## 3 Results and Discussions
### Microwave Absorption Properties
While, as shown in Figure 7b, with only 0.1% of GO amount in the FeSiAl system, the maximum reflection loss increases by 10% to \(-34.00\) dB at 0.5 GHz, and the effective bandwidth increases by 20% to 0.5 GHz. However, epoxy compounds with pure magnetic particles or a low GO amount show fairly narrow effective bandwidths, and strong absorption peaks only fall in a very low frequency band. As shown in Figure 7c for the GF-3 sample with 1% of GO, the maximum reflection loss increases to \(-48.29\) dB at 1.6 GHz and the effective bandwidth increases to 3.8 GHz, which exhibits a wider bandwidth (3.8 GHz vs. 3.12 GHz [42] and 3.52 GHz [43]) and a higher refection loss (\(-48.29\) dB vs. \(-47\) dB [44], \(-44.47\) dB [42] and \(-48.08\) dB [39]) in the most recent relevant literature, using FeSiAl as a microwave absorber. This provides a perfect match for 5G station application, as the effective bandwidth just falls in the range of the 5G antennas' operating frequency band in the 2.575-2.645 GHz range [45], as shown in Figure 8. It can be concluded that, in most cases, the microwave reflection loss increased greatly as the GO amount increased. However, it decreases as the amount of GO reaches 10% in GF-4, as shown in Figure 7d. This might result from the decrease of complex permittivity. Overall, controlling the amount of GO in GO/SiFeAl epoxy compounds can facilely adjust the dissociation and frequency of the absorption peak. Factors affecting the performance of wave absorption also include impedance matching and the attenuation constant. Generally, the closer the value of impedance matching \(Z\left(Z=Z_{in}/Z_{0}\right)\) is to 1, the more the incident electromagnetic wave can enter the material  
Figure 8: Reflection loss of the epoxy compound with GF-3 at different thicknesses. Figure 7: Three-dimensional (3D) projections of reflection loss of epoxy composites with (**a**) GF-1, (**b**) GF-2, (**c**) GF-3, and (**d**) GF-4. without being emitted. Another parameter reflecting the attenuation characteristics is the attenuation constant (\(\alpha\)), which can be calculated through the following equation:  
\[\alpha=\frac{\sqrt{2}\pi f}{c}\sqrt{(\mu^{\prime\prime}\varepsilon^{\prime\prime }-\mu^{\prime}\varepsilon^{\prime})+\sqrt{(\mu^{\prime\prime}\varepsilon^{ \prime\prime}-\mu^{\prime}\varepsilon^{\prime})^{2}+(\mu^{\prime}\varepsilon^ {\prime\prime}+\mu^{\prime\prime}\varepsilon^{\prime})^{2}}}. \tag{3}\]  
The attenuation constant reflects the material's ability to dissipate electromagnetic waves. However, a strong attenuation constant often leads to low impedance matching, so it is necessary to balance the effects of both. The attenuation constant of the compounds is shown in Figure 9 while the impedance matching is shown in Figure 10. As shown in Figure 9, the attenuation constant increases as the amount of GO grows, indicating more electromagnetic energy loss resulting from the porous structure and defects on the surface of GO. However, GF-4 with the largest GO amount and the highest attenuation constant shows a low reflection loss due to its low impedance matching as shown in Figure 10d, which is consistent with the conclusion from the reflection loss results. In conclusion, 1% of GO is a reasonable amount among others that reaches a balance between magnetic loss and conductive loss. Figure 11 is the schematic of the GO/FeSiAl microwave absorption mechanism. To begin with, GO and FeSiAl can perform as wave-absorbing agents separately. GO has a high dielectric loss from defect polarization and dipole polarization, while FeSiAl has a high magnetic loss from eddy current loss at a low frequency and nature resonance at a higher frequency. Then, since GO and FeSiAl have different polarity and conductivity, interfacial polarization occurs at the interface between GO and FeSiAl, which contributes greatly to the microwave dielectric loss. There is also conductive loss between FeSiAl interfaces.