History
The element was discovered in 1801 by British chemist Charles Hatchett during analysis of a black mineral sample from the British Museum, originally sent in 1753 from Connecticut. He named the element columbium, after the country of its origin, Columbia (United States). In 1844, Rose announced the discovery of a new element which he named as niobium, in honor of Niobe, the daughter of Tantalus, the mythological Goddess of Tears. Later, it was established that Hatchett’s columbium and Roses’ niobium were the same element. Both names remained in use for more than one hundred years. In 1949 at the Fifteenth International Union of Chemistry Congress held at Amsterdam, the name niobium was officially adopted as the international name.
Niobium was prepared in the metallic state for the first time by Blomstrand in 1866, later by Moissan, and still later, by Goldschmidt. While Blomstrand reduced niobium chloride with hydrogen to form niobium, Moissan and Goldschmidt reduced the oxide with carbon (in an electrical furnace) and aluminum powder, respectively.
Niobium occurs naturally in several minerals, mostly associated with tantalum and many rare earth elements. The metal is never found in free elemental form. It occurs mostly as hydroxide, silicate, or borate or as its oxy salt, niobate, which is mostly associated with isomorphous tantalate. The principal niobium minerals are pyrochlore, loparite, and koppite all of which contain titanium together with calcium and other metals, such as cerium. They are complex hydroxide minerals and their composition may vary with place. Another type of niobium mineral is the niobates-tantalates mixed ores of Nb2O6—Ta2O6 or of compositions (Nb,Ta)2O6. Such ores usually contain iron and sometimes manganese which partially replaces iron. A typical example is an isomorphous admixture of Fe(NbO3)2—Fe(TaO2)2. Many impurity metals, such as tungsten, titanium, and tin are also found in these ores.
The abundance of niobium in the earth’s crust is estimated to be in the range 20 mg/kg and its average concentration in sea water is 0.01 mg/L. The metal also is found in the solar system including the lunar surface. Radionucleides niobium-94 and -95 occur in the fission products of uranium- 235.
Uses
Niobium is a very important metal in both ferrous and nonferrous metallurgy. As an additive to alloys or when alloyed with other metals niobium imparts high mechanical strength, high electrical conductivity, and ductility to alloys. It enhances corrosion resistance of most alloys. The metal and several of its alloys exhibit superconductivity. Nobium is used as an additive in the manufacture of most high strength, low alloy carbon steels and microalloyed steels that are used in the construction of oil and gas pipelines, bridges, buildings, concrete bars, and automobiles.
Nobium also is added to nickel- and cobalt-based superalloys and is a component of zirconium, titanium and tungsten alloys.
Other applications of niobium are in electronic and propulsion devices, in electrodes; in catalysis; and in vacuum tubes and high-pressure sodium vapor lamps.
Production Methods
There are several processes for extracting and refining niobium from its ores. The process of choice depends on nature of the ore and end use intended for the metal. Some common steps in these recovery processes involve ore preconcentration, breaking or opening the ore, obtaining pure niobium compounds, reduction of niobium compounds to niobium metal, purification or refining metal and fabrication. If niobium is extracted from a niobium-tantalum ore, the most important step is separation of niobium from tantalum, both of which are chemically very similar.
Ferroniobium can be produced from the ore pyrochlore in batch process by thermal reduction in a refractory-lined steel or preferably an electric furnace reactor. Aluminum powder is used as a reducing agent.
Ore-opening is a key step in the recovery of niobium, and separation of niobium from tantalum and impurity metals is the most important step in its extraction from the ore. It may be achieved by several methods that include solvent extraction, ion exchange, fractional crystallization, fractional sublimation, and other techniques.
High purity grade metal may be produced by reduction of niobium pentaoxide, Nb2O5 or pentachloride, NbCl5 at elevated temperatures ranging from 1400 to 2000°C and often under vacuum using various reducing agents, such as carbon, hydrogen, sodium and other substances:
Nb2O5 + 7C → 2NbC + 5CO
Nb2O5 + 5NbC → 7Nb + 5CO
2NbCl5 + 5H2 → 2Nb + 10HCl
NbCl5 + 5Na → Nb + 5NaCl
Chemical Properties
Niobium was discovered by Charles Hatchett in 1801 and isolated by Christian Blomstrand of Sweden in 1964. Its name was given after the Greek mythological ?gure Niobe, the daughter of Tantalos; tantalum always was associated with niobium. For many years, the terms “niobium” and “columbium”wereusedinterchangeably;however,thename “niobium” was of?cially adopted by International Union of Pure and Applied Chemistry (IUPAC) in 1950. Niobium is not a very rare element; its crustal abundance is 24ppm, which is similar or greater than those of many common elements, such as lead or cobalt.
