Nickel

Related Topics:
Nickel :: Nickelodeon :: Nickelback :: Nickel_Creek :: Nickelsville :: Nickel_Cadmium

Nickel is a metallic chemical element in the periodic table that has the symbol Ni and atomic number 28.

Notable characteristics

Nickel is a silvery white metal that takes on a high polish. It belongs to the iron group, and is hard, malleable, and ductile. It occurs combined with sulfur in millerite, with arsenic in the mineral niccolite, and with arsenic and sulfur in nickel glance.

On account of its permanence in air and inertness to oxidation, it is used in the smaller coins, for plating iron, brass, etc., for chemical apparatus, and in certain alloys, as German silver. It is magnetic, and is very frequently accompanied by cobalt, both being found in meteoric iron. It is chiefly valuable for the alloys it forms, especially many superalloys.

Nickel is one of the five ferromagnetic elements. However, the US "nickel" coin is not magnetic, because it actually is mostly copper, but old Canadian nickels minted until 1958 were.

The most common oxidation state of nickel is +2, though 0, +1, +3 and +4 Ni complexes are observed. It is also thought that a +6 oxidation state may exist, however, results are inconclusive.

The unit cell of nickel is an FCC with a lattice parameter of 0.356 nm giving a radius of the atom of 0.126 nm.

Nickel-62 is the most stable nuclide of all the existing elements; it is more stable even than Iron-56.

History

Nickel use is ancient, and can be traced back as far as 3500 BCE. Bronzes from what is now Syria had a nickel content of up to two percent. Further, there are Chinese manuscripts suggesting that "white copper" (e.g. baitung) was used in the Orient between 1400 and 1700 BC. However, because the ores of nickel were easily mistaken for ores of silver, any understanding of this metal and its use dates to more contemporary times.

Minerals containing nickel (e.g. kupfernickel, or false copper) were of value for colouring glass green. In 1751, Baron Axel Fredrik Cronstedt was attempting to extract copper from kupfernickel (now called niccolite), and obtained instead a white metal that he called nickel.

Coins of pure nickel were first used 1881 in Switzerland. ^*

Biological role

Many but not all hydrogenases contain nickel in addition to iron-sulfur clusters. Nickel centres are a common element in those hydrogenases whose function is to oxidise rather than evolve hydrogen. The nickel centre appears to undergo changes in oxidation state, and evidence has been presented that the nickel centre might be the active site of these enzymes.

A nickel-tetrapyrrole coenzyme, Co-F430, is present in the methyl CoM reductase and in methanogenic bacteria. The tetrapyrrole is intermediate in structure between porphyrin and corrin. Changes in redox state, as well as changes in nickel coordination, have recently been observed.

There is also a nickel-containing carbon monoxide dehydrogenase. Little is known about the structure of the nickel site.

Studies on chicks and rats (the latter of which are relatively close to humans genetically) suggest that nickel is essential for proper liver function.

Occurrence

The bulk of the nickel mined comes from two types of ore deposits. The first are laterites where the principal ore minerals are nickeliferous limonite: (Fe,Ni)O(OH) and garnierite (a hydrous nickel silicate): (Ni,Mg)₃Si₂O₅(OH). The second are magmatic sulfide deposits where the principal ore mineral is pentlandite: (Ni,Fe)₉S₈.

see Ore genesis, Category:Nickel minerals

In terms of supply, the Sudbury region of Ontario, Canada, produces about 30 percent of the world's supply of nickel. The Sudbury Basin deposit is theorized to have been created by a massive meteorite impact event early in the geologic history of Earth. Russia contains about 40% of the world's known resources at the massive Norilsk deposit in Siberia. Russia mines this primarily for its own domestic supply, and for export of palladium. Other major deposits of nickel are found in New Caledonia, Australia, Cuba, and Indonesia. The deposits in tropical areas are typically laterites which are produced by the intense weathering of ultramafic igneous rocks and the resulting secondary concentration of nickel bearing oxide and silicate minerals. A recent development has been the exploitation of a deposit in western Turkey, especially convenient for European smelters, steelmakers and factories.

Based on geophysical evidence, most of the nickel on Earth is postulated to be concentrated in the Earth's core.

Applications

Nickel is used in many industrial and consumer products, including stainless steel, magnets, coinage, and special alloys. It is also used for plating and as a green tint in glass. Nickel is pre-eminently an alloy metal, and its chief use is in the nickel steels and nickel cast irons, of which there are innumberable varietes. It is also widely used for many other alloys, such as nickel brasses and bronzes, and alloys with copper, chromium, aluminum, lead, cobalt, silver and gold.

