======================================================================
= Niobium =
======================================================================
Introduction
======================================================================
Niobium is a chemical element; it has symbol Nb (formerly columbium,
Cb) and atomic number 41. It is a light grey, crystalline, and ductile
transition metal. Pure niobium has a Mohs hardness rating similar to
pure titanium, and it has similar ductility to iron. Niobium oxidizes
in Earth's atmosphere very slowly, hence its application in jewelry as
a hypoallergenic alternative to nickel. Niobium is often found in the
minerals pyrochlore and columbite. Its name comes from Greek
mythology: Niobe, daughter of Tantalus, the namesake of tantalum. The
name reflects the great similarity between the two elements in their
physical and chemical properties, which makes them difficult to
distinguish.
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
ferroniobium, an alloy of 60-70% niobium with iron. Niobium is used
mostly in alloys, the largest part in special steel such as that used
in gas pipelines. Although these alloys contain a maximum of 0.1%, the
small percentage of niobium enhances the strength of the steel by
scavenging carbide and nitride. The temperature stability of
niobium-containing superalloys is important for its use in jet and
rocket engines.
Niobium is used in various superconducting materials. These alloys,
also containing titanium and tin, are widely used in the
superconducting magnets of MRI scanners. Other applications of niobium
include welding, nuclear industries, electronics, optics, and jewelry.
In the last application, the low toxicity and iridescence produced by
anodization are highly desired properties.
History
======================================================================
Niobium was identified by English chemist Charles Hatchett in 1801. He
found a new element in a mineral sample that had been sent to England
from Connecticut, United States in 1734 by John Winthrop FRS (grandson
of John Winthrop the Younger) and named the mineral "columbite"" and
the new element "columbium" after 'Columbia', the poetic name for the
United States. 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,
English chemist William Hyde Wollaston compared the oxides derived
from both columbium--columbite, with a density 5.918 g/cm(3), and
tantalum--tantalite, with a density over 8 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 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). This confusion arose from the minimal observed
differences between tantalum and niobium. The claimed new elements
'pelopium', 'ilmenium', 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 Blomstrand and Henri Étienne
Sainte-Claire Deville, as well as Louis J. Troost, who determined the
formulas of some of the compounds in 1865 and finally by Swiss chemist
Jean Charles Galissard de Marignac in 1866, who all proved that there
were only two elements. Articles on 'ilmenium' continued to appear
until 1871.
Christian Wilhelm Blomstrand was the first to prepare the metal in
1866, when he reduced niobium chloride by heating it in an atmosphere
of hydrogen. 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 used in incandescent lamp filaments, the
first commercial application. This use quickly became obsolete through
the replacement of niobium with tungsten, which has a higher melting
point. That niobium improves the strength of steel was first
discovered in the 1920s, and this application remains its predominant
use. In 1961, the American physicist Eugene Kunzler and coworkers at
Bell Labs discovered that niobium-tin continues to exhibit
superconductivity in the presence of strong electric currents and
magnetic fields, making it the first material to support the high
currents and fields necessary for useful high-power magnets and
electrical power machinery. This discovery enabled--two decades
later--the production of long multi-strand cables wound into coils to
create large, powerful electromagnets for rotating machinery, particle
accelerators, and particle detectors.
Naming the element
====================
'Columbium' (symbol Cb) was the name originally given by Hatchett upon
his discovery of the metal in 1801. The name reflected that the type
specimen of the ore came from the United States of America (Columbia).
This name remained in use in American journals--the last paper
published by American Chemical Society 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 Chemistry (IUPAC) after 100 years of controversy,
despite the chronological precedence of the name 'columbium'. This was
a compromise of sorts; the IUPAC accepted tungsten instead of wolfram
in deference to North American usage; and niobium instead of
'columbium' in deference to European usage. While many US chemical
societies and government organizations typically use the official
IUPAC name, some metallurgists and metal societies still use the
original American name, 'columbium'.
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) and rhodium
(45).
!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 body-centered cubic crystal structure
from absolute zero to its melting point, high-resolution measurements
of the thermal expansion along the three crystallographic axes reveal
anisotropies which are inconsistent with a cubic structure. Therefore,
further research and discovery in this area is expected.
Niobium becomes a superconductor at cryogenic temperatures. At
atmospheric pressure, it has the highest critical temperature of the
elemental superconductors at 9.2 K. Niobium has the greatest magnetic
penetration depth of any element. In addition, it is one of the three
elemental type II superconductors, along with vanadium and technetium.
