## 3 Results and Discussion
### XPS Research of the Nanocomposites and Initial MWCNTs  
Figure 8 shows the XPS survey spectrum of the initial MWCNTs and WC1-x/MWCNT nanocomposite (sample 2). Figure 9a-c shows their photoelectron spectra in the C1, O1 and W4f regions, respectively. The photoelectron spectra of the initial MWCNTs are in good agreement in the peaks number, their energy positions and half-widths with the nanotubes XPS spectra from [73; 74; 75; 76; 77]. The MWCNT C1 spectrum consists of an intense asymmetric peak A (284.5 eV) with a smooth tail from the short-wave side (its binding energy corresponds to one of C1's electrons in the nanotubes graphene layers) and a wide P band with an energy of 291.0 eV due to additional excitation of \(\pi\) plasmon. It is significant that in the MWCNT XPS C1 spectrum (Figure 9a) there are no separate peaks related to carbon oxides, but in the survey spectrum in Figure 8 there is a low-intensity O1 peak in the 532 eV region, which indicates the presence of oxides on the initial nanotube surface. This band, as can be seen in Figure 9b, consists of two peaks B (531.6 eV) and C (533.4 eV), which are associated with transitions in the OH\({}^{\ast}\)[78] group and H2O[79] water molecule adsorbed on the nanotube surface upon their transfer to the atmosphere. The effect of these compounds on the states of carbon atoms on the nanotube outer surface is probably the reason for the appearance of a wide absorption band of 286-289 eV (Figure 7a) in the NEXAFS C1 absorption spectra of the initial MWCNTs. The percentage of oxygen atoms in the initial MWCNTs was determined by using the Thermo Avantage software package from comparing the integrated peak intensities in the C1 and O1 spectra of the MWCNT and equals to 2.3%. This result refines the data from EDS and NEXAFS spectroscopy. The initial MWCNT XPS spectra analysis demonstrates their high purity degree. Figure 8: The X-ray photoelectron spectroscopy (XPS) spectra of the WC1-x/MWCNTs sample 2 (black) and initial MWCNTs (red) in a wide energy range. For the WC\({}_{1\text{-}\text{x}}\)/MWCNT composite, the XPS signals of Tungsten 4f and 3d (centered at \(\sim\)35 eV and \(\sim\)245 eV), C1s (\(\sim\)285.0 eV) and O1s (\(\sim\)532 eV) were detected (Figure 8). A comparison of the XPS C1 spectra of the initial nanotubes and the WC\({}_{1\text{-}\text{x}}\)/MWCNT composite (Figure 9a) shows a strong decrease in intensity and an increase in half-width by 0.33 eV of the composite main peak A (284.5 eV), corresponding to the bond between carbon atoms in graphene layers. Moreover, there are two additional low-intensity details M (282.9 eV) and B\({}^{\prime}\) (287.5 eV) in the WC\({}_{1\text{-}\text{x}}\)/MWCNT spectrum. The energy position of the peak M corresponds to the C1 binding energy in tungsten carbides [80; 81; 82]. Therefore, its appearance is associated with transitions in carbon atoms of the WC\({}_{1\text{-}\text{x}}\) coating layer. The weak peak energy B\({}^{\prime}\) corresponds to the binding energy of the C1 electron in the C=O group [83; 84], the presence of which in the nanocomposite is confirmed by NEXAFS spectroscopy data (Figure 7a). It is significant that the relative carbon atoms amount in the C=O compound with respect to carbon atoms on the nanotube surface, determined by the ratio of the areas of the peaks A and B\({}^{\prime}\) in the WC\({}_{1\text{-}\text{x}}\)/MWCNT C1 spectrum (4.7%), is twice as large than the oxygen atoms proportion in the oxides adsorbed on the initial nanotube surface (2.3%). Since the peak B\({}^{\prime}\) in the nanocomposite XPS C1 spectrum indicates the chemical interaction of the MWCNT carbon atoms with oxides initially located on its surface, i.e., the formation of a C=O bond at a temperature of 300 \({}^{\circ}\)C during the tungsten carbide deposition. Therefore, the observed carbon atom amount increase is possible with the participation of the portion of the carbon atoms on the MWCNT surface in the tungsten carbide formation during pyrolysis.