In situ construction of Fe3Al@Al2O3 core-shell particles with excellent electromagnetic absorption.

ABSTRACT

To obtain Fe3Al@Al2O3 core-shell absorbents, DO3-type Fe3Al powder was thermal treated in an argon atmosphere containing a trace amount of oxygen at different temperatures. Since Al atoms have a higher diffusion rate than that of the Fe atoms, Al atoms can migrate to the surface of the Fe3Al particle and in-situ convert to Al2O3 nanoparticles during the thermal treatment process. With the increase of the thermal treatment temperature, the Al2O3 nanoparticles grow larger, exhibiting different microwave absorption properties. In particular, the Fe3Al@Al2O3 obtained by controllable oxidation at 800 ℃ exhibits the best microwave absorption properties, with the minimum reflection loss of -34 dB at 11.5 GHz when the thickness is 2 mm, and the bandwidth below -10 dB is as broad as 6.7 GHz. Since a dielectric Al2O3 shell with a proper thickness can increase the impedance matching ratio of the Fe3Al absorbent, more electromagnetic waves can come into the absorbent. In addition, the magnetic Fe3Al core can efficiently attenuate the absorbed electromagnetic waves by dimensional resonance and natural resonance.