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

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.