the Russian Federation , is a country in northern Eurasia . It is a semi-presidential republic, comprising 83 federal subjects...
.
Production
After the separation from the other minerals, the mixed oxides of tantalum Ta2O5Tantalum pentoxide is Ta2O5, also known as tantalum oxide. Both orthorhombic and hexagonal phases are known. Ta2O5 is a high refractive index, low absorption material useful for coatings in the near-UV to IR spectra regions; it decomposes only at...
and niobium Nb2O5Niobium pentoxide, is the chemical compound with the formula Nb2O5. It is used mainly in the production of capacitors, lithium niobate, and optical glass....
are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acidHydrofluoric acid is a solution of hydrogen fluoride in water. While it is extremely corrosive and difficult to handle, it is technically a weak acid...
:
- Ta2O5 + 14 HF → 2 H2[TaF7] + 5 H2O
- Nb2O5 + 10 HF → 2 H2[NbOF5] + 3 H2O
The first industrial scale separation, developed by de MarignacJean Charles Galissard de Marignac was a Swiss chemist whose work with atomic weights suggested the possibility of isotopes and the packing fraction of nuclei and whose study of the rare earth elements led to his discovery of ytterbium in 1878 and codiscovery of gadolinium in 1880.- Life and work...
, used the difference in solubility between the complex niobium and tantalum fluorideFluoride is the anion F
−, the reduced form of fluorine. Both organic and inorganic compounds containing the element fluorine are sometimes called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are distinct relative to other...
s, dipotassium oxypentafluoroniobate monohydrate (K2[NbOF5]·H2O) and dipotassium heptafluorotantalate (K2[TaF7]) in water. Newer processes use the liquid extraction of the fluorides from aqueous solution by organic solvents like cyclohexanoneCyclohexanone is the organic compound with the formula
5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oil has an odor reminiscent of peardrop sweets as well as acetone. Over time, samples assume a yellow color due to oxidation...
. The complex niobium and tantalum fluorides are extracted separately from the organic solvent with water and either precipitated by the addition of potassium fluoridePotassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali metal halide and occurs naturally as the rare mineral carobbiite...
to produce a potassium fluoride complex, or precipitated with ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
as the pentoxide:
- 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 reduction to metallic niobium. The electrolysisIn chemistry and manufacturing, electrolysis is a method of using an electric current to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially highly important as a stage in the separation of elements from naturally-occurring sources such as ores using an electrolytic...
of a molten mixture of K2[NbOF5] and sodium chlorideSodium chloride, also known as salt, common salt, table salt, or halite, is an ionic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
is one; the other is the reduction of the fluoride with sodiumSodium is a metallic element with a symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals within "group 1"...
. With this method niobium with a relatively high purity can be obtained. In large scale production the reduction of Nb2O5 with hydrogen or carbon is used. In the process involving the aluminothermic reactionAluminothermic reactions are exothermic chemical reactions using aluminium as the reducing agent at high temperature. The most prominent example is the thermite reaction between aluminium and iron oxides:-History:...
a mixture of iron oxideIron oxides are chemical compounds composed of iron and oxygen. Altogether, there are sixteen known iron oxides and oxyhydroxides.-Oxides:* FeO, iron oxide, * Fe3O4, iron oxide,...
and niobium oxide is reacted with aluminiumAluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances....
:
- 3 Nb2O5 + Fe2O3 + 12 Al → 6 Nb + 2 Fe + 6 Al2O3
To enhance the reaction, small amounts of oxidizers like sodium nitrateSodium nitrate is the chemical compound with the formula NaNO
3. This salt, also known as "Chile saltpeter" or "Peru saltpeter" , is a white solid which is very soluble in water...
are added. The result is aluminium oxideAluminium oxide is an amphoteric oxide of aluminium with the chemical formula
23. It is also commonly referred to as alumina, corundum, sapphire, ruby or aloxite in the mining, ceramic and materials science communities. It is produced by the Bayer process from bauxite...
and ferroniobiumFerroniobium is an important iron niobium alloy, with a niobium content of 60-70% It is the main source for niobium alloying of HSLA steel and covers more than 80% of the world wide niobium production. The niobium is mined from pyrochlore deposits and is subsequently transformed into the niobium...
, an alloy of iron and niobium used in the steel production. The ferroniobium contains between 60 and 70% of niobium. Without addition of iron oxide, aluminothermic process is used for the production of niobium. Further purification is necessary to reach the grade for superconductive alloys. Electron beam meltingElectron beam melting is a type of additive manufacturing for metal parts. It is often classified as a rapid manufacturing method. The technology manufactures parts by melting metal powder layer per layer with an electron beam in a high vacuum...
under vacuum is the method used by the two major distributors of niobium.
