## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Designation**} & \multicolumn{4}{c}{**Change in Mass, \%**} & \multicolumn{2}{c}{**Contact Angle, Deg**} \\ \cline{2-6}  & **H\({}_{2}\)O** & **HNO\({}_{3}\)** & **H\({}_{2}\)SO\({}_{4}\)** & **HCl** & **NaOH** & **H\({}_{2}\)O** \\ \hline T2 & +0.58 & +4.73 & +0.73 & +2.44 & \(-\)0.08 & 69.7 \(\pm\) 0.5 \\ T2-2 & +0.61 & +4.42 & +0.56 & +2.24 & \(-\)0.11 & 70.0 \(\pm\) 0.3 \\ SiC-1 & +0.45 & +1.63 & +0.07 & +0.86 & \(-\)0.05 & 64.5 \(\pm\) 0.8 \\ SiC-4 & +0.48 & +1.50 & +0.12 & +0.83 & \(-\)0.15 & 62.6 \(\pm\) 1.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Change in mass of carbonized composites after exposure to various liquids after 35 days. Figure 3: Water absorption (**a**) of the carbonized composites and (**b**) change in mass of SiC-1 compounds exposed to liquid chemicals. for all samples, and a gradual increase in mass was observed; however, in this case, the change in mass was much lower. Sulfuric acid only leads to a slight increase in mass (0.5-0.7%), which is close to the values of water absorption. The exposure to NaOH was accompanied by some loss of mass of the composites (about \(-0.15\%\)), which is caused by partial dissolution of silicon-containing fillers, both schungite and SiC, due to easy dissolution of the surface SiO\({}_{2}\) layer in alkalis. It is known that corrosion of the SiC- and silicon-containing ceramics in the HCl and H\({}_{2}\)NO\({}_{3}\) solutions is much weaker than that of in the NaOH solution, due to the easy dissolution of the SiO\({}_{2}\) layer on the ceramic surface into the alkaline solution [20]. Taking into account the simultaneous water absorption that masks the loss of mass, we can conclude that the real loss of mass does not exceed 0.8%. No visible changes in the structure, the sizes, and the colors were noticed, indicating that the composites are highly resistant to any attacks of the most common chemicals. The mechanical properties of the composites are shown in Table 2. The values of compressive strengths are close and lie in a range of 155-180 MPa for all the composites. It was found that an increase in CF content and the replacement of graphite by shungite fillers, whose average particle size is smaller (T2 and SiC-1), increases Young's modulus. However, in our previous work, it was shown that an increase in SiC content results in a decrease in the thermal conductivity of the composites due to a decrease in graphite content [11]. Carbon black and CNTs are active fillers that increase mechanical properties, but high filler content significantly reduces the plasticity of the elastomeric compounds, and the fillers tend to form agglomerates at high filling degrees. With an increase in SiC and a simultaneous decrease in graphite content, the tensile strength and Young's modulus of the composites increase from 62.9 MPa and 17.6 GPa (SiC-1) to 81.2 MPa and 21.3 GPa (SiC-4), respectively. Elongation at break is almost the same for all compositions and lies in a range of 0.4-0.5%. The mechanical properties of the composites are comparable with carbon-carbon composites reinforced with short CFs [21]. It should be noted that carbonized NBR with no fillers shows poor mechanical properties (tensile strength is about 2.7 MPa, Young's modulus is about 1.8 GPa, and elongation at break is about 0.4%). Therefore, the fillers used as well as high filling degrees (up to 300 PHR) mainly determine mechanical properties of the carbonized composites. Carbonization of the unfilled rubber is accompanied by significant shape changes and distortions of the experimental samples. High filling degrees of the rubber with all fillers used reduce form alterations of the produced composites during carbonization. It is important to note that Young's modulus has an asymmetrical character being almost two times higher at tension than at compression.