Nickel oxide is chemical compound produced from a hard white colored metal, Nickel. Nickel is 22nd most abundant element on earth. It is a malleable and ductile metal, which occurs in the form of cubic crystals. The metal exhibits superior strength and corrosion resistance. Nickel is a good conductor of electricity and heat.
Nickel oxide is obtained as either black or green crystalline powder. The compound becomes yellow on heating. The compound is represented by the chemical formula NiO. The mineralogical form of this Nickel compound is very rare. NiO adopts the structure of NaCl or Sodium Chloride. The conceptually basic structure is also known as the rock salt structure. The binary metal oxide is often non-stoichiometric. The ratio of Nickel and Oxygen deviates from 1:1. This non-stoichiometry of the nickel compound is accompanied by a distinct color change. The stoichiometrically correct Nickel compound is green in color. The non-stoichiometric Nickel compound is black in color.
Relative density of Nickel oxide is 6.75 g/cm3 at 20 degree Celsius. Melting point of the compound is 1984 degree Celsius. The chemical is readily soluble in acids. Further, it is insoluble in hot as well as cold water. The metal oxide can be prepared by several procedures. NiO is produced on heating Nickel powder above 400 degree Celsius. The powder reacts with Oxygen to produce Nickel Oxide. The compound is commercially produced by heating a mixture of water and nickel powder at 1000 degree Celsius. The rate of the chemical reaction can be enhanced by addition of NiO. One of the most successful and simplest methods of preparing NiO is through pyrolysis of Nickel hydroxide, Nickel nitrate, Nickel carbonate and other Nickel compounds.
Several million kilograms of NiO is produced annually. The compound is produced in varying quality. The compound is primarily produced as an intermediate during the production of Nickel alloys.
Nickel Oxide has a wide range of specialized applications. It is widely used for production of Nickel alloys. The compound is also used in the ceramic industry for manufacturing ferrites, frits and porcelain glazes. Also, the chemical is an important component of the Edison Battery, also known as the Nickel-iron battery. It is also an important component in fuel cells and NiCd rechargeable batteries.
Further, NiO is also used as a catalyst in several chemical reactions. Reacting NiO with acids produces commercially useful compounds, such as Nickel sulfamate and Nickel molybdate. Nickel sulfamate is used for electroplating. Gold doped NiO films are widely used in optoelectronic devices as transparent electrodes.