The superconductive properties 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 metal has a low neutron capture cross-section for thermal
neutrons; thus it is used in the nuclear industries where neutron
transparent structures are desired.
Chemical
==========
The metal takes on a bluish tinge when exposed to air at room
temperature for extended periods. Despite a high melting point in
elemental form (2468 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 electropositive and more compact than its
predecessor in the periodic table, zirconium, whereas it is virtually
identical in size to the heavier tantalum atoms, as a result of the
lanthanide contraction. As a result, niobium's chemical properties are
very similar to those for tantalum, which appears directly below
niobium in the periodic table. Although its corrosion resistance is
not as outstanding as that of tantalum, the lower price and greater
availability make niobium attractive for less demanding applications,
such as vat linings in chemical plants.
Isotopes
==========
Almost all of the niobium in Earth's crust is the one stable isotope,
{{chem2|^{93}Nb}}. The most stable radioisotope is {{chem2|^{92}Nb}}
with half-life 34.7 million years. {{chem2|^{92}Nb}}, along with the
next most stable one, {{chem2|^{94}Nb}} (20,400 years), has been
detected in refined samples of terrestrial niobium and may originate
from bombardment by cosmic ray muons in Earth's crust. Isotopes
lighter than the stable {{chem2|^{93}Nb}} tend to β(+) decay, and
those that are heavier tend to β(−) decay, with β(+)-delayed proton
emission observed for isotopes as heavy as {{chem2|^{84}Nb}}.
The most stable of isomeric state of a niobium isotope is
{{chem2|^{93m}Nb}} with half-life . The long-lived fission product
{{chem2|^{93}Zr}} decays, mainly through this isomer, to stable
niobium.
Occurrence
============
Niobium is estimated to be the 33rd most abundant element in the
Earth's crust, at . Some believe that the abundance on Earth is much
greater, and that the element's high density has concentrated it in
Earth's core. The free element is not found in nature, but niobium
occurs in combination with other elements in minerals. Minerals that
contain niobium often also contain tantalum. Examples include
ferrocolumbite () and coltan (). Columbite-tantalite minerals (the
most common species being columbite-(Fe) and tantalite-(Fe)) that are
most usually found as accessory minerals in pegmatite intrusions, and
in alkaline intrusive rocks. Less common are the niobates of calcium,
uranium, thorium and the rare earth elements. Examples of such
niobates are pyrochlores () and euxenite (). These large deposits of
niobium have been found associated with carbonatites
(carbonate-silicate igneous rocks) and as a constituent of pyrochlore.
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 largest deposit
is hosted within a carbonatite intrusion in Araxá, state of Minas
Gerais, Brazil, owned by CBMM (Companhia Brasileira de Metalurgia e
Mineração); the other active Brazilian deposit is located near
Catalão, state of Goiás, and owned by China Molybdenum, also hosted
within a carbonatite intrusion. Together, those two mines produce
about 88% of the world's supply. Brazil also has a large but still
unexploited deposit near São Gabriel da Cachoeira, state of Amazonas,
as well as a few smaller deposits, notably in the state of Roraima.
The third largest producer of niobium is the carbonatite-hosted Niobec
mine, in Saint-Honoré, Quebec, Canada, owned by Magris Resources. It
produces between 7% and 10% of the world's supply.
Production
======================================================================
After the separation from the other minerals, the mixed oxides of
tantalum () and niobium () are obtained. The first step in the
processing is the reaction of the oxides with hydrofluoric acid:
:
:
The first industrial scale separation, developed by Swiss chemist Jean
Charles Galissard de Marignac, exploits the differing solubilities of
the complex niobium and tantalum fluorides, dipotassium
oxypentafluoroniobate monohydrate () and dipotassium
heptafluorotantalate () in water. Newer processes use the liquid
extraction of the fluorides from aqueous solution by organic solvents
like cyclohexanone. The complex niobium and tantalum fluorides are
extracted separately from the organic solvent with water and either
precipitated by the addition of potassium fluoride to produce a
potassium fluoride complex, or precipitated with ammonia as the
pentoxide:
:
Followed by:
:
Several methods are used for the reduction to metallic niobium. The
electrolysis of a molten mixture of and sodium chloride is one; the
other is the reduction of the fluoride with sodium. With this method,
a relatively high purity niobium can be obtained. In large scale
production, is reduced with hydrogen or carbon. In the aluminothermic
reaction, a mixture of iron oxide and niobium oxide is reacted with
aluminium:
:
Small amounts of oxidizers like sodium nitrate are added to enhance
the reaction. The result is aluminium oxide and ferroniobium, an alloy
of iron and niobium used in steel production. Ferroniobium contains
between 60 and 70% niobium. Without iron oxide, the aluminothermic
process is used to produce niobium. Further purification is necessary
to reach the grade for superconductive alloys. Electron beam melting
under vacuum is the method used by the two major distributors of
niobium.
