Fig. 1. (a) Schematic diagram of the synthesis strategy of CFZD composites; (b-e) SEM images and corresponding (g-j) TEM images of CFZD composites with different oxidation time (b, g for S-0; c, h for S-0.5; d, i for S-1.0; e, j for S-2.0); (f) Elemental mapping images of S-0.5.

Fig. 2. (a) XRD patterns, (b) Raman spectra, (c) N2 adsorption and desorption isotherms, (d-f) high-resolution XPS spectra of Co 2p, C 1s and O 1s of CFZD composites at different oxidation time.

Fig. 3. The real part (a) and imaginary part (b) of complex permittivity of the CFZD composite (S-0, S-0.5, S-1.0 and S-2.0) in 2-18 GHz; (c) the tanδe values of CFZD in 2-18 GHz; the real part (d) and imaginary part (e) of complex permeability in 2-18 GHz; the (c) tanδm values of CFZD in 2-18 GHz.

Fig. 4. (a) Hysteresis loops of magnetic CFZD composites; (b) C0 values of CFZD composites in frequency of 2-18 GHz.

Fig. 5. (a) The α values and (b) the Zr values of CFZD in 2-18 GHz; (c) the dielectric loss mechanism and (d) the magnetic loss mechanism diagram of EM wave attenuation for CFZD composites.

Fig. 6. Two-dimensional images of calculated reflection loss values at different frequency and thickness for (a) S-0, (b) S-0.5, (c) S-1.0, (d) S-2.0, respectively; (e) bar chart of the bandwidths of all samples at different thickness; (f) the reflection loss peaks at different thickness of S-0.5.

Fig. 7. HFSS simulation results of the (a) PEC and the PEC substrates covered with the composites; (b) RCS reduction achieved from subtracting composite with PEC; (c) RCS simulated graphs of the sample S-0.5 at different thickness under different scanning angles; (d) The RCS reduction of S-0.5 at a thickness of 1.3 mm under the frequency of 2-18 GHz.