Carbonyl iron is a highly pure (97.5% for grade S, >99.5% for grade R) iron, 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, oxygen, and nitrogen.
BASF invented carbonyl iron powder in 1925[1] and claims to be the world's leading producer.[1] In 1934, BASF was also involved in the development of the very first magnetic tapes used by the AEGMagnetophon tape recorder.[2] Carbonyl iron became the first magnetic recording oxide (although quickly replaced in 1936 by iron oxide).
Applications
In electronics, carbonyl iron is used to manufacture magnetic cores for high-frequency coils and in production of some ferrites. 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.[3] 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 induction coils, filter and choke coils: higher grades were found to be especially suitable for carrier wave frequencies over 100 MHz.[4]
Powdered cores made of carbonyl iron have high stability of parameters across a wide range of temperatures and magnetic flux levels, with excellent Q factors between 50kHz and 200MHz. A popular application is in broadband inductors, 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.[5] It can efficiently handle alternating current (AC) signals at high frequencies, improving performance in power supplies, RF applications, and telecommunications.[6] Their fine particle size also helps reduce eddy current losses, enhancing overall efficiency.[7]
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.[9]
↑Li, Xiagguo; Yan, Haitian (2024). "Synthesis of double-shell carbonyl iron powder @SiO2 @C for enhanced electromagnetic wave absorption". Journal of Alloys and Compounds. 976 173233. doi:10.1016/j.jallcom.2023.173233.
↑Wang, Jinghui; Guo, Zhili (2020). "Magnetic properties regulation and loss contribution analysis for Fe-based amorphous powder cores doped with micron-sized FeSi powders". Journal of Magnetism and Magnetic Materials. 510 166931. Bibcode:2020JMMM..51066931W. doi:10.1016/j.jmmm.2020.166931.
↑Lee, Nicholas R.; Bikovtseva, Agata A.; Cortes-Clerget, Margery; Gallou, Fabrice; Lipshutz, Bruce H. (2017-12-05). "Carbonyl Iron Powder: A Reagent for Nitro Group Reductions under Aqueous Micellar Catalysis Conditions". Organic Letters. 19 (24): 6518–6521. doi:10.1021/acs.orglett.7b03216. ISSN1523-7060. PMID29206473.