, CBMM from Brazil controlled 85 percent of the world's niobium
production. The United States Geological Survey estimates that the
production increased from 38,700 tonnes in 2005 to 44,500 tonnes in
2006. Worldwide resources are estimated to be 4.4 million tonnes.
During the ten-year period between 1995 and 2005, the production more
than doubled, starting from 17,800 tonnes in 1995. Between 2009 and
2011, production was stable at 63,000 tonnes per year, with a slight
decrease in 2012 to only 50,000 tonnes per year.
Mine production (t) (USGS estimate)
World
|| **2000** || 30000 || 2290 || 160 || 35 || 28 || ? || ? || 32600
|| **2001** || 22000 || 3200 || 230 || 30 || 120 || ? || 50 || 25600
|| **2002** || 26000 || 3410 || 290 || 30 || 76 || 5 || 50 || 29900
|| **2003** || 29000 || 3280 || 230 || 190 || 22 || 34 || 13 || 32800
|| **2004** || 29900 || 3400 || 200 || 170 || 63 || 130 || 52 ||
34000
|| **2005** || 35000 || 3310 || 200 || 40 || 63 || 34 || 25 || 38700
|| **2006** || 40000 || 4167 || 200 || 35 || 80 || 29 || ? || 44500
|| **2007** || 57300 || 3020 || ? || ? || ? || ? || ? || 60400
|| **2008** || 58000 || 4380 || ? || ? || ? || ? || ? || 62900
|| **2009** || 58000 || 4330 || ? || ? || ? || 4 || ? || 62900
|| **2010** || 58000 || 4420 || ? || ? || ? || 10 || ? || 62900
|| **2011** || 58000 || 4630 || ? || ? || ? || 29 || ? || 63000
|| **2012** || 63000 || 5000 || ? || ? || ? || 30 || ? || 50100
|| **2013** || 53100 || 5260 || ? || ? || ? || 20 || ? || 59400
|| **2014** || 53000 || 5000 || ? || ? || ? || ? || ? || 59000
|| **2015** || 58000 || 5750 || ? || 29 || ? || ? || ? || 64300
|| **2016** || 57000 || 6100 || ? || 104 || ? || ? || ? || 63900
|| **2017** || 60700 || 6980 || ? || 122 || ? || ? || ? || 69100
|| **2018** || 59000 || 7700 || ? || 181 || ? || ? || ? || 68200
|| **2019** || 88900 || 6800 || ? || 150 || ? || ? || ? || 97000
|| **2020** || 59800 || 6500 || ? || ? || ? || ? || ? || 67700
Lesser amounts are found in Malawi's Kanyika Deposit (Kanyika mine).
Compounds
======================================================================
In many ways, niobium is similar to tantalum and zirconium. It reacts
with most nonmetals at high temperatures; with fluorine at room
temperature; with chlorine at 150 C and hydrogen at 200 C; and with
nitrogen at 400 C, with products that are frequently interstitial and
nonstoichiometric. The metal begins to oxidize in air at 200 C. It
resists corrosion by acids, including aqua regia, hydrochloric,
sulfuric, nitric and phosphoric acids. Niobium is attacked by hot
concentrated sulfuric acid, hydrofluoric acid and hydrofluoric/nitric
acid mixtures. It is also attacked by hot, saturated alkali metal
hydroxide solutions.
Although niobium exhibits all of the formal oxidation states from +5
to −1, the most common compounds have niobium in the +5 state.
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. Nb(V)
is also slightly soluble in alkaline media due to the formation of
soluble polyoxoniobate species.
Oxides, niobates and sulfides
===============================
Niobium forms oxides in the oxidation states +5 (Niobium pentoxide),
+4 (Niobium dioxide), and the rarer oxidation state, +2 (NbO). Most
common is the pentoxide, precursor to almost all niobium compounds and
alloys. Niobates are generated by dissolving the pentoxide in basic
hydroxide solutions or by melting it in alkali metal oxides. Examples
are lithium niobate () and lanthanum niobate (). Lithium niobate has a
trigonally distorted perovskite-like structure, whereas the lanthanum
niobate contains lone ions. The layered niobium sulfide () is also
known.
