Carbonyl iron is a highly pure (97.5% for grade S, 99.5+% for grade R)

iron Iron is a chemical element; it has symbol Fe () 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, forming much of Earth's o ...

, prepared by chemical decomposition of purified iron pentacarbonyl. It usually has the appearance of grey powder, composed of spherical microparticles. Most of the impurities are

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

, and

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

History

BASF BASF SE (), an initialism of its original name , is a European Multinational corporation, multinational company and the List of largest chemical producers, largest chemical producer in the world. Its headquarters are located in Ludwigshafen, Ge ...

invented carbonyl iron powder in 1925 and claims to be the world's leading producer. In 1934, BASF was also involved in the development of the very first magnetic tapes used by the

AEG The initials AEG are used for or may refer to: Common meanings * AEG (German company) ; AEG) was a German producer of electrical equipment. It was established in 1883 by Emil Rathenau as the ''Deutsche Edison-Gesellschaft für angewandte El ...

Magnetophon Magnetophon was the brand or model name of the pioneering reel-to-reel tape recorder developed by engineers of the German electronics company AEG in the 1930s, based on the magnetic tape invention by Fritz Pfleumer. AEG created the world's firs ...

tape recorder. Carbonyl iron became the first magnetic recording oxide (although quickly replaced in 1936 by iron oxide).

Applications

electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...

, carbonyl iron is used to manufacture

magnetic core A magnetic core is a piece of magnetism, magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, ele ...

s for high-frequency coils and in production of some

ferrites Ferrite may refer to: * Ferrite (iron), one of the allotropes of iron that is stable at room temperature and pressure, α-Fe * Ferrite (magnet), a ferromagnetic ceramic material See also * * Ferrite bead, a component placed on the end of a data c ...

. Spherical particles manufactured of carbonyl iron are used as a component of the radar absorbing materials used by the military, in stealth vehicles, for example. Carbonyl iron powder was used in Germany during World War II in the manufacture of radio frequency equipment, including radio transmitters and receivers, low

hysteresis Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of ...

induction coils, filter and choke coils: higher grades were found to be especially suitable for

carrier wave In telecommunications, a carrier wave, carrier signal, or just carrier, is a periodic waveform (usually sinusoidal) that conveys information through a process called ''modulation''. One or more of the wave's properties, such as amplitude or freq ...

frequencies over 100

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...

. Powdered cores made of carbonyl iron have high stability of parameters across a wide range of temperatures and

magnetic flux In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the we ...

levels, with excellent

Q factor In physics and engineering, the quality factor or factor is a dimensionless parameter that describes how underdamped an oscillator or resonator is. It is defined as the ratio of the initial energy stored in the resonator to the energy lost ...

s between 50 kHz and 200 MHz. A popular application is in broadband

inductor An inductor, also called a coil, choke, or reactor, is a Passivity (engineering), passive two-terminal electronic component, electrical component that stores energy in a magnetic field when an electric current flows through it. An inductor typic ...

s, especially in high-power applications. Due to its high permeability and low core losses, Carbonyl iron powder cores are utilized in high-frequency switching circuit output chokes and resonant

inductors An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when an electric current flows through it. An inductor typically consists of an insulated wire wound into a ...

. It can efficiently handle alternating current (AC) signals at high frequencies, improving performance in power supplies, RF applications, and telecommunications. Their fine particle size also helps reduce eddy current losses, enhancing overall efficiency. Carbonyl iron powder has been used for human ingestion, similarly to other food-grade

iron powder Iron powder has several uses; for example production of magnetic alloys and certain types of steels. Iron powder is formed as a whole from several other iron particles. The particle sizes vary anywhere from 20-200 μm. The iron properties dif ...

s like

direct reduced iron Direct reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron ore (in the form of lumps, pellets, or fines) into iron by a reducing gas which contains elemental carbon (produced from natural gas or coal) and/o ...

. One iron supplement from India uses this kind of powder to treat

iron deficiency Iron deficiency, or sideropenia, is the state in which a body lacks enough iron to supply its needs. Iron is present in all cells in the human body and has several vital functions, such as carrying oxygen to the tissues from the lungs as a key ...

. In 2017 carbonyl iron powder was reported as an effective reductant for aromatic nitro groups in water, an important reaction used in the synthesis of pharmaceuticals. Particles of carbonyl iron (20–40%) suspended in a carrier fluid (60–80%) are used as a magnetorheological fluid. Other uses are in

powder metallurgy Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes are sometimes used to reduce or eliminate the need for subtractive manufacturing, subtractive processes in ma ...

, metal injection molding, and in various specialty products. Nazi German scientists also found it to have anti-knock properties similar to lead tetraethyl.

References

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