The United States Geological SurveyThe United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning...
estimates that the production increased from 38,700 metric tonnes in 2005 to 44,500 tonnes in 2006. The worldwide resources are estimated to be 4,400,000 tonnes. During the ten-year period between 1995 and 2005, the production more than doubled, starting from 17,800 tonnes in 1995.
Applications
It is estimated that out of 44,500 metric tons of niobium mined in 2006, 90% ended up in the production of high-grade structural steel, followed by its use in superalloys. The use of niobium alloys for superconductors and in electronic components account only for a small share of the production.
Steel production
Niobium is an effective microalloyingMicroalloyed steel is a type of alloy steel that contains small amounts of alloying elements . Standard alloying elements include: niobium, vanadium, titanium, molybdenum, zirconium, boron, and rare-earth metals...
element for steel. Adding niobium to the steel causes the formation of niobium carbideNiobium carbide is an extremely hard refractory ceramic material, commercially used in tool bits for cutting tools. It is usually processed by sintering and is a frequent additive in cemented carbides. It has the appearance of a brown-gray metallic powder with purple lustre...
and niobium nitrideNiobium nitride is a compound of niobium and nitrogen with the chemical formula NbN. At low temperatures, niobium nitride becomes a superconductor, and is used in detectors for infrared light.- Uses :*Niobium nitride's main use is as a superconductor...
within the structure of the steel. These compounds improve the grain refining, retardation of recrystallization, and precipitation hardening of the steel. These effects in turn increase the toughness, strength, formability, and weldability of the microalloyed steel. Microalloyed stainless steelIn metallurgy, stainless steel, also known as inox steel or inox, is defined as a steel alloy with a minimum of 11% chromium content by mass. Stainless steel does not stain, corrode, or rust as easily as ordinary steel...
s have a niobium content of less than 0.1%. It is an important alloy addition to high strength low alloy steelsHigh-strength low-alloy steel is a type of alloy steel that provides better mechanical properties or greater resistance to corrosion than carbon steel. HSLA steels vary from other steels in that they aren't made to meet a specific chemical composition, but rather to specific mechanical properties...
which are widely used as structural components in modern automobiles. These niobium containing alloys are strong and are often used in pipeline construction.
Superalloys
Appreciable amounts of the element, either in its pure form or in the form of high-purity ferroniobium and nickelNickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium...
niobium, are used in nickel-, cobaltCobalt is a hard, lustrous, gray metal, a chemical element with symbol Co and atomic number 27. Although cobalt-based colors and pigments have been used since ancient times for making jewelry and paints, and miners have long used the name kobold ore for some minerals, the free metallic cobalt was...
-, and ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
-base superalloys for such applications as jet engineA jet engine is a reaction engine that discharges a fast moving jet of fluid to generate thrust in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets and pump-jets...
components, gas turbines, rocket subassemblies, and heat resisting and combustion equipment. Niobium precipitates a hardening γ-phase within the grain structure of the superalloy. The alloys contain up to 6.5% niobium. One example of a nickel-based niobium-containing superalloy is Inconel 718Inconel is a registered trademark of Special Metals Corporation that refers to a family of austenitic nickel-chromium-based superalloys . Inconel alloys are typically used in high temperature applications. It is often referred to in English as "Inco"...
, which consists of roughly 50% nickelNickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium...
, 18.6% chromiumChromium is a chemical element which has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odourless, tasteless, and malleable...
, 18.5% ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
, 5% niobium, 3.1% molybdenumMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The free element, which is a silvery metal, has the sixth-highest melting point of any element. It readily forms hard, stable carbides, and for this reason it is often used in high-strength steel alloys...
, 0.9% titaniumTitanium is a chemical element with the symbol Ti and atomic number 22. Sometimes called the “space age metal”, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color.Titanium can be alloyed with iron, aluminium, vanadium, molybdenum, among other...
, and 0.4% aluminiumAluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances....
. These superalloys are used, for example, in advanced air frame systems such as those used in the Gemini program.
An alloy used for liquid rocketA liquid-fuel rocket or a liquid rocket is a rocket with an engine that uses propellants in liquid form. Liquids are desirable because their reasonably high density allows the volume and hence the mass of the tanks to be relatively low, resulting in a high mass ratio...
thruster nozzles, such as in the main engine of the Apollo Lunar ModuleThe Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman to achieve the transit from lunar orbit to the surface and back...
s, is C103, which consists of 89% niobium, 10% hafniumHafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869. Hafnium was the penultimate stable...
and 1% titanium. Another niobium alloy was used for the nozzle of the Apollo Service Module. As niobium is oxidized at temperatures above 400 °C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle.
