Metal micro-powder absorbing materials mainly attenuate electromagnetic waves through magnetic loss and eddy current loss. They are generally made of superfine magnetic metal powder and polymer bonding compound. The electromagnetic wave can be adjusted by the mixing ratio of multiphase superfine magnetic metal powder. The parameters make it achieve a more ideal wave-absorbing effect.
The metal micro-powder absorbing material has the characteristics of high microwave permeability and good temperature stability. Metal powder absorbing materials have been widely used in stealth technology. For example, the American F/A-18C/D "Bumblebee" stealth aircraft uses carbonyl iron powder absorbing materials.
There are two main types of metal powder absorbing materials, one is carbonyl metal powder absorbing materials. Carbonyl metal powder includes carbonyl iron, carbonyl nickel and carbonyl cobalt, of which carbonyl iron powder is the most commonly used one. Carbonyl iron powder is thermally decomposed by a carbonyl iron compound in a preheated nitrogen atmosphere, and then the powders of different particle sizes are separated and collected by a separator, or directly irradiated with high-purity Fe(CO)5 by a laser beam, in the reaction chamber The photosensitizer initiates its decomposition to obtain a powder. The other type is magnetic metal powder absorbing materials obtained by evaporation, reduction, organic alkoxide and other processes, and their electromagnetic parameters are closely related to the composition and particle size.
It is pointed out that the shortcomings of metal micro-powder absorbing materials are: large electrical constant and poor spectral characteristics, poor low-frequency absorption performance; poor anti-oxidation, acid and alkali resistance, far inferior to ferrite; large dielectric density, and its absorbent volume The space ratio is generally greater than 50%.