Microwave absorption properties of Fe@Al2O3 nanoembedments prepared by mechanosynthesis

The iron nanoparticles embedded in alumina powder (Fe@Al2O3 nanoembedments) were prepared by a mechanochemical process. Their potential for microwave absorber is evaluated. The insulating embedment provides encapsulation and prevents oxidation and agglomeration of metal nanoparticles. The hysteresis loop of such nanoembedments at room temperature exhibits a superparamagnetic behavior, while the microwave permeability spectra show a multiresonance behavior. The maximum reflection loss can reach −21.4 dB at a higher frequency of ∼13.3 GHz as the thickness is 1.4 mm. The coexistence of superparamagnetic loss and multiresonant loss is responsible for microwave absorption. The Fe@Al2O3 nanoembedments may become attractive candidates for a new type of microwave absorber.