Superconducting magnets
Niobium becomes a superconductor when lowered to cryogenicIn physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. Rather than the familiar temperature scales of Fahrenheit and Celsius, cryogenicists use the Kelvin scales...
temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors: 9.2 KThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin...
. Niobium has the largest magnetic penetration depth of any element. In addition, it is one of the three elemental Type II superconductors, along with vanadiumVanadium is the chemical element with the symbol V and atomic number 23. It is a soft, silvery grey, ductile transition metal. The formation of an oxide layer stabilizes the metal against oxidation. Andrés Manuel del Río discovered vanadium in 1801 by analyzing the mineral vanadinite, and named it...
and technetiumTechnetium is the lightest chemical element with no stable isotope, and is therefore the lightest radioactive element. It has atomic number 43 and symbol Tc. Technetium occurs in nature only in minute amounts; as a spontaneous fission product in uranium ore or by neutron capture in molybdenum...
. Niobium-tinNiobium-tin or triniobium-tin is a metallic chemical compound of niobium and tin , used industrially as a type II superconductor...
and niobium-titaniumNiobium-titanium is an alloy of niobium and titanium, used industrially as a type II superconductor wire for superconducting magnets...
alloys are used as wires for superconducting magnets capable of producing exceedingly strong magnetic fieldMagnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges...
s. These superconducting magnets are used in magnetic resonance imagingMagnetic Resonance Imaging , or nuclear magnetic resonance imaging , is primarily a medical imaging technique most commonly used in radiology to visualize the internal structure and function of the body...
and nuclear magnetic resonanceNuclear magnetic resonance is a property that magnetic nuclei have in a magnetic field and applied electromagnetic pulse, which cause the nuclei to absorb energy from the EM pulse and radiate this energy back out...
instruments as well as in particle acceleratorA particle accelerator is a device that uses electric fields to propel ions or charged subatomic particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator...
s. For example, the Large Hadron ColliderThe Large Hadron Collider is the world's largest and highest-energy particle accelerator intended to collide opposing particle beams of either protons at an energy of 7 TeV per particle or lead nuclei at an energy of 574 TeV per nucleus...
uses 600 metric tons of superconducting strands, while the International Thermonuclear Experimental Reactor is estimated to use 600 metric tonnes of Nb3Sn strands and 250 metric tonnes of NbTi strands. In 1992 alone, niobium-titanium wires were used to construct more than 1 billion US dollarsThe United States dollar is the unit of currency of the United States. The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol. It is divided into 100 cents .The U.S...
worth of clinical magnetic resonance imaging systems.
Numismatics
Niobium is used as a precious metal in commemorative coins, often with silver or gold. For example, AustriaAustria , officially the Republic of Austria , is a landlocked country of roughly 8.3 million people in Central Europe. It borders both Germany and the Czech Republic to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the west...
produced a series of silver niobium euroThe euro is the official currency of 16 of the 27 Member States of the European Union . The states, known collectively as the Eurozone, are Austria, Belgium, Cyprus, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia and Spain...
coins starting in 2003; the colour in these coins is created by diffraction of light by a thin oxide layer produced by anodisingAnodizing, or anodising in British English, is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. The process is called "anodizing" because the part to be treated forms the anode electrode of an electrical circuit...
. In 2008, six 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 Years Semmering Alpine Railway commemorative coin, and the 2006 Austrian €25 European Satellite Navigation commemorative coin. Latvia produced a similar series of coins starting in 2004, with one following in 2007.
Other uses
Niobium and some niobium alloys are used in medical devices such as pacemakers, because they are physiologically inert (and thus hypoallergenicHypoallergenic is a term coined by advertisers and first used in a cosmetics campaign in 1953. It is used to describe items that cause or are claimed to cause fewer allergic reactions...
). Niobium treated with sodium hydroxideSodium hydroxide , also known as lye and caustic soda, is a caustic metallic base. It is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner. Worldwide production in 1998 was around...
forms a porous layer that aids osseointegrationOsseointegration is the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant, typically made of titanium. It is a property virtually unique to titanium and hydroxylapatite, and has enhanced the science of medical bone, and joint...
. Along with titanium, tantalum, and aluminium, niobium can also be electrically heated and anodized, resulting in a wide array of colours using a process known as reactive metal anodizing which is useful in making jewelry. The fact that niobium is hypoallergenic also benefits its use in jewelry.
