Electromagnetic wave absorption enhancement of double-layer structural absorbers based on carbon nanofibers and hollow Co2Y hexaferrite microfibers

Novel double-layer microwave absorbers possessing excellent absorption performances have been designed based on carbon nanofibers (CNFs) and hollow Ba2Co2Fe12O22 microfibers (Co2Y MFs). The electromagnetic wave absorbing characteristics of double-layer absorbers with different layer thicknesses and compositions are investigated over the 2–18 GHz range. Efficient coupling and synergistic effects between the absorbing layer and matching layer lead to a better impedance matching and in turn improve microwave absorption. The optimized double-layer structures exhibit far superior microwave absorbing properties with stronger absorption intensity and wider effective bandwidth compared with the corresponding single-layer ones. When the absorbing layer (1.15 mm in thickness) is filled with 5 wt% CNFs and the matching layer (0.85 mm) is filled with 67 wt% Co2Y MFs, a minimum reflection loss (RL) value of −85.5 dB is achieved at 16.1 GHz and the RL less than −10 dB is obtained in the 10.4–18 GHz. Conversely, as the absorbing layer (1.75 mm) is filled with 67 wt% Co2Y MFs and the matching layer (0.25 mm) is filled with 5 wt% CNFs, the minimum RL value reaches −68.7 dB at 14.8 GHz and the absorption frequency range with RL values below −10 dB is up to 10 GHz (from 8 to 18 GHz). Moreover, the position, intensity and effective bandwidth of the absorption peaks for the double-layer absorbers can be readily tuned by adjusting the stacking order, the thickness of each layer and total absorber thickness, showing good potential for practical application. •A novel double-layer microwave absorber based on Co2Y MFs and CNFs is designed.•The RLmin value of −85.5 dB and an effective bandwidth of 10 GHz can be obtained.•Double-layer absorber has much better absorption properties than single-layer one.•Impedance matching characteristics of the absorbers are comparatively analyzed.