Nickel is a strong, lustrous, silvery-white metal that was not isolated by scientists until the mid-18th century, but is now a staple of our daily lives and can be found in everything from the batteries that power our television remotes to the stainless steel that is used to make our kitchen sinks.
- Atomic Symbol: Ni
- Atomic Number: 28
- Element Category: Transition metal
- Density: 8.908 g/cm3
- Melting Point: 2651 °F (1455 °C)
- Boiling Point: 5275 °F (2913 °C)
- Moh’s Hardness: 4.0
Pure nickel reacts with oxygen and, therefore, is seldom found on the earth's surface, despite being the fifth most abundant element on (and in) our planet. In combination with iron, nickel is extremely stable, which explains both its occurrence in iron containing ores and its effective use in combination with iron to make stainless steel.
Nickel is very strong and resistant to corrosion, making it excellent for strengthening metal alloys. It is also very ductile and malleable, properties that allow its many alloys to be shaped into wire, rods, tubes and sheets.
Pure nickel was first extracted by Baron Axel Fredrik Cronstedt in 1751, but was known to exist much earlier. Chinese documents from around 1500BC make reference to 'white copper' (baitong), which was very likely an alloy of nickel and silver. Fifteenth century German miners, who believed they could extract copper from nickel ores in Saxony, referred to the metal as kupfernickel - 'the devil's copper' - partly due to their futile attempts to extract copper from the ore, but also likely in part due to the health effects caused by the high arsenic content in the ore.
In 1889, James Riley made a presentation to the Iron and Steel Institute of Great Britain on how the introduction of nickel could strengthen traditional steels. Riley's presentation resulted in a growing awareness of nickel's beneficial alloying properties and coincided with the discovery of large nickel deposits in New Caledonia and Canada.
By the early 20th century, the discovery of ore deposits in Russia and South Africa made large-scale production of nickel possible. Not long after, World War I and World War II resulted in a significant increase in steel and, consequently, nickel demand.
Nickel is primarily extracted from the nickel sulphides pentlandite, pyrrhotite and millerite, which contain about 1% nickel content, and the iron containing lateritic ores limonite and garnierite, which contain about 4% nickel content. Nickel ores are mined in 23 countries, while nickel is smelted in 25 different countries.
The separation process for nickel is highly dependent upon the type of ore. Nickel sulphides, such as those found in the Canadian Shield and Siberia, are generally found deep underground, making them labor intensive and expensive to extract. However, the separation process for these ores is much cheaper than for the lateritic variety, such as those found in New Caledonia. Moreover, nickel sulphides often have the benefit of containing impurities of other valuable elements that can be economically separated.
Sulphide ores can be separated using froth flotation and hydrometallurgical or magnetic processes to create nickel matte and nickel oxide. These intermediate products, which usually contain 40-70% nickel, are then further processed, often using the Sherritt-Gordon Process.
The Mond (or Carbonyl) Process is the most common and efficient method to treat nickel sulphide. In this process, the sulphide is treated with hydrogen and fed into a volatilization kiln. Here it meets carbon monoxide at about 140F° (60C°) to form nickel carbonyl gas. The nickel carbonyl gas decomposes on the surface of pre-heated nickel pellets that flow through a heat chamber until they reach the desired size. At higher temperatures, this process can be used to form nickel powder.
Lateritic ores, by contrast, are usually smelted by pyro-metallic methods because of their high iron content. Lateritic ores also have a high moisture content (35-40%) that requires drying in a rotary kiln furnace. This produces nickel oxide, which is then reduced using electric furnaces at temperatures between 2480-2930 F° (1360-1610 C°) and volatilized to produce Class I nickel metal and nickel sulfate.
Due to the naturally occurring iron content in lateritic ores, the end product of most smelters working with such ores is ferro-nickel, which can be used by steel producers after silicon, carbon and phosphorus impurities are removed.
By country, the largest producers of nickel in 2010 were Russia, Canada, Australia and Indonesia. The largest producers of refined nickel are Norilsk Nickel, Vale S.A., and Jinchuan Group Ltd. At present, only a small percentage of nickel is produced from recycled materials.
Nickel is one of the most widely used metals on the planet. According to the Nickel Institute, the metal is used in over 300,000 different products. Most often it is found in steels and metal alloys, but it is also used in the production of batteries and permanent magnets.
About 65% of all nickel produced goes into stainless steel. Nickel stabilizes the austenite (a high temperature solid solution of iron and carbon) and provides ductility, toughness and corrosion resistance. Nickel containing stainless steels are used to manufacture everything from kitchenware to surgical instruments and food storage equipment.
The first major application for nickel following James Riley's presentation in 1889 was in steels for armor plating military vehicles. Nickel steels are still used in many military applications, but also in aircraft undercarages, reinforced bars (rebar) and in tools for diecasting.
A further 20% of nickel produced is used in other types of steels and metal alloys, such as heat resistant alloys. Made with nickel chromium and some rare earth elements, heat resistant alloys prevent destructive oxidation at high temperatures while remaining highly ductile. A major application for heat resistant alloys, which use the trade names Nimonic and Inconel, is in spark plug electrodes.
Superalloys resist high temperatures 1472-2912F° (800-1600C°) and are often found in gas turbine engines, nuclear reactors and power generators. They are made with nickel, chromium and a mixture of other metals in smaller quantities.
Nickel, chromium and iron containing alloys are corrosion resistant and used to contain highly corrosive chemicals, in steam generators of pressurized nuclear reactors and in chemical plan furnaces; Whereas, nickel copper alloys, which are also resistant to corrosion, are specifically designed for application in marine environments, such as to coat the legs of oil rigs, propeller shafts of power boats and parts in desalination plants.
Finally, low expansion alloys contain nickel, iron and cobalt. These alloys can have a zero coefficient of expansion and go by the trade names Nilo and Invar. Low expansion alloys are used to line liquid natural gas (LNG) ship tanks, as well as to make thermostats and gas turbine casings.
Electroplating accounts for about 9% of all nickel use. This chemical process is used underneath a coat of chromium on base metals to form a corrosion resistant layer, which protects and decorates automotive parts, hardware and metal machine components.
Permanent magnets, made of aluminum, nickel and cobalt (Alnico) were first produced in the 1930s and were critical to the development of many electronic devices, including DC motors and auto-generators. However, recently, rare earth element magnets have increasingly replaced alnico magnets.
Nickel metal hydride (NiMH) and nickel cadmium (NiCd) batteries are rechargeable battery cells, which use nickel oxyhydroxide (NiOOH) for their positive electrode. NiMH batteries are used in more than two million hybrid cards worldwide, as well as in rechargeable batteries for consumer electronics. NiCd batteries are widely used in portable electronics, toys, flashlights (torches), cordless power tools and standby power units.
Street, Arthur. & Alexander, W. O. 1944. Metals in the Service of Man. 11th Edition (1998).
USGS. Mineral Commodity Summaries: Nickel (2011).
Encyclopedia Britannica. Nickel.