Nickel consumption can be summarized as: nickel steels (60%), nickel-copper alloys and nickel silver (14%), malleable nickel, nickel clad and Inconel (9%), plating (6%), nickel cast irons (3%), heat and electric resistance alloys (3%), nickel brasses and bronzes (2%), others (3%).

Extraction and Purification

Nickel can be recovered using extractive metallurgy. Most lateritic ores have traditionally been processed using pyrometallurgical techniques to produce a matte for further refining. Recent advances in hydrometallurgy have resulted in recent nickel processing operations being developed using these processes. Most sulphide deposits have traditionally been processed by concentration through a froth flotation process followed by pyrometallurgical extraction. Recent advances in hydrometallurgical processing of sulphides has led to some recent projects being built around this technology.

Nickel is extracted from its ores by conventional roasting and reduction processes which yield a metal of >75% purity. Final purification in the Mond process to >99.99% purity is performed by reacting nickel and carbon monoxide to form nickel carbonyl. This gas is passed into a large chamber at a higher temperature in which tens of thousands of nickel spheres are maintained in constant motion. The nickel carbonyl decomposes depositing pure nickel onto the nickel spheres. The resultant carbon monoxide is re-circulated through the process. The highly pure nickel produced by this process is known as carbonyl nickel. A second common form of refining involves the leaching of the metal matte followed by the electro-winning of the nickel from solution by platting it onto a cathode. In many stainless steel applications, the nickel can be taken directly in the 75% purity form, depending on the presence of any impurities.

The largest producer of nickel is Russia which extracts 267,000 tonnes of nickel per year. Australia and Canada (particularly the Sudbury Basin) are the second and third largest producers, making 207 and 189.3 thousand tonnes per year.

Compounds

Kamacite is a naturally occurring alloy of iron and nickel, usually in the proportion of 90:10 to 95:5 although impurities such as cobalt or carbon may be present. Kamacite occurs in nickel-iron meteorites.

See also Nickel compounds.

Isotopes

Naturally occurring nickel is composed of 5 stable isotopes; 58-Ni, 60-Ni, 61-Ni, 62-Ni and 64-Ni with 58-Ni being the most abundant (68.077% natural abundance). 18 radioisotopes have been characterised with the most stable being 59-Ni with a half-life of 76,000 years, 63-Ni with a half-life of 100.1 years, and 56-Ni with a half-life of 6.077 days. All of the remaining radioactive isotopes have half-lifes that are less than 60 hours and the majority of these have half lifes that are less than 30 seconds. This element also has 1 meta state.

Nickel-56 is produced in large quantities in type Ia supernovae and the shape of the light curve of these supernovae corresponds to the decay of nickel-56 to cobalt-56 and then to iron-56.

Nickel-59 is a long-lived cosmogenic radionuclide with a half-life of 76,000 years. ⁵⁹Ni has found many applications in isotope geology. ⁵⁹Ni has been used to date the terrestrial age of meteorites and to determine abundances of extraterrestrial dust in ice and sediment. Nickel-60 is the daughter product of the extinct radionuclide ⁶⁰Fe (half-life = 1.5 Myr). Because the extinct radionuclide ⁶⁰Fe had such a long half-life, its persistence in materials in the solar_system at high enough concentrations may have generated observable variations in the isotopic composition of ⁶⁰Ni. Therefore, the abundance of ⁶⁰Ni present in extraterrestrial material may provide insight into the origin of the solar system and its early history.

The isotopes of nickel range in atomic weight from 48 amu (48-Ni) to 78 amu (78-Ni). Nickel-78's half-life was recently measured to be 110 milliseconds and is believed to be an important isotope involved in supernova nucleosynthesis of elements heavier than iron. ^*

Precautions

Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour work week. Nickel sulfide fume and dust is believed to be carcinogenic, and various other nickel compounds may be as well.

Nickel carbonyl, ^*, is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of a metal as well as the carbonyl's ability to give off highly toxic carbon monoxide gas, and this one is no exception. It is explosive in air.

Sensitised individuals may show an allergy to nickel affecting their skin. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the European Union. In 2002 a report in the journal Nature researchers found amounts of nickel being emitted by 1 and 2 Euro coins far in excess of those standards. This is believed to be due to a galvanic reaction.

References

Los Alamos National Laboratory – Nickel

Notes

Production and consumption figures are from, The Economist: Pocket World in Figures 2005, Profile Books (2005), ISBN 1-86197-799-9

External links