Tunable Ni-Based Alloys as Electrons Donor in Dielectric Isolated Islands to Achieve Broad Frequency Electromagnetic Wave Absorption.

Nitrogen-doped carbon (NC) nanosheets with tunable electronic features have been considered as effective dielectric materials to tackle the severe electromagnetic pollution. However, it is still a critical issue to reconcile the contradiction between the skin effect originates from the intrinsic high conductivity of NC and the optimal dielectric loss capability. Herein, we prepared NC nanosheets consisting of numerous microdomain to simultaneously achieve good impedance matching and dielectric dissipation performance. The NC surfaces are separated by defect regions into numerous 50-100 nm dielectric isolated islands, while loading ≈40 nm Ni-based alloy nanoparticles (NPs) as tunable electron donating sources. The electron cloud density of the loaded NPs can be tuned by altering the alloy species including NiCo, NiFe and NiMn. NiFe and NiMn NPs with stronger electron donating ability can provide more mobile charges in the isolated islands than that of Ni and NiCo NPs, thereby facilitating the enhancement of electron migration and in-plane interfacial polarization. Consequently, NiFe@NC with better dielectric-magnetic synergy presented a maximum absorption intensity of -101.6 dB with a broadened absorption bandwidth of 10.7 GHz. This work proposes for the first time to effectively tailor the electron cloud density for absorbers utilizing alloying treatment and offers profound insights into dielectric loss mechanisms.