Niobium is a shiny white, soft, and malleable metal. The element is inert to HCl, HNO3, or aqua regia at room temperature, slightly soluble in HF, but is attacked by alkali hydroxides or oxidizing agents at all temperatures. In pure
form, niobium is ductile, unless it is allowed to associate at elevated temperatures with common gases such as N2,H 2, or O2. Thus, when processed, it must be placed in a protective environment
No data were found in the literature; however, it might be assumed that niobium and most of their compounds are odorless. Niobium pentachloride (NbCl5) has pungent odor, because it decomposes slowly when heated, with Cl2 formation. Niobium in the form of dust is moderately explosive when exposed to ?ame or by chemical reaction.
Chemical Properties
shiny grey metallic solid
Physical properties
Niobium is a soft grayish-silvery metal that resembles fresh-cut steel. It is usually found inminerals with other related metals. It neither tarnishes nor oxidizes in air at room temperaturebecause of a thin coating of niobium oxide. It does readily oxidize at high temperatures(above 200°C), particularly with oxygen and halogens (group 17). When alloyed with tin andaluminum, niobium has the property of superconductivity at 9.25 Kelvin degrees.
Its melting point is 2,468°C, its boiling point is 4,742°C, and its density is 8.57 g/cm
3.
Isotopes
There are 49 isotopes of niobium, ranging from Nb-81 to Nb-113. All are radioactiveand made artificially except niobium-93, which is stable and makes up all of theelement’s natural existence in the Earth’s crust.
Origin of Name
Niobium is named after the Greek mythological figure Niobe who was
the daughter of Tantalus. Tantalus was a Greek god whose name is the source of the
word “tantalize,” which implies torture: he cut up his son to make soup for other gods.
Occurrence
Niobium is the 33rd most abundant element in the Earth’s crust and is considered rare.It does not exist as a free elemental metal in nature. Rather, it is found primarily in severalmineral ores known as columbite (Fe, Mn, Mg, and Nb with Ta) and pyrochlore [(Ca,Na)
2Nb
2O
6 (O, OH, F)]. These ores are found in Canada and Brazil. Niobium and tantalum[(Fe, Mn)(Ta, Nb)
2O
6] are also products from tin mines in Malaysia and Nigeria. Niobium is a chemical “cousin” of tantalum and was originally purified by its separation through theprocess known as fractional crystallization (separation is accomplished as a result of the differentrates at which some elements crystallize) or by being dissolved in special solvents. Todaymost of the niobium metal is obtained from columbite and pyrochlore through a complicatedrefining process that ends with the production of niobium metal by electrolysis of moltenniobium potassium fluoride (K
2NbF
7).
History
Niobium was discovered in 1801 by Hatchett in an ore sent to England
more that a century before by John Winthrop the Younger,
first governor of Connecticut. The metal was first prepared
in 1864 by Blomstrand, who reduced the chloride by heating
it in a hydrogen atmosphere. The name niobium was adopted
by the International Union of Pure and Applied Chemistry in
1950 after 100 years of controversy. Most leading chemical societies
and government organizations refer to it by this name.
Some metallurgists and commercial producers, however, still
refer to the metal as “Niobium.” Niobium is found in
niobite (or columbite), niobite-tantalite, pyrochlore, and euxenite.
Large deposits of niobium have been found associated
with carbonatites (carbon-silicate rocks), as a constituent of
pyrochlore. Extensive ore reserves are found in Canada, Brazil,
Congo-Kinshasa, Rwanda, and Australia. The metal can be
isolated from tantalum, and prepared in several ways. It is a
shiny, white, soft, and ductile metal, and takes on a bluish cast
when exposed to air at room temperatures for a long time. The
metal starts to oxidize in air at 200°C, and when processed at
even moderate temperatures must be placed in a protective
atmosphere. It is used in arc-welding rods for stabilized grades
of stainless steel. Thousands of pounds of niobium have been
used in advanced air frame systems such as were used in the
Gemini space program. It has also found use in super-alloys
for applications such as jet engine components, rocket subassemblies,
and heat-resisting equipment. The element has
superconductive properties; superconductive magnets have
been made with Nb-Zr wire, which retains its superconductivity
in strong magnetic fields. Natural niobium is composed
of only one isotope, 93Nb. Forty-seven other isotopes and isomers
of niobium are now recognized. Niobium metal (99.9%
pure) is priced at about 50￠/g.
