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Niobium wire

   

Grade

Specifications

Purity

Standard

RO4200-1

¢0.25~¢3.0mm

>=99.9%  or 99.95%

ASTM B392

RO4210-2

Mechanical requirements (annealed condition)

Grade

Tensile strength  δbpsi (MPa), ≥

Yield strength  δ0.2, psi (MPa),≥

Elongation in 1"/2" gage length, %, ≥

RO4200-1
RO4210-2

18000 (125)

10500 (73)

25

Special requirements to be agreed on by the supplier and buyer of negotiations

    Niobium, formerly columbium, is a chemical element with the symbol Nb (formerly Cb) and atomic number 41. It is a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite. The name comes from Greek mythology: Niobe, daughter of Tantalus.


    Niobium has physical and chemical properties similar to those of the element tantalum, and the two are therefore difficult to distinguish. The English chemist Charles Hatchett reported a new element similar to tantalum in 1801 and named it columbium. In 1809, the English chemist William Hyde Wollaston wrongly concluded that tantalum and columbium were identical. The 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. Brazil is the leading producer of niobium and ferroniobium, an alloy of niobium and iron. Niobium is used mostly in alloys, the largest part in special steel such as that used in gas pipelines. 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 superalloys is important for its use in jet and rocket engines. Niobium is used in various super conducting materials. These superconducting alloys, also containing titanium and tin, are widely used in the superconducting magnets of MRI scanners. Other applications of niobium include its use in welding, nuclear industries, electronics, optics, numismatics and jewelry. In the last two applications, niobium's low toxicity and ability to be colored by anodization are particular advantages.

Characteristics
Physical
    Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), although it has an atypical configuration in its outermost electron shells compared to the rest of the members.

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 (predicted)

    Niobium becomes a superconductor at cryogenictemperatures. Under atmospheric pressure, it has the highest critical temperature of the elemental superconductors: 9.2 K. Niobium has the largest 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 capture cross-section for thermal neutrons; thus it is used in the nuclear industries.

Chemical
    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 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, owing to 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, its lower price and greater availability make niobium attractive for less demanding uses such as linings in chemical plants.

Production
    After the separation from the other minerals, the mixed oxides of tantalum Ta2O5 and niobium Nb2O5 are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acid:[31]
Ta2O5 + 14 HF → 2 H2[TaF7] + 5 H2O       Nb2O5 + 10 HF → 2 H2[NbOF5] + 3 H2O


    The first industrial scale separation, developed by de Marignac, exploits the differing solubilities of the complex niobium and tantalum fluorides, 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 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: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 electrolysis of a molten mixture of K2[NbOF5] and sodium chloride is one; the other is the reduction of the fluoride with sodium. With this method niobium with a relatively high purity can be obtained. In large scale production the reduction of Nb2O5 with hydrogen or carbon[35] is used. In the process involving the aluminothermic reaction a mixture of iron oxideand niobium oxide is reacted with aluminium:3 Nb2O5 + Fe2O3 + 12 Al → 6 Nb + 2 Fe + 6 Al2O3


    To enhance the reaction, small amounts of oxidizers like sodium nitrate are added. The result is aluminium oxide and ferroniobium, 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 melting under vacuum is the method used by the two major distributors of niobium.


    As of 2013, the Brazilian company Cia. Brasileira de Metalurgia & Mineracao "controls 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. 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. Since 2009 production is stable at around 63,000 tonnes per year.

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