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.
Halides
=========
Niobium forms halides in the oxidation states of +5 and +4 as well as
diverse substoichiometric compounds. The pentahalides () feature
octahedral Nb centres. Niobium pentafluoride () is a white solid with
a melting point of 79 C and niobium pentachloride () is yellow (see
image at right) with a melting point of 203.4 C. Both are hydrolyzed
to give oxides and oxyhalides, such as . The pentachloride is a
versatile reagent used to generate the organometallic compounds, such
as niobocene dichloride (). The tetrahalides () are dark-coloured
polymers with Nb-Nb bonds; for example, the black hygroscopic niobium
tetrafluoride () and dark violet niobium tetrachloride ().
Anionic halide compounds of niobium are well known, owing in part to
the Lewis acidity of the pentahalides. The most important is , an
intermediate in the separation of Nb and Ta from the ores. This
heptafluoride tends to form the oxopentafluoride more readily than
does the tantalum compound. Other halide complexes include octahedral
[](−):
:
As with other metals with low atomic numbers, a variety of reduced
halide cluster ions is known, the prime example being .
Nitrides and carbides
=======================
Other binary compounds of niobium include niobium nitride (NbN), which
becomes a superconductor at low temperatures and is used in detectors
for infrared light. The main niobium carbide is NbC, an extremely
hard, refractory, ceramic material, commercially used in cutting tool
bits.
Applications
======================================================================
Out of 44500 tonne of niobium mined in 2006, an estimated 90% was used
in high-grade structural steel. The second-largest application is
superalloys. Niobium alloy superconductors and electronic components
account for a very small share of the world production.
Steel production
==================
Niobium is an effective microalloying element for steel, within which
it forms niobium carbide and niobium nitride. These compounds improve
the grain refining, and retard recrystallization and precipitation
hardening. These effects in turn increase the toughness, strength,
formability, and weldability. Within microalloyed stainless steels,
the niobium content is a small (less than 0.1%) but important addition
to high-strength low-alloy steels that are widely used structurally in
modern automobiles. Niobium is sometimes used in considerably higher
quantities for highly wear-resistant machine components and knives, as
high as 3% in Crucible CPM S110V stainless steel.
These same niobium alloys are often used in pipeline construction.
Superalloys
=============
Quantities of niobium are used in nickel-, cobalt-, and iron-based
superalloys in proportions as great as 6.5% for such applications as
jet engine components, gas turbines, rocket subassemblies,
turbocharger systems, heat resisting, and combustion equipment.
Niobium precipitates a hardening γ'-phase within the grain structure
of the superalloy.
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.
These superalloys were used, for example, in advanced air frame
systems for the Gemini program. Another niobium alloy was used for the
nozzle of the Apollo Service Module. Because niobium is oxidized at
temperatures above 400 °C, a protective coating is necessary for these
applications to prevent the alloy from becoming brittle.
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 niobium
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 descent engine of the
Apollo Lunar Modules.
The reactivity of niobium with oxygen requires it to be worked in a
vacuum or inert atmosphere, which significantly increases the cost and
difficulty of production. Vacuum arc remelting (VAR) and electron beam
melting (EBM), novel processes at the time, enabled the development of
niobium and other reactive metals. The project that yielded C-103
began in 1959 with as many as 256 experimental niobium alloys in the
"C-series" that could be melted as buttons and rolled into sheet. Wah
Chang Corporation had an inventory of hafnium, refined from
nuclear-grade zirconium alloys, that it wanted to put to commercial
use. The 103rd experimental composition of the C-series alloys,
Nb-10Hf-1Ti, had the best combination of formability and
high-temperature properties. Wah Chang fabricated the first 500 lb of
C-103 in 1961, ingot to sheet, using EBM and VAR. The intended
applications included turbine engines and liquid metal heat
exchangers. Competing niobium alloys from that era included FS85
(Nb-10W-28Ta-1Zr) from Fansteel Metallurgical Corp., Cb129Y
(Nb-10W-10Hf-0.2Y) from Wah Chang and Boeing, Cb752 (Nb-10W-2.5Zr)
from Union Carbide, and Nb1Zr from Superior Tube Co.
The nozzle of the Merlin Vacuum series of engines developed by SpaceX
for the upper stage of its Falcon 9 rocket is made from a C-103
niobium alloy.
