 Perhaps the earliest application was the extraction and purification of nickel via nickel tetracarbonyl by the Mond process (see also carbonyl metallurgy).By a similar process carbonyl iron, a highly pure metal powder, is prepared by thermal decomposition of iron pentacarbonyl.Carbonyl iron is used inter alia for the preparation of inductors, pigments, as dietary supplements, in the production of radar-absorbing materials in the stealth technology, and in thermal spraying.