niobium
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What is niobium?
Niobium (Nb), element number 41, is a refractory metal in Group 5 (Vb) of the periodic table. The English chemist Charles Hatchett discovered niobium in 1801 in an ore sample from Connecticut and named it columbium. The name niobium was adopted around 1950, although the U.S. metallurgical industry still uses columbium.
Niobium is more plentiful than lead but less abundant than copper in the Earth’s crust. The pure metal resembles steel or platinum when polished and is soft and ductile. It has excellent corrosion resistance but is susceptible to oxidation above approximately 400 °C (750 °F). Niobium is used in alloys, tools and dies, and superconductive magnets. It is added to some stainless steels to provide stability during welding or heating and is a major alloying element in nickel-based superalloys.
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Where is niobium found on the periodic table?
Niobium (Nb) is a chemical element and a refractory metal that can be found in Group 5 (Vb) of the periodic table. Its atomic number is 41. Niobium is closely associated with tantalum in ores and properties. The main commercial sources of niobium are the columbite–tantalite series and pyrochlore. Niobium is used in alloys, tools and dies, and superconductive magnets.
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What are some physical properties of niobium?
Niobium (Nb) is a chemical element and a refractory metal that looks like steel or platinum when polished. It has a body-centred cubic crystal structure and a melting point of 2,468 °C (4,474 °F). Niobium has the lowest density and best workability of the refractory metals.
Other physical properties include:
* Atomic number: 41
* Atomic weight: 92.906
* Boiling point: 4,927 °C (8,901 °F)
* Specific gravity: 8.57 (at 20 °C)
* Oxidation states: +2, +3, +4, +5Niobium is a soft, ductile metal with excellent corrosion resistance, though it is susceptible to oxidation above 400° C (750° F). Niobium-titanium and niobium-tin alloys are used as superconducting materials.
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How is niobium used in industry or everyday life?
Niobium (Nb) is a chemical element used in various industrial and everyday applications due to its unique properties.
Niobium is a crucial additive in high-strength, low-alloy (HSLA) steels, enhancing their strength, toughness, and weldability while reducing the need for carbon and manganese. Niobium is also added to stainless steel to prevent intergranular corrosion.
Because niobium alloys have the highest transition temperature, they are used in superconducting applications such as machinery, magnetically levitated trains, high-energy physics, and magnetic resonance imaging. Niobium is also used to make lenses for cameras, eyeglasses, and copying machines.
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Why is niobium important for making alloys?
Niobium is a crucial element in alloy creation due to its ability to enhance the strength, toughness, and weldability of steel, particularly in high-strength, low-alloy (HSLA) steels. When added to stainless steel, niobium forms carbide precipitates that improve dispersion hardening and prevent chromium carbide formation, which can cause embrittlement. Niobium also refines grain size in martensitic stainless steel, boosting creep resistance and toughness, and stabilizes interstitial impurities in ferritic stainless steels to prevent intergranular corrosion. Furthermore, niobium-based alloys are utilized in rocket nozzles and reentry guides because of their good workability and strength at high temperatures. Because of its compatibility with uranium, resistance to corrosion by molten alkali-metal coolants, and low thermal-neutron cross section, it has been used alone or alloyed with zirconium in claddings for nuclear reactor cores.
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How is niobium extracted and processed from its ores?
Niobium extraction from ores involves complex procedures due to its chemical similarity to tantalum. The primary commercial sources are the columbite-tantalite series and pyrochlore.
Processing typically begins with separating niobium from tantalum through liquid-liquid solvent extraction. The ore or ferroalloy is crushed, ground, and decomposed in hydrofluoric acid. Niobium remains in the aqueous residue and is precipitated as a fluoride by adding ammonium hydroxide. The precipitate is then calcined at high temperatures to obtain niobium pentoxide.
Niobium pentoxide can be reduced aluminothermically to produce niobium reguli, further purified by electron-beam melting into ingots or processed into niobium powder through a hydriding and dehydriding process. Vacuum sintering is also used for consolidation.
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niobium (Nb), chemical element, refractory metal of Group 5 (Vb) of the periodic table, used in alloys, tools and dies, and superconductive magnets. Niobium is closely associated with tantalum in ores and in properties.
Due to the great chemical similarity of niobium and tantalum, the establishment of the individual identities of the two elements was very difficult. Niobium was first discovered (1801) in an ore sample from Connecticut by the English chemist Charles Hatchett, who called the element columbium in honour of the country of its origin, Columbia being a synonym for the United States. In 1844 a German chemist, Heinrich Rose, discovered what he considered to be a new element occurring along with tantalum and named it niobium after Niobe, the mythological goddess who was the daughter of Tantalus. After considerable controversy it was decided that columbium and niobium were the same element. Eventually international agreement (about 1950) was reached to adopt the name niobium, though columbium persisted in the U.S. metallurgical industry.
Niobium is roughly 10 times more abundant in the crust of the Earth than is tantalum. Niobium, more plentiful than lead and less abundant than copper in the Earth’s crust, occurs dispersed except for relatively few minerals. Of these minerals, the columbite–tantalite series, in which columbite (FeNb2O6) and tantalite (FeTa2O6) occur in highly variable ratios, is the main commercial source. Pyrochlore, a calcium sodium niobate, is also the principal commercial source. Natural niobium occurs entirely as the stable isotope niobium-93.
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The production procedures for niobium are complex, the major problem being its separation from tantalum. Separation from tantalum, when necessary, is effected by solvent extraction in a liquid-liquid process; the niobium is then precipitated and roasted to niobium pentoxide, which is reduced to niobium powder through metallothermic and hydriding processes. The powder is consolidated and purified further by electron-beam melting. Vacuum sintering of powder is also used for consolidation. Niobium can also be obtained by either electrolysis of fused salts or reduction of fluoro complexes with a very reactive metal such as sodium. (For information on the mining, recovery, and applications of niobium, see niobium processing.)
The pure metal is soft and ductile; it looks like steel or, when polished, like platinum. Although it has excellent corrosion resistance, niobium is susceptible to oxidation above about 400° C (750° F). Niobium can best be dissolved in a mixture of nitric and hydrofluoric acids. Completely miscible with iron, it is added in the form of ferroniobium to some stainless steels to give stability on welding or heating. Niobium is used as a major alloying element in nickel-based superalloys and as a minor but important additive to high-strength, low-alloy steels. Because of its compatibility with uranium, resistance to corrosion by molten alkali-metal coolants, and low thermal-neutron cross section, it has been used alone or alloyed with zirconium in claddings for nuclear reactor cores. Cemented carbides used as hot-pressing dies and cutting tools are made harder and more resistant to shock and erosion by the presence of niobium. Niobium is useful in constructing cryogenic (low temperature) electronic devices of low power consumption. Niobium-tin (Nb3Sn) is a superconductor below 18.45 Kelvins (K), and niobium metal itself, below 9.15 K.
Compounds of niobium are of relatively minor importance. Those found in nature have the +5 oxidation state, but compounds of lower oxidation states (+2 to +4) have been prepared. Quadruply charged niobium, for example, in the form of the carbide, NbC, is used for making cemented carbides.
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| atomic number | 41 |
|---|---|
| atomic weight | 92.906 |
| melting point | 2,468° C (4,474° F) |
| boiling point | 4,927° C (8,901° F) |
| specific gravity | 8.57 (20° C) |
| oxidation states | +2, +3, +4, +5 |
| electron config. | [Kr]4d45s1 |