## 4 Conclusions  
The aim of this study is to examine the dielectric properties of epoxy composites filled with graphite and carbon black for potential use as electromagnetic interference (EMI) shielding material. Composite materials are produced by mechanical mixing. Samples have different filling ratios between 1 and 7 wt%. The coaxial method is used to obtain these properties in the frequency range of 1-14 GHz at the Vector Network Analyzer. The results showed that the addition of fillers significantly affected the dielectric and shielding properties of the composites. The real part of permittivity (\(\epsilon^{\prime}\)) increased with increasing amounts of carbon black in the composition, while the permittivity values of graphite-filled samples were very close to each other. On the other hand, the imaginary part of permittivity (\(\epsilon^{\prime\prime}\)) increased across the entire frequency range used as the amount of carbon black increased. This frequency-dependent behavior of \(\epsilon^{\prime\prime}\) suggests the formation of more conductive pathways within the sample. Measurements show that although carbon black-filled samples have more AC conductivity, graphite-filled samples' shielding efficiencies are higher. The graphite-added samples exhibited a slightly higher \(SE_{T}\) of 19-21 dB compared to the carbon black-added samples, which had a \(SE_{T}\) of 8-17 dB. The epoxy composites with graphite filler tend to exhibit higher shielding efficiency compared to the epoxy composites with carbon black filler due to the segregation of carbon black. In the graphite-added samples, different filling ratios resulted in a more consistent shielding behavior compared to the carbon black-added coatings. However, increasing the carbon-black filler ratio resulted in higher shielding efficiency. The shielding efficiencies of both types of filling materials showed little variation with frequency. Overall, the results suggest that composite materials containing carbon black and graphite fillers look promising and have a good potential for isolating static structures. After the epoxy matrix composite shielding material is produced and cured in plate-shaped molds, it can be used by sticking to the walls of the structure to be shielded with a suitable adhesive. Graphite-filled shielding materials have higher shielding efficiency at lower rates than carbon black, and it can be advantageous for low-cost applications. Carbon black-added shielding materials can be more effective if they are used with higher than 7 wt% filling ratios. Since carbon black has fine particle size, sample integrity could not be achieved in compositions above 7 wt% in the mechanical mixing method. For this, it may be necessary to adopt a different production method, but this may be a factor that increases the production cost. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Matrix** & **Filler** & **Filler Amount wt. \%** & **EMI SE (dB)** & **Frequency Range (GHz)** & **Ref.** \\ \hline Polyurethane & CB & 6.51 & 13–14 & 8–18 & [43] \\ Ethylene Methyl & CB & 10 & 10 & 8.2–12.4 & [44] \\ Acrylate & & & & & \\ Epoxy & CB & 30 & 44 & 1–10 & [45] \\ Polypropylene & CB & 22.5 & 17–20 & 5.5–8 & [46] \\ Polyurethane & Graphite & 20 & 20 & 8.2–12.3 & [47] \\ Polyaniline & Graphite & 20 & 18–5 & 2.5–2.7 & [48] \\ Polypropylene & Graphite & 20 & 10.3 & 8–12 & [49] \\ Polypropylene & Graphite & & & & \\ Carbon fiber & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: EMI SE values of different polymer matrix composites were reported in earlier studies. **Author Contributions:** Conceptualization, E.G., M.Y. and E.A; methodology, E.G., validation, E.G., M.Y. and E.A. ; formal analysis, E.G., investigation, E.G., resources, E.G., M.Y. and E.A. ; data curation, E.G., writing--original draft preparation, E.G., writing--review and editing, E.G., visualization, E.G., supervision, M.Y. and E.A. ; project administration, E.G., funding acquisition, E.G. and M.Y. All authors have read and agreed to the published version of the manuscript.