Fernico describe a family of

metal alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

s made primarily of

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

and

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...

. The family includes Kovar, FerNiCo I, FerNiCo II, and Dumet. The name is made up of the chemical symbols of its constituent three elements. "Dumet" is a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of wordsalloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

, usually fabricated in the form of a wire with an alloy core and a

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

cladding. These alloys possess the properties of electrical conductivity, minimal oxidation and formation of porous surfaces at working temperatures of glass and thermal coefficients of expansion which match glass closely. These requirements allow the alloys to be used in glass seals, such that the seal does not crack, fracture or leak with changes in temperature. Dumet is most commonly used in seals where lead-in wires pass through the glass bulb wall of standard household electric lamps (light bulbs) among other things. The two Fernico alloys both consist of

(Fe),

(Ni), and

(Co). Fernico is used at high temperatures and is identical to

Kovar Kovar (trademark of CRS Holdings, inc., Delaware) is a nickel–cobalt ferrous alloy compositionally identical to Fernico 1, designed to have substantially the same thermal expansion characteristics as borosilicate glass (~5 × 10−6 /K betwe ...

. Fernico II is used at cryogenic temperatures in the range. Both are used to create electrically conductive paths through the walls of sealed

borosilicate Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...

glass containers. Dumet is used for a similar purpose, but is tailored for seals through

soda lime Soda lime is a mixture of NaOH and CaO chemicals, used in granular form in closed breathing environments, such as general anaesthesia, submarines, rebreathers and recompression chambers, to remove carbon dioxide from breathing gases to prevent ...

and lead alkali silicate glasses. These alloys adhere to lead-tin, tin, and

silver solder Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...

s. Other metals, including copper, molybdenum, nickel, and steel can be spot-welded to the FerNiCo alloys forming low resistance electrical connections.

Typical compositions

Given in weight % FerNiCo I has the same linear coefficient of expansion as certain types of borosilicate ("hard" glass), (c6.5 × 10⁻⁶K⁻¹, thus serving as an ideal material for the lead-out wires or other seal structures in

light bulb An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the soc ...

s and

thermionic valve A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a ...

s. Dumet is also used for this purpose, but for passing through softer soda-lime and lead-alkali glasses. This wire is often coated with a glass-like film of sodium

metaborate A metaborate is an anion (negative ion) consisting of boron and oxygen, with empirical formula ; or any salt with such anions, such as sodium metaborate, or calcium metaborate . It is one of the boron oxoanions or borates In aqueous solution ...

, (), so the molten glass will "wet" and adhere to it. 25% by mass of the finished wire is copper.S.T. Henderson and A.M. Marsden, "Lamps and Lighting" 2nd Ed., Edward Arnold Press,

Cunife Cunife is an alloy of copper (Cu), nickel (Ni), iron (Fe), and in some cases cobalt (Co). The alloy has the same linear coefficient of expansion as certain types of glass, and thus makes an ideal material for the lead out wires in light bulbs and ...

exhibits a similar property.

Uses

There are very few uses of Fernico. Some of them are: * It is used to seal metals and glass. * It is often used in the form of nanopowder.

References

External links

FerNiCo composition page
Ferrous alloys Magnetic alloys Ferromagnetic materials {{alloy-stub

Typical compositions

Uses

See also

References

External links