## 3 Results
### The Point Tribological Contact
On the counterpart surface outside the TF, the spectrum was characterized by nearly zero intensity in the entire range of wavenumbers (Figure 6; curve 1, given as a reference). On the spectrum for the TF on the counterface (Figure 6a; curve 2), the intensity increased. Nevertheless, it was impossible to state more about the formation of individual pronounced sharp peaks; rather, there was an extended maximum in the range of 100-1670 cm\({}^{-1}\). At the same time, peaks were distinguished in the regions of 1680-1450 and 900-\(\leq\)600 cm\({}^{-1}\) that could be attributed to nitrogen NO\({}_{2}\), C-N and organosilicon compounds, respectively [47]. For the PEI/10 CCF/1 HNT nanocomposite, the Raman spectrum outside the wear track was characterized by the absence of arbitrarily pronounced peaks, although the intensity gradually increased as the wavenumber decreased (Figure 7b; curve 1). On the wear track surface, the spectrum pattern was expectedly similar to that in the TF (Figure 6a,b; curve 2), which proved their identical compositions. An increase in the overall intensity level for the spectrum on the wear track surface relative to that outside it (Figure 6b) indicated the development of structure-ordering processes during the formation of the TL, including due to tribo-chemical reactions. Figure 5: Optical photographs of the steel counterpart surfaces (**a**,**d**), wear tracks (**b**,**e**) and wear track profiles (**c**,**f**) after the tribological tests of the PEI/10 CCF/1 CNT (**a**–**c**) and PEI/10 CCF/1 HNT (**d**–**f**) nanocomposites. Point tribological contact. White arrows denote sliding direction. An additional characterization of the structures of the TL and TF for the PEI/10 CCF/1 HNT nanocomposite was performed using SEM (Figure 7) in an EDS analysis (Table 4). In general, the obtained data supplemented the above results from the Raman spectra and confirmed the identity of the chemical compositions of the TF on the counterface and the TL on the nanocomposite's wear track surface. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Element**} & **Spectrum 1** & **Spectrum 2** & **Spectrum 3** & **Spectrum 4** & **Spectrum 5** & **Spectrum 6** & **Spectrum 7** \\  & **at. \%** & **at. \%** & **at. \%** & **at. \%** & **at. \%** & **at. \%** & **at. \%** \\ \hline \multicolumn{8}{c}{Metal counterface} \\ \hline C & 7.21 & 10.56 & 9.60 & 6.15 & 5.33 & 8.72 & 12.83 \\ \hline O & 54.47 & 6.61 & 5.98 & 58.94 & 49.05 & 48.03 & 21.13 \\ \hline Al & 6.50 & 0.59 & 0.32 & 6.63 & 5.96 & 4.91 & 1.84 \\ \hline Si & 7.03 & 1.03 & 0.96 & 7.15 & 6.65 & 5.49 & 2.16 \\ \hline Cr & 0.44 & 0.99 & 1.68 & 0.28 & 0.53 & 1.09 & 1.82 \\ \hline Fe & 24.35 & 80.22 & 81.46 & 20.85 & 32.48 & 31.76 & 60.22 \\ \hline \multicolumn{8}{c}{PEI/10 CCF/1 HNT} \\ \hline C & 69.29 & 61.67 & 64.42 & 23.11 & 54.86 & 23.84 & 61.07 \\ \hline O & 29.48 & 32.88 & 34.07 & 53.26 & 41.20 & 43.65 & 34.76 \\ \hline Al & 0.09 & 0.25 & 0.10 & 0.45 & 0.46 & 0.34 & 0.19 \\ \hline Si & 0.22 & 0.37 & 0.32 & 0.77 & 0.75 & 0.86 & 0.19 \\ \hline Cr & 0.02 & 0.09 & - & 0.52 & 0.09 & 0.63 & 0.08 \\ \hline Fe & 0.90 & 4.74 & 1.09 & 21.89 & 2.64 & 30.68 & 3.71 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The results of EDS analysis on the wear track surfaces shown in Figure 7.  
Figure 6: The Raman spectra on the steel counterpart (**a**) and the PEI/10 CCF/1 HNT nanocomposite (**b**): (**a**) outside (1) and inside (2) the TF; (**b**) outside (1) and inside (2) the TL.