The arc-tube seals of high pressure sodium vapor lampA Sodium vapor lamp is a gas discharge lamp which uses sodium in an excited state to produce light. There are two varieties of such lamps: low pressure and high pressure...
s are made from niobium, or niobium with 1% of zirconiumZirconium is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray-white, strong transition metal that resembles titanium. Zirconium is used as an alloying agent due to its high resistance to corrosion. It is never found as a native metal; it is obtained mainly from...
, because niobium has a very similar coefficient of thermal expansion to the sintered alumina arc tube ceramic, a translucent material which resists chemical attack or reductionRedox describes all chemical reactions in which atoms have their oxidation number changed....
by the hot liquid sodium and sodium vapour contained inside the operating lamp. The metal is also used in arc weldingArc welding uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct or alternating current, and consumable or non-consumable electrodes...
rods for some stabilized grades of stainless steel.
Niobium was evaluated as a cheaper alternative to tantalum in capacitorThe tantalum capacitor is a highly reliable type of electrolytic capacitor in which the dielectric is formed from a very thin anodized layer of tantalum pentoxide....
s, but tantalum capacitors are still predominant. Niobium is added to glass in order to attain a higher refractive indexThe refractive index of a medium is a measure of how much the speed of light is reduced inside the medium. For example, typical soda-lime glass has a refractive index close to 1.5, which means that in glass, light travels at 1 / 1.5 = 2/3 the speed of light in a vacuum...
, a property of use to the optical industry in making thinner corrective glassesGlasses are frames bearing lenses worn in front of the eyes, normally for vision correction, eye protection, or for protection from UV rays....
. The metal has a low capture cross-section for thermal neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
s; thus it is used in the nuclear industries.
The Superconducting Radio FrequencySuperconducting Radio Frequency science and technology involves the application of electrical superconductors to radio frequency devices. The ultra-low electrical loss of the superconductor yields RF resonators with extremely high quality factors, or Q...
(RF) cavities used in the free electron laserA free-electron laser, or FEL, is a laser that shares the same optical properties as conventional lasers such as emitting a beam consisting of coherent electromagnetic radiation which can reach high power, but which uses some very different operating principles to form the beam...
s TESLA and XFELThe European x-ray free electron laser is an international project with 14 particpating countries that is located between the German federal states of Hamburg and Schleswig-Holstein. A free electron laser generates high intensity electromagnetic radiation by accelerating electrons to relativistic...
are made from pure niobium.
The high sensitivity of superconducting niobium nitride bolometersA microbolometer is a specific type of bolometer used as a detector in a thermal camera. Infrared radiation with wavelengths between 8-13 μm strikes the detector material, heating it, and thus changing its electrical resistance. This resistance change is measured and processed into temperatures...
make them an ideal detector for electromagnetic radiationElectromagnetic radiation is a ubiquitous phenomenon that takes the form of self-propagating waves in a vacuum or in matter. It consists of electric and magnetic field components which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation...
in the THz frequency band. These detectors were tested at the Heinrich Hertz Submillimeter TelescopeThe Submillimeter Telescope , formerly known as the Heinrich Hertz Submillimeter Telescope, is a submillimeter wavelength radio telescope located on Mount Graham, Arizona. It is a 10-meter-wide parabolic dish inside a building to protect it from bad weather. The building can be completely rolled...
, the South Pole TelescopeThe South Pole Telescope is a 10 meter The South Pole Telescope (SPT) is a 10 meter The South Pole Telescope (SPT) is a 10 meter (394 in diameter telescope located at the Amundsen-Scott South Pole Station, Antarctica. It is a microwave/millimeter-wave telescope that observes in a frequency...
, the Receiver Lab Telescope, and at APEXThe Atacama Pathfinder Experiment is a radio telescope located at 5,100 meters above sea level, at Llano de Chajnantor in the Atacama desert, in northern Chile, 50 kilometers to the east of San Pedro de Atacama....
and are now used in the HIFI instrument on board the Herschel Space ObservatoryThe Herschel Space Observatory is a space observatory from the European Space Agency . It was originally proposed in 1982 by a consortium of European scientists...
.
Precautions
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 frequently used in jewelry and has been tested for use in some medical implants.
Niobium-containing compounds are rarely encountered by most people, but some are toxic and should be treated with care. The short and long term exposure to niobates and niobium chloride, two chemicals that are water soluble, 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. For oral administration the toxicity is lower; a study with rats yielded a LD50 after seven days of 940 mg/kg.
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