CoNi alloy with tunable magnetism encapsulated by N-doped carbon nanosheets toward high-performance microwave attenuation

Dual dielectric relaxation and multiple magnetic resonances contribute to form dielectric-magnetic matching effect, which tends to become a strategy to explore the optimization of magnetic components for improved the microwave absorption (MA) performance. Herein, CoNi alloy with tunable magnetism embedded in N-doped carbon (NC) nanosheets has been successfully fabricated by facile pyrolysis process. It is worth noting that the saturation magnetization of these nanocomposites will be regulated effectively via changing the Co²⁺/Ni²⁺ ratio. The results confirm that the wave attenuation ability is relevant with the ratio of Co to Ni. The optimized Co_0·80Ni_0.20-NC/PVDF composites exhibit extraordinary wave attenuation capacity with a minimum reflection loss value of up to −61.26 dB at a low filler amount of 10 wt% (2.4 mm). Moreover, the effective absorption bandwidth can reach 4.55 GHz (12.95–17.50 GHz) when the thickness is only 1.7 mm. The composites well achieve wide and strong absorption at low filler amount and thin thickness. The superior MA performance is attributed to dielectric loss and better impedance matching characteristic caused by CoNi alloy. This work guided a promising direction for synthesizing dielectric-magnetic composites with excellent MA property by varying their magnetism.