Electromagnetic Wave Absorption Properties and Mechanism of Graphene/${\mathbf{Ni}}_{\mathbf{0.4}}{\mathbf{Zn}}_{\mathbf{0.6}}{\mathbf{Fe}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{4}}$ Cement Composites

Electromagnetic waves (EMWs) absorption cement composites were widely demanded in urban construction in the near future with increasingly serious electromagnetic pollution in rapid development and application of electronic communication technology. To fully utilize the influence of graphene nanoplates (GNPs) and ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ on EMWs absorption properties of cement composites, various dosages of dispersed GNPs, ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$, and hybrid mixtures were incorporated in cement, and the electromagnetic reflectivity loss, electromagnetic parameter were tested and discussed in the frequency range of $2–18\mathrm{GHz}$. Also, the effects of GNPs and ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ on complex permittivity, complex permeability of cement composites were analyzed for further mechanism analysis combined with XRD, MIP, and SEM micrographs. The results showed that 1.0% GNPs and 30% ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ were the optimal dosages in cement composites, which could absorb more than 80% incident EMWs energy in 8–18 GHz. Furthermore, the ${\mathrm{GNPs}/\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ (1%, 30%) cement composites exhibit lower EMWs reflectivity loss compared to GNPs or ${\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ added individually, and the effective absorption frequency width (lower than $-10\mathrm{dB}$) was 5.4 GHz, of which more than 90% EMWs energy was translated to thermal energy and absorbed by the matrix, reaching similar EMWs absorption effect of absorption coating materials. Essentially, the imaginary part of complex permittivity and the real part and imaginary part of complex permeability of cement composites could be improved conspicuously when ${\mathrm{GNPs}/\mathrm{Ni}}_{0.4}{\mathrm{Zn}}_{0.6}{\mathrm{Fe}}_2{\mathrm{O}}_4$ was incorporated, indicating higher dielectric loss angle tangent and magnetic loss angle tangent of cement composites achieved. Thus, the impedance matching, dielectric loss, and the magnetic loss of cement composites under incident EMWs increased.