Synthesis of u-channelled spherical Fex(CoyNi1−y)100−x Janus colloidal particles with excellent electromagnetic wave absorption performance

Due to their distinctive structure, inherently anisotropic properties and broad applications, Janus colloidal particles have attracted tremendous attention and it is significant to synthesize high yield Janus colloidal particles in a cost-effective and reliable way. On the other hand, due to the expanded electromagnetic interference problems, it is highly desired to develop excellent electromagnetic wave absorbing materials with an ultra-wide absorption bandwidth for practical application. Herein, a confined liquid–solid redox reaction strategy has been developed to fabricate a series of Fex(CoyNi1−y)100−x ternary alloy particles. The as-prepared particles are in the form of u-channelled noncentrosymmetric spheres, one kind of Janus colloidal particles which have been rarely observed. Due to the combination and synergy effects of multi-magnetic metals, the polycrystalline structure and their specific morphology, the as-prepared particles possess multiple magnetic resonance and multiple dielectric relaxation processes, and therefore show excellent electromagnetic wave absorption performances. In particular, the strongest reflection loss (RL) of the Fe15(Co0.2Ni0.8)85 Janus colloidal particles is up to −36.9 dB with a thickness of 2.5 mm, and the effective absorption (RL < −10 dB) bandwidth can reach 9.2 GHz (8–17.2 GHz) with a thickness of 2 mm. Such a wide bandwidth has barely been reported for magnetic metal alloys under a single thickness. These results suggest that the Fex(CoyNi1−y)100−x Janus particles could be a promising candidate for highly efficient electromagnetic wave absorbing materials for practical application.