Characteristics
Some of niobium’s characteristics and properties resemble several other neighboring elementson the periodic table, making them, as well as niobium, difficult to identify. This isparticularly true for tantalum, which is located just below niobium on the periodic table.
Niobium is not attacked by cold acids but is very reactive with several hot acids such ashydrochloric, sulfuric, nitric, and phosphoric acids. It is ductile (can be drawn into wiresthrough a die) and malleable, which means it can be worked into different forms.
Uses
Refined niobium metal is most useful as an alloy with other metals. It is used to producespecial stainless steel alloys, to make high-temperature magnets, as special metals for rocketsand missiles, and for high- and low-temperature–resistant ceramics. Stainless steel that hasbeen combined with niobium is less likely to break down under very high temperatures.This physical attribute is ideal for construction of both land- and sea-based nuclear reactors.Niobium has special cryogenic properties. It can withstand very cold temperatures, whichimproves its ability to conduct electricity. This characteristic makes it an excellent metal forlow-temperature electrical superconductors.
Niobium alloyed with germanium becomes a superconductor of electricity that does notlose its superconductivity at 23.2° Kelvin as large amounts of electrical current are passedthrough it, as do some other superconductive alloys. In the pure metallic state, niobium wiresare also superconductors when the temperatures are reduced to near absolute zero (–273°C).Niobium alloys are also used to make superconductive magnets as well as jewelry.
.
Uses
Niobium sputtering target is used in high temperature engineering products. It is also used as an alloying agent for certain steels where it greatly improves the strength of the resulting material. It is also finds applications in atomic reactors due to its corrosion resistance and, when combined with either tin (Nb3Sn) or zirconium, it has a high degree of superconductivity.
Uses
In ferrous metallurgy: Ferroniobium (produced by silicon reduction of columbite) is used to alloy stainless steels and metals for welding rods. In niobium base alloys for high temperatures and nuclear reactions. Niobium has some use as a getter in electronic vacuum tubes.
Definition
The name niobium is officially approved by chemical authorities, but columbium is still used chiefly
by metallurgists. Metallic element, atomic number
41, group VB of the periodic table, aw 92.9064,
valences of 2, 3, 4, 5; no stable isotopes
Definition
Columbium: a former name for theelement niobium.
Definition
A soft silvery
transition element used in welding, special
steels, and nuclear reactor work.
Symbol: Nb; m.p. 2468°C; b.p.
4742°C; r.d. 8.570 (20°C); p.n. 41; r.a.m.
92.90638.
Definition
niobium: Symbol Nb. A soft ductilegrey-blue metallic transition element;a.n. 41; r.a.m. 92.91; r.d. 8.57;m.p. 2468°C; b.p. 4742°C. It occurs inseveral minerals, including niobite(Fe(NbO
3)
2), and is extracted by severalmethods including reduction ofthe complex fluoride K
2NbF
7 usingsodium. It is used in special steelsand in welded joints (to increasestrength). Niobium–zirconium alloysare used in superconductors. Chemically,the element combines with thehalogens and oxidizes in air at 200°C.It forms a number of compounds andcomplexes with the metal in oxidationstates 2, 3, or 5. The elementwas discovered by Charles Hatchett(c. 1765–1847) in 1801 and first isolatedby Christian Blomstrand(1826–97) in 1864. Formerly, it wascalled columbium.
Production Methods
Theextractingandre?ningprocessesforniobiumfromore are extremely complex and consist of a series of operations,
starting from upgrading the ores by concentration. Disruption of the niobium-containing matrix is then performed by an ore-opening procedure with hot HF or fusion with alkali ?uxes. The next steps include pure niobium compound preparation and reduction to metallic niobium, followed by re?ning, consolidation, and fabrication of the metal. Niobium is so closely associated with tantalum that they must be separated by fractional crystallization or by solvent extraction before puri?cation.
Hazard
Niobium is not considered reactive at normal room temperatures. However, it is toxic in itsphysical forms as dust, powder, shavings, and vapors, and it is carcinogenic if inhaled or ingested.
Carcinogenicity
No evidence was found that niobiumiscarcinogenic.Indeed,therearesomestudiessuggesting its antitumor activity. In the mouse study of Schroeder et al., occurrence of 23.6% of tumors in the niobiumtreated group (5–6.62ppm niobium in drinking water and diet for a lifetime) versus 34.8% for the controls was documented.