Niobium-based superalloys are used to produce components of hypersonic
missile systems.
Superconducting magnets
=========================
Niobium-germanium (), niobium-tin (), as well as the niobium-titanium
alloys are used as a type II superconductor wire for superconducting
magnets. These superconducting magnets are used in magnetic resonance
imaging and nuclear magnetic resonance instruments as well as in
particle accelerators. For example, the Large Hadron Collider uses 600
ST of superconducting strands, while the International Thermonuclear
Experimental Reactor uses an estimated 600 LT of strands and 250 LT
of NbTi strands. In 1992 alone, more than one billion US dollars'
worth of clinical magnetic resonance imaging systems were constructed
with niobium-titanium wire.
Other superconductors
=======================
The superconducting radio frequency (SRF) cavities used in the
free-electron lasers FLASH (result of the cancelled TESLA linear
accelerator project) and XFEL are made from pure niobium. A cryomodule
team at Fermilab used the same SRF technology from the FLASH project
to develop nine-cell SRF cavities made from pure niobium. The
cavities will be used in the linear particle accelerator of the
International Linear Collider. The same technology will be used in
LCLS-II at SLAC National Accelerator Laboratory and PIP-II at
Fermilab.
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 Heinrich Hertz
Submillimeter Telescope, the South Pole Telescope, the Receiver Lab
Telescope, and at Atacama Pathfinder Experiment (APEX), and are now
used in the HIFI instrument on board the Herschel Space Observatory.
Electroceramics
=================
Lithium niobate, which is a ferroelectric, is used extensively in
mobile telephones and optical modulators, and for the manufacture of
surface acoustic wave devices. It belongs to the perovskite ()
structure ferroelectrics like lithium tantalate and barium titanate.
Niobium capacitors are available as alternatives to tantalum
capacitors, but tantalum capacitors still predominate. Niobium is
added to glass to obtain a higher refractive index, making possible
thinner and lighter corrective lenses for eyeglasses.
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. Niobium treated with sodium
hydroxide forms a porous layer that aids osseointegration.
Like titanium, tantalum, and aluminium, niobium can be heated and
anodized to produce a wide array of iridescent colours for jewelry,
where its hypoallergenic property is highly desirable.
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. 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, and the 2006 Austrian €25 European
Satellite Navigation commemorative coin. The Austrian mint produced
for Latvia a similar series of coins starting in 2004, with one
following in 2007. In 2011, the Royal Canadian Mint started production
of a $5 sterling silver and niobium coin named 'Hunter's Moon' 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 sodium vapor lamps are made from
niobium, sometimes alloyed with 1% of zirconium; niobium has a very
similar coefficient of thermal expansion, matching the sintered
alumina arc tube ceramic, a translucent material which resists
chemical attack or reduction by the hot liquid sodium and sodium
vapour contained inside the operating lamp.
Niobium is used in arc welding rods for some stabilized grades of
stainless steel and in anodes for cathodic protection systems on some
water tanks, which are then usually plated with platinum.
Niobium is used to make the high voltage wire of the solar corona
particles receptor module of the Parker Solar Probe.
Niobium is a constituent of a lightfast chemically stable inorganic
yellow pigment that has the trade name NTP Yellow. It is Niobium
Sulfur Tin Zinc Oxide, a pyrochlore, produced via high-temperature
calcination. The pigment is also known as pigment yellow 227, commonly
listed as PY 227 or PY227.
Niobium is employed in the atomic energy industry for its high
temperature and corrosion resistance, as well as its stability under
radiation. It is used in nuclear reactors for components like fuel
rods and reactor cores.
Nickel niobium alloys are used in aerospace, oil and gas,
construction. They are used in components of jet engines, in ground
gas turbines, elements of bridges and high-rise buildings.
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 often used in jewelry and has been tested for use in
some medical implants.
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 (LD) between 10 and 100 mg/kg. For oral administration the
toxicity is lower; a study with rats yielded a LD after seven days of
.
External links
======================================================================
* [
http://www.tanb.org/ Tantalum-Niobium International Study Center]
*
[
https://web.archive.org/web/20061002182416/http://www.symmetrymag.org/cms/?pid=1000173
Niobium for particle accelerators eg ILC. 2005]
*
*
*
* [
http://www.periodicvideos.com/videos/041.htm Niobium] at 'The
Periodic Table of Videos' (University of Nottingham)
License
=========
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Original Article:
http://en.wikipedia.org/wiki/Niobium
