## 3 Results and Discussion
### (Pyrolytic WC)/MWCNT Nanocomposite Research  
During the study it was found that the deposition conditions and the mass of pyrolytic tungsten carbide coating highly determine the hybrid nanomaterials morphology. In Figure 3 the SEM images of hybrid materials obtained with initial MWCNT/W(CO)\({}_{6}\) ratios of 1:3 (sample 1), 1:4 (sample 2) and 1:5 (sample 3) are shown. The coating weight gain was 0.3, 0.426 and 0.723 g for samples 1-3 respectively. It was discovered that if the ratio of MWCNTs/W(CO)\({}_{6}\) is smaller 1:3 then the coating is discontinuous (Figure 3a). In addition, nanoparticle sizes vary from few nm to few tens nm. The hybrid materials synthesized with an initial ratio of 1:4 have a continuous coating of pyrolytic tungsten carbide, but at the same time there are MWCNT areas free of coating. According to TEM data, the MWCNTs coated with pyrolytic tungsten carbide (Figure 3b) have an average thickness of about 20-30 nm. The hybrid materials with a large initial ratio of 1:5 have a continuous coating of pyrolytic tungsten carbide with a thickness of more than 100 nm (Figure 3c). It is shown by SEM (Figure 3b,c) that the pyrolytic tungsten carbide coating thickness varies widely, and the coating is granular. All this suggests that coatings are not deposited as continuous thin layers covering the entire MWCNT surface, they become continuous only if grains increase sizes and coalesce at a relatively high initial W(CO)\({}_{6}\) concentration. According to the EDS results (Figure 3d), the atomic composition of the obtained MWCNTs coating is mainly represented by tungsten, carbon and oxygen. The EDS spectra were recorded for various points of the sample. The error of the atom concentrations determined from them was 30%. This is due to the sample characteristics, namely the cylindrical surface of the structural elements, the presence of spaces between them and the coating multilayer composition. For the samples with a thin coating, less than the electron penetration depth, the contribution to the intensity of the characteristic MWCNT carbon K\({}_{\alpha}\)-line is large, and the coating quantitative chemical analysis cannot be carried out. Samples with a thick coating are preferable in this regard, but the contribution of the MWCNT CK\({}_{\alpha}\)-line introduces a distortion into the quantitative analysis. In addition, the emission of carbon and oxygen atoms can be absorbed by a tungsten compound coating, which will also increase the error in determining the concentrations of these atoms in the sample. As a result of EDS measurements, the atomic composition of the sample with a thick coating (sample 3) of pyrolytic tungsten carbide after its transfer into air estimated as \(\sim\)15% (W), \(\sim\)10% (O) and \(\sim\)75% (C). In the case of samples 1 and 2 with a thinner and non-continuous coating, the atomic composition according to EDS varies within 5-10% for tungsten, 5-10% for oxygen and 90-80% for carbon. The presence of oxygen atoms in the samples can be associated with the tungsten oxide formation on the outer surface of the pyrolytic tungsten carbide coating. Figure 2: The X-ray powder diffraction patterns of (**a**) the initial MWCNTs and (**b**) as-prepared composite material sample MWCNTs coated with pyrolytic tungsten carbide with initial MWCNTs/W(CO)\({}_{6}\) ratio of 1:3 (sample 1). To determine the phase composition of the coating, the method of X-ray diffractometry was used. A typical X-ray powder diffraction pattern of the as-prepared composite material sample MWCNTs coated with pyrolytic tungsten carbide with the initial MWCNT and W(CO)\({}_{6}\) precursor ratio of 1:3 (sample 1) is presented in Figure 2b. The XRD results show the presence of the carbon nanotubes phase and the nonstoichiometric WC\({}_{1\text{-x}}\) phase. It should be noted that the diffraction pattern of the sample does not contain reflections related to tungsten oxides. This suggests that the oxide content in the pyrolytic tungsten carbide coating is negligible.